Battery operated preconcentration-assisted lateral flow assay.

PubMed

Kim, Cheonjung; Yoo, Yong Kyoung; Han, Sung Il; Lee, Junwoo; Lee, Dohwan; Lee, Kyungjae; Hwang, Kyo Seon; Lee, Kyu Hyoung; Chung, Seok; Lee, Jeong Hoon

2017-07-11

Paper-based analytical devices (e.g. lateral flow assays) are highly advantageous as portable diagnostic systems owing to their low costs and ease of use. Because of their low sensitivity and detection limits for biomolecules, these devices have several limitations in applications for real-field diagnosis. Here, we demonstrate a paper-based preconcentration enhanced lateral flow assay using a commercial β-hCG-based test. Utilizing a simple 9 V battery operation with a low power consumption of approximately 81 μW, we acquire a 25-fold preconcentration factor, demonstrating a clear sensitivity enhancement in the colorimetric lateral flow assay; consequently, clear colors are observed in a rapid kit test line, which cannot be monitored without preconcentration. This device can also facilitate a semi-quantitative platform using the saturation value and/or color intensity in both paper-based colorimetric assays and smartphone-based diagnostics.

Real-time dual-loop electric current measurement for label-free nanofluidic preconcentration chip.

PubMed

Chung, Pei-Shan; Fan, Yu-Jui; Sheen, Horn-Jiunn; Tian, Wei-Cheng

2015-01-07

An electrokinetic trapping (EKT)-based nanofluidic preconcentration device with the capability of label-free monitoring trapped biomolecules through real-time dual-loop electric current measurement was demonstrated. Universal current-voltage (I-V) curves of EKT-based preconcentration devices, consisting of two microchannels connected by ion-selective channels, are presented for functional validation and optimal operation; universal onset current curves indicating the appearance of the EKT mechanism serve as a confirmation of the concentrating action. The EKT mechanism and the dissimilarity in the current curves related to the volume flow rate (Q), diffusion coefficient (D), and diffusion layer (DL) thickness were explained by a control volume model with a five-stage preconcentration process. Different behaviors of the trapped molecular plug were categorized based on four modes associated with different degrees of electroosmotic instability (EOI). A label-free approach to preconcentrating (bio)molecules and monitoring the multibehavior molecular plug was demonstrated through real-time electric current monitoring, rather than through the use of microscope images.

Radionuclide Sensors and Systems for Monitoring Technetium-99 and Strontium-90 in Groundwater at the Hanford Site

NASA Astrophysics Data System (ADS)

Grate, J. W.; O'Hara, M. J.; Egorov, O. B.; Burge, S. R.

2009-12-01

We have developed automated sensor and analyzer devices for detection and monitoring of trace radionuclides in water, using preconcentrating columns and radiometric detection. The preconcentrating minicolumn sensor concept combines selective capture and detection in a single functional unit, where the column contains tens to hundreds of milligrams of selectively sorbent material, and the entire column content is monitored with a radiometric detector. Compared to thin film sensors with a few microgram of sorbent, this approach achieves tremendous preconcentration with efficient mass transport via pumping. Furthermore, in an equilibration-based mode of operation, the preconcentration by the sensor is maximized while eliminating the need for consumable reagents to regenerate the column; it can simply be re-equilibrated. We have demonstrated quantification of radionuclides such as technetium-99 to levels below drinking water standards in an equilibration-based process that produces steady state signals, signal proportional to concentration, and easy re-equilibration to new concentration levels. Alternatively, analyzers can be developed with separate separation and detection units that are fluidically linked. We have demonstrated detection of strontium-90 to levels below drinking water standards by this approach. We are developing autonomous systems for at-site monitoring on the Hanford Site in Washington State, using the fluidic sensor and analyzer methods, with the aim of monitoring natural and accelerated attenuation processes, remediation and barrier performance, and contaminant fluxes in the environment. Figure 1. The strontium-90 monitoring method deployed as part of the Burge Environmental Universal Sensor Platform, shown on the shores of the Columbia River on the Hanford site in Washington State.

High-throughput liquid-absorption preconcentrator sampling methods

DOEpatents

Zaromb, Solomon

1994-01-01

A system for detecting trace concentrations of an analyte in air includes a preconcentrator for the analyte and an analyte detector. The preconcentrator includes an elongated tubular container comprising a wettable material. The wettable material is continuously wetted with an analyte-sorbing liquid which flows from one part of the container to a lower end. Sampled air flows through the container in contact with the wetted material with a swirling motion which results in efficient transfer of analyte vapors or aerosol particles to the sorbing liquid and preconcentration of traces of analyte in the liquid. The preconcentrated traces of analyte may be either detected within the container or removed therefrom for injection into a separate detection means or for subsequent analysis.

High-throughput liquid-absorption preconcentrator sampling methods

DOEpatents

Zaromb, S.

1994-07-12

A system for detecting trace concentrations of an analyte in air includes a preconcentrator for the analyte and an analyte detector. The preconcentrator includes an elongated tubular container comprising a wettable material. The wettable material is continuously wetted with an analyte-sorbing liquid which flows from one part of the container to a lower end. Sampled air flows through the container in contact with the wetted material with a swirling motion which results in efficient transfer of analyte vapors or aerosol particles to the sorbing liquid and preconcentration of traces of analyte in the liquid. The preconcentrated traces of analyte may be either detected within the container or removed therefrom for injection into a separate detection means or for subsequent analysis. 12 figs.

Graphene oxide sheets immobilized polystyrene for column preconcentration and sensitive determination of lead by flame atomic absorption spectrometry.

PubMed

Islam, Aminul; Ahmad, Hilal; Zaidi, Noushi; Kumar, Suneel

2014-08-13

A novel solid-phase extractant was synthesized by coupling graphene oxide (GO) on chloromethylated polystyrene through an ethylenediamine spacer unit to develop a column method for the preconcentration/separation of lead prior to its determination by flame atomic absorption spectrometry. It was characterized by Fourier transform infrared spectroscopy, far-infrared spectroscopy, thermogravimetric analysis/differential thermal analysis, scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy. The abundant oxygen-containing surface functional groups form a strong complex with lead, resulting in higher sorption capacity (227.92 mg g(-1)) than other nanosorbents used for sorption studies of the column method. Using the column procedure here is an alternative to the direct use of GO, which restricts irreversible aggregation of GO and its escape into the ecosystem, making it an environmentally sustainable method. The column method was optimized by varying experimental variables such as pH, flow rate for sorption/desorption, and elution condition and was observed to exhibit a high preconcentration factor (400) with a low preconcentration limit (2.5 ppb) and a high degree of tolerance for matrix ions. The accuracy of the proposed method was verified by determining the Pb content in the standard reference materials and by recovery experiments. The method showed good precision with a relative standard deviation <5%. The proposed method was successfully applied for the determination of lead in tap water, electroplating wastewater, river water, and food samples after preconcentration.

A microextraction procedure based on a task-specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves.

PubMed

Saljooqi, Asma; Shamspur, Tayebeh; Mohamadi, Maryam; Afzali, Daryoush; Mostafavi, Ali

2015-05-01

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task-specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho-positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0-24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Justification of rapid prototyping in the development cycle of thermoplastic-based lab-on-a-chip.

PubMed

Preywisch, Regina; Ritzi-Lehnert, Marion; Drese, Klaus S; Röser, Tina

2011-11-01

During the developmental cycle of lab-on-a-chip devices, various microstructuring techniques are required. While in the designing and assay implementation phase direct structuring or so-called rapid-prototyping methods such as milling or laser ablation are applied, replication methods like hot embossing or injection moulding are favourable for large quantity manufacturing. This work investigated the applicability of rapid-prototyping techniques for thermoplastic chip development in general, and the reproducibility of performances in dependency of the structuring technique. A previously published chip for prenatal diagnosis that preconcentrates DNA via electrokinetic trapping and field-amplified-sample-stacking and afterwards separates it in CGE was chosen as a model. The impact of structuring, sealing, and the integration of membranes on the mobility of the EOF, DNA preconcentration, and DNA separation was studied. Structuring methods were found to significantly change the location where preconcentration of DNA occurs. However, effects on the mobility of the EOF and the separation quality of DNA were not observed. Exchange of the membrane has no effect on the chip performance, whereas the sealing method impairs the separation of DNA within the chip. The overall assay performance is not significantly influenced by different structuring methods; thus, the application of rapid-prototyping methods during a chip development cycle is well justified. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Problem of Preconcentration of Uranium Ores by Physical Processes; LES PROBLEMES DE LA PRECONCENTRATION DES MINERAIS D'URANIUM PAR VOIE PHYSIQUE. LE TRIAGE ELECTRONIQUE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vuchot, L.; Ginocchio, A. et al.

1959-10-31

As uranium ores, like most other ores, are not definite substances which can be treated directly for the production of the metal, the ores must be concentrated. The common physical processes used for all ores, such as sieving, gravimetric separation, flotation, electromagnetic separation, and electrostatic separation, are applicable to the beneficiation of uranium. The radioactivity of uranium ores has led to a radiometric method for the concentration. This method is described in detail. As an example, the preconcentration of Forez ores is discussed. (J.S.R.)

Ultrasonic-energy enhance the ionic liquid-based dual microextraction to preconcentrate the lead in ground and stored rain water samples as compared to conventional shaking method.

PubMed

Nizamani, Sooraj; Kazi, Tasneem G; Afridi, Hassan I

2018-01-01

An efficient preconcentration technique based on ultrasonic-assisted ionic liquid-based dual microextraction (UA-ILDµE) method has been developed to preconcentrate the lead (Pb +2 ) in ground and stored rain water. In the current proposed method, Pb +2 was complexed with a chelating agent (dithizone), whereas an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) was used for extraction purpose. The ultrasonic irradiation and electrical shaking system were applied to enhance the dispersion and extraction of Pb +2 complex in aqueous samples. For second phase, dual microextraction (DµE phase), the enriched Pb +2 complex in ionic liquid, extracted back into the acidic aqueous solution and finally determined by flame atomic absorption spectrometry. Some major analytical parameters that influenced the extraction efficiency of developed method, such as pH, concentration of ligand, volume of ionic liquid and samples, time of shaking in thermostatic electrical shaker and ultrasonic bath, effect of back extracting HNO 3 volume, matrix effect, centrifugation time and rate were optimized. At the sample volume of 25mL, the calculated preconcentration factor was 62.2. The limit of detection of proposed procedure for Pb +2 ions was found to be 0.54μgL -1 . The validation of developed method was performed by the analysis of certified sample of water SRM 1643e and standard addition method in a real water sample. The extraction recovery of Pb +2 was enhanced≥2% with shaking time of 80s in ultrasonic bath as compared to used thermostatic electrical shaker, where for optimum recovery up to 10min was required. The developed procedure was successfully used for the enrichment of Pb +2 in ground and stored rain water (surface water) samples of an endemic region of Pakistan. The resulted data indicated that the ground water samples were highly contaminated with Pb +2 , while some of the surface water samples were also have higher values of Pb +2 than permissible limit of WHO. The concentration of Pb +2 in surface and ground water samples was found in the range of 17.5-24.5 and 25.6-99.1μgL - 1 respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhancement in the sensitivity of microfluidic enzyme-linked immunosorbent assays through analyte preconcentration.

PubMed

Yanagisawa, Naoki; Dutta, Debashis

2012-08-21

In this Article, we describe a microfluidic enzyme-linked immunosorbent assay (ELISA) method whose sensitivity can be substantially enhanced through preconcentration of the target analyte around a semipermeable membrane. The reported preconcentration has been accomplished in our current work via electrokinetic means allowing a significant increase in the amount of captured analyte relative to nonspecific binding in the trapping/detection zone. Upon introduction of an enzyme substrate into this region, the rate of generation of the ELISA reaction product (resorufin) was observed to increase by over a factor of 200 for the sample and 2 for the corresponding blank compared to similar assays without analyte trapping. Interestingly, in spite of nonuniformities in the amount of captured analyte along the surface of our analysis channel, the measured fluorescence signal in the preconcentration zone increased linearly with time over an enzyme reaction period of 30 min and at a rate that was proportional to the analyte concentration in the bulk sample. In our current study, the reported technique has been shown to reduce the smallest detectable concentration of the tumor marker CA 19-9 and Blue Tongue Viral antibody by over 2 orders of magnitude compared to immunoassays without analyte preconcentration. When compared to microwell based ELISAs, the reported microfluidic approach not only yielded a similar improvement in the smallest detectable analyte concentration but also reduced the sample consumption in the assay by a factor of 20 (5 μL versus 100 μL).

Nano magnetic solid phase extraction for preconcentration of lead ions in environmental samples by a newly synthesized reagent.

PubMed

Golshekan, Mostafa; Shariati, Shahab

2013-01-01

In this study, magnetite nanoparticles with particle size lower than 47 nm were synthesized and were applied for preconcentration of Pb2+ ions from aqueous solutions. To preconcentrate the Pb2+ ions, the surface of the synthesized nano particles was modified with sodium dodecyl sulfate (SDS) as an anionic surfactant. A new chelating agent (2-((E)-2-amino-4,5-dinitrophenylimino)methyl)phenol) was synthesized and used to form a very stable complex with Pb2+ ions. The lead ions formed complexes and were quantitatively extracted with SDS-coated magnetite nanoparticles. After magnetic separation of adsorbent, the adsorbent was eluted with 0.5% (v/v) HC1 in dimethyl sulfoxide (DMSO) prior to analysis by flame atomic absorption spectrometry (FAAS). Orthogonal array design (OAD) was used to study and optimize the different experimental parameters. Under the optimum conditions, enhancement factor up to 63.5 was achieved for extraction from only 10 mL of sample solution and the relative standard deviation (RSD %) of the method was lower than 2.8%. The obtained calibration curve was linear in the range of 1-300 pg L-' with reasonable linearity (r2 > 0.998). The limit of detection (LOD) based on S/N = 3 was 0.04 microg L(-1) for 10 mL sample volumes. Finally, applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of lead ions in environmental samples and satisfactory results were obtained.

The Trace Analysis of DEET in Water using an On-line Preconcentration Column and Liquid Chromatography with UV Photodiode Array Detection

EPA Science Inventory

A method for the detection of trace levels of N,N-diethyl-m-toluamide (DEET) in water is discussed. The method utilizes an on-line preconcentration column in series with high performance liquid chromatography (HPLC) and UV photodiode array detection. DEET, a common insect repel...

PNEUMATIC MICROVALVE FOR ELECTROKINETIC SAMPLE PRECONCENTRATION AND CAPILLARY ELECTROPHORESIS INJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cong, Yongzheng; Rausch, Sarah J.; Geng, Tao

2014-10-27

Here we show that a closed pneumatic microvalve on a PDMS chip can serve as a semipermeable membrane under an applied potential, enabling current to pass through while blocking the passage of charged analytes. Enrichment of both anionic and cationic species has been demonstrated, and concentration factors of ~70 have been achieved in just 8 s. Once analytes are concentrated, the valve is briefly opened and the sample is hydrodynamically injected onto an integrated microchip or capillary electrophoresis (CE) column. In contrast to existing preconcentration approaches, the membrane-based method described here enables both rapid analyte concentration as well as highmore » resolution separations.« less

In-Syringe Micro Solid-Phase Extraction Method for the Separation and Preconcentration of Parabens in Environmental Water Samples.

PubMed

Mashile, Geaneth Pertunia; Mpupa, Anele; Nomngongo, Philiswa Nosizo

2018-06-14

In this study, a simple, rapid and effective in-syringe micro-solid phase extraction (MSPE) method was developed for the separation and preconcetration of parabens (methyl, ethyl, propyl and butyl paraben) in environmental water samples. The parabens were determined and quantified using high performance liquid chromatography and a photo diode array detector (HPLC-PDA). Chitosan-coated activated carbon (CAC) was used as the sorbent in the in-syringe MSPE device. A response surface methodology based on central composite design was used for the optimization of factors (eluent solvent type, eluent volume, number of elution cycles, sample volume, sample pH) affecting the extraction efficiency of the preconcentration procedure. The adsorbent used displayed excellent absorption performance and the adsorption capacity ranged from 227⁻256 mg g −1 . Under the optimal conditions the dynamic linear ranges for the parabens were between 0.04 and 380 µg L −1 . The limits of detection and quantification ranged from 6⁻15 ng L −1 and 20⁻50 ng L −1 , respectively. The intraday (repeatability) and interday (reproducibility) precisions expressed as relative standard deviations (%RSD) were below 5%. Furthermore, the in-syringe MSPE/HPLC procedure was validated using spiked wastewater and tap water samples and the recoveries ranged between from 96.7 to 107%. In conclusion, CAC based in-syringe MSPE method demonstrated great potential for preconcentration of parabens in complex environmental water.

Application of Ultrasound-Assisted Surfactant-Enhanced Emulsification Microextraction Based on Solidification of Floating Organic Droplets and High Performance Liquid Chromatography for Preconcentration and Determination of Alprazolam and Chlordiazepoxide in Human Serum Samples.

PubMed

Goudarzi, Nasser; Amirnavaee, Monavar; Arab Chamjangali, Mansour; Farsimadan, Sahar

2017-07-01

An improved microextraction method is proposed on the basis of ultrasound-assisted surfactant-enhanced emulsification and solidification of a floating organic droplet procedure combined with high performance liquid chromatography for the preconcentration and quantification of alprazolam (ALP) and chlordiazepoxide (CHL) present in a number of human serum samples. Several parameters affecting the extraction efficiency were investigated by the Plackett -Burman factorial design as the screening design. Then the response surface methodology based on the Box-Behnken design was used to optimize the effective parameters in the proposed procedure. The limits of detection for the proposed method were found to be 3.0 and 3.1 ng mL-1 for CHL and ALP, respectively. The calibration curves obtained for the method were linear in the ranges of 10.0-3,500.0 and 10.0-3,000.0 ng mL-1 for CHL and ALP, respectively, with a good determination coefficient. The recoveries of the drugs in the spiked human serum samples were above 93.0%. The developed method was successfully applied to the analysis of these studied drugs in human serum samples. The pre-treatment of the serum samples was performed using acetonitrile to remove the proteins. The proposed procedure was an accurate and reliable one for the determination and preconcentration of these drugs in blood samples. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Pyridine-functionalized Fe₃O₄ nanoparticles as a novel sorbent for the preconcentration of lead and cadmium ions in tree leaf as a bioindicator of urban traffic pollution.

PubMed

Sayar, Omid; Zhad, Hamid Reza Lotfi Zadeh; Sadeghi, Omid; Amani, Vahid; Najafi, Ezzatolla; Tavassoli, Najmeh

2012-12-01

We have developed a facile and highly sensitive sorbent for cadmium and lead ions. It is based on Fe₃O₄ nanoparticles functionalized with a derivative of picoline and was characterized by scanning electron microscopy, differential thermographic analysis, and elemental analysis. The material can be applied to the preconcentration of lead and cadmium ions. Factors such as the type, concentration and volume of eluent, the pH of the sample solution, the time for extraction, and the volume of the sample were studied. The effects of a variety of ions on preconcentration and recovery of these ions were also investigated. The ions were determined by FAAS, and the limits of detection are <0.8 and <0.061 μg L⁻¹ for lead and cadmium, respectively. Recoveries and precisions are >98.0 % and <1.3 %, respectively. The method was validated by analyzing several certified leaf reference materials.

Effective determination of a pharmaceutical, sulpiride, in river water by online SPE-LC-MS using a molecularly imprinted polymer as a preconcentration medium.

PubMed

Kubo, Takuya; Kuroda, Kenta; Tominaga, Yuichi; Naito, Toyohiro; Sueyoshi, Kenji; Hosoya, Ken; Otsuka, Koji

2014-02-01

We report an effective and a quantitative analysis method for one of pharmaceuticals, sulpiride, in river water by online solid phase extraction (SPE) connected with liquid chromatography-mass spectrometry (LC-MS) using a molecularly imprinted polymer as a preconcentration medium. The polymer prepared with a pseudo template molecule showed the selective retention ability based on the interval recognition of functional groups in sulpiride. Also, the imprinted polymer provided an effective concentration of a trace level of sulpiride in offline SPE with dual washing processes using water and acetonitrile, although another imprinted polymer prepared by an authentic method using sulpiride and methacrylic acid as a template and a functional monomer, respectively, showed the selective adsorption only in organic solvents. Furthermore, we employed the imprinted polymer as the preconcentration column of online SPE-LC-MS and the results supposed that the proposed system allowed the quantitative analysis of sulpiride with high sensitivity and recovery (10ng/L at 96%). Additionally, the determination of sulpiride in real river water without an additional spiking was effectively achieved by the system. Copyright © 2013 Elsevier B.V. All rights reserved.

Analysis of isothiazolinones in environmental waters by gas chromatography-mass spectrometry.

PubMed

Rafoth, Astrid; Gabriel, Sabine; Sacher, Frank; Brauch, Heinz-Jürgen

2007-09-14

This paper describes an analytical method for the determination of five biocides of isothiazolinone type (2-methyl-3-isothiazolinone (MI), 5-chloro-2-methyl-3-isothiazolinone (CMI), 1,2-benzisothiazolinone (BIT), 2-octyl-3-isothiazolinone (OI), 4,5-dichloro-2-octyl-3-isothiazolinone (DCOI)) in environmental waters. The method is based on pre-concentration of the analytes by solid-phase extraction onto a mixture of a polymeric material and RP-C18 material and subsequent determination by gas chromatography-mass spectrometry (GC-MS). One of the target compounds (BIT) is derivatised with diazomethane after pre-concentration to improve its chromatographic performance. The method was optimised with respect to pre-concentration conditions (liquid-liquid extraction versus solid-phase extraction, solid-phase material, elution solvent and volume) and extensively validated. Applying the method to surface waters, groundwaters, and drinking waters, limits of detection between 0.01 and 0.1 microg/l could be achieved and the repeatability was below 10% for all compounds except for MI. Additional investigations showed that the stability of the isothiazolinones in environmental waters is limited and sample storage at 4 degrees C is mandatory to preserve the target biocides. First investigations of influents and effluents of a wastewater treatment plant showed that conventional wastewater treatment exhibits a high efficiency for removal of the isothiazolinones. In river waters, the target isothiazolinones could not be detected.

Pre-concentration and determination of tartrazine dye from aqueous solutions using modified cellulose nanosponges.

PubMed

Shiralipour, Roohollah; Larki, Arash

2017-01-01

In this study, a new absorbent based on cellulose nanosponges modified with methyltrioctylammonium chloride (aliquat 336) was prepared and used for pre-concentration, removal and determination of tartrazine dye, using UV-vis spectrophotometry. This adsorbent was fully characterized using various instrumental techniques such as SEM, FTIR and XRD spectra. The pre-concentration and removal procedures were studied in column and batch modes, respectively. The effects of parameters such as pH of the aqueous medium, methyltrioctylammounium chloride dose, adsorbent amount, desorbing conditions and interfering ions on the adsorption of tartrazine were investigated and optimized. The fitting experimental data with conventional isotherm models revealed that the adsorption followed the Brunauer-Emmett-Teller (BET) model and the maximum adsorption capacity for tartrazine was 180mg/g with modified nanosponges. Under the optimized conditions, the calibration curve was linear over the range of 2-300ng/mL and the limit of detection was 0.15ng/mL. The relative standard deviation (RSD) for 20 and 100ng/mL of tartrazine were 3.1% and 1.5%, respectively. The proposed method was applied for pre-concentration and determination of tartrazine dye in different water samples. Copyright © 2016 Elsevier Inc. All rights reserved.

Preconcentration of heavy metals on activated carbon and their determination in fruits by inductively coupled plasma optical emission spectrometry.

PubMed

Feist, Barbara; Mikula, Barbara

2014-03-15

A method of separation and preconcentration of cadmium, cobalt, copper, nickel, lead, and zinc at trace level using activated carbon is proposed. Activated carbon with the adsorbed trace metals was mineralised using a high-pressure microwave mineraliser. The heavy metals were determined after preconcentration by inductively coupled plasma optical emission spectrometry (ICP-OES). The influence of several parameters, such as pH, sorbent mass, shaking time was examined. Moreover, effects of inorganic matrix on recovery of the determined elements were studied. The experiment shows that foreign ions did not influence recovery of the determined elements. The detection limits (DL) of Cd, Co, Cu, Ni, Pb, and Zn were 0.17, 0.19, 1.60, 2.60, 0.92 and 1.50 μg L(-)(1), respectively. The recovery of the method for the determined elements was better than 95% with relative standard deviation from 1.3% to 3.7%. The preconcentration factor was 80. The proposed method was applied for determination of Cd, Co, Cu, Ni, Pb, and Zn in fruits materials. Accuracy of the proposed method was verified using certified reference material (NCS ZC85006 Tomato). Copyright © 2013 Elsevier Ltd. All rights reserved.

Integrated microfluidic systems for sample preparation and detection of respiratory pathogen Bordetella pertussis.

PubMed

de la Rosa, Carlos; Prakash, Ranjit; Tilley, Peter A; Fox, Julie D; Kaler, Karan V i S

2007-01-01

An integrated microfluidic system for combined manipulation, pre-concentration, and lysis of samples containing Bordetella pertussis by dielectrophoresis and electroporation has been developed and implemented. The microfluidic device was able to pre-concentrate the amount of B. pertussis cells present in 200 microl of a B. pertussis suspension stock into a 20 microl volume. The device exhibited optimal sample pre-concentration of 6.7x at a stock value of 10(3) cfu/ml and at a flow rate of 250 microl/h. Electro-disruption experiments showed that on-chip-based electroporation is an effective solution for lysis of B. pertussis cells that is easily integrated with dielectrophoresis assisted pre-concentration procedures. Pulsed voltage applied, number of pulses, and presence of potassium chloride in a B. pertussis suspension showed a reduction in B. pertussis cell viability by electroporation; and transmission electron microscopy confirmed B. pertussis cell disruption by electroporation. Genetic amplification and detection of the pre-concentrated sample employing an integrated chip-based system demonstrated a complete chip approach for pathogen detection.

Application of polyurethane foam as a sorbent for trace metal pre-concentration — A review

NASA Astrophysics Data System (ADS)

Lemos, V. A.; Santos, M. S.; Santos, E. S.; Santos, M. J. S.; dos Santos, W. N. L.; Souza, A. S.; de Jesus, D. S.; das Virgens, C. F.; Carvalho, M. S.; Oleszczuk, N.; Vale, M. G. R.; Welz, B.; Ferreira, S. L. C.

2007-01-01

The first publication on the use of polyurethane foam (PUF) for sorption processes dates back to 1970, and soon after the material was applied for separation processes. The application of PUF as a sorbent for solid phase extraction of inorganic analytes for separation and pre-concentration purposes is reviewed. The physical and chemical characteristics of PUF (polyether and polyester type) are discussed and an introduction to the characterization of these sorption processes using different types of isotherms is given. Separation and pre-concentration methods using unloaded and loaded PUF in batch and on-line procedures with continuous flow and flow injection systems are presented. Methods for the direct solid sampling analysis of the PUF after pre-concentration are discussed as well as approaches for speciation analysis. Thermodynamic proprieties of some extraction processes are evaluated and the interpretation of determined parameters, such as enthalpy, entropy and Gibbs free energy in light of the physico-chemical processes is explained.

Microwave acid digestion and preconcentration neutron activation analysis of biological and diet samples for iodine.

PubMed

Rao, R R; Chatt, A

1991-07-01

A simple preconcentration neutron activation analysis (PNAA) method has been developed for the determination of low levels of iodine in biological and nutritional materials. The method involves dissolution of the samples by microwave digestion in the presence of acids in closed Teflon bombs and preconcentration of total iodine, after reduction to iodide with hydrazine sulfate, by coprecipitation with bismuth sulfide. The effects of different factors such as acidity, time for complete precipitation, and concentrations of bismuth, sulfide, and diverse ions on the quantitative recovery of iodide have been studied. The absolute detection limit of the PNAA method is 5 ng of iodine. Precision of measurement, expressed in terms of relative standard deviation, is about 5% at 100 ppb and 10% at 20 ppb levels of iodine. The PNAA method has been applied to several biological reference materials and total diet samples.

Determination of molybdenum in sea and estuarine water with BETA-naphthoin oxime and neutron activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuathilake, A.I.; Chatt, A.

1980-05-01

An analytical method has been developed for the determination of submicrogram quantities of molybdenum in sea and esturaine water. The method consists of preconcentration of molybdenum with BETA-naphthoin oxime followed by the determination of the element employing neutron activation analysis. Various factors that can influence yield and selectivity of the preconcentration process have been investigated in detail. A comparison study between ..cap alpha..-benzoin oxime and BETA-naphthoin oxime in preconcentrating molybdenum has been carried out using a standard steel sample. The method has been applied to determine molybdenum content of sea and estuarine water. A detection limit of 0.32 ..mu..g Momore » L/sup -1/ seawater has been acheived. The precision and accuracy of the method have been evaluated using an intercomparison fresh water and a biological standard reference material. 1 figure, 9 tables.« less

Paper-based ion concentration polarization device for selective preconcentration of muc1 and lamp-2 genes

NASA Astrophysics Data System (ADS)

Son, Seok Young; Lee, Hyomin; Kim, Sung Jae

2017-12-01

Recently, novel biomolecules separation and detection methods based on ion concentration polarization (ICP) phenomena have been extensively researched due to its high amplification ratio and high-speed accumulation. Despite of these bright advances, the fabrication of conventional ICP devices still have complicated and times-consuming tasks. As an alternative platform, a paper have been recently used for the identical ICP operations. In this work, we demonstrated the selective preconcentration of a muc1 gene fragment as human breast cancer marker and a lamp-2 gene fragment as the cause of Danon disease in paper-based ICP devices. As a result, these two DNA fragments were successfully concentrated up to 60 fold at different location in a single paper-channel. The device would be a promising platform for point-of-care device due to an economic fabrication, the easy extraction of concentrated sample and an easy disposability.

Method for preconcentrating a sample for subsequent analysis

DOEpatents

Zaromb, Solomon

1990-01-01

A system for analysis of trace concentration of contaminants in air includes a portable liquid chromatograph and a preconcentrator for the contaminants to be analyzed. The preconcentrator includes a sample bag having an inlet valve and an outlet valve for collecting an air sample. When the sample is collected the sample bag is connected in series with a sorbing apparatus in a recirculation loop. The sorbing apparatus has an inner gas-permeable container containing a sorbent material and an outer gas-impermeable container. The sample is circulated through the outer container and around the inner container for trapping and preconcentrating the contaminants in the sorbent material. The sorbent material may be a liquid having the same composition as the mobile phase of the chromatograph for direct injection thereinto. Alternatively, the sorbent material may be a porous, solid body, to which mobile phase liquid is added after preconcentration of the contaminants for dissolving the contaminants, the liquid solution then being withdrawn for injection into the chromatograph.

Simultaneous multicomponent spectrophotometric monitoring of methyl and propyl parabens using multivariate statistical methods after their preconcentration by robust ionic liquid-based dispersive liquid-liquid microextraction.

PubMed

Khani, Rouhollah; Ghasemi, Jahan B; Shemirani, Farzaneh

2014-03-25

A powerful and efficient signal-preprocessing technique that combines local and multiscale properties of the wavelet prism with the global filtering capability of orthogonal signal correction (OSC) is applied for pretreatment of spectroscopic data of parabens as model compounds after their preconcentration by robust ionic liquid-based dispersive liquid-liquid microextraction method (IL-DLLME). In the proposed technique, a mixture of a water-immiscible ionic liquid (as extraction solvent) [Hmim][PF6] and disperser solvent is injected into an aqueous sample solution containing one of the IL's ions, NaPF6, as extraction solvent and common ion source. After preconcentration, the absorbance of the extracted compounds was measured in the wavelength range of 200-700 nm. The wavelet orthogonal signal correction with partial least squares (WOSC-PLS) method was then applied for simultaneous determination of each individual compound. Effective parameters, such as amount of IL, volume of the disperser solvent and amount of NaPF6, were inspected by central composite design to identify the most important parameters and their interactions. The effect of pH on the sensitivity and selectivity was studied according to the net analyte signal (NAS) for each component. Under optimum conditions, enrichment factors of the studied compounds were 75 for methyl paraben (MP) and 71 for propyl paraben (PP). Limits of detection for MP and PP were 4.2 and 4.8 ng mL(-)(1), respectively. The root mean square errors of prediction for MP and PP were 0.1046 and 0.1275 μg mL(-)(1), respectively. The practical applicability of the developed method was examined using hygienic, cosmetic, pharmaceutical and natural water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Partition/Ion-Exclusion Chromatographic Ion Stacking for the Analysis of Trace Anions in Water and Salt Samples by Ion Chromatography.

PubMed

Akter, Fouzia; Saito, Shingo; Tasaki-Handa, Yuiko; Shibukawa, Masami

2018-01-01

A new analytical methodology for a simple and efficient on-line preconcentration of trace inorganic anions in water and salt samples prior to ion chromatographic determination is proposed. The preconcentration method is based on partition/ion-exclusion chromatographic ion stacking (PIEC ion stacking) with a hydrophilic polymer gel column containing a small amount of fixed anionic charges. The developed on-line PIEC ion stacking-ion chromatography method was validated by recovery experiments for the determination of nitrate in tap water in terms of both accuracy and precision, and the results showed the reliability of the method. The method proposed was also successfully applied to the determination of trace impurity nitrite and nitrate in reagent-grade salts of sodium sulfate. A low background level can be achieved since pure water is used as the eluant for the PIEC ion stacking. It is possible to reach sensitive detection at sub-μg L -1 levels by on-line PIEC ion stacking-ion chromatography.

Combination of solid-phase extraction with dispersive liquid-liquid microextraction followed by GC-MS for determination of pesticide residues from water, milk, honey and fruit juice.

PubMed

Shamsipur, Mojtaba; Yazdanfar, Najmeh; Ghambarian, Mahnaz

2016-08-01

In this work, an effective preconcentration method for the extraction and determination of traces of multi-residue pesticides was developed using solid-phase extraction (SPE) coupled with dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry (GC-MS). Variables affecting the performance of both extraction steps such as type and volume of elution and extraction solvents, breakthrough volume, salt addition, extraction time were thoroughly investigated. The proposed method resulted in good linearities (R(2)>0.9915) over the ranges of 1-10,000ngkg(-1), limits of detection (LODs) in the range of 0.5-1.0ngkg(-1) at S/N=3, and precision of RSD% of ⩽11.8. Under optimal conditions, the preconcentration factors were obtained in the range of 2362-10,593 for 100mL sample solutions. Comparison of the proposed method with other ones demonstrated that SPE-DLLME method provides higher extraction efficiency and larger preconcentration factor for determination of pesticides residues. Further, it is simple, inexpensive, highly sensitive, and can be successfully applied to separation, preconcentration and determination of the pesticides (and other noxious materials) in different real food samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fast preconcentration of trace rare earth elements from environmental samples by di(2-ethylhexyl)phosphoric acid grafted magnetic nanoparticles followed by inductively coupled plasma mass spectrometry detection

NASA Astrophysics Data System (ADS)

Yan, Ping; He, Man; Chen, Beibei; Hu, Bin

2017-10-01

In this work, di(2-ethylhexyl)phosphoric acid (P204) grafted magnetic nanoparticles were synthesized by fabricating P204 onto Fe3O4@TiO2 nanoparticles based on Lewis acid-base interaction between Ti and phosphate group under weakly acidic condition. The prepared Fe3O4@TiO2@P204 nanoparticles exhibited excellent selectivity for rare earth elements, and good anti-interference ability. Based on it, a method of magnetic solid phase extraction (MSPE) combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for fast preconcentration and determination of trace rare earth elements in environmental samples. Under the optimal conditions, the detection limits of rare earth elements were in the range of 0.01 (Tm)-0.12 (Nd) ng L- 1 with an enrichment factor of 100-fold, and the relative standard deviations ranged from 4.9 (Pr) to 10.7% (Er). The proposed method was successfully applied to the determination of rare earth elements in environmental samples, including river water, lake water, seawater and sediment.

Modification of gold nanoparticle loaded on activated carbon with bis(4-methoxysalicylaldehyde)-1,2-phenylenediamine as new sorbent for enrichment of some metal ions.

PubMed

Karimipour, Gholamreza; Ghaedi, Mehrorang; Sahraei, Reza; Daneshfar, Ali; Biyareh, Mehdi Nejati

2012-01-01

In this study, a new sorbent based on the gold nanoparticle loaded in activated carbon (Au-NP-AC) was synthesized and modified by bis(4-methoxy salicylaldehyde)-1,2-phenylenediamine (BMSAPD). This sorbent, which is abbreviated as Au-NP-AC-BMSAPD, has been applied for the enrichment and preconcentration of trace amounts of Co(2+), Cu(2+), Ni(2+), Fe(2+), Pb(2+), and Zn(2+) ions in real samples. All metal ions under study were retained on the Au-NP-AC-BMSAPD sorbent by complexation of the ions with the BMSAPD ligand, providing an efficient preconcentration fashion. The retained metal ions were then eluted from the sorbent by HNO(3) and detected by flame atomic absorption spectrometry. The analytical parameters including pH, amount of ligand, and the nature of the eluent and solid phase were evaluated to obtain the optimum condition for the preconcentration factor. Following the optimum conditions, a preconcentration factor of 200 was obtained for all the metal ions under study with detection limits of 1.4-2.6 ng mL(-1). The method has been successfully applied for the extraction and determination of the ion content in the same real samples with recoveries in the range of 95-99.6% and a relative standard deviation lower than 4.0%.

Flame Atomic Absorption Spectrometric Determination of Trace Metal Ions in Environmental and Biological Samples After Preconcentration on a Newly Developed Amberlite XAD-16 Chelating Resin Containing p-Aminobenzene Sulfonic Acid.

PubMed

Islam, Aminul; Ahmad, Akil; Laskar, Mohammad Asaduddin

2015-01-01

Amberlite® XAD-16 was functionalized with p-aminobenzene sulfonic acid via an azo spacer in order to prepare a new chelating resin, which was then characterized by water regain value, hydrogen ion capacity, elemental analyses, and IR spectral and thermal studies. The maximum uptake of Cu(II), Ni(II), Zn(II), Co(II), Cr(III), Fe(III), and Pb(II) ions was observed in the pH range 4.0-6.0 with the corresponding half-loading times of 6.5, 7.0, 8.0, 9.0, 11.0, 8.5, and 16.5 min. The sorption data followed Langmuir isotherms and a pseudo-second-order model. Thermodynamic quantities, ΔH and ΔS, based on the variation of the distribution coefficient with temperature were also evaluated. High preconcentration factors of 60-100 up to a low preconcentration limit of 4.0-6.6 μg/L have been achieved for the metal ions. The validity of the method was checked by analyzing standard reference materials and recoveries of trace metals after spiking. The analytical applications of the method were explored by analyzing natural water, mango pulp, mint leaves, and fish.

Analysis of biogenic carbonates by inductively coupled plasma-mass spectrometry (ICP-MS). Flow injection on-line solid-phase preconcentration for trace element determination in fish otoliths.

PubMed

Arslan, Z; Paulson, A J

2002-04-01

The aragonite deposits within the ear bones (otoliths) of teleost fish retain a chemical signal reflecting the life history of fish (similar to rings of trees) and the nature of fish habitats. Otoliths dissolved in acid solutions contain high concentrations of calcium and a variety of proteins. Elimination of matrix salts and organic interferences during preconcentration is essential for accurate determination of trace elements in otolith solutions by inductively coupled plasma-quadrupole mass spectrometry. An iminodiacetate-based chelating resin (Toyopearl AF-Chelate 650 M) has been used for on-line preconcentration and matrix separation for the determination of 31 transition and rare elements. Successful preconcentration of the elements was achieved at pH 5 by on-line buffering, except Mn which required pH 8.8. Sample solutions were loaded on to the column for 1 min at 3.2 mL min(-1), and then eluted directly into the mass spectrometer with 4% v/v nitric acid. This procedure enabled up to 25-fold preconcentration with successful removal of the calcium matrix. The effect of heat-assisted oxidation with concentrated nitric acid was investigated to eliminate the organic matrix. It was found that heating to dryness after dissolution and further mineralization with the acid significantly improved the retention of the transition elements. The method was validated by analysis of a certified reference material produced from saggittal otoliths of emperor snapper ( Lutjanus sebae), and then applied to the determination of trace metal concentrations in juvenile bluefin tuna ( Thunnus thynnus) from the Western Pacific Ocean.

Mechanisms of deterioration of nutrients. [of freeze dried foods

NASA Technical Reports Server (NTRS)

Karel, M.; Flink, J. M.

1976-01-01

Methods which produce freeze dried foods of improved quality were examined with emphasis on storage stability. Specific topics discussed include: microstructure of freeze dried systems, investigation of structural changes in freeze dried systems, artificial food matrices, osmotic preconcentration to yield improved quality freeze dried fruits, and storage stability of osmotically preconcentrated freeze dried fruits.

Graphene-based solid-phase extraction disk for fast separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples.

PubMed

Wang, Zonghua; Han, Qiang; Xia, Jianfei; Xia, Linhua; Ding, Mingyu; Tang, Jie

2013-06-01

Graphene has great potentials for the use in sample preparation due to its ultra high specific surface area, superior chemical stability, and excellent thermal stability. In our work, a novel graphene-based SPE disk was developed for separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples. Based on the strong π-π stacking interaction between the analytes and graphene, the analytes extracted by graphene were eluted by cyclohexane and then determined by GC-MS. Under the optimized conditions, high flow rate (30 mL/min) and sensitivity (0.84-13 ng/L) were achieved. The proposed method was successfully applied to the analysis of real environmental water samples with recoveries ranging from 72.8 to 106.2%. Furthermore, the property of anticlogging and reusability was also improved. This work reveals great potentials of graphene-based SPE disk in environmental analytical. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of scandium in acid mine drainage by ICP-OES with flow injection on-line preconcentration using oxidized multiwalled carbon nanotubes.

PubMed

Jerez, Javier; Isaguirre, Andrea C; Bazán, Cristian; Martinez, Luis D; Cerutti, Soledad

2014-06-01

An on-line scandium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry associated with flow injection was studied. Trace amounts of scandium were preconcentrated by sorption on a minicolumn packed with oxidized multiwalled carbon nanotubes, at pH 1.5. The retained analyte was removed from the minicolumn with 30% (v/v) nitric acid. A total enrichment factor of 225-fold was obtained within a preconcentration time of 300 s (for a 25 mL sample volume). The overall time required for preconcentration and elution of 25 mL of sample was about 6 min; the throughput was about 10 samples per hour. The value of the detection limit was 4 ng L(-1) and the precision for 10 replicate determinations at 100 ng L(-1) Sc level was 5% relative standard deviation, calculated from the peak heights obtained. The calibration graph using the preconcentration system was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 10 mg L(-1). After optimization, the method was successfully applied to the determination of Sc in an acid drainage from an abandoned mine located in the province of San Luis, Argentina. Copyright © 2014 Elsevier B.V. All rights reserved.

Room temperature ionic liquid-based dispersive liquid phase microextraction for the separation/preconcentration of trace Cd(2+) as 1-(2-pyridylazo)-2-naphthol (PAN) complex from environmental and biological samples and determined by FAAS.

PubMed

Khan, Sumaira; Soylak, Mustafa; Kazi, Tasneem Gul

2013-12-01

The current work develops a new green methodology for the separation/preconcentration of cadmium ions (Cd(2+)) using room temperature ionic liquid-dispersive liquid phase microextraction (RTIL-DLME) prior to analysis by flame atomic absorption spectrometry with microsample introduction system. Room temperature ionic liquids (RTIL) are considered "Green Solvents" for their thermally stable and non-volatile properties, here 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] was used as an extractant. The preconcentration of Cd(2+) in different waters and acid digested scalp hair samples were complexed with 1-(2-pyridylazo)-2-naphthol and extracted into the fine drops of RTILs. Some significant factors influencing the extraction efficiency of Cd(2+) and its subsequent determination, including pH, amount of ligand, volume of RTIL, dispersant solvent, sample volume, temperature, and incubation time were investigated in detail. The limit of detection and the enhancement factor under the optimal conditions were 0.05 μg/L and 50, respectively. The relative standard deviation of 100 μg/L Cd(2+) was 4.3 %. The validity of the proposed method was checked by determining Cd(2+) in certified reference material (TM-25.3 fortified water). The sufficient recovery (>98 %) of Cd(2+) with the certified value. The mean concentrations of Cd in lake water 13.2, waste water 15.7 and hair sample 16.8 μg/L, respectively and the developed method was applied satisfactorily to the preconcentration and determination of Cd(2+) in real samples.

Magnetic Droplet Microfluidics as a Platform for the Concentration of [18F]Fluoride and Radiosynthesis of Sulfonyl [18F]Fluoride.

PubMed

Fiel, Somewhere A; Yang, Hua; Schaffer, Paul; Weng, Samuel; Inkster, James A H; Wong, Michael C K; Li, Paul C H

2015-06-17

The radioisotope 18F is often considered the best choice for positron emission tomography (PET) owing to its desirable chemical and radiochemical properties. However, nucleophilic 18F-fluorination of large, water-soluble biomolecules, based on C-F bond formation, has traditionally been difficult. Thus, several aqueous fluorination approaches that offer significant versatility in radiopharmaceutical synthesis with sensitive targeting vectors have been developed. Furthermore, because 18F decays rapidly, production of these 18F-labeled compounds requires an automated process to reduce production time, reduce radiation exposure, and minimize losses due to the transfer of reagents during tracer synthesis. Herein, we report the use of magnetic droplet microfluidics (MDM) as a means to concentrate [18F]fluoride from the cyclotron target solution, followed by the synthesis of an 18F-labeled compound on a microfluidic platform. Using this method, we have demonstrated 18F preconcentration in a small-volume droplet through the use of anion exchanging magnetic particles. By using MDM, the preconcentration step took approximately 5 min, and the [18F]fluoride solution was preconcentrated by 15-fold. After the preconcentration step, an 18F-labeling reaction was performed on the MDM platform using the S-F bond formation in aqueous conditions to produce an arylsulfonyl [18F]fluoride compound which can be used as a prosthetic group to label PET targeting ligands. The high radiochemical purity of 95±1% was comparable to the 96% previously reported using a conventional method. In addition, when MDM was used, the total synthesis time was improved to 15 min with lower reagent volumes (50-60 μL) used.

On-line preconcentration/determination of lead in Ilex paraguariensis samples (mate tea) using polyurethane foam as filter and USN-ICP-OES.

PubMed

Marchisio, P F; Sales, A; Cerutti, S; Marchevski, E; Martinez, L D

2005-09-30

The present paper proposes an on-line preconcentration procedure for lead determination in Ilex paraguariensis (St. Hilaire) samples by ultrasonic nebulization associated to inductively coupled plasma optical emission spectrometry (USN-ICP-OES). It is based on the precipitation of lead(II) ion on a minicolumn packed with polyurethane foam using 2-(5-bromo-2-pyridilazo)-5-diethylaminophenol (5-Br-PADAP) as precipitating reagent. The collected analyte precipitate was quantitatively eluted from the minicolumn with 20% (v/v) nitric acid. An enhancement factor of 225-fold was obtained (15 for USN and 15 for preconcentration). The detection limit (DL) value for the preconcentration of 10.0 ml of sample was 40.0 ng/l. The relative standard deviation (R.S.D.) was 3.0% for a Pb concentration of 1 microg/l, calculated from the peak heights obtained. The calibration graph using the preconcentration system for lead was linear with a correlation coefficient of 0.9997, at levels near the detection limits up to at least 100 microg/l. The preconcentration procedure was successfully applied to the determination of lead in mate tea samples.

An Enhanced Platform to Analyse Low-Affinity Amyloid β Protein by Integration of Electrical Detection and Preconcentrator.

PubMed

Yoo, Yong Kyoung; Yoon, Dae Sung; Kim, Gangeun; Kim, Jinsik; Han, Sung Il; Lee, Junwoo; Chae, Myung-Sic; Lee, Sang-Myung; Lee, Kyu Hyoung; Hwang, Kyo Seon; Lee, Jeong Hoon

2017-10-30

Sensitivity and limit of detection (LOD) enhancement are essential criteria for the development of ultrasensitive molecular sensors. Although various sensor types have been investigated to enhance sensitivity and LOD, analyte detection and its quantification are still challenging, particularly for protein-protein interactions with low association constants. To solve this problem, here, we used ion concentration polarization (ICP)-based preconcentration to increase the local concentration of analytes in a microfluidic platform for LOD improvement. This was the first demonstration of a microfluidic device with an integrated ICP preconcentrator and interdigitated microelectrode (IME) sensor to detect small changes in surface binding between antigens and antibodies. We detected the amyloid beta (Aβ) protein, an Alzheimer's disease marker, with low binding affinity to its antibodies by adopting ICP preconcentration phenomena. We demonstrated that a combination of ICP preconcentrator and IME sensor increased the LOD by 13.8-fold to femtomolar level (8.15 fM), which corresponds to a significant advance for clinical applications.

Further research on iodine speciation in seawater by capillary zone electrophoresis with isotachophoresis preconcentration.

PubMed

Huang, Zhuo; Ito, Kazuaki; Hirokawa, Takeshi

2004-11-05

A novel, simple and highly sensitive CE method was developed to determine total iodine (TI) in seawater. The method is based on the on-capillary reduction of iodine species to iodide by a reductant, introduced into the capillary before sample injection, the preconcentration of iodide using isotachophoresis, followed by its UV detection. Under optimized conditions for reduction and CE separation, the limit of detection for TI (S/N = 3) reached 0.4 microg L(-1) (226 nm). The repeatability of migration time and peak area, expressed by relative standard deviation, was 0.46 and 1.45%, respectively (n = 19). The correlation factor was 0.9991 (n = 10) for the concentration range of 12-115 microg I L(-1). The CE results obtained for the real seawater analysis agreed with the data of ion chromatography. To determine the genuine TI by the proposed method, organic iodinated compounds in the sample were treated with H202 and irradiation with UV light before analysis.

A Facile Vortex-Assisted Dispersive Liquid-Liquid Microextraction Method for the Determination of Uranyl Ion at Low Levels by Spectrophotometry.

PubMed

Corazza, Marcela Zanetti; Pires, Igor Matheus Ruiz; Diniz, Kristiany Moreira; Segatelli, Mariana Gava; Tarley, César Ricardo Teixeira

2015-08-01

A facile and reliable UV-Vis spectrophotometric method associated with vortex-assisted dispersive liquid-liquid microextraction has been developed and applied to the determination of U(VI) at low levels in water samples. It was based on preconcentration of 24.0 mL sample at pH 8.0 in the presence of 7.4 µmol L(-1) 1-(2-pyridylazo)-2-naphthol, 1.0 mL of methanol as disperser solvent and 1.0 mL of chloroform as extraction solvent. A high preconcentration factor was achieved (396 times), thus providing a wide analytical curve from 6.9 up to 75.9 µg L(-1) (r=0.9982) and limits of detection and quantification of 0.40 and 1.30 µg L(-1), respectively. When necessary, EDTA or KCN can be used to remove interferences of foreign ions. The method was applied to the analysis of real water samples, such as tap, mineral and lake waters with good recovery values.

Development of a pre-concentration system and auto-analyzer for dissolved methane, ethane, propane, and butane concentration measurements with a GC-FID

NASA Astrophysics Data System (ADS)

Chepigin, A.; Leonte, M.; Colombo, F.; Kessler, J. D.

2014-12-01

Dissolved methane, ethane, propane, and butane concentrations in natural waters are traditionally measured using a headspace equilibration technique and gas chromatograph with flame ionization detector (GC-FID). While a relatively simple technique, headspace equilibration suffers from slow equilibration times and loss of sensitivity due to concentration dilution with the pure gas headspace. Here we present a newly developed pre-concentration system and auto-analyzer for use with a GC-FID. This system decreases the time required for each analysis by eliminating the headspace equilibration time, increases the sensitivity and precision with a rapid pre-concentration step, and minimized operator time with an autoanalyzer. In this method, samples are collected from Niskin bottles in newly developed 1 L plastic sample bags rather than glass vials. Immediately following sample collection, the sample bags are placed in an incubator and individually connected to a multiport sampling valve. Water is pumped automatically from the desired sample bag through a small (6.5 mL) Liqui-Cel® membrane contactor where the dissolved gas is vacuum extracted and directly flushed into the GC sample loop. The gases of interest are preferentially extracted with the Liqui-Cel and thus a natural pre-concentration effect is obtained. Daily method calibration is achieved in the field with a five-point calibration curve that is created by analyzing gas standard-spiked water stored in 5 L gas-impermeable bags. Our system has been shown to substantially pre-concentrate the dissolved gases of interest and produce a highly linear response of peak areas to dissolved gas concentration. The system retains the high accuracy, precision, and wide range of measurable concentrations of the headspace equilibration method while simultaneously increasing the sensitivity due to the pre-concentration step. The time and labor involved in the headspace equilibration method is eliminated and replaced with the immediate and automatic analysis of a maximum of 13 sequential samples. The elapsed time between sample collection and analysis is reduced from approximately 12 hrs to < 10 min, enabling dynamic and highly resolved sampling plans.

Zinc oxide nanorods functionalized paper for protein preconcentration in biodiagnostics

NASA Astrophysics Data System (ADS)

Tiwari, Sadhana; Vinchurkar, Madhuri; Rao, V. Ramgopal; Garnier, Gil

2017-03-01

Distinguishing a specific biomarker from a biofluid sample containing a large variety of proteins often requires the selective preconcentration of that particular biomarker to a detectable level for analysis. Low-cost, paper-based device is an emerging opportunity in diagnostics. In the present study, we report a novel Zinc oxide nanorods functionalized paper platform for the preconcentration of Myoglobin, a cardiac biomarker. Zinc oxide nanorods were grown on a Whatman filter paper no. 1 via the standard hydrothermal route. The growth of Zinc oxide nanorods on paper was confirmed by a combination of techniques consisting of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS,) scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDX) analysis. The Zinc oxide nanorods modified Whatman filter paper (ZnO-NRs/WFP) was further tested for use as a protein preconcentrator. Paper-based ELISA was performed for determination of pre-concentration of cardiac marker protein Myoglobin using the new ZnO-NRs/WFP platform. The ZnO-NRs/WFP could efficiently capture the biomarker even from a very dilute solution (Myoglobin < 50 nM). Our ELISA results show a threefold enhancement in protein capture with ZnO-NRs/WFP compared to unmodified Whatman filter paper, allowing accurate protein analysis and showing the diagnostic concept.

Non-chromatographic speciation analysis of mercury by flow injection on-line preconcentration in combination with chemical vapor generation atomic fluorescence spectrometry

NASA Astrophysics Data System (ADS)

Wu, Hong; Jin, Yan; Han, Weiying; Miao, Qiang; Bi, Shuping

2006-07-01

A novel non-chromatographic approach for direct speciation of mercury, based on the selective retention inorganic mercury and methylmercury on the inner wall of a knotted reactor by using ammonium diethyl dithiophosphate and dithizone as complexing agents respectively, was developed for flow injection on-line sorption preconcentration coupled with chemical vapor generation non-dispersive atomic fluorescence spectrometry. With the sample pH kept at 2.0, the preconcentration of inorganic mercury on the inner walls of the knotted reactor was carried out based on the exclusive retention of Hg-DDP complex in the presence of methylmercury via on-line merging the sample solution with ammonium diethyl dithiophosphate solution, and selective preconcentration methylmercury was achieved with dithizone instead of ammonium diethyl dithiophosphate. A 15% (v/v) HCl was introduced to elute the retained mercury species and merge with KBH 4 solution for atomic fluorescence spectrometry detection. Under the optimal experimental conditions, the sample throughputs of inorganic mercury and methylmercury were 30 and 20 h - 1 with the enhancement factors of 13 and 24. The detection limits were found to be 3.6 ng l - 1 for Hg 2+ and 2.0 ng l - 1 for CH 3Hg +. The precisions (RSD) for the 11 replicate measurements of each 0.2 μg l - 1 of Hg 2+ and CH 3Hg + were 2.2% and 2.8%, respectively. The developed method was validated by the analysis of certified reference materials (simulated natural water, rice flour and pork) and by recovery measurements on spiked samples, and was applied to the determination of inorganic mercury and methylmercury in biological and environmental water samples.

Adsorption studies of Cd(II) onto Al 2O 3/Nb 2O 5 mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Mendonça Costa, Lucimara; Ribeiro, Emerson Schwingel; Segatelli, Mariana Gava; do Nascimento, Danielle Raphael; de Oliveira, Fernanda Midori; Tarley, César Ricardo Teixeira

2011-05-01

The present study describes the adsorption characteristic of Cd(II) onto Nb 2O 5/Al 2O 3 mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area ( SBET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g -1. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO 2/Al 2O 3/Nb 2O 5 at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L -1 hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 2 4 full factorial design and Doehlert matrix. The effect of SO 42-, Cu 2+, Zn 2+ and Ni 2+ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h -1, concentration efficiency of 4.35 min -1, linear range from 5.0 up to 35.0 μg L -1 and limits of detection and quantification of 0.19 and 0.65 μg L -1 respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).

Methods for improved preconcentrators

DOEpatents

Manginell, Ronald P [Albuquerque, NM; Lewis, Patrick R [Albuquerque, NM; Okandan, Murat [Edgewood, NM

2010-06-01

The present invention relates generally to chemical analysis (e.g. by gas chromatography), and in particular to a compact chemical preconcentrator formed on a substrate with a heatable sorptive membrane that can be used to accumulate and concentrate one or more chemical species of interest over time and then rapidly release the concentrated chemical species upon demand for chemical analysis.

Ultratrace determination of arsenic in water samples by electrothermal atomic absorption spectrometry after pre-concentration with Mg-Al-Fe ternary layered double hydroxide nano-sorbent.

PubMed

Abdolmohammad-Zadeh, Hossein; Jouyban, Abolghasem; Amini, Roghayeh

2013-11-15

A selective solid phase extraction method, based on nano-structured Mg-Al-Fe(NO3(-)) ternary layered double hydroxide as a sorbent, is developed for the pre-concentration of ultra-trace levels of arsenic (As) prior to determination by electrothermal atomic absorption spectrometry. It is found that both As(III) and As(V) could be quantitatively retained on the sorbent within a wide pH range of 4-12. Accordingly, the presented method is applied to determination of total inorganic As in aqueous solutions. Maximum analytical signal of As is achieved when the pyrolysis and atomization temperatures are close to 900 °C and 2300 °C, respectively. Several variables affecting the extraction efficiency including pH, sample flow rate, amount of nano-sorbent, elution conditions and sample volume are optimized. Under the optimized conditions, the limit of detection (3Sb/m) and the relative standard deviation are 4.6 pg mL(-1) and 3.9%, respectively. The calibration graph is linear in the range of 15.0-650 pg mL(-1) with a correlation coefficient of 0.9979, sorption capacity and pre-concentration factor are 8.68 mg g(-1) and 300, respectively. The developed method is validated by the analysis of a standard reference material (SRM 1643e) and is successfully applied to the determination of ultra-trace amounts of As in different water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Combination of solid phase extraction and dispersive liquid-liquid microextraction for separation/preconcentration of ultra trace amounts of uranium prior to its fiber optic-linear array spectrophotometry determination.

PubMed

Dadfarnia, Shayessteh; Shabani, Ali Mohammad Haji; Shakerian, Farid; Shiralian Esfahani, Golnaz

2013-12-15

A simple and sensitive method for the separation and preconcentration of the ultra trace amounts of uranium and its determination by spectrophotometry was developed. The method is based on the combination of solid phase extraction and dispersive liquid-liquid microextraction. Thus, by passing the sample through the basic alumina column, the uranyl ion and some cations are separated from the sample matrix. The retained uranyl ion along with the cations are eluted with 5 mL of nitric acid (2 mol L(-1)) and after neutralization of the eluent, the extracted uranyl ion is converted to its anionic benzoate complex and is separated from other cations by extraction of its ion pair with malachite green into small volume of chloroform using dispersive liquid-liquid microextraction. The amount of uranium is then determined by the absorption measurement of the extracted ion pair at 621 nm using flow injection spectrophotometry. Under the optimum conditions, with 500 mL of the sample, a preconcentration factor of 1980, a detection limit of 40 ng L(-1), and a relative standard deviation of 4.1% (n=6) at 400 ng L(-1) were obtained. The method was successfully applied to the determination of uranium in mineral water, river water, well water, spring water and sea water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Liquid electrode plasma-optical emission spectrometry combined with solid-phase preconcentration for on-site analysis of lead.

PubMed

Barua, Suman; Rahman, Ismail M M; Alam, Iftakharul; Miyaguchi, Maho; Sawai, Hikaru; Maki, Teruya; Hasegawa, Hiroshi

2017-08-15

A relatively rapid and precise method is presented for the determination of lead in aqueous matrix. The method consists of analyte quantitation using the liquid electrode plasma-optical emission spectrometry (LEP-OES) coupled with selective separation/preconcentration by solid-phase extraction (SPE). The impact of operating variables on the retention of lead in SPEs such as pH, flow rate of the sample solution; type, volume, flow rate of the eluent; and matrix effects were investigated. Selective SPE-separation/preconcentration minimized the interfering effect due to manganese in solution and limitations in lead-detection in low-concentration samples by LEP-OES. The LEP-OES operating parameters such as the electrical conductivity of sample solution; applied voltage; on-time, off-time, pulse count for applied voltage; number of measurements; and matrix effects have also been optimized to obtain a distinct peak for the lead at λ max =405.8nm. The limit of detection (3σ) and the limit of quantification (10σ) for lead determination using the technique were found as 1.9 and 6.5ng mL -1 , respectively. The precision, as relative standard deviation, was lower than 5% at 0.1μg mL -1 Pb, and the preconcentration factor was found to be 187. The proposed method was applied to the analysis of lead contents in the natural aqueous matrix (recovery rate:>95%). The method accuracy was verified using certified reference material of wastewaters: SPS-WW1 and ERM-CA713. The results from LEP-OES were in good agreement with inductively coupled plasma optical emission spectrometry measurements of the same samples. The application of the method is rapid (≤5min, without preconcentration) with a reliable detection limit at trace levels. Copyright © 2017 Elsevier B.V. All rights reserved.

Optimization of a novel method for determination of benzene, toluene, ethylbenzene, and xylenes in hair and waste water samples by carbon nanotubes reinforced sol-gel based hollow fiber solid phase microextraction and gas chromatography using factorial experimental design.

PubMed

Es'haghi, Zarrin; Ebrahimi, Mahmoud; Hosseini, Mohammad-Saeid

2011-05-27

A novel design of solid phase microextraction fiber containing carbon nanotube reinforced sol-gel which was protected by polypropylene hollow fiber (HF-SPME) was developed for pre-concentration and determination of BTEX in environmental waste water and human hair samples. The method validation was included and satisfying results with high pre-concentration factors were obtained. In the present study orthogonal array experimental design (OAD) procedure with OA(16) (4(4)) matrix was applied to study the effect of four factors influencing the HF-SPME method efficiency: stirring speed, volume of adsorption organic solvent, extraction and desorption time of the sample solution, by which the effect of each factor was estimated using individual contributions as response functions in the screening process. Analysis of variance (ANOVA) was employed for estimating the main significant factors and their percentage contributions in extraction. Calibration curves were plotted using ten spiking levels of BTEX in the concentration ranges of 0.02-30,000ng/mL with correlation coefficients (r) 0.989-0.9991 for analytes. Under the optimized extraction conditions, the method showed good linearity (0.3-20,000ng/L), repeatability, low limits of detections (0.49-0.7ng/L) and excellent pre-concentration factors (185-1872). The best conditions which were estimated then applied for the analysis of BTEX compounds in the real samples. Copyright © 2011 Elsevier B.V. All rights reserved.

A new open tubular capillary microextraction and sweeping for the analysis of super low concentration of hydrophobic compounds.

PubMed

Xia, Zhining; Gan, Tingting; Chen, Hua; Lv, Rui; Wei, Weili; Yang, Fengqing

2010-10-01

A sample pre-concentration method based on the in-line coupling of in-tube solid-phase microextraction and electrophoretic sweeping was developed for the analysis of hydrophobic compounds. The sample pre-concentration and electrophoretic separation processes were simply and sequentially carried out with a (35%-phenyl)-methylpolysiloxane-coated capillary. The developed method was validated and applied to enrich and separate several pharmaceuticals including loratadine, indomethacin, ibuprofen and doxazosin. Several parameters of microextration were investigated such as temperature, pH and eluant. And the concentration of microemulsion that influences separation efficiency and microextraction efficiency were also studied. Central composite design was applied for the optimization of sampling flow rate and sampling time that interact in a very complex way with each other. The precision, sensitivity and recovery of the method were investigated. Under the optimal conditions, the maximum enrichment factors for loratadine, indomethacin, ibuprofen and doxazosin in aqueous solutions are 1355, 571, 523 and 318, respectively. In addition, the developed method was applied to determine loratadine in rabbit blood sample.

Toward the use of surface modified activated carbon in speciation: selective preconcentration of selenite and selenate in environmental waters.

PubMed

Tsoi, Yeuk-Ki; Leung, Kelvin Sze-Yin

2011-04-22

This paper describes a novel application of tetrabutylammonium hydroxide-modified activated carbon (AC-TBAH) to the speciation of ultra-trace Se(IV) and Se(VI) using LC-ICP-DRC-MS. The anion exchange functionality was immobilized onto the AC surface enables selective preconcentration of inorganic Se anions in a wide range of working pHs. Simultaneous retention and elution of both analytes, followed by subsequent analysis with LC-ICP-DRC-MS, allows to accomplish speciation analysis in natural samples without complicated redox pre-treatment. The laboratory-made column of immobilized AC (0.4 g of sorbent packed in a 6 mL syringe barrel) has achieved analyte enrichment factors of 76 and 93, respectively, for Se(IV) and Se(VI), thus proving its superior preconcentration efficiency and selectivity over common AC. The considerable enhancement in sensitivity achieved by using the preconcentration column has improved the method's detection limits to 1.9-2.2 ng L(-1), which is a 100-fold improvement compared with direct injection. The analyte recoveries from heavily polluted river matrix were between 95.3 and 107.7% with less than 5.0% RSD. The robustness of the preconcentration and speciation method was validated by analysis of natural waters collected from rivers and reservoirs in Hong Kong. The modified AC material is hence presented as a low-cost yet robust substitute for conventional anion exchange resins for routine applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Determination of Hg(II) in waters by on-line preconcentration using Cyanex 923 as a sorbent — Cold vapor atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Duan, Taicheng; Song, Xuejie; Xu, Jingwei; Guo, Pengran; Chen, Hangting; Li, Hongfei

2006-09-01

Using a solid phase extraction mini-column home-made from a neutral extractant Cyanex 923, inorganic Hg could be on-line preconcentrated and simultaneously separated from methyl mercury. The preconcentrated Hg (II) was then eluted with 10% HNO 3 and subsequently reduced by NaBH 4 to form Hg vapor before determination by cold vapor atomic absorption spectrometry (CVAAS). Optimal conditions for and interferences on the Hg preconcentration and measurement were at 1% HCl, for a 25 mL sample uptake volume and a 10 mL min - 1 sample loading rate. The detection limit was 0.2 ng L - 1 and much lower than that of conventional method (around 15.8 ng L - 1 ). The relative standard deviation (RSD) is 1.8% for measurements of 40 ng L - 1 of Hg and the linear working curve is from 20 to 2000 ng L - 1 (with a correlation coefficient of 0.9996). The method was applied in determination of inorganic Hg in city lake and deep well water (from Changchun, Jilin, China), and recovery test results for both samples were satisfactory.

Determination of simazine in water samples by HPLC after preconcentration with diatomaceous earth.

PubMed

Katsumata, Hideyuki; Fujii, Aya; Kaneco, Satoshi; Suzuki, Tohru; Ohta, Kiyohisa

2005-01-15

A sensitive and selective batch adsorption method is proposed for the preconcentration and determination of simazine. Simazine was preconcentrated on diatomaceous earth as an adsorbent and then determined by high-performance liquid chromatography (HPLC). Several parameters on the recovery of the analyte were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 2 using 100mL of validation solution containing 1.5mug of simazine and 5mL of ethanol as an eluent. Recovery of simazine was 89.0 +/- 1.6% with a relative standard deviation for seven determinations of 1.5% under optimum conditions. The maximum preconcentration factor was 100 for simazine when 500mL of sample solution volume was used. The linear range of calibration curve was 1-200ngmL(-1) with a correlation coefficient of 0.996 and the detection limit (3S/N) was 0.3ngmL(-1). The capacity of the adsorbent was also examined and found to be 1.1mgg(-1) for simazine. The proposed method was successfully applied to the determination of simazine in river water with high precision and accuracy.

Electrochemical detection of dopamine based on pre-concentration by graphene nanosheets.

PubMed

Bagherzadeh, Mojtaba; Heydari, Maryam

2013-10-21

Herein, graphene nanosheets (GNS) were synthesized, by a green and facile method based on reduction by glucose, and characterized. Afterwards, a carbon paste electrode (CPE) was modified with GNS by casting and drying GNS on top of the CPE (CPE/GNS). The behavior of the CPE/GNS towards dopamine (DA) and ascorbic acid (AA) was investigated by electrochemical methods and the obtained results showed that the CPE/GNS had adsorbed only DA. Based on this behavior, the DA molecules were pre-concentrated on top of the CPE/GNS, followed by stripping in DA free solution. Subsequent to experimental and instrumental optimization, a calibration curve from 2.0 × 10(-6) to 1.0 × 10(-3) M DA, r(2) = 0.99 (±0.01), with detection limit (DL) = 8.5 × 10(-7) M DA, sensitivity = 15.4 (±0.94) μA, and RSD = 6.1 was observed in the presence of 1.0 × 10(-3) M AA. Finally, the performance of the CPE/GNS was successfully tested in a pharmaceutical sample. This work provides a promising strategy for DA detection in the presence of biological interferences, e.g. AA, with high sensitivity and simple characteristics.

Preconcentration of lead using solidification of floating organic drop and its determination by electrothermal atomic absorption spectrometry

PubMed Central

Chamsaz, Mahmoud; Akhoundzadeh, Jeiran; Arbab-zavar, Mohammad Hossein

2012-01-01

A simple microextraction method based on solidification of a floating organic drop (SFOD) was developed for preconcentration of lead prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Ammonium pyrolidinedithiocarbamate (APDC) was used as complexing agent, and the formed complex was extracted into a 20 μL of 1-undecanol. The extracted complex was diluted with ethanol and injected into a graphite furnace. An orthogonal array design (OAD) with OA16 (45) matrix was employed to study the effects of different parameters such as pH, APDC concentration, stirring rate, sample solution temperature and the exposure time on the extraction efficiency. Under the optimized experimental conditions the limit of detection (based on 3 s) and the enhancement factor were 0.058 μg L−1 and 113, respectively. The relative standard deviation (RSD) for 8 replicate determinations of 1 μg L−1 of Pb was 8.8%. The developed method was validated by the analysis of certified reference materials and was successfully applied to the determination of lead in water and infant formula base powder samples. PMID:25685441

On-line solid phase selective separation and preconcentration of Cd(II) by solid-phase extraction using carbon active modified with methyl thymol blue.

PubMed

Ensafi, Ali A; Ghaderi, Ali R

2007-09-05

An on-line flow system was used to develop a selective and efficient on-line sorbent extraction preconcentration system for cadmium. The method is based on adsorption of cadmium ions onto the activated carbon modified with methyl thymol blue. Then the adsorbed ions were washed using 0.5M HNO(3) and the eluent was used to determine the Cd(II) ions using flame atomic absorption spectrometry. The results obtained show that the modified activated carbon has the greatest adsorption capacity of 80 microg of Cd(II) per 1.0 g of the solid phase. The optimal pH value for the quantitative preconcentration was 9.0 and full desorption is achieved by using 0.5M HNO(3) solution. It is established that the solid phase can be used repeatedly without a considerable adsorption capacity loss. The detection limit was less than 1 ngmL(-1) Cd(II), with an enrichment factor of 1000. The calibration graph was linear in the range of 1-2000 ngmL(-1) Cd(II). The developed method has been applied to the determination of trace cadmium (II) in water samples and in the following reference materials: sewage sludge (CRM144R), and sea water (CASS.4) with satisfactory results. The accuracy was assessed through recovery experiments.

Copper(II)-rubeanic acid coprecipitation system for separation-preconcentration of trace metal ions in environmental samples for their flame atomic absorption spectrometric determinations.

PubMed

Soylak, Mustafa; Erdogan, Nilgun D

2006-09-21

A simple and facile preconcentration procedure based on the coprecipitation of trace heavy metal ions with copper(II)-rubeanic acid complex has been developed. The analytical parameters including pH, amounts of rubeanic acid, sample volume, etc. was investigated for the quantitative recoveries of Pb(II), Fe(III), Cd(II), Au(III), Pd(II) and Ni(II). No interferic effects were observed from the concomitant ions. The detection limits for analyte ions by 3 sigma were in the range of 0.14 microg/l for iron-3.4 microg/l for lead. The proposed coprecipitation method was successfully applied to water samples from Palas Lake-Kayseri, soil and sediment samples from Kayseri and Yozgat-Turkey.

Natural analcime zeolite modified with 5-Br-PADAP for the preconcentration and anodic stripping voltammetric determination of trace amount of cadmium.

PubMed

Afzali, Darush; Mostafavi, Ali; Taher, Mohammad Ali; Rezaeipour, Ebrahim; Khayatzadeh Mahani, Mohammad

2005-04-01

A procedure for separation and preconcentration of trace amounts of cadmium has been proposed. A column of analcime zeolite modified with benzyldimethyltetradecylammonium chloride and loaded with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) was used for retention of cadmium. The cadmium was quantitatively retained on the column at pH approximately 9 and was recovered from column with 5 ml of 2 M nitric acid with a preconcentration factor of 140. Anodic stripping differential pulse voltammetry was used for determination of cadmium. A 0.05 ng/ml detection limit for the preconcentration of aqueous solution of cadmium was obtained. The relative standard deviation (RSD) for eight replicate determinations at the 1 microg/ml cadmium levels was 0.31% (calculated with the peak height obtained). The calibration graph using the preconcentration system was linear from 0.01 to 150 microg/ml in final solution with a correlation coefficient of 0.9997. For optimization of conditions, various parameters such as the effect of pH, flow rate, instrumental conditions and interference of number of ions, were studied in detail. This method was successfully applied for determination of cadmium in various complex samples.

Optimization of headspace solid phase microextraction based on nano-structured ZnO combined with gas chromatography-mass spectrometry for preconcentration and determination of ultra-traces of chlorobenzenes in environmental samples.

PubMed

Ghasemi, Ensieh; Sillanpää, Mika

2014-12-01

In this study, a simple, novel and efficient preconcentration method for the determination of some chlorobenzenes (monochlorobenzene (MCB), three isomeric forms of dichlorobenzene (diCB), 1,3,5-trichlorobenzene (triCB) and hexachlorobenze (hexaCB)) has been developed using a headspace solid phase microextraction (HS-SPME) based on nano-structured ZnO combined with capillary gas chromatography-mass spectrometry (GC-MS). ZnO nanorods have been grown on fused silica fibers using a hydrothermal process. The diameter of ZnO nanorods was in the range of 50-80 nm. The effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the HS-SPME were stirring rate, desorption time and temperature, ionic strength, extraction time and temperature. For this purpose, a multivariate strategy was applied based on an experimental design using a Plackett-Burman design for screening and a Box-Behnken design for optimizing of the significant factors. The detection limit and relative standard deviation (RSD) (n=5) for the target analytes were in the range of 0.01-0.1 ng L(-1) and 4.3-7.6%, respectively. The developed technique was found to be successfully applicable to preconcentration and determination of the target analytes in environmental water and soil samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Determination of Three Organochlorine Pesticides in Aqueous Samples by Solid-Phase Extraction Based on Natural Nano Diatomite in Packed Syringe Coupled to Gas Chromatography-Mass Spectrometry.

PubMed

Taghani, Abdollah; Goudarzi, Nasser; Bagherian, Ghadamali; Chamjangali, Mansour Arab

2017-01-01

A rapid, simple, and sensitive technique is proposed based on a miniaturized solid-phase extraction method named mictroextraction in a packed syringe coupled with gas chromatography-mass spectrometry for the preconcentration and determination of three organochlorine pesticides. These include hexachlorobenzene, heptachlor and aldrine in aqueous samples. For the first time, the natural nano diatomite is used a sorbent. Based on this technique, 6.0 mg of the nano sorbent is inserted in a syringe between two polypropylene frits. The analytes would be adsorbed on the solid phase, and would subsequently be eluted using organic solvents. The influence of some important parameters, such as the solution pH, type and volume of the organic desorption solvent, and amount of sorbent on the extraction efficiency of the selected pesticides, is investigated. The proposed method shows good linearity in the range of 0.1 - 40.0 μg L -1 , and at low limits of detection in the range of 0.02 - 0.13 μg L -1 using the selected ion-monitoring mode. The reproducibility of this method was found to be in the range of 3.5 - 11.1% for the understudied pesticides. In order to evaluate the matrix effect, the developed method is also applied to the preconcentration and determination of the selected pesticides in different water samples.

Microchip integrating magnetic nanoparticles for allergy diagnosis.

PubMed

Teste, Bruno; Malloggi, Florent; Siaugue, Jean-Michel; Varenne, Anne; Kanoufi, Frederic; Descroix, Stéphanie

2011-12-21

We report on the development of a simple and easy to use microchip dedicated to allergy diagnosis. This microchip combines both the advantages of homogeneous immunoassays i.e. species diffusion and heterogeneous immunoassays i.e. easy separation and preconcentration steps. In vitro allergy diagnosis is based on specific Immunoglobulin E (IgE) quantitation, in that way we have developed and integrated magnetic core-shell nanoparticles (MCSNPs) as an IgE capture nanoplatform in a microdevice taking benefit from both their magnetic and colloidal properties. Integrating such immunosupport allows to perform the target analyte (IgE) capture in the colloidal phase thus increasing the analyte capture kinetics since both immunological partners are diffusing during the immune reaction. This colloidal approach improves 1000 times the analyte capture kinetics compared to conventional methods. Moreover, based on the MCSNPs' magnetic properties and on the magnetic chamber we have previously developed the MCSNPs and therefore the target can be confined and preconcentrated within the microdevice prior to the detection step. The MCSNPs preconcentration factor achieved was about 35,000 and allows to reach high sensitivity thus avoiding catalytic amplification during the detection step. The developed microchip offers many advantages: the analytical procedure was fully integrated on-chip, analyses were performed in short assay time (20 min), the sample and reagents consumption was reduced to few microlitres (5 μL) while a low limit of detection can be achieved (about 1 ng mL(-1)).

Determination of trace inorganic mercury species in water samples by cloud point extraction and UV-vis spectrophotometry.

PubMed

Ulusoy, Halil Ibrahim

2014-01-01

A new micelle-mediated extraction method was developed for preconcentration of ultratrace Hg(II) ions prior to spectrophotometric determination. 2-(2'-Thiazolylazo)-p-cresol (TAC) and Ponpe 7.5 were used as the chelating agent and nonionic surfactant, respectively. Hg(II) ions form a hydrophobic complex with TAC in a micelle medium. The main factors affecting cloud point extraction efficiency, such as pH of the medium, concentrations of TAC and Ponpe 7.5, and equilibration temperature and time, were investigated in detail. An overall preconcentration factor of 33.3 was obtained upon preconcentration of a 50 mL sample. The LOD obtained under the optimal conditions was 0.86 microg/L, and the RSD for five replicate measurements of 100 microg/L Hg(II) was 3.12%. The method was successfully applied to the determination of Hg in environmental water samples.

Pre-concentration of trace elements in short chain alcohols using different commercial cation exchange resins prior to inductively coupled plasma-optical emission spectrometric detection.

PubMed

Nomngongo, Philiswa N; Catherine Ngila, J; Kamau, Joseph N; Msagati, Titus A M; Marjanovic, Ljiljana; Moodley, Brenda

2013-07-17

Chelex-100, Dowex 50W-x8 and Dowex MAC-3 exchange resins were investigated for separation and pre-concentration of trace amounts of Cd, Cr, Cu, Fe, Mn, Pb, Ti and Zn in alcohols with respect to retention and desorption characteristics. Dowex 50W-x8 was found to be the best sorbent with percentages recoveries >95%. In addition, Chelex-100 appeared to be suitable for the pre-concentration of Cu, Fe and Zn, whereas Dowex MAC-3 was selective for Cu and Fe. Therefore, Dowex 50W-x8 was used for further investigations. The relative standard deviations <4% (n=20), limits of detection and quantification were 0.1-1.2 μg L(-1) and 0.3-1.5 μg L(-1), respectively. The SPE method was validated against a certified reference material and the results were in agreement with certified values. The accuracy of the optimized method was verified by the recovery test in the spiked alcohol samples. The accuracy and spike recovery test for different metal ions were in the range 98-102% and 95-105%, respectively. The optimized method was applied to the separation and pre-concentration of metal ions in different commercial alcohol samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Rapid and sensitive detection of malachite green in aquaculture water by electrochemical preconcentration and surface-enhanced Raman scattering.

PubMed

Xu, Kai-Xuan; Guo, Mei-Hong; Huang, Yu-Ping; Li, Xiao-Dong; Sun, Jian-Jun

2018-04-01

A highly sensitive and rapid method of in-situ surface-enhanced Raman spectroscopy (SERS) combining with electrochemical preconcentration (EP) in detecting malachite green (MG) in aquaculture water was established. Ag nanoparticles (AgNPs) were synthesized and spread onto the surface of gold electrodes after centrifuging to produce SERS-active substrates. After optimizing the pH values, preconcentration potentials and times, in-situ EP-SERS detection was carried out. A sensitive and rapid analysis of the low-concentration MG was accomplished within 200s and the limit of detection was 2.4 × 10 -16 M. Copyright © 2017 Elsevier B.V. All rights reserved.

Analytical instrument with apparatus and method for sample concentrating

DOEpatents

Zaromb, S.

1986-08-04

A system for analysis of trace concentrations of contaminants in air includes a portable liquid chromatograph and a preconcentrator for the contaminants to be analyzed. The preconcentrator includes a sample bag having an inlet valve and an outlet valve for collecting an air sample. When the sample is collected the sample bag is connected in series with a sorbing apparatus in a recirculation loop. The sorbing apparatus has an inner gas-permeable container containing a sorbent material and an outer gas-impermeable container. The sample is circulated through the outer container and around the inner container for trapping and preconcentrating the contaminants in the sorbent material. The sorbent material may be a liquid having the same composition as the mobile phase of the chromatograph for direct injection thereinto. Alternatively, the sorbent material may be a porous, solid body, to which mobile phase liquid is added after preconcentration of the contaminants for dissolving the contaminants, the liquid solution then being withdrawn for injection into the chromatograph.

Development of a FI-HG-ICP-OES solid phase preconcentration system for inorganic selenium speciation in Argentinean beverages.

PubMed

Escudero, Luis A; Pacheco, Pablo H; Gasquez, José A; Salonia, José A

2015-02-15

A preconcentration system has been developed to determine inorganic selenium species. Selenium was retained by a column filled with polyvinyl chloride (PVC) with lanthanum hydroxide co-precipitation. Speciation was achieved by selective photoreduction previous Se preconcentration. The retention pH was optimized at 10.0. Two multivariate calibrations and a central composite design were employed for optimization of the system. Sample, reagents and acid flow rates are significant variables affecting the system. Employing HG-ICP-OES as detection, the optimized system reached a detection limit of 0.03μg/L, and an enhancement factor of 14875 (25 for preconcentration system, 595 for hydride generation). To verify the method' accuracy, two certified reference materials, BCR® 414 Plankton & IRMM-804 Rice Flour, were analysed. The system was applied to inorganic selenium speciation in several Argentinean beverages to estimate their selenium contribution to diet. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electrokinetic Sample Preconcentration and Hydrodynamic Sample Injection for Microchip Electrophoresis Using a Pneumatic Microvalve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cong, Yongzheng; Katipamula, Shanta; Geng, Tao

2016-02-01

A microfluidic platform was developed to perform online electrokinetic sample preconcentration and rapid hydrodynamic sample injection for electrophoresis using a single microvalve. The PDMS microchip consists of a separation channel, a side channel for sample introduction, and a control channel which is used as a pneumatic microvalve aligned at the intersection of the two flow channels. The closed microvalve, created by multilayer soft lithography, can serve as a preconcentrator under an applied electric potential, enabling current to pass through while blocking bulk flow. Once analytes are concentrated, the valve is briefly opened and the stacked sample is pressure injected intomore » the separation channel for electrophoretic separation. Fluorescently labeled peptides were enriched by a factor of ~450 in 230 s. The performance of the platform was validated by the online preconcentration, injection and electrophoretic separation of fluorescently labeled peptides. This method enables both rapid analyte concentration and controlled injection volume for high sensitivity, high resolution capillary electrophoresis.« less

Isolation, Separation, and Preconcentration of Biologically Active Compounds from Plant Matrices by Extraction Techniques.

PubMed

Raks, Victoria; Al-Suod, Hossam; Buszewski, Bogusław

2018-01-01

Development of efficient methods for isolation and separation of biologically active compounds remains an important challenge for researchers. Designing systems such as organomineral composite materials that allow extraction of a wide range of biologically active compounds, acting as broad-utility solid-phase extraction agents, remains an important and necessary task. Selective sorbents can be easily used for highly selective and reliable extraction of specific components present in complex matrices. Herein, state-of-the-art approaches for selective isolation, preconcentration, and separation of biologically active compounds from a range of matrices are discussed. Primary focus is given to novel extraction methods for some biologically active compounds including cyclic polyols, flavonoids, and oligosaccharides from plants. In addition, application of silica-, carbon-, and polymer-based solid-phase extraction adsorbents and membrane extraction for selective separation of these compounds is discussed. Potential separation process interactions are recommended; their understanding is of utmost importance for the creation of optimal conditions to extract biologically active compounds including those with estrogenic properties.

Application of NaClO-treated multiwalled carbon nanotubes as solid phase extraction sorbents for preconcentration of trace 2,4-dichlorophenoxyacetic acid in aqueous samples.

PubMed

Lu, Ping; Deng, Dayi; Ni, Xiaodan

2012-09-01

Multiwalled carbon nanotubes functionalized by oxidation of original multiwalled carbon nanotubes with NaClO were prepared and their application as solid phase extraction sorbent for 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated systemically, and a new method was developed for the determination of trace 2,4-D in water samples based on extraction and preconcentration of 2,4-D with solid phase extraction columns packed with NaClO-treated multiwalled carbon nanotubes prior to its determination by HPLC. The optimum experimental parameters for preconcentration of 2,4-D, including the column activating conditions, the amount of the sorbent, pH of the sample, elution composition, and elution volume, were investigated. The results indicated 2,4-D could be quantitatively retained by 100 mg NaClO-treated multiwalled carbon nanotubes at pH 5, and then eluted completely with 10 mL 3:1 (v/v) methanol-ammonium acetate solution (0.3 mol/L). The detection limit of this method for 2,4-D was 0.15 μg/L, and the relative standard deviation was 2.3% for fortified tap water samples and 2.5% for fortified riverine water sample at the 10 μg/L level. The method was validated using fortified tap water and riverine water samples with known amount of 2,4-D at the 0.4, 10, and 30 μg/L levels, respectively. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Applicability of multisyringe chromatography coupled to on-line solid-phase extraction to the simultaneous determination of dicamba, 2,4-D, and atrazine.

PubMed

Chávez-Moreno, C A; Guzmán-Mar, J L; Hinojosa-Reyes, L; Hernández-Ramírez, A; Ferrer, L; Cerdà, V

2012-07-01

Simultaneous determination of three herbicides (dicamba, 2,4-D, and atrazine) has been achieved by on-line solid-phase extraction (SPE) coupled to multisyringe chromatography (MSC) with UV detection. The preconcentration conditions were optimized; a preconcentration flow rate of 0.5 mL min(-1) and elution at 0.8 mL min(-1) were the optimum conditions. A C(18) (8 mm i.d.) membrane extraction disk conditioned with 0.3 mol L(-1) HCl in 0.5% MeOH was used. A 3-mL sample was preconcentrated, then eluted with 0.43 mL 40:60 water-MeOH. A C(18) monolithic column (25 mm × 4.6 mm) was used for chromatographic separation. Separation of the three compounds was achieved in 10 min by use of 0.01% aqueous acetic acid-MeOH (60:40) as mobile phase at a flow rate of 0.8 mL min(-1). The limits of detection (LOD) were 13, 57, and 22 μg L(-1) for dicamba, 2,4-D, and atrazine, respectively. The sampling frequency was three analyses per hour, and each analysis consumed only 7.3 mL solvent. The method was applied to spiked water samples, and recovery between 85 and 112% was obtained. Recovery was significantly better than in the conventional HPLC-UV method. These results indicated the reliability and accuracy of this flow-based method. This is the first time this family of herbicides has been simultaneously analyzed by on-line SPE-MSC using a monolithic column.

Simultaneous spectrophotometric determination of crystal violet and malachite green in water samples using partial least squares regression and central composite design after preconcentration by dispersive solid-phase extraction.

PubMed

Razi-Asrami, Mahboobeh; Ghasemi, Jahan B; Amiri, Nayereh; Sadeghi, Seyed Jamal

2017-04-01

In this paper, a simple, fast, and inexpensive method is introduced for the simultaneous spectrophotometric determination of crystal violet (CV) and malachite green (MG) contents in aquatic samples using partial least squares regression (PLS) as a multivariate calibration technique after preconcentration by graphene oxide (GO). The method was based on the sorption and desorption of analytes onto GO and direct determination by ultraviolet-visible spectrophotometric techniques. GO was synthesized according to Hummers method. To characterize the shape and structure of GO, FT-IR, SEM, and XRD were used. The effective factors on the extraction efficiency such as pH, extraction time, and the amount of adsorbent were optimized using central composite design. The optimum values of these factors were 6, 15 min, and 12 mg, respectively. The maximum capacity of GO for the adsorption of CV and MG was 63.17 and 77.02 mg g -1 , respectively. Preconcentration factors and extraction recoveries were obtained and were 19.6, 98% for CV and 20, 100% for MG, respectively. LOD and linear dynamic ranges for CV and MG were 0.009, 0.03-0.3, 0.015, and 0.05-0.5 (μg mL -1 ), respectively. The intra-day and inter-day relative standard deviations were 1.99 and 0.58 for CV and 1.69 and 3.13 for MG at the concentration level of 50 ng mL -1 , respectively. Finally, the proposed DSPE/PLS method was successfully applied for the simultaneous determination of the trace amount of CV and MG in the real water samples.

Preconcentration and separation of analytes in microchannels

DOEpatents

Hatch, Anson; Singh, Anup K.; Herr, Amy E.; Throckmorton, Daniel J.

2010-11-09

Disclosed herein are methods and devices for preconcentrating and separating analytes such as proteins and polynucleotides in microchannels. As disclosed, at least one size-exclusion polymeric element is adjacent to processing area or an assay area in a microchannel which may be porous polymeric element. The size-exclusion polymeric element may be used to manipulate, e.g. concentrate, analytes in a sample prior to assaying in the assay area.

Living organisms as an alternative to hyphenated techniques for metal speciation. Evaluation of baker's yeast immobilized on silica gel for Hg speciation*1

NASA Astrophysics Data System (ADS)

Pérez-Corona, Teresa; Madrid-Albarrán, Yolanda; Cámara, Carmen; Beceiro, Elisa

1998-02-01

The use of living organisms for metal preconcentration and speciation is discussed. Among substrates, Saccharomyces cerevisiae baker's yeast has been successfully used for the speciation of mercury [Hg(II) and CH 3Hg +], selenium [Se(IV) and Se(VI)] and antimony [Sb(III) and Sb(V)]. To illustrate the capabilities of these organisms, the analytical performance of baker's yeast immobilized on silica gel for on-line preconcentration and speciation of Hg(II) and methylmercury is reported. The immobilized cells were packed in a PTFE microcolumn, through which mixtures of organic and inorganic mercury solutions were passed. Retention of inorganic and organic mercury solutions took place simultaneously, with the former retained in the silica and the latter on the yeast. The efficiency uptake for both species was higher than 95% over a wide pH range. The speciation was carried out by selective and sequential elution with 0.02 mol L -1 HCl for methylmercury and 0.8 mol L -1 CN - for Hg(II). This method allows both preconcentration and speciation of mercury. The preconcentration factors were around 15 and 100 for methylmercury and mercury(II), respectively. The method has been successfully applied to spiked sea water samples.

Rapid method for the determination of 226Ra in hydraulic fracturing wastewater samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, Sherrod L.; Culligan, Brian K.; Warren, Richard A.

A new method that rapidly preconcentrates and measures 226Ra from hydraulic fracturing wastewater samples was developed in the Savannah River Environmental Laboratory. The method improves the quality of 226Ra measurements using gamma spectrometry by providing up to 100x preconcentration of 226Ra from this difficult sample matrix, which contains very high levels of calcium, barium, strontium, magnesium and sodium. The high chemical yield, typically 80-90%, facilitates a low detection limit, important for lower level samples, and indicates method ruggedness. Ba-133 tracer is used to determine chemical yield and correct for geometry-related counting issues. The 226Ra sample preparation takes < 2 hours.

Rapid method for the determination of 226Ra in hydraulic fracturing wastewater samples

DOE PAGES

Maxwell, Sherrod L.; Culligan, Brian K.; Warren, Richard A.; ...

2016-03-24

A new method that rapidly preconcentrates and measures 226Ra from hydraulic fracturing wastewater samples was developed in the Savannah River Environmental Laboratory. The method improves the quality of 226Ra measurements using gamma spectrometry by providing up to 100x preconcentration of 226Ra from this difficult sample matrix, which contains very high levels of calcium, barium, strontium, magnesium and sodium. The high chemical yield, typically 80-90%, facilitates a low detection limit, important for lower level samples, and indicates method ruggedness. Ba-133 tracer is used to determine chemical yield and correct for geometry-related counting issues. The 226Ra sample preparation takes < 2 hours.

Development of a New Microextraction Fiber Combined to On-Line Sample Stacking Capillary Electrophoresis UV Detection for Acidic Drugs Determination in Real Water Samples.

PubMed

Espina-Benitez, Maria; Araujo, Lilia; Prieto, Avismelsi; Navalón, Alberto; Vílchez, José Luis; Valera, Paola; Zambrano, Ana; Dugas, Vincent

2017-07-07

A new analytical method coupling a (off-line) solid-phase microextraction with an on-line capillary electrophoresis (CE) sample enrichment technique was developed for the analysis of ketoprofen, naproxen and clofibric acid from water samples, which are known as contaminants of emerging concern in aquatic environments. New solid-phase microextraction fibers based on physical coupling of chromatographic supports onto epoxy glue coated needle were studied for the off-line preconcentration of these micropollutants. Identification and quantification of such acidic drugs were done by capillary zone electrophoresis (CZE) using ultraviolet diode array detection (DAD). Further enhancement of concentration sensitivity detection was achieved by on-line CE "acetonitrile stacking" preconcentration technique. Among the eight chromatographic supports investigated, Porapak Q sorbent showed higher extraction and preconcentration capacities. The screening of parameters that influence the microextraction process was carried out using a two-level fractional factorial. Optimization of the most relevant parameters was then done through a surface response three-factor Box-Behnken design. The limits of detection and limits of quantification for the three drugs ranged between 0.96 and 1.27 µg∙L -1 and 2.91 and 3.86 µg∙L -1 , respectively. Recovery yields of approximately 95 to 104% were measured. The developed method is simple, precise, accurate, and allows quantification of residues of these micropollutants in Genil River water samples using inexpensive fibers.

Development of a New Microextraction Fiber Combined to On-Line Sample Stacking Capillary Electrophoresis UV Detection for Acidic Drugs Determination in Real Water Samples

PubMed Central

Araujo, Lilia; Prieto, Avismelsi; Navalón, Alberto; Vílchez, José Luis; Valera, Paola; Zambrano, Ana; Dugas, Vincent

2017-01-01

A new analytical method coupling a (off-line) solid-phase microextraction with an on-line capillary electrophoresis (CE) sample enrichment technique was developed for the analysis of ketoprofen, naproxen and clofibric acid from water samples, which are known as contaminants of emerging concern in aquatic environments. New solid-phase microextraction fibers based on physical coupling of chromatographic supports onto epoxy glue coated needle were studied for the off-line preconcentration of these micropollutants. Identification and quantification of such acidic drugs were done by capillary zone electrophoresis (CZE) using ultraviolet diode array detection (DAD). Further enhancement of concentration sensitivity detection was achieved by on-line CE “acetonitrile stacking” preconcentration technique. Among the eight chromatographic supports investigated, Porapak Q sorbent showed higher extraction and preconcentration capacities. The screening of parameters that influence the microextraction process was carried out using a two-level fractional factorial. Optimization of the most relevant parameters was then done through a surface response three-factor Box-Behnken design. The limits of detection and limits of quantification for the three drugs ranged between 0.96 and 1.27 µg∙L−1 and 2.91 and 3.86 µg∙L−1, respectively. Recovery yields of approximately 95 to 104% were measured. The developed method is simple, precise, accurate, and allows quantification of residues of these micropollutants in Genil River water samples using inexpensive fibers. PMID:28686186

On-line ion-exchange preconcentration and determination of traces of platinum by electrothermal atomic absorption spectrometry.

PubMed

González García, M M; Sánchez Rojas, F; Bosch Ojeda, C; García de Torres, A; Cano Pavón, J M

2003-04-01

A method to determine trace amounts of platinum in different samples based on electrothermal atomic absorption spectrometry is described. The preconcentration step is performed on a chelating resin microcolumn [1,5-bis(2-pyridyl)-3-sulfophenyl methylene thiocarbonohydrazide (PSTH) immobilized on an anion-exchange resin (Dowex 1x8-200)] placed in the autosampler arm. The combination of a peristaltic pump for sample loading and the atomic absorption spectrometer pumps for elution through a selection valve simplifies the hardware. The peristaltic pump and the selection valve are easily controlled electronically with two switches placed in the autosampler, which are activated when the autosampler arm is down. Thus, the process is fully automated without any modification of the software of the atomic absorption spectrometer. Under the optimum conditions with a 60-s preconcentration time, a sample flow rate of 2.4 mL min(-1), and an injection volume of eluent of 40 microL, a linear calibration graph was obtained in the range 0-100 ng mL(-1). The enrichment factor was 14. The detection limit under these conditions is 1 ng mL(-1), and the relative standard deviation (RSD) is 1.6% for 10 ng mL(-1) of Pt. The method has been applied to the determination of platinum in catalyst, vegetation, soil, and natural water samples. The results showed good agreement with the certified value and the recoveries of Pt added to samples were 98-105%.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop for preconcentration and determination of trace amounts of copper by flame atomic absorption spectrometry.

PubMed

Karadaş, Cennet; Kara, Derya

2017-04-01

A novel, simple, rapid, sensitive, inexpensive and environmentally friendly dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO) was developed for the determination of copper by flame atomic absorption spectrometry (FAAS). N-o-Vanillidine-2-amino-p-cresol was used as a chelating ligand and 1-undecanol was selected as an extraction solvent. The main parameters affecting the performance of DLLME-SFO, such as sample pH, volume of extraction solvent, extraction time, concentration of the chelating ligand, salt effect, centrifugation time and sample volume were investigated and optimized. The effect of interfering ions on the recovery of copper was also examined. Under the optimum conditions, the detection limit (3σ) was 0.93μgL -1 for Cu using a sample volume of 20mL, yielding a preconcentration factor of 20. The proposed method was successfully applied to the determination of Cu in tap, river and seawater, rice flour and black tea samples as well as certified reference materials. Copyright © 2016. Published by Elsevier Ltd.

Continuous ultrasound-assisted extraction of hexavalent chromium from soil with or without on-line preconcentration prior to photometric monitoring.

PubMed

Luque-García, J L; Luque de Castro, M D

2002-08-01

A continuous ultrasound-assisted extractor was coupled to a photometric detector in order to obtain a fully automated approach for the determination of CrVI in soil. The use of a flow injection (FI) manifold as interface between the extractor and the photometric detector allowed the monitoring of CrVI after extraction in a continuous manner. The coloured complex formed between 1,5-diphenylcarbazide (DPC) and CrVI was used as recommended in EPA method 7196A because it is one of the most sensitive and selective reactions for CrVI determination. A preconcentration minicolumn packed with a strong anion-exchange resin was placed between the extractor and the detector, providing a more sensitive method. The linear dynamic ranges were 1-10 and 0.25-7.5 mg l-1 for the methods without (method A) and with preconcentration (method B), respectively. The limits of detection were 4.52 ng for method A and 1.23 ng for method B. Both methods were applied to a natural contaminated soil and the results obtained agreed well with those obtained by the reference EPA method 3060A. The influence of different amounts of CrIII in the samples was also studied and the results showed that the proposed methods did not disturb the original species distribution.

Solid-phase extraction of copper(II) in water and food samples using silica gel modified with bis(3-aminopropyl)amine and determination by flame atomic absorption spectrometry.

PubMed

Cagirdi, Duygu; Altundag, Hüseyin; Imamoglu, Mustafa; Tuzen, Mustafa

2014-01-01

A simple and selective separation and preconcentration method was developed for the determination of Cu(ll) ions. This method is based on adsorption of Cu(ll) ions from aqueous solution on a bis(3-aminopropyl)amine modified silica gel column and flame atomic absorption spectrometric determination after desorption. Various analytical parameters such as pH, type of eluent solution and its volume, flow rate of sample and eluent, and sample volume were optimized. Effects of some cation, anion, and transition metal ions on the recoveries of Cu(ll) ions were also investigated. Cu(ll) ions were quantitatively recovered at pH 6; 5.0 mL of 2 M HCI was used as the eluent. The preconcentration factor was found to be 150. The LOD was 0.12 microg/L for Cu(ll). The accuracy of the method was confirmed by analysis of Tea Leaves (INCT-TL-1) and Fish Protein (DORM-3) certified reference materials. The optimized method was applied to various water and food samples for the determination of Cu(ll).

Development of a portable preconcentrator/ion mobility spectrometer system for the trace detection of narcotics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parmeter, J.E.; Custer, C.A.

This project was supported by LDRD funding for the development and preliminary testing of a portable narcotics detection system. The system developed combines a commercial trace detector known as an ion mobility spectrometer (IMS) with a preconcentrator originally designed by Department 5848 for the collection of explosives molecules. The detector and preconcentrator were combined along with all necessary accessories onto a push cart, thus yielding a fully portable detection unit. Preliminary testing with both explosives and narcotics molecules shown that the system is operational, and that it can successfully detect drugs as marijuana, methamphetamine (speed), and cocaine based on theirmore » characteristics IMS signatures.« less

Determination of heavy metals by ICP-OES and F-AAS after preconcentration with 2,2'-bipyridyl and erythrosine.

PubMed

Feist, Barbara; Mikula, Barbara; Pytlakowska, Katarzyna; Puzio, Bozena; Buhl, Franciszek

2008-04-15

The applicability of 2,2'-bipyridyl and erythrosine co-precipitation method for the separation and preconcentration of some heavy metals, such as Cd, Co, Cu, Ni, Pb and Zn in actual samples for their determination by ICP-OES and F-AAS was studied. Experimental conditions influencing the recovery of the investigated metals, such as pH, molar ratio of 2,2'-bipyridyl to erythrosine, the effect of time on co-precipitation were optimized. The analytical characteristics of the method (e.g. limit of detection, sensitivity, linear range and preconcentration factor) were obtained. The limits of detection LOD (ng mL(-1)) of the ICP-OES (F-AAS) method were: Cd: 4.0 (7.75), Co: 3.1 (57.2), Cu: 18 (10.3), Ni 21.3 (32.8), Pb: 35.9 (29.2) and Zn: 10.2 (6.90). The recovery of all the elements tested was more than 93%. The influence of inorganic matrix was examined. The proposed method was applied to determination of Cd, Co, Cu, Ni, Pb and Zn in vegetables and certified reference material (NCS ZC85006 Tomato).

Efficient sample preparation method based on solvent-assisted dispersive solid-phase extraction for the trace detection of butachlor in urine and waste water samples.

PubMed

Aladaghlo, Zolfaghar; Fakhari, Alireza; Behbahani, Mohammad

2016-10-01

In this work, an efficient sample preparation method termed solvent-assisted dispersive solid-phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 μL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 μg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent-assisted dispersive solid-phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Particle preconcentrator

DOEpatents

Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

1998-01-01

An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

Particle preconcentrator

DOEpatents

Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

2005-09-20

An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

Particle preconcentrator

DOEpatents

Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

2000-01-01

An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

Simultaneous preconcentration of cadmium and lead in water samples with silica gel and determination by flame atomic absorption spectrometry.

PubMed

Xu, Hongbo; Wu, Yun; Wang, Jian; Shang, Xuewei; Jiang, Xiaojun

2013-12-01

A new method that utilizes pretreated silica gel as an adsorbent has been developed for simultaneous preconcentration of trace Cd(II) and Pb(II) prior to the measurement by flame atomic absorption spectrometry. The effects of pH, the shaking time, the elution condition and the coexisting ions on the separation/preconcentration conditions of analytes were investigated. Under optimized conditions, the static adsorption capacity of Cd(II) and Pb(II) were 45.5 and 27.1mg/g, the relative standard deviations were 3.2% and 1.7% (for n = 11), and the limits of detection obtained were 4.25 and 0.60 ng/mL, respectively. The method was validated by analyzing the certified reference materials GBW 07304a (stream sediment) and successfully applied to the analysis of various treated wastewater samples with satisfactory results. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Particle preconcentrator

DOEpatents

Linker, K.L.; Conrad, F.J.; Custer, C.A.; Rhykerd, C.L. Jr.

1998-12-29

An apparatus and method are disclosed for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents. 3 figs.

Applications of organo-silica nanocomposites for SPNE of Hg(II)

NASA Astrophysics Data System (ADS)

Kaur, Anupreet

2016-02-01

An analytical method using modified SiO2 nanoparticles as solid-phase extractant has been developed for the preconcentration of trace amounts of Hg(II) in different water samples. Conditions of the analysis such as preconcentration factor, effect of pH, sample volume, shaking time, elution conditions and effects of interfering ions for the recovery of analyte were investigated. The adsorption capacity of nanometer SiO2-APTMS was found to be 181.42 µmol g-1 at optimum pH and the detection limit (3σ) was 0.45 µg L-1. The extractant showed rapid kinetic sorption. The adsorption equilibrium of Hg(II) on nanometer SiO2-APTMS was achieved just in 15 min. Adsorbed Hg(II) was easily eluted with 4 mL of 2.0 M hydrochloric acid. The maximum preconcentration factor was 75. The method was applied for the determination of trace amounts of Hg(II) in various synthetic samples and water samples.

Comparison of activated carbon and oxidized multiwalled carbon nanotubes modified with bis(3-nitrobenzylidene)-1,2-ethanediamine for enrichment of trace amounts of some metal ions.

PubMed

Ghaedi, Mehrorang; Montazerozohori, Mortaza; Tabatabie, Maryam; Noormohamadi, Hamid; Haghighi, Alireza Borhan

2012-01-01

The efficiency of modified activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) for the separation/preconcentration and determination of Co, Cd, Pb, Zn, and Cu following their complexation by bis(3-nitrobenzylidene)-1,2-ethanediamine has been described and compared. A one-at-a-time optimization method investigated the influence of various parameters that significantly influence the recoveries of the studied metal ions. At the optimum values of all variables, the response was linear over the range of 0.01-0.3 microg/mL, and detection limit (3 SDb/m, n = 10) was between 1.41-2.05 ng/mL for both sorbents while the preconcentration factor was 100 for AC and 500 for MWCNTs. The method was successfully applied for preconcentration and determination of trace amount of the aforementioned ions in various real samples such as orange, lettuce, bread, and pear.

Method and Apparatus for Concentrating Vapors for Analysis

DOEpatents

Grate, Jay W.; Baldwin, David L.; Anheier, Jr., Norman C.

2008-10-07

An apparatus and method are disclosed for pre-concentrating gaseous vapors for analysis. The invention finds application in conjunction with, e.g., analytical instruments where low detection limits for gaseous vapors are desirable. Vapors sorbed and concentrated within the bed of the apparatus can be thermally desorbed achieving at least partial separation of vapor mixtures. The apparatus is suitable, e.g., for preconcentration and sample injection, and provides greater resolution of peaks for vapors within vapor mixtures, yielding detection levels that are 10-10,000 times better than for direct sampling and analysis systems. Features are particularly useful for continuous unattended monitoring applications.

Micelle-mediated extraction and cloud point preconcentration for the analysis of aesculin and aesculetin in Cortex fraxini by HPLC.

PubMed

Shi, Zhihong; Zhu, Xiaomin; Zhang, Hongyi

2007-08-15

In this paper, a micelle-mediated extraction and cloud point preconcentration method was developed for the determination of less hydrophobic compounds aesculin and aesculetin in Cortex fraxini by HPLC. Non-ionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) was employed as the extraction solvent. Various experimental conditions were investigated to optimize the extraction process. Under optimum conditions, i.e. 5% Genapol X-080 (w/v), pH 1.0, liquid/solid ratio of 400:1 (ml/g), ultrasonic-assisted extraction for 30 min, the extraction yield reached the highest value. For the preconcentration of aesculin and aesculetin by cloud point extraction (CPE), the solution was incubated in a thermostatic water bath at 55 degrees C for 30 min, and 20% NaCl (w/v) was added to the solution to facilitate the phase separation and increase the preconcentration factor during the CPE process. Compared with methanol, which was used in Chinese Pharmacopoeia (2005 edition) for the extraction of C. fraxini, the extraction efficiency of 5% Genapol X-080 reached higher value.

On-line Determination of Zinc in Water and Biological Samples after Its Preconcentration onto Zincon Anchored Polyurethane Foam.

PubMed

Azeem, Sami M Abdel; Hanafi, Hassan A; El-Shahat, M F

2015-01-01

A fast and sensitive on-line procedure for the determination of zinc in water and biological samples was developed. Zinc was preconcentrated in a mini-column packed with polyurethane foam (PUF) chemically modified with zincon via -N=N- bonding. The optimal conditions for preconcentration were pH 8.5 and sample flow rate of 4.0 mL min(-1). Quantitative desorption of Zn(II) was obtained by 0.1 mol L(-1) hydrochloric acid and subsequent spectrophotmetric determination using 4-(2-pyridylazo)-resorcinol at 498 nm. The obtained detection limit was found to be 3.0 ng mL(-1), precision (RSD) was 4.8 and 6.7% at 20 and 110 ng mL(-1), respectively, for 60 s preconcentration time and enrichment factor was 31. The linearity range was from 10 to 120 ng mL(-1) and maximum sample throughput was 20 h(-1). Finally, the method was successfully applied to the determination of zinc in tap water, Nile River water and human urine samples with RSD in the range of 1.1 - 8.3%.

Determination of trace level bromate and perchlorate in drinking water by ion chromatography with an evaporative preconcentration technique.

PubMed

Liu, Yongjian; Mou, Shifen; Heberling, Shawn

2002-05-17

A simple sample preconcentration technique employing microwave-based evaporation for the determination of trace level bromate and perchlorate in drinking water with ion chromatography is presented. With a hydrophilic anion-exchange column and a sodium hydroxide eluent in linear gradient, bromate and perchlorate can be determined in one injection within 35 min. Prior to ion chromatographic analysis, the drinking water sample was treated with an OnGuard-Ag cartridge to remove the superfluous chloride and concentrated 20-fold using a PTFE beaker in a domestic microwave oven for 15 min. The recoveries of the anions ranged from 94.6% for NO2- to 105.2% for F-. The detection limits for bromate, perchlorate, iodate and chlorate were 0.1, 0.2, 0.1 and 0.2 microg/l, respectively. The developed method is applicable for the quantitation of bromate and perchlorate in drinking water samples.

Solid-phase extraction of heavy metal ions on bucky tubes disc in natural water and herbal plant samples.

PubMed

Soylak, Mustafa; Unsal, Yunus Emre

2011-10-01

A preconcentration-separation procedure has been established based on solid-phase extraction of Fe(III) and Pb(II) on bucky tubes (BTs) disc. Fe(III) and Pb(II) ions were quantitatively recovered at pH 6. The influences of the analytical parameters like sample volume, flow rates on the recoveries of analytes on BT disc were investigated. The effects of co-existing ions on the recoveries were also studied. The detection limits for iron and lead were found 1.6 and 4.9 μg L⁻¹, respectively. The validation of the presented method was checked by the analysis of TMDA-51.3 fortified water certified reference material. The presented procedure was successfully applied to the separation-preconcentration and determination of iron and lead content of some natural water and herbal plant samples from Kayseri, Turkey.

An on-line SPE-HPLC method for effective sample preconcentration and determination of fenoxycarb and cis, trans-permethrin in surface waters.

PubMed

Šatínský, Dalibor; Naibrtová, Linda; Fernández-Ramos, Carolina; Solich, Petr

2015-09-01

A new on-line SPE-HPLC method using fused-core columns for on-line solid phase extraction and large volume sample injection for increasing the sensitivity of detection was developed for the determination of insecticides fenoxycarb and cis-, trans-permethrin in surface waters. The separation was carried out on fused-core column Phenyl-Hexyl (100×4.6 mm), particle size 2.7 µm with mobile phase acetonitrile:water in gradient mode at flow rate 1.0 mL min(-1), column temperature 45°C. Large volume sample injection (1500 µL) to the extraction dimension using short precolumn Ascentis Express RP C-18 (5×4.6 mm); fused-core particle size 2.7 µm allowed effective sample preconcentration and efficient ballast sample matrix removal. The washing mobile phase consisting of a mixture of acetonitrile:water; 30:70, (v/v) was pumped at flow rate of 0.5 mL min(-1) through the extraction precolumn to the waste. Time of the valve switch for transferring the preconcentrated sample zone from the extraction to the separation column was set at 3rd min. Elution of preconcentrated insecticides from the extraction precolumn and separation on the analytical column was performed in gradient mode. Linear gradient elution started from 40% of acetonitrile at time of valve switch from SPE column (3rd min) to 95% of acetonitrile at 7th min. Synthetic dye sudan I was chosen as an internal standard. UV detection at wavelength 225 nm was used and the method reached the limits of detection (LOD) at ng mL(-1) levels for both insecticides. The method showing on-line sample pretreatment and preconcentration with highly sensitive determination of insecticides was applied for monitoring of fenoxycarb and both permethrin isomers in different surface water samples in Czech Republic. The time of whole analysis including on-line extraction, interferences removal, chromatography separation and system equilibration was less than 8 min. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrochemical detection of a powerful estrogenic endocrine disruptor: ethinylestradiol in water samples through bioseparation procedure.

PubMed

Martínez, Noelia A; Pereira, Sirley V; Bertolino, Franco A; Schneider, Rudolf J; Messina, Germán A; Raba, Julio

2012-04-20

The synthetic estrogen ethinylestradiol (EE2) is an active component of oral contraceptives (OCs), considered as an endocrine disrupting compound (EDC). It is excreted from humans and released via sewage treatment plant effluents into aquatic environments. EDCs are any environmental pollutant chemical that, once incorporated into an organism, affects the hormonal balance of various species including humans. Its presence in the environment is becoming of great importance in water quality. This paper describes the development of an accurate, sensitive and selective method for capture, preconcentration and determination of EE2 present in water samples using: magnetic particles (MPs) as bioaffinity support for the capture and preconcentration of EE2 and a glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNTs/GCE) as detection system. The capture procedure was based on the principle of immunoaffinity, the EE2 being extracted from the sample using the anti-EE2 antibodies (anti-EE2 Ab) which were previously immobilized on MPs. Subsequently the analyte desorption was done employing a sulfuric acid solution and the determination of the EE2 in the pre-concentrated solution was carried out by square wave voltammetry (SWV). This method can be used to determine EE2 in the range of 0.035-70 ng L(-1) with a detection limit (LOD) of 0.01 ng L(-1) and R.S.D.<4.20%. The proposed method has been successfully applied to the determination of EE2 in water samples and it has promising analytical applications for the direct determination of EE2 at trace levels. Copyright © 2012 Elsevier B.V. All rights reserved.

Superparamagnetic graphene oxide-based dispersive-solid phase extraction for preconcentration and determination of tamsulosin hydrochloride in human plasma by high performance liquid chromatography-ultraviolet detection.

PubMed

Pashaei, Yaser; Ghorbani-Bidkorbeh, Fatemeh; Shekarchi, Maryam

2017-05-26

In the present study, superparamagnetic graphene oxide-Fe 3 O 4 nanocomposites were successfully prepared by a modified impregnation method (MGO mi ) and their application as a sorbent in the magnetic-dispersive solid phase extraction (M-dSPE) mode to the preconcentration and determination of tamsulosin hydrochloride (TMS) in human plasma was investigated by coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV). The structure, morphology and magnetic properties of the prepared nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). Some factors affecting the extraction efficiency, including the pH value, amount of sorbent, extraction time, elution solvent and its volume, and desorption time were studied and optimized. Magnetic nanocomposites plasma extraction of TMS following HPLC analyses showed a linear calibration curve in the range of 0.5-50.0ngmL -1 with an acceptable correlation coefficient (R 2 =0.9988). The method was sensitive, with a low limit of detection (0.17ngmL -1 ) and quantification (0.48ngmL -1 ). Inter- and intra-day precision expressed as relative standard deviation (n=3) and the preconcentration factor, were found to be 5.6-7.2%, 2.9-4.2% and 10, respectively. Good recoveries (98.1-101.4%) with low relative standard deviations (4.2-5.0%) indicated that the matrices under consideration do not significantly affect the extraction process. Due to its high precision and accuracy, the developed method may be a HPLC-UV alternative with M-dSPE for bioequivalence analysis of TMS in human plasma. Copyright © 2017 Elsevier B.V. All rights reserved.

Cloud point extraction-flame atomic absorption spectrometry for pre-concentration and determination of trace amounts of silver ions in water samples.

PubMed

Yang, Xiupei; Jia, Zhihui; Yang, Xiaocui; Li, Gu; Liao, Xiangjun

2017-03-01

A cloud point extraction (CPE) method was used as a pre-concentration strategy prior to the determination of trace levels of silver in water by flame atomic absorption spectrometry (FAAS) The pre-concentration is based on the clouding phenomena of non-ionic surfactant, triton X-114, with Ag (I)/diethyldithiocarbamate (DDTC) complexes in which the latter is soluble in a micellar phase composed by the former. When the temperature increases above its cloud point, the Ag (I)/DDTC complexes are extracted into the surfactant-rich phase. The factors affecting the extraction efficiency including pH of the aqueous solution, concentration of the DDTC, amount of the surfactant, incubation temperature and time were investigated and optimized. Under the optimal experimental conditions, no interference was observed for the determination of 100 ng·mL -1 Ag + in the presence of various cations below their maximum concentrations allowed in this method, for instance, 50 μg·mL -1 for both Zn 2+ and Cu 2+ , 80 μg·mL -1 for Pb 2+ , 1000 μg·mL -1 for Mn 2+ , and 100 μg·mL -1 for both Cd 2+ and Ni 2+ . The calibration curve was linear in the range of 1-500 ng·mL -1 with a limit of detection (LOD) at 0.3 ng·mL -1 . The developed method was successfully applied for the determination of trace levels of silver in water samples such as river water and tap water.

Ultrasound assisted extraction of Maxilon Red GRL dye from water samples using cobalt ferrite nanoparticles loaded on activated carbon as sorbent: Optimization and modeling.

PubMed

Mehrabi, Fatemeh; Vafaei, Azam; Ghaedi, Mehrorang; Ghaedi, Abdol Mohammad; Alipanahpour Dil, Ebrahim; Asfaram, Arash

2017-09-01

In this research, a selective, simple and rapid ultrasound assisted dispersive solid-phase micro-microextraction (UA-DSPME) was developed using cobalt ferrite nanoparticles loaded on activated carbon (CoFe 2 O 4 -NPs-AC) as an efficient sorbent for the preconcentration and determination of Maxilon Red GRL (MR-GRL) dye. The properties of sorbent are characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Vibrating sample magnetometers (VSM), Fourier transform infrared spectroscopy (FTIR), Particle size distribution (PSD) and Scanning Electron Microscope (SEM) techniques. The factors affecting on the determination of MR-GRL dye were investigated and optimized by central composite design (CCD) and artificial neural networks based on genetic algorithm (ANN-GA). CCD and ANN-GA were used for optimization. Using ANN-GA, optimum conditions were set at 6.70, 1.2mg, 5.5min and 174μL for pH, sorbent amount, sonication time and volume of eluent, respectively. Under the optimized conditions obtained from ANN-GA, the method exhibited a linear dynamic range of 30-3000ngmL -1 with a detection limit of 5.70ngmL -1 . The preconcentration factor and enrichment factor were 57.47 and 93.54, respectively with relative standard deviations (RSDs) less than 4.0% (N=6). The interference effect of some ions and dyes was also investigated and the results show a good selectivity for this method. Finally, the method was successfully applied to the preconcentration and determination of Maxilon Red GRL in water and wastewater samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Preconcentration and Determination of Trace Vanadium(V) in Beverages by Combination of Ultrasound Assisted-cloud Point Extraction with Spectrophotometry.

PubMed

Kartal Temel, Nuket; Gürkan, Ramazan

2018-03-01

A novel ultrasound assisted-cloud point extraction method was developed for preconcentration and determination of V(V) in beverage samples. After complexation by pyrogallol in presence of safranin T at pH 6.0, V(V) ions as ternary complex are extracted into the micellar phase of Triton X-114. The complex was monitored at 533 nm by spectrophotometry. The matrix effect on the recovery of V(V) from the spiked samples at 50 μg L-1 was evaluated. In optimized conditions, the limits of detection and quantification of the method, respectively, was 0.58 and 1.93 μg L-1 in linear range of 2-500 μg L-1 with sensitivity enhancement and preconcentration factors of 47.7 and 40 for preconcentration from 15 mL of sample solution. The recoveries from spiked samples were in range of 93.8-103.2% with a relative standard deviation ranging from 2.6% to 4.1% (25, 100 and 250 μg L-1, n: 5). The accuracy was verified by analysis of two certified samples, and the results were in a good agreement with the certified values. The intra-day and inter-day precision were tested by reproducibility (as 3.3-3.4%) and repeatability (as 3.4-4.1%) analysis for five replicate measurements of V(V) in quality control samples spiked with 5, 10 and 15 μg L-1. Trace V(V) contents of the selected beverage samples by the developed method were successfully determined.

Ionic liquid ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of the aqueous phase for preconcentration of heavy metals ions prior to determination by LC-UV.

PubMed

Werner, Justyna

2018-05-15

Ionic liquid ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of the aqueous phase was used for preconcentration of Ni 2+ , Co 2+ , Cd 2+ , Cu 2+ , Pb 2+ in natural water samples prior to liquid chromatography with UV detection. In the proposed method, the ammonium pyrrolidinedithiocarbamate was used as a complexing agent and the phosphonium ionic liquid trihexyl(tetradecyl)phosphonium bis[(2,4,4-trimethyl)pentyl]phosphinate (Cyphos IL 104) was used as an extractant. Ultrasound energy was used to disperse the extractant in the aqueous phase. After microextraction, the ionic liquid and aqueous phases were separated by centrifugation. Then the aqueous phase was frozen and the lighter than water ionic liquid phase containing metal ions complexes with pyrrolidinedithiocarbamate was separated and dissolved in a small volume of methanol prior to injection into the liquid chromatograph. Several parameters including the volume of extractant, the pH of the sample, the concentration of complexing agent, the time of ultrasound energy treatment, the time and speed of centrifugation and the effect of ionic strength were optimized. Under the optimized conditions (10 µL of Cyphos IL 104, pH = 5, 0.3% w/v ammonium pyrrolidinedithiocarbamate, 60 s of ultrasound use, 5 min/5000 rpm (2516×g) of centrifugation, 2.0 mg of NaCl), preconcentration factors were 211, 210, 209, 207 and 211 for Ni 2+ , Co 2+ , Cd 2+ , Cu 2+ and Pb 2+ respectively. Linearity was observed in the ranges 0.2-75.0 µg L -1 for Pb 2+ , Cd 2+ , Co 2+ and 0.5-100.0 µg L -1 for Cu 2+ , Ni 2+ . The limits of detection were 0.03 µg L -1 for Ni 2+ , 0.03 µg L -1 for Co 2+ , 0.03 µg L -1 for Cd 2+ , 0.02 µg L -1 for Cu 2+ , 0.02 µg L -1 for Pb 2+ , respectively. The accuracy of this method was evaluated by preconcentration and determination of Ni 2+ , Co 2+ , Cd 2+ , Cu 2+ , Pb 2+ in certified reference materials (TMRAIN-04 and NIST 1643e) with the recovery values in the range of 97-102%. The presented method has been successfully applied for the determination of analytes in natural water samples (river and lake waters). Copyright © 2018 Elsevier B.V. All rights reserved.

Activated biochar: Preparation, characterization and electroanalytical application in an alternative strategy of nickel determination.

PubMed

Kalinke, Cristiane; Oliveira, Paulo Roberto; Oliveira, Geovane Arruda; Mangrich, Antonio Sálvio; Marcolino-Junior, Luiz H; Bergamini, Márcio F

2017-08-29

This work reports for the first time the use of chemically activated biochar as electrode modifier for nickel determination. The biochar activation was performed by refluxing with HNO 3 , which promoted a higher nickel preconcentration compared to unmodified and modified biochar precursor electrodes. Morphological and structural characterization revealed the increase of surface acid groups, surface area and porosity of biochar after activation. Nickel determination was investigated adopting an alternative voltammetric methodology based on monitoring the Ni(II)/Ni(III) redox couple. In the proposed method, it was not necessary to use a complexing agent and the biochar itself was responsible for the analyte preconcentration. A linear response for Ni(II) concentration range from 1.0 to 30 μmol L -1 and a limit of detection of 0.25 μmol L -1 were obtained. The method was successfully applied for Ni(II) determination in spiked samples of bioethanol fuel and discharge water, with recoveries values between 103 and 109%. Copyright © 2017 Elsevier B.V. All rights reserved.

Fully 3D-Printed Preconcentrator for Selective Extraction of Trace Elements in Seawater.

PubMed

Su, Cheng-Kuan; Peng, Pei-Jin; Sun, Yuh-Chang

2015-07-07

In this study, we used a stereolithographic 3D printing technique and polyacrylate polymers to manufacture a solid phase extraction preconcentrator for the selective extraction of trace elements and the removal of unwanted salt matrices, enabling accurate and rapid analyses of trace elements in seawater samples when combined with a quadrupole-based inductively coupled plasma mass spectrometer. To maximize the extraction efficiency, we evaluated the effect of filling the extraction channel with ordered cuboids to improve liquid mixing. Upon automation of the system and optimization of the method, the device allowed highly sensitive and interference-free determination of Mn, Ni, Zn, Cu, Cd, and Pb, with detection limits comparable with those of most conventional methods. The system's analytical reliability was further confirmed through analyses of reference materials and spike analyses of real seawater samples. This study suggests that 3D printing can be a powerful tool for building multilayer fluidic manipulation devices, simplifying the construction of complex experimental components, and facilitating the operation of sophisticated analytical procedures for most sample pretreatment applications.

Modified surface based on magnetic nanocomposite of dithiooxamide/Fe3O4 as a sorbent for preconcentration and determination of trace amounts of copper

NASA Astrophysics Data System (ADS)

Mirabi, Ali; Shokuhi Rad, Ali; Khodadad, Hadiseh

2015-09-01

Magnetic nanocomposites surface (MNCS) which has anionic surfactant sodium dodecyl sulfate (SDS) coating and has undergone dithiooxamide treatment as the sorbent could be an easy and useful method to extract and make a pre-concentrated in detecting the copper ions before they are determined via the flame atomic absorption spectrometry (FAAS). The influences of the experimental parameters such as the pH of the sample, the type and concentration of the eluent, dithiooxamide concentration and volume, amount of sorbent and the interactions of ions with respect to the copper ion detection have been studied. The calibration graph was linear in the range of 2-600 ng ml-1 with detection limit of 0.2 ng ml-1. Relative standard deviation (RSD) for 6 replicate measurements was 1.8%. This method of detection has been applied to the determination of Cu ions at levels in real samples such as wheat flour, tomatoes, potatoes, red beans, oat, tap water, river water and sea water with satisfactory results.

Determination of some metal ions in various meat and baby food samples by atomic spectrometry.

PubMed

Daşbaşı, Teslima; Saçmacı, Şerife; Ülgen, Ahmet; Kartal, Şenol

2016-04-15

In this paper, we report a simple and rapid solid phase extraction system for the separation/preconcentration and determination of Cd(II), Co(II), Cu(II), Fe(III), Cr(III), Pb(II), and Zn(II) ions by flame atomic absorption spectrometry (FAAS). This method is based upon the retention of metal ions on a column packed with poly[N-(3-methyl-1H-indole-1-yl)]-2-methacrylamide-co-2-acrylamido-2-methyl-1-propane sulphonic acid-co divinylbenzene] (MMAD) resin as a solid-phase extraction (SPE) sorbent at pH 8. At the optimized conditions, the limits of detection (3 s/b) between 0.12 and 1.6 μg L(-1), preconcentration factor of 100, and the relative standard deviation of ⩽1.8% were achieved (n=10). The accuracy of the method was verified by analyzing certified reference materials (CRMs) and performing recovery experiments. The developed method was successfully applied to the various natural water, meat products and baby food samples. The recoveries of analyte ions were found in added real samples and CRMs from 95% to 102%. Copyright © 2015 Elsevier Ltd. All rights reserved.

Determination of trace mercury in water based on N-octylpyridinium ionic liquids preconcentration and stripping voltammetry.

PubMed

Li, Zhenhan; Xia, Shanhong; Wang, Jinfen; Bian, Chao; Tong, Jianhua

2016-01-15

A novel method for determination of trace mercury in water is developed. The method is performed by extracting mercury firstly with ionic liquids (ILs) and then detecting the concentration of mercury in organic media with anodic stripping voltammetry. Liquid-liquid extraction of mercury(II) ions by four ionic liquids with N-octylpyridinium cations ([OPy](+)) was studied. N-octylpyridinium tetrafluoroborate and N-octylpyridinium trifluoromethylsulfonate were found to be efficient and selective extractant for mercury. Temperature controlled dispersive liquid phase microextraction (TC-DLPME) technique was utilized to improve the performance of preconcentration. After extraction, precipitated IL was diluted by acetonitrile buffer and mercury was detected by differential pulse stripping voltammetry (DPSV) with gold disc electrode. Mercury was enriched by 17 times while interfering ions were reduced by two orders of magnitude in the organic media under optimum condition. Sensitivity and selectivity for electrochemical determination of mercury were improved by using the proposed method. Tap, pond and waste water samples were analyzed with recoveries ranging from 81% to 107% and detection limit of 0.05 μg/L. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of antimony and tin in beverages using inductively coupled plasma-optical emission spectrometry after ultrasound-assisted ionic liquid dispersive liquid-liquid phase microextraction.

PubMed

Biata, N Raphael; Nyaba, Luthando; Ramontja, James; Mketo, Nomvano; Nomngongo, Philiswa N

2017-12-15

The aim of this study was to develop a simple and fast ultrasound-assisted ionic liquid dispersive liquid-liquid phase microextraction (UA-IL-DLLME) method for preconcetration of trace antimony and tin in beverage samples. The novelty of this study was based on the application of ligandless UA-IL-DLLME using low-density ionic liquid and organic solvents for preconcentration of Sb and Sn. The concentration of Sb and Sn were quantified using ICP-OES. Under the optimum conditions, the calibration graph was found to be LOQ-250µgL -1 (r 2 =0.9987) for Sb and LOQ-350µgL -1 for Sn. The LOD and LOQ of Sb and Sn ranged from 1.2to 2.5ngL -1 and 4.0 to 8.3ngL -1 , respectively, with high preconcentration factors. The precisions (%RSD) of the proposed method ranged from 2.1% to 2.5% and 3.9% to 4.7% for Sb and Sn, respectively. The proposed method was successfully applied for determination of Sb and Sn in beverages. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of ultra-trace aluminum in human albumin by cloud point extraction and graphite furnace atomic absorption spectrometry.

PubMed

Sun, Mei; Wu, Qianghua

2010-04-15

A cloud point extraction (CPE) method for the preconcentration of ultra-trace aluminum in human albumin prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS) had been developed in this paper. The CPE method was based on the complex of Al(III) with 1-(2-pyridylazo)-2-naphthol (PAN) and Triton X-114 was used as non-ionic surfactant. The main factors affecting cloud point extraction efficiency, such as pH of solution, concentration and kind of complexing agent, concentration of non-ionic surfactant, equilibration temperature and time, were investigated in detail. An enrichment factor of 34.8 was obtained for the preconcentration of Al(III) with 10 mL solution. Under the optimal conditions, the detection limit of Al(III) was 0.06 ng mL(-1). The relative standard deviation (n=7) of sample was 3.6%, values of recovery of aluminum were changed from 92.3% to 94.7% for three samples. This method is simple, accurate, sensitive and can be applied to the determination of ultra-trace aluminum in human albumin. 2009 Elsevier B.V. All rights reserved.

Improved coupled-column liquid chromatographic method for the determination of glyphosate and aminomethylphosphonic acid residues in environmental waters.

PubMed

Hidalgo, Carmén; Rios, Carolina; Hidalgo, Manuela; Salvadó, Victòria; Sancho, Juan V; Hernández, Félix

2004-04-30

An existing method for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water has been improved. It is based on precolumn derivatization with the fluorescent reagent 9-fluorenylmethylcloroformate (FMOC) followed by large-volume injection in a coupled-column LC system using fluorescence detection (LC-LC-FD). The derivatization step was slightly modified by changing parameters such as volume and/or concentration of sample and reagents to decrease the limits of quantification (LOQ) of glyphosate and AMPA to 0.1 microg/l. Additionally, the use of Amberlite IRA-900 for preconcentration of glyphosate, prior to the derivatization step, was investigated; the LOQ of glyphosate was lowered to 0.02 microg/l. Drinking, surface and ground water spiked with glyphosate and AMPA at 0.1-10 microg/l concentrations were analysed by the improved LC-LC-FD method. Recoveries were 87-106% with relative standard deviations lower than 8%. Drinking and ground water spiked with glyphosate at 0.02 and 0.1 microg/l were analysed after preconcentration on the anion-exchange resin with satisfactory recoveries (94-105%) and precision (better than 8%).

Determination of Iodate in Food, Environmental, and Biological Samples after Solid-Phase Extraction with Ni-Al-Zr Ternary Layered Double Hydroxide as a Nanosorbent

PubMed Central

Abdolmohammad-Zadeh, Hossein; Tavarid, Keyvan; Talleb, Zeynab

2012-01-01

Nanostructured nickel-aluminum-zirconium ternary layered double hydroxide was successfully applied as a solid-phase extraction sorbent for the separation and pre-concentration of trace levels of iodate in food, environmental and biological samples. An indirect method was used for monitoring of the extracted iodate ions. The method is based on the reaction of the iodate with iodide in acidic solution to produce iodine, which can be spectrophotometrically monitored at 352 nm. The absorbance is directly proportional to the concentration of iodate in the sample. The effect of several parameters such as pH, sample flow rate, amount of nanosorbent, elution conditions, sample volume, and coexisting ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.12 μg mL−1 and 20, respectively. The calibration graph using the preconcentration system was linear in the range of 0.2–2.8 μg mL−1 with a correlation coefficient of 0.998. In order to validate the presented method, a certified reference material, NIST SRM 1549, was also analyzed. PMID:22619590

Zincon-modified activated carbon for solid-phase extraction and preconcentration of trace lead and chromium from environmental samples.

PubMed

Li, Zhenhua; Chang, Xijun; Hu, Zheng; Huang, Xinping; Zou, Xiaojun; Wu, Qiong; Nie, Rong

2009-07-15

A new method that utilizes zincon-modified activated carbon (AC-ZCN) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III) and Pb(II) prior to the measurement by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 4, the maximum adsorption capacity of Cr(III) and Pb(II) onto the AC-ZCN were 17.9 and 26.7 mg g(-1), respectively. The adsorbed metal ions were quantitatively eluted by 1 mL of 0.1 mol L(-1) HCl. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3 sigma) of this method for Cr(III) and Pb(II) were 0.91 and 0.65 ng mL(-1), respectively. The relative standard deviation under optimum condition is less than 3.5% (n=8). The method has been applied for the determination of Cr(III) and Pb(II) in biological materials and water samples with satisfactory results.

On-line ionic liquid-based preconcentration system coupled to flame atomic absorption spectrometry for trace cadmium determination in plastic food packaging materials.

PubMed

Martinis, Estefanía M; Olsina, Roberto A; Altamirano, Jorgelina C; Wuilloud, Rodolfo G

2009-05-15

A novel on-line preconcentration method based on liquid-liquid (L-L) extraction with room temperature ionic liquids (RTILs) coupled to flame atomic absorption spectrometry (FAAS) was developed for cadmium determination in plastic food packaging materials. The methodology is based on the complexation of Cd with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) reagent after sample digestion followed by extraction of the complex with the RTIL 1-butyl-3-methylimidazolium hexafluorophosphate ([C(4)mim][PF(6)]). The mixture was loaded into a flow injection analysis (FIA) manifold and the RTIL rich-phase was retained in a microcolumn filled with silica gel. The RTIL rich-phase was then eluted directly into FAAS. A enhancement factor of 35 was achieved with 20 mL of sample. The limit of detection (LOD), obtained as IUPAC recommendation, was 6 ng g(-1) and the relative standard deviation (R.S.D.) for 10 replicates at 10 microg L(-1) Cd concentration level was 3.9%, calculated at the peak heights. The calibration graph was linear and a correlation coefficient of 0.9998 was achieved. The accuracy of the method was evaluated by both a recovery study and comparison of results with direct determination by electrothermal atomic absorption spectrometry (ETAAS). The method was successfully applied for Cd determination in plastic food packaging materials and Cd concentrations found were in the range of 0.04-10.4 microg g(-1).

Preparation and characterization of magnetic nanocomposite of Schiff base/silica/magnetite as a preconcentration phase for the trace determination of heavy metal ions in water, food and biological samples using atomic absorption spectrometry.

PubMed

Bagheri, Hasan; Afkhami, Abbas; Saber-Tehrani, Mohammad; Khoshsafar, Hosein

2012-08-15

A versatile and robust solid phase with both magnetic property and a very high adsorption capacity is presented on the basis of modification of iron oxide-silica magnetic particles with a newly synthesized Schiff base (Fe(3)O(4)/SiO(2)/L). The structure of the resulting product was confirmed by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) spectrometry and transmission electron microscopy (TEM). We developed an efficient and cost-effective method for the preconcentration of trace amounts of Pb(II), Cd(II) and Cu(II) in environmental and biological samples using this novel magnetic solid phase. Prepared magnetic solid phase is an ideal support because it has a large surface area, good selectivity and can be easily retrieved from large volumes of aqueous solutions. The possible parameters affecting the enrichment were optimized. Under the optimal conditions, the method detection limit was 0.14, 0.19 and 0.12 μg L(-1) for Pb(II), Cd(II) and Cu(II) ions, respectively. The established method has been successfully applied to analyze real samples, and satisfactory results were obtained. All these indicated that this magnetic phase had a great potential in environmental and biological fields. Copyright © 2012 Elsevier B.V. All rights reserved.

Air-assisted dispersive liquid-liquid microextraction based on a new hydrophobic deep eutectic solvent for the preconcentration of benzophenone-type UV filters from aqueous samples.

PubMed

Ge, Dandan; Zhang, Yi; Dai, Yixiu; Yang, Shumin

2018-04-01

Deep eutectic solvents are considered as new and green solvents that can be widely used in analytical chemistry such as microextraction. In the present work, a new dl-menthol-based hydrophobic deep eutectic solvent was synthesized and used as extraction solvents in an air-assisted dispersive liquid-liquid microextraction method for preconcentration and extraction of benzophenone-type UV filters from aqueous samples followed by high-performance liquid chromatography with diode array detection. In an experiment, the deep eutectic solvent formed by dl-menthol and decanoic acid was added to an aqueous solution containing the UV filters, and then the mixture was sucked up and injected five times by using a glass syringe, and a cloudy state was achieved. After extraction, the solution was centrifuged and the upper phase was subjected to high-performance liquid chromatography for analysis. Various parameters such as the type and volume of the deep eutectic solvent, number of pulling, and pushing cycles, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the developed method exhibited low limits of detection and limits of quantitation, good linearity, and precision. Finally, the proposed method was successfully applied to determine the benzophenone-type filters in environmental water samples with relative recoveries of 88.8-105.9%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of modified magnetic nanoparticles as a sorbent for the preconcentration and determination of cadmium ions in food and environmental water samples prior to flame atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Mirabi, Ali; Dalirandeh, Zeinab; Rad, Ali Shokuhi

2015-05-01

A new method has been developed for the separation/preconcentration of trace level cadmium ions using diphenyl carbazone/sodium dodecyl sulfate immobilized on magnetic nanoparticle Fe3O4 as a new sorbent SPE and their determination by flame atomic absorption spectrometry (FAAS). Synthesized nanoparticle was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Various influencing parameters on the separation and preconcentration of trace level cadmium ions such as, pH value, amount of nanoparticles, amount of diphenyl carbazone, condition of eluting solution, the effects of matrix ions were examined. The cadmium ions can be eluted from the modified magnetic nanoparticle using 1 mol L-1 HCl as a desorption reagent. The detection limit of this method for cadmium was 3.71 ng ml-1 and the R.S.D. was 0.503% (n=6). The advantages of this new method include rapidity, easy preparation of sorbents and a high concentration factor. The proposed method has been applied to the determination of Cd ions at trace levels in real samples such as, green tea, rice, tobacco, carrot, lettuce, ginseng, spice, tap water, river water, sea water with satisfactory results.

Preconcentration of valsartan by dispersive liquid-liquid microextraction based on solidification of floating organic drop and its determination in urine sample: Central composite design.

PubMed

Pebdani, Arezou Amiri; Shabani, Ali Mohammad Haji; Dadfarnia, Shayesteh; Talebianpoor, Mohammad Sharif; Khodadoust, Saeid

2016-05-01

In this work, a fast, easy, and efficient dispersive liquid-liquid microextraction method based on solidification of floating organic drop followed by high-performance liquid chromatography with UV detection was developed for the separation/preconcentration and determination of the drug valsartan. Experimental design was applied for the optimization of the effective variables (such as volume of extracting and dispersing solvents, ionic strength, and pH) on the extraction efficiency of valsartan from urine samples. The optimized values were 250.0 μL ethanol, 65.0 μL 1-dodecanol, 4.0% w/v NaCl, pH 3.8, 1.0 min extraction time, and 4.0 min centrifugation at 4000 rpm min(-1) . The linear response (r(2) = 0.997) was obtained in the range of 0.013-10.0 μg mL(-1) with a limit of detection of 4.0 ng mL(-1) and relative standard deviations of less than 5.0 % (n = 6). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ring-oven based preconcentration technique for microanalysis: simultaneous determination of Na, Fe, and Cu in fuel ethanol by laser induced breakdown spectroscopy.

PubMed

Cortez, Juliana; Pasquini, Celio

2013-02-05

The ring-oven technique, originally applied for classical qualitative analysis in the years 1950s to 1970s, is revisited to be used in a simple though highly efficient and green procedure for analyte preconcentration prior to its determination by the microanalytical techniques presently available. The proposed preconcentration technique is based on the dropwise delivery of a small volume of sample to a filter paper substrate, assisted by a flow-injection-like system. The filter paper is maintained in a small circular heated oven (the ring oven). Drops of the sample solution diffuse by capillarity from the center to a circular area of the paper substrate. After the total sample volume has been delivered, a ring with a sharp (c.a. 350 μm) circular contour, of about 2.0 cm diameter, is formed on the paper to contain most of the analytes originally present in the sample volume. Preconcentration coefficients of the analyte can reach 250-fold (on a m/m basis) for a sample volume as small as 600 μL. The proposed system and procedure have been evaluated to concentrate Na, Fe, and Cu in fuel ethanol, followed by simultaneous direct determination of these species in the ring contour, employing the microanalytical technique of laser induced breakdown spectroscopy (LIBS). Detection limits of 0.7, 0.4, and 0.3 μg mL(-1) and mean recoveries of (109 ± 13)%, (92 ± 18)%, and (98 ± 12)%, for Na, Fe, and Cu, respectively, were obtained in fuel ethanol. It is possible to anticipate the application of the technique, coupled to modern microanalytical and multianalyte techniques, to several analytical problems requiring analyte preconcentration and/or sample stabilization.

Non-aqueous electrolytes for isotachophoresis of weak bases and its application to the comprehensive preconcentration of the 20 proteinogenic amino acids in column-coupling ITP/CE-MS.

PubMed

Kler, Pablo A; Huhn, Carolin

2014-11-01

Isotachophoresis (ITP) has long been used alone but also as a preconcentration technique for capillary electrophoresis (CE). Unfortunately, up to now, its application is restricted to relatively strong acids and bases as either the degree of (de)protonation is too low or the water dissociation is too high, evoking zone electrophoresis. With the comprehensive ITP analysis of all 20 proteinogenic amino acids as model analytes, we, here, show that non-aqueous ITP using dimethylsulfoxide as a solvent solves this ITP shortcoming. Dimethylsulfoxide changes the pH regime of analytes and electrolytes but, more importantly, strongly reduces the proton mobility by prohibiting hydrogen bonds and thus, the so-called Zundel-Eigen-Zundel electrical conduction mechanism of flipping hydrogen bonds. The effects are demonstrated in an electrolyte system with taurine or H(+) as terminator, and imidazole as leader together with strong acids such as oxalic and even trifluoroacetic acid as counterions, both impossible to use in aqueous solution. Mass spectrometric as well as capacitively coupled contactless conductivity detection (C(4)D) are used to follow the ITP processes. To demonstrate the preconcentration capabilities of ITP in a two-dimensional set-up, we, here, also demonstrate that our non-aqueous ITP method can be combined with capillary electrophoresis-mass spectrometry in a column-coupling system using a hybrid approach of capillaries coupled to a microfluidic interface. For this, C(4)D was optimized for on-chip detection with the electrodes aligned on top of a thin glass lid of the microfluidic chip.

Tuning direct current streaming dielectrophoresis of proteins

PubMed Central

Nakano, Asuka; Camacho-Alanis, Fernanda; Chao, Tzu-Chiao; Ros, Alexandra

2012-01-01

Dielectrophoresis (DEP) of biomolecules has large potential to serve as a novel selectivity parameter for bioanalytical methods such as (pre)concentration, fractionation, and separation. However, in contrast to well-characterized biological cells and (nano)particles, the mechanism of protein DEP is poorly understood, limiting bioanalytical applications for proteins. Here, we demonstrate a detailed investigation of factors influencing DEP of diagnostically relevant immunoglobulin G (IgG) molecules using insulator-based DEP (iDEP) under DC conditions. We found that the pH range in which concentration of IgG due to streaming iDEP occurs without aggregate formation matches the pH range suitable for immunoreactions. Numerical simulations of the electrokinetic factors pertaining to DEP streaming in this range further suggested that the protein charge and electroosmotic flow significantly influence iDEP streaming. These predictions are in accordance with the experimentally observed pH-dependent iDEP streaming profiles as well as the determined IgG molecular properties. Moreover, we observed a transition in the streaming behavior caused by a change from positive to negative DEP induced through micelle formation for the first time experimentally, which is in excellent qualitative agreement with numerical simulations. Our study thus relates molecular immunoglobulin properties to observed iDEP, which will be useful for the future development of protein (pre)concentration or separation methods based on DEP. PMID:23908679

Dispersive liquid-liquid microextraction of copper ions as neocuproine complex in environmental aqueous samples.

PubMed

Shariati, Shahab; Golshekan, Mostafa

2011-06-01

In the present study, a simple and efficient extraction method based on dispersive liquid-liquid microextraction prior to UV-Vis spectrophotometry was developed for the preconcentration and determination of copper ions in environmental samples. Briefly, cupric ions (Cu II) were reduced to cuprous (Cu I) with addition of hydroxyl amine hydrochloride and formed hydrophobic chelates with neocuproine. Then, a proper mixture of acetonitrile (as dispersive solvent) and choloroform (as extraction solvent) was rapidly injected into the solution and a cloudy solution was formed. After centrifuging, choloroform was sedimented at the bottom of a conical tube and diluted with 100 µL of methanol for further UV-Vis spectrophotometry measurement. An orthogonal array design (OAD) was employed to study the effects of different parameters on the extraction efficiency. Under the optimum experimental conditions, a preconcentration factor up to 63.6 was achieved for extraction from 5.0 mL of sample solution. The limit of detection (LOD) based on S/N = 3 was 0.33 µg L-1 and the calibration curve was linear in the range of 1-200 µg L-1 with reasonable linearity (r2 > 0.997). Finally, the accuracy of the proposed method was successfully evaluated by determination of trace amounts of copper ions in different water samples and satisfactory results were obtained.

Separation and preconcentration of Ag(I) in aqueous samples by flotation as an ion-associate using iodide and ferroin followed the determination by flame atomic absorption spectrometry.

PubMed

Hosseini, Mohammad Saeid; Hashemi-Moghaddam, Hamid; Kardan-Moghaddam, Gholamreza

2007-01-01

A simple method for separation/preconcentration and determination of Ag(I) in aqueous samples is described. The method is based on formation of an ion-associate between Ag(I)-iodide complex and ferroin, which can be floated at the interface of the aqueous/n-heptane phases. The flotation process was carried out using 500-ml aliquot of the aqueous solution and the floated layer was dissolved in 5 ml of 1 M HNO3 containing methanol (50% v/v) as the solvent. The Ag(I) content was then determined by flame atomic absorption spectrometry (FAAS). The method so could be considered as an enrichment process, was achieved to a quantitative feature, when the pH of the solution was adjusted to 4 and the concentrations of iodide and ferroin were about 3.2 x 10(-4) M and 6.25 x 10(-5) M, respectively. The LOD and RSD (n = 7) were obtained 1.0 x 10(-8) M and 2.4%, respectively. It was found that a large number of cations and anions even at high considerably foreign ion/Ag(I) ratios were not interfered. The method was applied satisfactorily to recovery of Ag(I) from different aqueous samples.

Whole air canister sampling coupled with preconcentration GC/MS analysis of part-per-trillion levels of trimethylsilanol in semiconductor cleanroom air.

PubMed

Herrington, Jason S

2013-08-20

The costly damage airborne trimethylsilanol (TMS) exacts on optics in the semiconductor industry has resulted in the demand for accurate and reliable methods for measuring TMS at trace levels (i.e., parts per trillion, volume per volume of air [ppt(v)] [~ng/m(3)]). In this study I developed a whole air canister-based approach for field sampling trimethylsilanol in air, as well as a preconcentration gas chromatography/mass spectrometry laboratory method for analysis. The results demonstrate clean canister blanks (0.06 ppt(v) [0.24 ng/m(3)], which is below the detection limit), excellent linearity (a calibration relative response factor relative standard deviation [RSD] of 9.8%) over a wide dynamic mass range (1-100 ppt(v)), recovery/accuracy of 93%, a low selected ion monitoring method detection limit of 0.12 ppt(v) (0.48 ng/m(3)), replicate precision of 6.8% RSD, and stability (84% recovery) out to four days of storage at room temperature. Samples collected at two silicon wafer fabrication facilities ranged from 10.0 to 9120 ppt(v) TMS and appear to be associated with the use of hexamethyldisilazane priming agent. This method will enable semiconductor cleanroom managers to monitor and control for trace levels of trimethylsilanol.

Amplified electrochemical detection of nucleic acid hybridization via selective preconcentration of unmodified gold nanoparticles.

PubMed

Li, Yuan; Tian, Rui; Zheng, Xingwang; Huang, Rongfu

2016-08-31

The common drawback of optical methods for rapid detection of nucleic acid by exploiting the differential affinity of single-/double-stranded nucleic acids for unmodified gold nanoparticles (AuNPs) is its relatively low sensitivity. In this article, on the basis of selective preconcentration of AuNPs unprotected by single-stranded DNA (ssDNA) binding, a novel electrochemical strategy for nucleic acid sequence identification assay has been developed. Through detecting the redox signal mediated by AuNPs on 1, 6-hexanedithiol blocked gold electrode, the proposed method is able to ensure substantial signal amplification and a low background current. This strategy is demonstrated for quantitative analysis of the target microRNA (let-7a) in human breast adenocarcinoma cells, and a detection limit of 16 fM is readily achieved with desirable specificity and sensitivity. These results indicate that the selective preconcentration of AuNPs for electrochemical signal readout can offer a promising platform for the detection of specific nucleic acid sequence. Copyright © 2016 Elsevier B.V. All rights reserved.

Solid phase extraction for the speciation and preconcentration of inorganic selenium in water samples: a review.

PubMed

Herrero Latorre, C; Barciela García, J; García Martín, S; Peña Crecente, R M

2013-12-04

Selenium is an essential element for the normal cellular function of living organisms. However, selenium is toxic at concentrations of only three to five times higher than the essential concentration. The inorganic forms (mainly selenite and selenate) present in environmental water generally exhibit higher toxicity (up to 40 times) than organic forms. Therefore, the determination of low levels of different inorganic selenium species in water is an analytical challenge. Solid-phase extraction has been used as a separation and/or preconcentration technique prior to the determination of selenium species due to the need for accurate measurements for Se species in water at extremely low levels. The present paper provides a critical review of the published methods for inorganic selenium speciation in water samples using solid phase extraction as a preconcentration procedure. On the basis of more than 75 references, the different speciation strategies used for this task have been highlighted and classified. The solid-phase extraction sorbents and the performance and analytical characteristics of the developed methods for Se speciation are also discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

A Micro-Preconcentrator Combined Olfactory Sensing System with a Micromechanical Cantilever Sensor for Detecting 2,4-Dinitrotoluene Gas Vapor

PubMed Central

Chae, Myung-Sic; Kim, Jinsik; Yoo, Yong Kyoung; Kang, Ji Yoon; Lee, Jeong Hoon; Hwang, Kyo Seon

2015-01-01

Preventing unexpected explosive attacks and tracing explosion-related molecules require the development of highly sensitive gas-vapor detection systems. For that purpose, a micromechanical cantilever-based olfactory sensing system including a sample preconcentrator was developed to detect 2,4-dinitrotoluene (2,4-DNT), which is a well-known by-product of the explosive molecule trinitrotoluene (TNT) and exists in concentrations on the order of parts per billion in the atmosphere at room temperature. A peptide receptor (His-Pro-Asn-Phe-Ser-Lys-Tyr-Ile-Leu-His-Gln-Arg) that has high binding affinity for 2,4-DNT was immobilized on the surface of the cantilever sensors to detect 2,4-DNT vapor for highly selective detection. A micro-preconcentrator (µPC) was developed using Tenax-TA adsorbent to produce higher concentrations of 2,4-DNT molecules. The preconcentration was achieved via adsorption and thermal desorption phenomena occurring between target molecules and the adsorbent. The µPC directly integrated with a cantilever sensor and enhanced the sensitivity of the cantilever sensor as a pretreatment tool for the target vapor. The response was rapidly saturated within 5 min and sustained for more than 10 min when the concentrated vapor was introduced. By calculating preconcentration factor values, we verified that the cantilever sensor provides up to an eightfold improvement in sensing performance. PMID:26213944

Spectrophotometric determination of paracetamol in urine with tetrahydroxycalix[4]arene as a coupling reagent and preconcentration with triton X-114 using cloud point extraction.

PubMed

Filik, Hayati; Sener, Izzet; Cekiç, Sema Demirci; Kiliç, Emine; Apak, Reşat

2006-06-01

In the present paper, conventional spectrophotometry in conjunction with cloud point extraction-preconcentration were investigated as alternative methods for paracetamol (PCT) assay in urine samples. Cloud point extraction (CPE) was employed for the preconcentration of p-aminophenol (PAP) prior to spectrophotometric determination using the non-ionic surfactant Triton X-114 (TX-114) as an extractant. The developed methods were based on acidic hydrolysis of PCT to PAP, which reacted at room temperature with 25,26,27,28-tetrahydroxycalix[4]arene (CAL4) in the presence of an oxidant (KIO(4)) to form an blue colored product. The PAP-CAL4 blue dye formed was subsequently entrapped in the surfactant micelles of Triton X-114. Cloud point phase separation with the aid of Triton X-114 induced by addition of Na(2)SO(4) solution was performed at room temperature as an advantage over other CPE assays requiring elevated temperatures. The 580 nm-absorbance maximum of the formed product was shifted bathochromically to 590 nm with CPE. The working range of 1.5-12 microg ml(-1) achieved by conventional spectrophotometry was reduced down to 0.14-1.5 microg ml(-1) with cloud point extraction, which was lower than those of most literature flow-through assays that also suffer from nonspecific absorption in the UV region. By preconcentrating 10 ml sample solution, a detection limit as low as 40.0 ng ml(-1) was obtained after a single-step extraction, achieving a preconcentration factor of 10. The stoichiometric composition of the dye was found to be 1 : 4 (PAP : CAL4). The impact of a number of parameters such as concentrations of CAL4, KIO(4), Triton X-100 (TX-100), and TX-114, extraction temperature, time periods for incubation and centrifugation, and sample volume were investigated in detail. The determination of PAP in the presence of paracetamol in micellar systems under these conditions is limited. The established procedures were successfully adopted for the determination of PCT in urine samples. Since the drug is rapidly absorbed and excreted largely in urine and its high doses have been associated with lethal hepatic necrosis and renal failure, development of a rapid, sensitive and selective assay of PCT is of vital importance for fast urinary screening and antidote administration before applying more sophisticated, but costly and laborious hyphenated instrumental techniques of HPLC-SPE-NMR-MS.

Comparison of solidification of floating drop and homogenous liquid-liquid microextractions for the extraction of two plasticizers from the water kept in PET-bottles.

PubMed

Yamini, Yadollah; Ghambarian, Mahnaz; Khalili-Zanjani, Mohammad Reza; Faraji, Mohammad; Shariati, Shahab

2009-09-01

Two approaches based on solidification of floating drop microextraction (SFDME) and homogenous liquid-liquid microextraction (HLLE) were compared for the extraction and preconcentration of di-(2-ethylhexyl) phthalate (DEHP) and di-(2-ethylhexyl) adipate (DEHA) from the mineral water samples. In SFDME, a floated drop of the mixture of acetophenone/1-undecanol (1:8) was exposed on the surface of the aqueous solution and extraction was permitted to occur. In HLLE, a homogenous ternary solvent system was used by water/methanol/chloroform and the phase separation phenomenon occurred by salt addition. Under the optimal conditions, the LODs for the two target plasticizers (DEHA and DEHP), obtained by SFDME-GC-FID and HLLE-GC-FID, were ranged from 0.03 to 0.01 microg/L and 0.02 to 0.01 microg/L, respectively. HLLE provided higher preconcentration factors (472.5- and 551.2-fold) within the shorter extraction time as well as better RSDs (4.5-6.9%). While, in SFDME, high preconcentration factors in the range of 162-198 and good RSDs in the range of 5.2-9.6% were obtained. Both methods were applied for the analysis of two plasticizers in different water samples and two target plasticizers were found in the bottled mineral water after the expiring time and the boiling water was exposed to a polyethylene vial.

Differential determination of chromium(VI) and total chromium in natural waters using flow injection on-line separation and preconcentration electrothermal atomic absorption spectrometry.

PubMed

Sperling, M; Yin, X; Welz, B

1992-03-01

A rapid, sensitive and selective method for the differential determination of CrIII and CrVI in natural waters is described. Chromium(vi) can be determined directly by flow injection on-line sorbent extraction preconcentration coupled with electrothermal atomic absorption spectrometry using sodium diethyldithiocarbamate as the complexing agent and C18 bonded silica reversed-phase sorbent as the column material. Total Cr can be determined after oxidation of CrIII to CrVI by potassium peroxydisulfate. Chromium(III) can be calculated by difference. The optimum conditions for sorbent extraction of CrVI and oxidation of CrIII to CrVI are evaluated. A 12-fold enhancement in sensitivity compared with direct introduction of 40 microliters samples was achieved after preconcentration for 60 s, giving detection limits of 16 ng l-1 for CrVI and 18 ng l-1 for total Cr (based on 3 sigma). Results obtained for sea-water and river water reference materials were all within the certified range for total Cr with a precision of better than 10% relative standard deviation in the range 100-200 ng l-1. The selectivity of the determination of CrVI was evaluated by analysing spiked reference materials in the presence of CrIII, resulting in quantitative recovery of CrVI.

SP70-alpha-benzoin oxime chelating resin for preconcentration-separation of Pb(II), Cd(II), Co(II) and Cr(III) in environmental samples.

PubMed

Narin, Ibrahim; Surme, Yavuz; Bercin, Erdogan; Soylak, Mustafa

2007-06-25

In the presented work, alpha-benzoin oxime immobilized SP70 chelating resin was synthesized for separation and preconcentration of Pb(II), Cd(II), Co(II) and Cr(III). The optimization procedure for analytical parameters including pH, eluent type, flow rate, etc. was examined in order to gain quantitative recoveries of analyte ions. The effects of foreign ions on the recoveries of studied metal ions were also investigated. The detection limits (3sigma) were found to be 16.0, 4.2, 1.3, 2.4microgL(-1) for Pb, Cd, Co and Cr, respectively. The preconcentration factor was 75 for Pb, 100 for Cd, Co and Cr. The optimized method was validated with certified reference materials and successfully applied to the waters, crops and pharmaceutical samples with good results (recoveries greater than 95%, R.S.D. lower than 10%).

Electrokinetic sample preconcentration and hydrodynamic sample injection for microchip electrophoresis using a pneumatic microvalve.

PubMed

Cong, Yongzheng; Katipamula, Shanta; Geng, Tao; Prost, Spencer A; Tang, Keqi; Kelly, Ryan T

2016-02-01

A microfluidic platform was developed to perform online electrokinetic sample preconcentration and rapid hydrodynamic sample injection for zone electrophoresis using a single microvalve. The polydimethylsiloxane microchip comprises a separation channel, a side channel for sample introduction, and a control channel which is used as a pneumatic microvalve aligned at the intersection of the two flow channels. The closed microvalve, created by multilayer soft lithography, serves as a nanochannel preconcentrator under an applied electric potential, enabling current to pass through while preventing bulk flow. Once analytes are concentrated, the valve is briefly opened and the stacked sample is pressure injected into the separation channel for electrophoretic separation. Fluorescently labeled peptides were enriched by a factor of ∼450 in 230 s. This method enables both rapid analyte concentration and controlled injection volume for high sensitivity, high-resolution CE. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Force fields of charged particles in micro-nanofluidic preconcentration systems

NASA Astrophysics Data System (ADS)

Gong, Lingyan; Ouyang, Wei; Li, Zirui; Han, Jongyoon

2017-12-01

Electrokinetic concentration devices based on the ion concentration polarization (ICP) phenomenon have drawn much attention due to their simple setup, high enrichment factor, and easy integration with many subsequent processes, such as separation, reaction, and extraction etc. Despite significant progress in the experimental research, fundamental understanding and detailed modeling of the preconcentration systems is still lacking. The mechanism of the electrokinetic trapping of charged particles is currently limited to the force balance analysis between the electric force and fluid drag force in an over-simplified one-dimensional (1D) model, which misses many signatures of the actual system. This letter studies the particle trapping phenomena that are not explainable in the 1D model through the calculation of the two-dimensional (2D) force fields. The trapping of charged particles is shown to significantly distort the electric field and fluid flow pattern, which in turn leads to the different trapping behaviors of particles of different sizes. The mechanisms behind the protrusions and instability of the focused band, which are important factors determining overall preconcentration efficiency, are revealed through analyzing the rotating fluxes of particles in the vicinity of the ion-selective membrane. The differences in the enrichment factors of differently sized particles are understood through the interplay between the electric force and convective fluid flow. These results provide insights into the electrokinetic concentration effect, which could facilitate the design and optimization of ICP-based preconcentration systems.

Method modification of the Legipid® Legionella fast detection test kit.

PubMed

Albalat, Guillermo Rodríguez; Broch, Begoña Bedrina; Bono, Marisa Jiménez

2014-01-01

Legipid(®) Legionella Fast Detection is a test based on combined magnetic immunocapture and enzyme-immunoassay (CEIA) for the detection of Legionella in water. The test is based on the use of anti-Legionella antibodies immobilized on magnetic microspheres. Target microorganism is preconcentrated by filtration. Immunomagnetic analysis is applied on these preconcentrated water samples in a final test portion of 9 mL. The test kit was certified by the AOAC Research Institute as Performance Tested Method(SM) (PTM) No. 111101 in a PTM validation which certifies the performance claims of the test method in comparison to the ISO reference method 11731-1998 and the revision 11731-2004 "Water Quality: Detection and Enumeration of Legionella pneumophila" in potable water, industrial water, and waste water. The modification of this test kit has been approved. The modification includes increasing the target analyte from L. pneumophila to Legionella species and adding an optical reader to the test method. In this study, 71 strains of Legionella spp. other than L. pneumophila were tested to determine its reactivity with the kit based on CEIA. All the strains of Legionella spp. tested by the CEIA test were confirmed positive by reference standard method ISO 11731. This test (PTM 111101) has been modified to include a final optical reading. A methods comparison study was conducted to demonstrate the equivalence of this modification to the reference culture method. Two water matrixes were analyzed. Results show no statistically detectable difference between the test method and the reference culture method for the enumeration of Legionella spp. The relative level of detection was 93 CFU/volume examined (LOD50). For optical reading, the LOD was 40 CFU/volume examined and the LOQ was 60 CFU/volume examined. Results showed that the test Legipid Legionella Fast Detection is equivalent to the reference culture method for the enumeration of Legionella spp.

Modular manifold for integrated fluidics and electronics

DOEpatents

Adkins, Douglas Ray

2010-03-30

An airtight preconcentrator housing and/or a sensor housing for chemical testing, the housing(s) comprising internal dimensions such that a pre-manufactured preconcentrator and/or sensor can be disposed therein. The housings can also comprise electrical contacts disposed therein which align with and thus provide electrical connection to the preconcentrator and/or sensor. The preconcentrator and/or sensor can be easily and quickly replaced.

Nanofluidic Pre-Concentration Devices for Enhancing the Detection Sensitivity and Selectivity of Biomarkers for Human Performance Monitoring

DTIC Science & Technology

2014-11-24

aptamers to enhance specificity. Additionally, pre-concentration was coupled to various detection paradigms to achieve high-sensitivity biomarker... Aptamers , Biomarkers, Nanofluidics, Pre-concentration Devices, Sensing 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER...devices and optimized electrokinetic pre-concentration conditions for key neurological biomarkers of interest, by using nanoparticles and aptamers to

Automated cassette-based production of high specific activity [203/212Pb]peptide-based theranostic radiopharmaceuticals for image-guided radionuclide therapy for cancer.

PubMed

Li, Mengshi; Zhang, Xiuli; Quinn, Thomas P; Lee, Dongyoul; Liu, Dijie; Kunkel, Falk; Zimmerman, Brian E; McAlister, Daniel; Olewein, Keith; Menda, Yusuf; Mirzadeh, Saed; Copping, Roy; Johnson, Frances L; Schultz, Michael K

2017-09-01

A method for preparation of Pb-212 and Pb-203 labeled chelator-modified peptide-based radiopharmaceuticals for cancer imaging and radionuclide therapy has been developed and adapted for automated clinical production. Pre-concentration and isolation of radioactive Pb2+ from interfering metals in dilute hydrochloric acid was optimized using a commercially-available Pb-specific chromatography resin packed in disposable plastic columns. The pre-concentrated radioactive Pb2+ is eluted in NaOAc buffer directly to the reaction vessel containing chelator-modified peptides. Radiolabeling was found to proceed efficiently at 85°C (45min; pH 5.5). The specific activity of radiolabeled conjugates was optimized by separation of radiolabeled conjugates from unlabeled peptide via HPLC. Preservation of bioactivity was confirmed by in vivo biodistribution of Pb-203 and Pb-212 labeled peptides in melanoma-tumor-bearing mice. The approach has been found to be robustly adaptable to automation and a cassette-based fluid-handling system (Modular Lab Pharm Tracer) has been customized for clinical radiopharmaceutical production. Our findings demonstrate that the Pb-203/Pb-212 combination is a promising elementally-matched radionuclide pair for image-guided radionuclide therapy for melanoma, neuroendocrine tumors, and potentially other cancers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of a new extraction method based on counter current salting-out homogenous liquid-liquid extraction followed by dispersive liquid-liquid microextraction: Application for the extraction and preconcentration of widely used pesticides from fruit juices.

PubMed

Farajzadeh, Mir Ali; Feriduni, Behruz; Mogaddam, Mohammad Reza Afshar

2016-01-01

In this paper, a new extraction method based on counter current salting-out homogenous liquid-liquid extraction (CCSHLLE) followed by dispersive liquid-liquid microextraction (DLLME) has been developed for the extraction and preconcentration of widely used pesticides in fruit juice samples prior to their analysis by gas chromatography-flame ionization detection (GC-FID). In this method, initially, sodium chloride as a separation reagent is filled into a small column and a mixture of water (or fruit juice) and acetonitrile is passed through the column. By passing the mixture sodium chloride is dissolved and the fine droplets of acetonitrile are formed due to salting-out effect. The produced droplets go up through the remained mixture and collect as a separated layer. Then, the collected organic phase (acetonitrile) is removed with a syringe and mixed with 1,1,2,2-tetrachloroethane (extraction solvent at µL level). In the second step, for further enrichment of the analytes the above mixture is injected into 5 mL de-ionized water placed in a test tube with conical bottom in order to dissolve acetonitrile into water and to achieve a sedimented phase at µL-level volume containing the enriched analytes. Under the optimal extraction conditions (extraction solvent, 1.5 mL acetonitrile; pH, 7; flow rate, 0.5 mL min(-1); preconcentration solvent, 20 µL 1,1,2,2-tetrachloroethane; NaCl concentration; 5%, w/w; and centrifugation rate and time, 5000 rpm and 5 min, respectively), the extraction recoveries and enrichment factors ranged from 87% to 96% and 544 to 600, respectively. Repeatability of the proposed method, expressed as relative standard deviations, ranged from 2% to 6% for intra-day (n=6, C=250 or 500 µg L(-1)) and inter-days (n=4, C=250 or 500 µg L(-1)) precisions. Limits of detection are obtained between 2 and 12 µg L(-1). Finally, the proposed method is applied for the determination of the target pesticide residues in the juice samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Improved limits and portability over currently employed cadmium monitoring systems through preconcentration for detection by way of micro-/nanofluidic mechanisms

NASA Astrophysics Data System (ADS)

Wach, Paul

Due to risk of environmental and biological accumulation of Cadmium (Cd), improved methods of early detection and monitoring must be explored as a preventative measure. Listed as one of the top three toxic heavy metals by the Environmental Protection Agency (EPA), the effects on ecological and human systems have well documented side-effects of physical mutation, reproductive sterility, kidney failure, liver disease, bone loss, and death. Found in batteries, metal plating, pigments, plastics, and cigarettes, Cd is also used as a neutron absorber in the nuclear industry as well as having 3 known radioactive isotopes. Urine Cd levels, which have been widely used to predict whole body levels, increase when kidney damage occurs, thus increasing the importance to monitor and detect as early as possible. Although several methods of detection and monitoring are currently in use, they are insufficient for reasons including massive expense, weak specificity causing false readings, and/or a lack of portability. By exploiting naturally occurring mechanisms known to micro-/nanofluidics, a novel approach to Cd detection, measurement, and preconcentration was explored using the finite element computational software COMSOL. An open flow system of a nanochannel was explored through manipulation of the surface charge density. With a dominant negatively charged density on the walls, positive surface charge densities were adjacently placed at the center of the nanochannel causing a constriction of flow and allowing preconcentration of the analytes. When the open flow system was scaled up to a microchannel, the mechanism was found to have little effect on constriction of the flow. A preconcentration effect was discovered in a closed flow system when the adjacent patches were modeled as being impermeable to charge, causing the molecules to migrate to and remain at the central region of the microchannel once the dynamic process reached steady state. It was found to have the ability to concentrate Cd at an initial concentration of 0.5 mol/m3, which is nearly half the limit of commercially available technology. Additionally, this preconcentration mechanism was demonstrated to potentially advance its capabilities by attaching channels in series or parallel to further preconcentrate for improved detection. Finally, measurement of extremely low concentrations of Cd is possible due to differences seen in the concentration distribution profiles once steady-state is reached.

Development of a novel mixed hemimicelles dispersive micro solid phase extraction using 1-hexadecyl-3-methylimidazolium bromide coated magnetic graphene for the separation and preconcentration of fluoxetine in different matrices before its determination by fiber optic linear array spectrophotometry and mode-mismatched thermal lens spectroscopy.

PubMed

Kazemi, Elahe; Haji Shabani, Ali Mohammad; Dadfarnia, Shayessteh; Abbasi, Amir; Rashidian Vaziri, Mohammad Reza; Behjat, Abbas

2016-01-28

This study aims at developing a novel, sensitive, fast, simple and convenient method for separation and preconcentration of trace amounts of fluoxetine before its spectrophotometric determination. The method is based on combination of magnetic mixed hemimicelles solid phase extraction and dispersive micro solid phase extraction using 1-hexadecyl-3-methylimidazolium bromide coated magnetic graphene as a sorbent. The magnetic graphene was synthesized by a simple coprecipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The retained analyte was eluted using a 100 μL mixture of methanol/acetic acid (9:1) and converted into fluoxetine-β-cyclodextrin inclusion complex. The analyte was then quantified by fiber optic linear array spectrophotometry as well as mode-mismatched thermal lens spectroscopy (TLS). The factors affecting the separation, preconcentration and determination of fluoxetine were investigated and optimized. With a 50 mL sample and under optimized conditions using the spectrophotometry technique, the method exhibited a linear dynamic range of 0.4-60.0 μg L(-1), a detection limit of 0.21 μg L(-1), an enrichment factor of 167, and a relative standard deviation of 2.1% and 3.8% (n = 6) at 60 μg L(-1) level of fluoxetine for intra- and inter-day analyses, respectively. However, with thermal lens spectrometry and a sample volume of 10 mL, the method exhibited a linear dynamic range of 0.05-300 μg L(-1), a detection limit of 0.016 μg L(-1) and a relative standard deviation of 3.8% and 5.6% (n = 6) at 60 μg L(-1) level of fluoxetine for intra- and inter-day analyses, respectively. The method was successfully applied to determine fluoxetine in pharmaceutical formulation, human urine and environmental water samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Flow injection on-line displacement/solid phase extraction system coupled with flame atomic absorption spectrometry for selective trace silver determination in water samples.

PubMed

Christou, Chrysoula K; Anthemidis, Aristidis N

2009-04-15

A novel flow injection (FI) on-line displacement solid phase extraction preconcentration and/or separation method coupled with FAAS in order to minimize interference from other metals was developed for trace silver determination. The proposed method involved the on-line formation and subsequently pre-sorption of lead diethyldithiocarbamate (Pb-DDTC) into a column packed with PTFE-turnings. The preconcentration and/or separation of the Ag(I) took place through a displacement reaction between Ag(I) and Pb(II) of the pre-sorbed Pb-DDTC. Finally, the retained analyte was eluted with isobutyl methyl ketone (IBMK) and delivered directly to nebulizer for measuring. Interference from co-existing ions with lower DDTC complex stability in comparison with Pb-DDTC, was eliminated without need for any masking reagent. With 120 s of preconcentration time at a sample flow rate of 7.6 mL min(-1), an enhancement factor of 110 and a detection limit (3s) of 0.2 microg L(-1) were obtained. The precision (RSD, n=10) was 3.1% at the 10 mug L(-1) level. The developed method was successfully applied to trace silver determination in a variety of environmental water samples and certified reference material.

Solid Phase Extraction of Inorganic Mercury Using 5-Phenylazo-8-hydroxyquinoline and Determination by Cold Vapor Atomic Fluorescence Spectroscopy in Natural Water Samples

PubMed Central

Daye, Mirna; Halwani, Jalal; Hamzeh, Mariam

2013-01-01

8-Hydroxyquinoline (8-HQ) was chosen as a powerful ligand for Hg solid phase extraction. Among several chelating resins based on 8-HQ, 5-phenylazo-8-hydroxyquinoline (5Ph8HQ) is used for mercury extraction in which the adsorption dynamics were fully studied. It has been shown that Hg(II) is totally absorbed by 5Ph8HQ within the first 30 minutes of contact time with t 1/2 5 minutes, following Langmuir adsorption model. At pH 4, the affinity of mercury is unchallenged by other metals except, for Cu(II), which have shown higher Kd value. With these latter characteristics, 5Ph8HQ was examined for the preconcentration of trace levels of Hg(II). The developed method showed quantitative recoveries of Hg(II) with LOD = 0.21 pg mL−1 and RSD = 3–6% using cold vapor atomic fluorescence spectroscopy (CV-AFS) with a preconcentration factor greater than 250. PMID:24459417

Application of l-cystine modified zeolite for preconcentration and determination of ultra-trace levels of cadmium by flame atomic absorption spectrometry.

PubMed

Rezvani, Seyyed Ahmad; Soleymanpour, Ahmad

2016-03-04

A very convenient, sensitive and precise solid phase extraction (SPE) system was developed for enrichment and determination of ultra-trace of cadmium ion in water and plant samples. This method was based on the retention of cadmium(II) ions by l-cystine adsorbed in Y-zeolite and carry out in a packed mini-column. The retained cadmium ions then were eluted and determined by flame atomic absorption spectrometry. The scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy techniques were applied for the characterization of cystine modified zeolite (CMZ). Some experimental conditions affecting the analytical performance such as pH, eluent type, concentration of sample, eluent flow rate and also the presence of interfering ions were investigated. The calibration graph was linear within the range of 0.1-7.5ngmL(-1) and limit of detection was obtained 0.04ngmL(-1) with the preconcentration factor of 400. The relative standard deviation (RSD) was obtained 1.4%, indicating the excellent reproducibility of this method. The proposed method was successfully applied for the extraction and determination of cadmium(II) ion in black tea, cigarette's tobacco and also various water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Concurrent DNA Preconcentration and Separation in Bipolar Electrode-Based Microfluidic Device

PubMed Central

Song, Hongjun; Wang, Yi; Garson, Charles; Pant, Kapil

2015-01-01

This paper presents a bipolar electrode (BPE) device in a microfluidic dual-channel design for concurrent preconcentration and separation of composite DNA containing samples. The novelty of the present effort relies on the combination of BPE-induced ion concentration polarization (ICP) and end-labeled free-solution electrophoresis (ELFSE). The ion concentration polarization effect arising from the faradaic reaction on the BPE is utilized to exert opposing electrophoretic and electroosmotic forces on the DNA samples. Meanwhile, end-labeled free-solution electrophoresis alters the mass-charge ratio to enable simultaneous DNA separation in free solution. The microfluidic device was fabricated using standard and soft lithography techniques to form gold-on-glass electrode capped with a PDMS microfluidic channel. Experimental testing with various DNA samples was carried out over a range of applied electric field. Concentration ratios up to 285× within 5 minutes for a 102-mer DNA, and concurrent preconcentration and free-solution separation of binary mixture of free and bound 102-mer DNA within 6 minutes was demonstrated. The effect of applied electric field was also interrogated with respect to pertinent performance metrics of preconcentration and separation. PMID:26005497

Tortuous path chemical preconcentrator

DOEpatents

Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Wheeler, David R.; Simonson, Robert J.

2010-09-21

A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

Integrated explosive preconcentrator and electrochemical detection system for 2,4,6-trinitrotoluene (TNT) vapor.

PubMed

Cizek, Karel; Prior, Chad; Thammakhet, Chongdee; Galik, Michal; Linker, Kevin; Tsui, Ray; Cagan, Avi; Wake, John; La Belle, Jeff; Wang, Joseph

2010-02-19

This article reports on an integrated explosive-preconcentration/electrochemical detection system for 2,4,6-trinitrotoluene (TNT) vapor. The challenges involved in such system integration are discussed. A hydrogel-coated screen-printed electrode is used for the detection of the thermally desorbed TNT from a preconcentration device using rapid square wave voltammetry. Optimization of the preconcentration system for desorption of TNT and subsequent electrochemical detection was conducted yielding a desorption temperature of 120 degrees C under a flow rate of 500 mL min(-1). Such conditions resulted in a characteristic electrochemical signal for TNT representing the multi-step reduction process. Quantitative measurements produced a linear signal dependence on TNT quantity exposed to the preconcentrator from 0.25 to 10 microg. Finally, the integrated device was successfully demonstrated using a sample of solid TNT located upstream of the preconcentrator. Copyright 2009 Elsevier B.V. All rights reserved.

Determination of herbicides in mineral and stagnant waters at ng/L levels using capillary electrophoresis and UV detection combined with solid-phase extraction and sample stacking.

PubMed

Hernández-Borges, Javier; García-Montelongo, Francisco J; Cifuentes, Alejandro; Rodríguez-Delgado, Miguel Angel

2005-04-08

In this work, the combined use of solid-phase extraction (SPE) and on-line preconcentration strategies as normal stacking mode (NSM) and stacking with matrix removal (SWMR) for the ultrasensitive and simultaneous capillary electrophoresis-ultraviolet analysis (CE-UV) of five triazolopyrimidine sulfonanilide pesticides (i.e., diclosulam, cloransulam-methyl, flumetsulam, metosulam and florasulam) in different types of water is investigated. An adequate separation electrolyte for the separation and stacking of these pesticides was obtained, considering also its compatibility with MS detection, which consisted of 24 mM formic acid and 16 mM ammonium carbonate at pH 6.4. It was observed that the use of this running buffer together with the SWMR preconcentration method provided the best results in terms of sensitivity (between 6.54 and 11.9 microg/L) and peak efficiency (up to 550000 theoretical plates per meter, NTP/m). When this on-line preconcentration procedure was combined with an off-line sample preconcentration step as SPE using C18 cartridges, the selected herbicides could be detected in the ng/L range. The optimized SPE-SWMR-CE-UV method was applied to the determination of the selected group of pesticides in spiked and non-spiked mineral and stagnant waters. Recoveries ranged between 55 and 110% and limits of detection between 131 and 342 ng/L. This work shows the great possibilities of the combined use of SPE-SWMR-CE-UV to overcome the sensitivity problems usually linked to CE analysis.

Determination of atrazine and simazine in water samples by high-performance liquid chromatography after preconcentration with heat-treated diatomaceous earth.

PubMed

Katsumata, Hideyuki; Kaneco, Satoshi; Suzuki, Tohru; Ohta, Kiyohisa

2006-09-08

A sensitive and selective column adsorption method is proposed for the preconcentration and determination of atrazine and simazine. Atrazine and simazine were preconcentrated on heat-treated diatomaceous earth as an adsorbent and then determined by high-performance liquid chromatography (HPLC). Several parameters on the recoveries of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 2 using 100 mL of validation solution containing 1.5 microg of triazines and 5 mL of ethanol as an eluent. Recoveries of atrazine and simazine were 95.7+/-4.2% and 75.0+/-1.9% with a relative standard deviation for seven determinations of 4.7% and 2.7% under optimum conditions. The maximum preconcentration factor was 100 for triazines when 500 mL of sample solution volume was used. The linear ranges of calibration curves for atrazine and simazine were 1-150 ng mL(-1) and 1-300 ng mL(-1), respectively, with correlation coefficients of 0.999 and the detection limits (3Signal-to-Noise) were 0.24 ng mL(-1) and 0.21 ng mL(-1) for atrazine and simazine. The capacity of the adsorbent was also examined and found to be 0.8 mg g(-1) and 1.3 mg g(-1) for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of triazines in river water and tap water samples with high precision and accuracy.

Graphene-sensitized microporous membrane/solvent microextraction for the preconcentration of cinnamic acid derivatives in Rhizoma Typhonii.

PubMed

Xing, Rongrong; Hu, Shuang; Chen, Xuan; Bai, Xiaohong

2014-09-01

A novel graphene-sensitized microporous membrane/solvent microextraction method named microporous membrane/graphene/solvent synergistic microextraction, coupled with high-performance liquid chromatography and UV detection, was developed and introduced for the extraction and determination of three cinnamic acid derivatives in Rhizoma Typhonii. Several factors affecting performance were investigated and optimized, including the types of graphene and extraction solvent, concentration of graphene dispersed in octanol, sample phase pH, ionic strength, stirring rate, extraction time, extraction temperature, and sample volume. Under optimized conditions, the enrichment factors of cinnamic acid derivatives ranged from 75 to 269. Good linearities were obtained from 0.01 to 10 μg/mL for all analytes with regression coefficients between 0.9927 and 0.9994. The limits of quantification were <1 ng/mL, and satisfactory recoveries (99-104%) and precision (1.1-10.8%) were also achieved. The synergistic microextraction mechanism based on graphene sensitization was analyzed and described. The experimental results showed that the method was simple, sensitive, practical, and effective for the preconcentration and determination of cinnamic acid derivatives in Rhizoma Typhonii. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alternative solvent-based methyl benzoate vortex-assisted dispersive liquid-liquid microextraction for the high-performance liquid chromatographic determination of benzimidazole fungicides in environmental water samples.

PubMed

Santaladchaiyakit, Yanawath; Srijaranai, Supalax

2014-11-01

Vortex-assisted dispersive liquid-liquid microextraction using methyl benzoate as an alternative extraction solvent for extracting and preconcentrating three benzimidazole fungicides (i.e., carbendazim, thiabendazole, and fluberidazole) in environmental water samples before high-performance liquid chromatographic analysis has been developed. The selected microextraction conditions were 250 μL of methyl benzoate containing 300 μL of ethanol, 1.0% w/v sodium acetate, and vortex agitation speed of 2100 rpm for 30 s. Under optimum conditions, preconcentration factors were 14.5-39.0 for the target fungicides. Limits of detection were obtained in the range of 0.01-0.05 μg/L. The proposed method was then applied to surface water samples and the recovery evaluations at three spiked concentration levels of 5, 30, and 50 μg/L were obtained in the range of 77.4-110.9% with the relative standard deviation <7.4%. The present method was simple, rapid, low cost, sensitive, environmentally friendly, and suitable for the trace analysis of the studied fungicides in environmental water samples. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Specific extraction of chromium as tetrabutylammonium-chromate and spectrophotometric determination by diphenylcarbazide: speciation of chromium in effluent streams.

PubMed

Noroozifar, M; Khorasani-Motlagh, M

2003-05-01

A very specific, selective, simple, and inexpensive procedure was developed for the speciation of CrVI and CrIII. This method is based on the quantitative extraction of chromate and CrIII (previously oxidized to CrVI) as a tetrabutylammonium-chromate ion-pair in methyl isobutyl ketone (MIBK), and then back extraction and preconcentration with an acidic diphenylcarbazide (DPC) solution. Back extraction was applied to achieve further preconcentration by a final factor of 20. The CrVI-DPC complex was determined in back-extract by a spectrophotometer at 548 nm. Under these extraction conditions, most of the probable concomitant cations and anions remained in the first inorganic phase. The calibration curve was linear up to 0.14 microg L(-1) of CrVI with a detection limit of 2.22 ng L(-1). The developed procedure was found to be suitable for the determination of the CrVI and CrIII species in various natural water samples with a relative standard deviation of better than 1.6%. The method was successfully applied to the speciation of chromium in spiked natural water samples, and also samples of effluent from a leather treatment plant.

Dispersive liquid-liquid microextraction combined with online preconcentration MEKC for the determination of some phenoxyacetic acids in drinking water.

PubMed

Zhang, Yaohai; Jiao, Bining

2013-09-01

A fast and simple technique composed of dispersive liquid-liquid microextraction (DLLME) and online preconcentration MEKC with diode array detection was developed for the determination of four phenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2,6-dichlorophenoxyacetic acid, and 4-chlorophenoxyacetic acid, in drinking water. The four phenoxyacetic acids were separated in reversed-migration MEKC to the baseline. About 145-fold increases in detection sensitivity were observed with online concentration strategy, compared with standard hydrodynamic injection (5 s at 25 mbar pressure). LODs ranged from 0.002 to 0.005 mg/L using only the online preconcentration procedures without any offline concentration of the extract. A DLLME procedure was used in combination with the proposed online preconcentration strategies, which achieved the determination of analytes at limits of quantification ranging from 0.2 to 0.5 μg/kg, which is far lower than the maximum residue limits established by China. The satisfactory recoveries obtained by DLMME spiked at two levels ranged from 67.2 to 99.4% with RSD <15%, making this proposed method suitable for the determination of phenoxyacetic acids in water samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analytical evaluation of BEA zeolite for the pre-concentration of polycyclic aromatic hydrocarbons and their subsequent chromatographic analysis in water samples.

PubMed

Wilson, Walter B; Costa, Andréia A; Wang, Huiyong; Dias, José A; Dias, Sílvia C L; Campiglia, Andres D

2012-07-06

The analytical performance of BEA - a commercial zeolite - is evaluated for the pre-concentration of fifteen Environmental Protection Agency - polycyclic aromatic hydrocarbons and their subsequent HPLC analysis in tap and lake water samples. The pre-concentration factors obtained with BEA have led to a method with excellent analytical figures of merit. One milliliter aliquots were sufficient to obtain excellent precision of measurements at the parts-per-trillion concentration level with relative standard deviations varying from 4.1% (dibenzo[a,h]anthracene) to 13.4% (pyrene). The limits of detection were excellent as well and varied between 1.1 (anthracene) and 49.9 ng L(-1) (indeno[1,2,3-cd]pyrene). The recovery values of all the studied compounds meet the criterion for regulated polycyclic aromatic hydrocarbons, which mandates relative standard deviations equal or lower than 25%. The small volume of organic solvents (100 μL per sample) and amount of BEA (2 mg per sample) makes sample pre-concentration environmentally friendly and cost effective. The extraction procedure is well suited for numerous samples as the small working volume (1 mL) facilitates the implementation of simultaneous sample extraction. These are attractive features when routine monitoring of numerous samples is contemplated. Copyright © 2012 Elsevier B.V. All rights reserved.

The use of graphene-based magnetic nanoparticles as adsorbent for the extraction of triazole fungicides from environmental water.

PubMed

Wang, Weina; Ma, Xiaoxing; Wu, Qiuhua; Wang, Chun; Zang, Xiaohuan; Wang, Zhi

2012-09-01

A graphene-based magnetic nanocomposite (graphene-ferriferrous oxide; G-Fe(3)O(4)) was synthesized and used as an effective adsorbent for the preconcentration of some triazole fungicides (myclobutanil, tebuconazole, and hexaconazole) in environmental water samples prior to high-performance liquid chromatography-ultraviolet detection. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid the time-consuming experimental procedures commonly involved in the traditional solid phase extraction such as centrifugation and filtrations. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, the pH values of the sample solution, salt concentration, and desorption conditions were investigated. Under the optimum conditions, the enrichment factors of the method for the three analytes were 5824, 3600, and 4761, respectively. A good linearity was observed in the range of 0.1-50 ng/mL for tebuconazole and 0.05-50 ng/mL for myclobutanil and hexaconazole, respectively, with the correlation coefficients ranging from 0.9992 to 0.9996. The limits of detection (S/N = 3) of the method were between 0.005 and 0.01 ng/mL. The results indicated that as a magnetic solid-phase extraction adsorbent, the graphene-ferriferrous oxide (G-Fe(3)O(4)) has a great potential for the preconcentration of some compounds from liquid samples. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Capillary ion chromatography with on-column focusing for ultra-trace analysis of methanesulfonate and inorganic anions in limited volume Antarctic ice core samples.

PubMed

Rodriguez, Estrella Sanz; Poynter, Sam; Curran, Mark; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Paull, Brett

2015-08-28

Preservation of ionic species within Antarctic ice yields a unique proxy record of the Earth's climate history. Studies have been focused until now on two proxies: the ionic components of sea salt aerosol and methanesulfonic acid. Measurement of the all of the major ionic species in ice core samples is typically carried out by ion chromatography. Former methods, whilst providing suitable detection limits, have been based upon off-column preconcentration techniques, requiring larger sample volumes, with potential for sample contamination and/or carryover. Here, a new capillary ion chromatography based analytical method has been developed for quantitative analysis of limited volume Antarctic ice core samples. The developed analytical protocol applies capillary ion chromatography (with suppressed conductivity detection) and direct on-column sample injection and focusing, thus eliminating the requirement for off-column sample preconcentration. This limits the total sample volume needed to 300μL per analysis, allowing for triplicate sample analysis with <1mL of sample. This new approach provides a reliable and robust analytical method for the simultaneous determination of organic and inorganic anions, including fluoride, methanesulfonate, chloride, sulfate and nitrate anions. Application to composite ice-core samples is demonstrated, with coupling of the capillary ion chromatograph to high resolution mass spectrometry used to confirm the presence and purity of the observed methanesulfonate peak. Copyright © 2015 Elsevier B.V. All rights reserved.

Cloud-point extraction and reversed-phase high-performance liquid chromatography for the determination of synthetic phenolic antioxidants in edible oils.

PubMed

Chen, Miao; Xia, Qinghai; Liu, Mousheng; Yang, Yaling

2011-01-01

A cloud-point extraction (CPE) method using Triton X-114 (TX-114) nonionic surfactant was developed for the extraction and preconcentration of propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) from edible oils. The optimum conditions of CPE were 2.5% (v/v) TX-114, 0.5% (w/v) NaCl and 40 min equilibration time at 50 °C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 280 nm, using a gradient mobile phase consisting of methanol and 1.5% (v/v) acetic acid. Under the studied conditions, 4 synthetic phenolic antioxidants (SPAs) were successfully separated within 24 min. The limits of detection (LOD) were 1.9 ng mL(-1) for PG, 11 ng mL(-1) for TBHQ, 2.3 ng mL(-1) for BHA, and 5.9 ng mL(-1) for BHT. Recoveries of the SPAs spiked into edible oil were in the range 81% to 88%. The CPE method was shown to be potentially useful for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environment-friendly. Practical Application: The method established in this article uses less organic solvent to extract SPAs from edible oils; it is simple, highly sensitive and results in no pollution to the environment.

Molecularly imprinted solid-phase extraction combined with high performance liquid chromatography for analysis of phenolic compounds from environmental water samples.

PubMed

Feng, Qin-Zhong; Zhao, Li-Xia; Yan, Wei; Lin, Jin-Ming; Zheng, Zhi-Xia

2009-08-15

The molecularly imprinted bulk polymer with 2,4,6-trichlorophenol (2,4,6-TCP) as the template molecule and methylacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA) as functional monomer and the crosslinker, respectively, has been prepared and applied to the molecularly imprinted solid-phase extraction (MISPE) procedure for selective preconcentration of phenolic compounds from environmental water samples. Various parameters affecting the extraction efficiency of the polymer have been evaluated to optimize the selective preconcentration of the phenolic compounds from aqueous samples. The characteristics of the MISPE method were validated by HPLC. The recoveries ranged between 90% and 98% (RSD: 0.9-2.3%, n=3) for tap water, between 85% and 105% (RSD: 2.6-4.9%, n=3) for river water, between 78% and 98% (RSD: 2.6-5.4%, n=3) for sewage water fortified with 0.4 mg L(-1) of phenol, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), pentachlorophenol (PCP). It was demonstrated that this MISPE-HPLC method could be applied to direct preconcentration and determination of phenolic compounds in environmental water samples.

Determination of sub-ng g-1 levels of total inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry after pre-concentration.

PubMed

Altunay, Nail; Gürkan, Ramazan

2017-03-01

A new and simple ultrasonic-assisted extraction (UAE) procedure was developed for the determination of inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry (HG-AAS). The various analytical variables affecting complex formation and extraction efficiency were investigated and optimised. The method is based on selective complex formation of As(III) and Se(IV) in the presence of excess As(V) and Se(VI) with toluidine red in the presence of tartaric acid at pH 4.5, and then extraction of the resulting condensation products into the micellar phase of non-ionic surfactant, polyethylene glycol dodecyl ether, Brij 35. Under optimised conditions, good linear relationships were obtained in the ranges of 4-225 and 12-400 ng l - 1 with limits of detection of 1.1 and 3.5 ng l - 1 for As(III) and Se(IV), respectively. The repeatability was better than 3.9% for both analytes (n = 10, 25 ng l - 1 ) while reproducibility ranged from 4.2% to 4.8%. The recoveries of As(III) and Se(IV) spiked at 25-100 ng l - 1 were in the range of 94.2-104.8%. After pre-concentration of a 5.0 ml sample, the sensitivity enhancement factors for As(III) and Se(IV) were 185 and 140, respectively. Accuracy was assessed by analysis of two standard reference materials (SRMs) and spiked recovery experiments. The method was successfully applied to the accurate and reliable determination of total As and total Se by HG-AAS after pre-reduction with a mixture of L-cysteine and tartaric acid. Finally, the method was shown to be rapid and sensitive, with good results for extraction, pre-concentration and determination of total As and Se contents (as As(III) and Se(IV)) from food samples.

A simple and efficient ultrasonic-assisted extraction procedure combined with UV-Vis spectrophotometry for the pre-concentration and determination of folic acid (vitamin B9) in various sample matrices.

PubMed

Gürkan, Ramazan; Altunay, Nail

2016-07-01

A simple and efficient ultrasonic-assisted extraction (UAE) procedure has been proposed for the pre-concentration of (2S)-2-[(4-{[(2-amino-4-hydroxypteridin-yl)methyl]amino}phenyl)formamido]pentanedioic acid (folic acid) in vegetables, pharmaceuticals and foods prior to determination at 540 nm using UV-Vis spectrophotometry. The method is based on hydrophobic ternary complex formation of folic acid with silver ions in the presence of cetyltrimethylammonium bromide (CTAB) as a sensitivity enhancer counter ion at pH 7.0, and then extraction into a micellar phase of polyethylene glycol monoalkyl ether (Genapol X-080). The impacts on the extraction efficiency and complex formation of analytical parameters such as sample pH, concentration of silver, concentration of surfactants and extraction time, ultrasonic time and sample volume, were investigated and optimised in detail. The matrix effect on the pre-concentration and determination of folic acid was investigated, and it was observed that the proposed method was highly selective against possible matrix co-extractives. Under optimised conditions, a good linear relationship between the analytical signal and folic acid concentration was obtained in the range of 0.6-180 μg l(-1) with a detection limit of 0.19 μg l(-1) and quantification limit of 0.63 μg l(-1). The applicability was evaluated using samples fortified at different concentration levels, and recoveries higher than 94.1% were obtained. The precision as the percent relative standard deviation (RSD%) was in range of 2.5-3.8% (10 and 40 μg l(-1), n = 5). The proposed method was validated by analysis of two standard reference materials (SRMs) and various real samples, and satisfactory results were obtained.

Dithizone-modified graphene oxide nano-sheet as a sorbent for pre-concentration and determination of cadmium and lead ions in food.

PubMed

Moghadam Zadeh, Hamid Reza; Ahmadvand, Parvaneh; Behbahani, Ali; Amini, Mostafa M; Sayar, Omid

2015-01-01

Graphene oxide nano-sheet was modified with dithizone as a novel sorbent for selective pre-concentration and determination of Cd(II) and Pb(II) in food. The sorbent was characterised by various analytical methods and the effective parameters for Cd(II) and Pb(II) adsorption were optimised during this work. The high adsorption capacity and selectivity of this sorbent makes the method capable of fast determinations of the Cd(II) and Pb(II) content in complicated matrices even at μg l(-1) levels using commonly available instrumentation. The precision of this method was < 1.9% from 10 duplicate determinations and its accuracy verified using standard reference materials. Finally, this method was applied to the determination of Cd(II) and Pb(II) ions in common food samples and satisfactory results were obtained.

Graphene/graphene oxide and their derivatives in the separation/isolation and preconcentration of protein species: A review.

PubMed

Chen, Xuwei; Hai, Xin; Wang, Jianhua

2016-05-30

The distinctive/unique electrical, chemical and optical properties make graphene/graphene oxide-based materials popular in the field of analytical chemistry. Its large surface offers excellent capacity to anchor target analyte, making it an powerful sorbent in the adsorption and preconcentration of trace level analyte of interest in the field of sample preparation. The large delocalized π-electron system of graphene framework provides strong affinity to species containing aromatic rings, such as proteins, and the abundant active sites on its surface offers the chance to modulate adsorption tendency towards specific protein via functional modification/decoration. This review provides an overview of the current research on graphene/graphene oxide-based materials as attractive and powerful adsorption media in the separation/isolation and preconcentration of protein species from biological sample matrixes. These practices are aiming at providing protein sample of high purity for further investigations and applications, or to achieve certain extent of enrichment prior to quantitative assay. In addition, the challenges and future perspectives in the related research fields have been discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

New solid surface fluorescence methodology for lead traces determination using rhodamine B as fluorophore and coacervation scheme: Application to lead quantification in e-cigarette refill liquids.

PubMed

Talio, María C; Zambrano, Karen; Kaplan, Marcos; Acosta, Mariano; Gil, Raúl A; Luconi, Marta O; Fernández, Liliana P

2015-10-01

A new environmental friendly methodology based on fluorescent signal enhancement of rhodamine B dye is proposed for Pb(II) traces quantification using a preconcentration step based on the coacervation phenomenon. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) and potassium iodine were chosen for this aim. The coacervate phase was collected on a filter paper disk and the solid surface fluorescence signal was determined in a spectrofluorometer. Experimental variables that influence on preconcentration step and fluorimetric sensitivity have been optimized using uni-variation assays. The calibration graph using zero th order regression was linear from 7.4×10(-4) to 3.4 μg L(-1) with a correlation coefficient of 0.999. Under the optimal conditions, a limit of detection of 2.2×10(-4) μg L(-1) and a limit of quantification of 7.4×10(-4) μg L(-1) were obtained. The method showed good sensitivity, adequate selectivity with good tolerance to foreign ions, and was applied to the determination of trace amounts of Pb(II) in refill solutions for e-cigarettes with satisfactory results validated by ICP-MS. The proposed method represents an innovative application of coacervation processes and of paper filters to solid surface fluorescence methodology. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrodialytic in-line preconcentration for ionic solute analysis.

PubMed

Ohira, Shin-Ichi; Yamasaki, Takayuki; Koda, Takumi; Kodama, Yuko; Toda, Kei

2018-04-01

Preconcentration is an effective way to improve analytical sensitivity. Many types of methods are used for enrichment of ionic solute analytes. However, current methods are batchwise and include procedures such as trapping and elution. In this manuscript, we propose in-line electrodialytic enrichment of ionic solutes. The method can enrich ionic solutes within seconds by quantitative transfer of analytes from the sample solution to the acceptor solution under an electric field. Because of quantitative ion transfer, the enrichment factor (the ratio of the concentration in the sample and to that in the obtained acceptor solution) only depends on the flow rate ratio of the sample solution to the acceptor solution. The ratios of the concentrations and flow rates are equal for ratios up to 70, 20, and 70 for the tested ionic solutes of inorganic cations, inorganic anions, and heavy metal ions, respectively. The sensitivity of ionic solute determinations is also improved based on the enrichment factor. The method can also simultaneously achieve matrix isolation and enrichment. The method was successively applied to determine the concentrations of trace amounts of chloroacetic acids in tap water. The regulated concentration levels cannot be determined by conventional high-performance liquid chromatography with ultraviolet detection (HPLC-UV) without enrichment. However, enrichment with the present method is effective for determination of tap water quality by improving the limits of detection of HPLC-UV. The standard addition test with real tap water samples shows good recoveries (94.9-109.6%). Copyright © 2017 Elsevier B.V. All rights reserved.

Electrolytic preconcentration in instrumental analysis.

PubMed

Sioda, R E; Batley, G E; Lund, W; Wang, J; Leach, S C

1986-05-01

The use of electrolytic deposition as a separation and preconcentration step in trace metal analysis is reviewed. Both the principles and applications of the technique are dealt with in some detail. Electrolytic preconcentration can be combined with a variety of instrumental techniques. Special attention is given to stripping voltammetry, potentiometric stripping analysis, different combinations with atomic-absorption spectrometry, and the use of flow-through porous electrodes. It is pointed out that the electrolytic preconcentration technique deserves more extensive use as well as fundamental investigation.

High throughput liquid absorption preconcentrator sampling instrument

DOEpatents

Zaromb, Solomon; Bozen, Ralph M.

1992-01-01

A system for detecting trace concentrations of an analyte in air includes a preconcentrator for the analyte and an analyte detector. The preconcentrator includes an elongated tubular container comprising a wettable material. The wettable material is continuously wetted with an analyte-sorbing liquid which flows from one part of the container to a lower end. Sampled air flows through the container in contact with the wetted material with a swirling motion which results in efficient transfer of analyte vapors or aerosol particles to the sorbing liquid and preconcentration of traces of analyte in the liquid. The preconcentrated traces of analyte may be either detected within the container or removed therefrom for injection into a separate detection means or for subsequent analysis.

High throughput liquid absorption preconcentrator sampling instrument

DOEpatents

Zaromb, S.; Bozen, R.M.

1992-12-22

A system for detecting trace concentrations of an analyte in air includes a preconcentrator for the analyte and an analyte detector. The preconcentrator includes an elongated tubular container comprising a wettable material. The wettable material is continuously wetted with an analyte-sorbing liquid which flows from one part of the container to a lower end. Sampled air flows through the container in contact with the wetted material with a swirling motion which results in efficient transfer of analyte vapors or aerosol particles to the sorbing liquid and preconcentration of traces of analyte in the liquid. The preconcentrated traces of analyte may be either detected within the container or removed therefrom for injection into a separate detection means or for subsequent analysis. 12 figs.

Design and Analysis of a Preconcentrator for the ChemLab

DOE Office of Scientific and Technical Information (OSTI.GOV)

WONG,CHUNGNIN C.; FLEMMING,JEB H.; MANGINELL,RONALD P.

2000-07-17

Preconcentration is a critical analytical procedure when designing a microsystem for trace chemical detection, because it can purify a sample mixture and boost the small analyte concentration to a much higher level allowing a better analysis. This paper describes the development of a micro-fabricated planar preconcentrator for the {mu}ChemLab{trademark} at Sandia. To guide the design, an analytical model to predict the analyte transport, adsorption and resorption process in the preconcentrator has been developed. Experiments have also been conducted to analyze the adsorption and resorption process and to validate the model. This combined effort of modeling, simulation, and testing has ledmore » us to build a reliable, efficient preconcentrator with good performance.« less

Simultaneous determination of nickel and copper by H-point standard addition method-first-order derivative spectrophotometry in plant samples after separation and preconcentration on modified natural clinoptilolite as a new sorbent.

PubMed

Roohparvar, Rasool; Taher, Mohammad Ali; Mohadesi, Alireza

2008-01-01

For the simultaneous determination of nickel(ll) and copper(ll) in plant samples, a rapid and accurate method was developed. In this method, solid-phase extraction (SPE) and first-order derivative spectrophotometry (FDS) are combined, and the result is coupled with the H-point standard addition method (HPSAM). Compared with normal spectrophotometry, derivative spectrophotometry offers the advantages of increased selectivity and sensitivity. As there is no need for carrying out any pretreatment of the sample, the spectrophotometry method is easy, but because of a high detection limit, it is not so practical. In order to decrease the detection limit, it is suggested to combine spectrophotometry with a preconcentration method such as SPE. In the present work, after separation and preconcentration of Ni(ll) and Cu(ll) on modified clinoptilolite zeolite that is loaded with 2-[1-(2-hydroxy-5-sulforphenyl)-3-phenyl-5-formaza-no]-benzoic acid monosodium salt (zincon) as a selective chromogenic reagent, FDS-HPSAM, which is a simple and selective spectrophotometric method, has been applied for simultaneous determination of these ions. With optimum conditions, the detection limit in original solutions is 0.7 and 0.5 ng/mL, respectively, for nickel and copper. The linear concentration ranges in the proposed method for nickel and copper ions in original solutions are 1.1 to 3.0 x 10(3) and 0.9 to 2.0 x 10(3) ng/mL, respectively. The recommended procedure is applied to successful determination of Cu(ll) and Ni(ll) in standard and real samples.

A preconcentration method for indirect determination of acrylamide from chips, crackers and cereal-based baby foods using flame atomic absorption spectrometry.

PubMed

Altunay, Nail; Gürkan, Ramazan; Orhan, Ulaş

2016-12-01

Acrylamide is a toxic species for human health, and is a Maillard reaction product which forms spontaneously in heat treatment process of foods. Therefore, a simple, fast and cost-effective method was developed for the indirect determination of acrylamide in processed foods particularly consumed by children. The method is based on ion-pairing of acrylamide with fluorescein (F 2- ) in presence of Ni(II) ions at pH 9.0, and then extraction of the formed ternary complex into micellar phase of poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) before analysis by flame atomic absorption spectrometry (FAAS). The ultrasonic-assisted cloud point extraction (UA-CPE) has been used for the preconcentration of acrylamide in the samples prior to its FAAS detection. The matrix matched calibration curve is linear in range of 0.3-150µgkg -1 under optimal reagent conditions (1.75mL of 0.1molL -1 ammonia buffer at pH 9.0, 2.2mgL -1 Ni(II), 4.0×10 -4 molL -1 F 2- , 0.4% (w/v) NH 4 Cl and 0.7% (v/v) PONPE 7.5) with sensitivity enhancement of 160-fold. The proposed method has been validated by assessment of the following parameters; the limits of detection (LOD) and quantification (LOQ) (0.08µgkg -1 and 0.28µgkg -1 , respectively) with a relative standard deviation (RSD%) lower than 6.3%, and extractive recovery higher than 95% for acrylamide spiked at levels of 5 and 25µgkg -1 . The method was successfully applied to the indirect determination of acrylamide in the processed foods and two CRMs with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

Dispersive solid phase microextraction with magnetic graphene oxide as the sorbent for separation and preconcentration of ultra-trace amounts of gold ions.

PubMed

Kazemi, Elahe; Dadfarnia, Shayessteh; Haji Shabani, Ali Mohammad

2015-08-15

A selective, simple and rapid dispersive solid phase microextraction was developed using magnetic graphene oxide (MGO) as an efficient sorbent for the separation and preconcentration of gold ions. The MGO was synthesized by means of the simple one step chemical coprecipitation method, characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Gold ions retained by the sorbent were eluted using 0.5mol L(-)(1) thiourea in 0.1mol L(-1) HCl solution and determined by the flow injection flame atomic absorption spectrometry (FI-FAAS). The factors affecting the separation and preconcentration of gold were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0.02-100.0µg L(-)(1) with a detection limit of 4ng L(-1) and an enrichment factor of 500. The relative standard deviations of 3.2% and 4.7% (n=6) were obtained at 20µg L(-1) level of gold ions for the intra and the inter day analysis, respectively. The method was successfully applied to the determination of gold ions in water and waste water samples as well as a certified reference material (CCU-1b, copper flotation concentrate). Copyright © 2015 Elsevier B.V. All rights reserved.

Adsorption and preconcentration of divalent metal ions in fossil fuels and biofuels: gasoline, diesel, biodiesel, diesel-like and ethanol by using chitosan microspheres and thermodynamic approach.

PubMed

Prado, Alexandre G S; Pescara, Igor C; Evangelista, Sheila M; Holanda, Matheus S; Andrade, Romulo D; Suarez, Paulo A Z; Zara, Luiz F

2011-05-15

Biodiesel and diesel-like have been obtained from soybean oil by transesterification and thermal cracking process, respectively. These biofuels were characterized as according to ANP standards by using specific ASTM methods. Ethanol, gasoline, and diesel were purchased from a gas station. Deacetylation degree of chitosan was determined by three distinct methods (conductimetry, FTIR and NMR), and the average degree was 78.95%. The chitosan microspheres were prepared from chitosan by split-coating and these spheres were crosslinked using glutaraldehyde. The surface area of microspheres was determined by BET method, and the surface area of crosslinked microspheres was 9.2m(2)g(-1). The adsorption isotherms of cooper, nickel and zinc on microspheres of chitosan were determined in petroleum derivatives (gasoline and diesel oil), as well as in biofuels (alcohol, biodiesel and diesel-like). The adsorption order in all fuels was: Cu>Ni>Zn. The elution tests presented the following preconcentration degrees: >4.5 to ethanol, >4.4 to gasoline, >4.0 to diesel, >3.8 to biodiesel and >3.6 to diesel-like. The application of chitosan microspheres in the metal ions preconcentration showed the potential of this biopolymer to enrich fuel sample in order to be analyzed by flame atomic absorption spectrometry. Copyright © 2011 Elsevier B.V. All rights reserved.

Spectrophotometric determination of low levels arsenic species in beverages after ion-pairing vortex-assisted cloud-point extraction with acridine red.

PubMed

Altunay, Nail; Gürkan, Ramazan; Kır, Ufuk

2016-01-01

A new, low-cost, micellar-sensitive and selective spectrophotometric method was developed for the determination of inorganic arsenic (As) species in beverage samples. Vortex-assisted cloud-point extraction (VA-CPE) was used for the efficient pre-concentration of As(V) in the selected samples. The method is based on selective and sensitive ion-pairing of As(V) with acridine red (ARH(+)) in the presence of pyrogallol and sequential extraction into the micellar phase of Triton X-45 at pH 6.0. Under the optimised conditions, the calibration curve was highly linear in the range of 0.8-280 µg l(-1) for As(V). The limits of detection and quantification of the method were 0.25 and 0.83 µg l(-1), respectively. The method was successfully applied to the determination of trace As in the pre-treated and digested samples under microwave and ultrasonic power. As(V) and total As levels in the samples were spectrophotometrically determined after pre-concentration with VA-CPE at 494 nm before and after oxidation with acidic KMnO4. The As(III) levels were calculated from the difference between As(V) and total As levels. The accuracy of the method was demonstrated by analysis of two certified reference materials (CRMs) where the measured values for As were statistically within the 95% confidence limit for the certified values.

A Simple and Fast Method Based on New Magnetic Ion Imprinted Polymer as a Highly Selective Sorbent for Preconcentration and Determination of Cadmium in Environmental Samples

PubMed Central

PANJALI, Zahra; ASGHARINEZHAD, Ali Akbar; EBRAHIMZADEH, Homeira; JALILIAN, Niloofar; YARAHMADI, Rasoul; SHAHTAHERI, Seyed Jamaleddin

2016-01-01

Background: The analysis of heavy metals at trace level is one of the main toxicologists concern, due to their vital rules in human`s life. Cadmium is one of these toxic heavy metals, which released to the environment from various industries. Methods: In order to determine Cd (II) ions in various matrices magnetic ion-imprinted polymer (IIP) method has been developed and applied. This nano-sorbent has been synthesized by coating an IIP compound on Fe3O4 nanoparticles core to achieve highest surface area. This polymer has been used to evaluate Cd (II) levels in food, river, and wastewater in Tehran, Iran. Results: Fe3O4@Cd-IIP was stable up to 300 °C. The various factors such as sample pH (optimized as 7), elution/sorption time (5 min), eluent amount (4 mL HCL), and its concentration (2 mol L−1) were optimized. Analysis instrument in all steps was Flame Atomic Abortion Spectrophotometer (FAAS). In this study, the detection limit was determined down to 0.6 μg L−1. Conclusion: This method was applied successfully for the preconcentration and determination of Cd (II) ions in environmental samples obtained from rivers, various foods and wastewater. In addition, the accuracy of the method was confirmed by analyzing a certified reference material (Seronorm LOT NO2525) and spiked real samples. PMID:27928531

A fully-integrated aptamer-based affinity assay platform for monitoring astronaut health in space.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xianbin; Durland, Ross H.; Hecht, Ariel H.

2010-07-01

Here we demonstrate the suitability of robust nucleic acid affinity reagents in an integrated point-of-care diagnostic platform for monitoring proteomic biomarkers indicative of astronaut health in spaceflight applications. A model thioaptamer targeting nuclear factor-kappa B (NF-{kappa}B) is evaluated in an on-chip electrophoretic gel-shift assay for human serum. Key steps of (i) mixing sample with the aptamer, (ii) buffer exchange, and (iii) preconcentration of sample were successfully integrated upstream of fluorescence-based detection. Challenges due to (i) nonspecific interactions with serum, and (ii) preconcentration at a nanoporous membrane are discussed and successfully resolved to yield a robust, rapid, and fully-integrated diagnostic system.

On-line preconcentration and speciation of arsenic by flow injection hydride generation atomic absorption spectrophotometry.

PubMed

Narcise, Cristine Ingrid S; Coo, Lilibeth Dlc; Del Mundo, Florian R

2005-12-15

A flow injection-column preconcentration-hydride generation atomic absorption spectrophotometric (FI-column-HGAAS) method was developed for determining mug/l levels of As(III) and As(V) in water samples, with simultaneous preconcentration and speciation. The speciation scheme involved determining As(V) at neutral pH and As(III+V) at pH 12, with As(III) obtained by difference. The enrichment factor (EF) increased with increase in sample loading volume from 2.5 to 10ml, and for preconcentration using the chloride-form anion exchange column, EFs ranged from 5 to 48 for As(V) and 4 to 24 for As(III+V), with corresponding detection limits of 0.03-0.3 and 0.07-0.3mug/l. Linear concentration range (LCR) also varied with sample loading volume, and for a 5-ml sample was 0.3-5 and 0.2-8mug/l for As(V) and As(III+V), respectively. Sample throughput, which decreased with increase in sample volume, was 8-17 samples/h. For the hydroxide-form column, the EFS for 2.5-10ml samples were 3-23 for As(V) and 2-15 for As(III+V), with corresponding detection limits of 0.07-0.4 and 0.1-0.5mug/l. The LCR for a 5-ml sample was 0.3-10mug/l for As(V) and 0.2-20mug/l for As(III+V). Sample throughput was 10-20 samples/h. The developed method has been effectively applied to tap water and mineral water samples, with recoveries ranging from 90 to 102% for 5-ml samples passed through the two columns.

Determination of fluorine in herbs and water samples by molecular absorption spectrometry after preconcentration on nano-TiO2 using ultrasound-assisted dispersive micro solid phase extraction.

PubMed

Krawczyk-Coda, Magdalena; Stanisz, Ewa

2017-11-01

This work presents ultrasound-assisted dispersive micro solid phase extraction (USA DMSPE) for preconcentration of fluorine (F) in water and herb samples. TiO 2 nanoparticles (NPs) were used as an adsorbent. The determination with slurry sampling was performed via molecular absorption of calcium monofluoride (CaF) at 606.440 nm using a high-resolution continuum source electrothermal absorption spectrometry (HR-CS ET MAS). Several factors influencing the efficiency of the preconcentration technique, such as the amount of TiO 2 , pH of sample solution, ultrasonication and centrifugation time and TiO 2 slurry solution preparation before injection to HR-CS ET MAS, were investigated in detail. The conditions of detection step (wavelength, calcium amount, pyrolysis and molecule-forming temperatures) were also studied. After extraction, adsorbent with the analyte was mixed with 200 μL of H 2 O to prepare a slurry solution. The concentration limit of detection was 0.13 ng mL -1 . The achieved preconcentration factor was 7. The relative standard deviations (RSDs, %) for F in real samples were 3-15%. The accuracy of this method was evaluated by analyses of certified reference materials after spiking: INCT-MPH-2 (Mixed Polish Herbs), INCT-SBF-4 (Soya Bean Flour), ERM-CAO11b (Hard Drinking Water) and TMDA-54.5 (Lake Ontario Water). The measured F contents in reference materials were in satisfactory agreement with the added amounts, and the recoveries were found to be 97-109%. Under the developed extraction conditions, the proposed method has been successfully applied for the determination of F in real water samples (lake, sea, tap water) and herbs.

Non-planar chemical preconcentrator

DOEpatents

Manginell, Ronald P [Albuquerque, NM; Adkins, Douglas R [Albuquerque, NM; Sokolowski, Sara S [Albuquerque, NM; Lewis, Patrick R [Albuquerque, NM

2006-10-10

A non-planar chemical preconcentrator comprises a high-surface area, low mass, three-dimensional, flow-through sorption support structure that can be coated or packed with a sorptive material. The sorptive material can collect and concentrate a chemical analyte from a fluid stream and rapidly release it as a very narrow temporal plug for improved separations in a microanalytical system. The non-planar chemical preconcentrator retains most of the thermal and fabrication benefits of a planar preconcentrator, but has improved ruggedness and uptake, while reducing sorptive coating concerns and extending the range of collectible analytes.

Odor Sensing System Using Preconcentrator with Variable Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaka, Y; Nakamoto, Takamichi; Moriizumi, T

1999-01-01

An odor sensing system using QCM gas sensor array and pattern recognition technique is useful to identify various kinds of odors. A preconcentrator with variable temperature is promising to obtain further pattern separation after the appropriate temperature changes, whereas it has been so far used to enhance sensor sensitivity. After the preconcentrator collects the vapors, it is heated so that they can be thermally desorbed. The combination of the preconcentrator with the sensor array enhances the capability of discrimination among vapors since their desorption temperatures depend upon vapor kinds.

Chemical preconcentrator with integral thermal flow sensor

DOEpatents

Manginell, Ronald P.; Frye-Mason, Gregory C.

2003-01-01

A chemical preconcentrator with integral thermal flow sensor can be used to accurately measure fluid flow rate in a microanalytical system. The thermal flow sensor can be operated in either constant temperature or constant power mode and variants thereof. The chemical preconcentrator with integral thermal flow sensor can be fabricated with the same MEMS technology as the rest of the microanlaytical system. Because of its low heat capacity, low-loss, and small size, the chemical preconcentrator with integral thermal flow sensor is fast and efficient enough to be used in battery-powered, portable microanalytical systems.

Preconcentration of Zn2+ and Cu2+ ions from food and vegetable samples using modified activated carbon.

PubMed

Ghaedi, M; Tavallali, H; Montazerozohori, M; Zahedi, E; Amirineko, M; Khodadoust, S; Karimipour, G

2012-11-01

In this work, two N/S-containing chelating agents 2-(4-methoxybenzylideneamino)thiophenol (2-4-MBAT) and 2-(4-chlorobenzylideneamino) benzenethiol (2-4-CBABT) were synthesized as new sorbents and were used for preconcentration of Zn(2+) and Cu(2+) ions in food and vegetable samples. In the proposed procedure, the trace amount of Zn(2+) and Cu(2+) ions from 250 mL of sample solution at pH = 5.0 was preconcentrated by 1 g of activated carbon (AC) loaded with 15 mg of 2-4-MBAT and 2-4-CBABT separately. The breakthrough volumes (maximum sample volume that their metal ions quantitatively can be enriched) for solid-phase extraction (SPE) procedure based on the AC modified with 2-4-MBAT and 2-4-CBABT were 800 and 750 mL, respectively. The sorbed Zn(2+) and Cu(2+) ions were efficiently eluted by 8 mL of 4 mol L(-1) HNO(3) and preconcentration factor of 112.5 and 93.7 and experimental enhancement factor of 30 and 35 ions were obtained for Zn(2+) and Cu(2+), respectively. The application of this enrichment procedure allowed the extraction of trace metal ions with recoveries exceeding of 90%.

Single-step enantioselective amino acid flux analysis by capillary electrophoresis using on-line sample preconcentration with chemical derivatization.

PubMed

Ptolemy, Adam S; Tran, Lara; Britz-McKibbin, Philip

2006-07-15

Capillary electrophoresis (CE) represents a versatile platform for integrating sample pretreatment with chemical analysis because of its ability to tune analyte electromigration and band dispersion properties in discontinuous electrolyte systems. In this article, a single-step method that combines on-line sample preconcentration with in-capillary chemical derivatization is developed for rapid, sensitive, and enantioselective analysis of micromolar levels of amino acids that lack intrinsic chromophores by CE with UV detection. Time-resolved electrophoretic studies revealed two distinct stages of amino acid band narrowing within the original long sample injection plug occurring both prior to and after in-capillary labeling via zone passing by ortho-phthalaldehyde/N-acetyl l-cysteine (OPA/NAC). This technique enabled direct analysis of d-amino acids in a 95% enantiomeric excess mixture with sub-micromolar detection limits and minimal sample handling, where the capillary functions as a preconcentrator, microreactor, and chiral selector. On-line sample preconcentration with chemical derivatization CE (SPCD-CE) was applied to study the enantioselective amino acid flux in Escherichia coli bacteria cultures, which demonstrated a unique l-Ala efflux into the extracellular medium. New strategies for high-throughput analyses of low-abundance metabolites are important for understanding fundamental physiological processes in bacteria required for screening the efficacy of new classes of antibiotics as well as altered metabolism in genetically modified mutant strains.

Determination of alkenylbenzenes and related flavour compounds in food samples by on-column preconcentration-capillary liquid chromatography.

PubMed

Avila, Mónica; Zougagh, Mohammed; Escarpa, Alberto; Ríos, Angel

2009-10-23

A new, simple and versatile method is presented for the determination of different concentration levels of alkenylbenzenes (eugenol, isoeugenol, eugenol methyl ether, myristicin, anethole and estragole) and the related flavour compounds (coumarin and pulegone) in food samples. The method involves the use of a stationary phase (capillary column) for the enrichment with appropriate elution. After the sample had completely passed through the capillary column the eluent was changed and the separation/detection was achieved. Excellent linearity was obtained under the proposed conditions for a direct determination method and a method including on-line preconcentration. The limits of detection were in the ranges 97-148 and 9.5-14.2 ng/mL, respectively. Evidence for a matrix effect was not found and recoveries between 92 and 110% were obtained. The precision of the method, expressed as relative standard deviation values, was below 5% in all cases. The applicability of this methodology was tested by analyzing synthetic and real food samples.

Electroanalytical method for determination of lead(II) in orange and apple using kaolin modified platinum electrode.

PubMed

El Mhammedi, M A; Achak, M; Bakasse, M; Chtaini, A

2009-08-01

This paper reports on the use of platinum electrode modified with kaolin (K/Pt) and square wave voltammetry for analytical detection of trace lead(II) in pure water, orange and apple samples. The electroanalytical procedure for determination of the Pb(II) comprises two steps: the chemical accumulation of the analyte under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using square wave voltammetry. The analytical performances of the extraction method has been explored by studying the incubating time, and effect of interferences due to other ions. During the preconcentration step, Pb(II) was accumulated on the surface of the kaolin. The observed detection and quantification limits in pure water were 3.6x10(-9)molL(-1) and 1.2x10(-8)molL(-1), respectively. The precision of the method was also determined; the results was 2.35% (n=5).

Preconcentration for Improved Long-Term Monitoring of Contaminants in Groundwater: Sorbent Development

DTIC Science & Technology

2013-02-11

calibration curves was ±5%. Ion chromatography (IC) was used for analysis of perchlorate and other ionic targets. Analysis was carried out on a...The methods utilize liquid or gas chromatography , techniques that do not lend themselves well to portable devices and methods. Portable methods are...

Simultaneous preconcentrations of Co(2+), Cr(6+), Hg(2+) and Pb(2+) ions by Bacillus altitudinis immobilized nanodiamond prior to their determinations in food samples by ICP-OES.

PubMed

Ozdemir, Sadin; Kilinc, Ersin; Celik, Kadir Serdar; Okumus, Veysi; Soylak, Mustafa

2017-01-15

A novel solid phase extraction method was developed for simultaneous preconcentration-separation of Co(2+), Cr(6+), Hg(2+) and Pb(2+) ions prior to their determinations in food samples by ICP-OES. Thermophilic Bacillus altitudinis immobilized nanodiamond was used as a new biosorbent. SEM and FT-IR analysis were studied to characterize the biosorbent. The optimum pH values of quantitative biosorption for Co(2+), Cr(6+), Hg(2+) and Pb(2+) were found to be 5.0, 6.0, 6.0 and 6.0, respectively. A flow rate of 3.0mLmin(-1) was selected as optimum for all metal ions. 5mL of 1mol/L HCl was used as eluent. Preconcentration factor was achieved as 80. LODs were calculated as 0.071, 0.023, 0.016 and 0.034ngmL(-1), respectively for Hg(2+), Co(2+), Cr(6+) and Pb(2+). The biosorption capacities were calculated for Co(2+), Cr(6+), Hg(2+) and Pb(2+) as 26.4, 30.4, 19.5, and 35.2mg/g, respectively. The developed method was successfully applied to food samples to determine analyte concentrations. Copyright © 2016. Published by Elsevier Ltd.

Application of dual-cloud point extraction for the trace levels of copper in serum of different viral hepatitis patients by flame atomic absorption spectrometry: A multivariate study

NASA Astrophysics Data System (ADS)

Arain, Salma Aslam; Kazi, Tasneem G.; Afridi, Hassan Imran; Abbasi, Abdul Rasool; Panhwar, Abdul Haleem; Naeemullah; Shanker, Bhawani; Arain, Mohammad Balal

2014-12-01

An efficient, innovative preconcentration method, dual-cloud point extraction (d-CPE) has been developed for the extraction and preconcentration of copper (Cu2+) in serum samples of different viral hepatitis patients prior to couple with flame atomic absorption spectrometry (FAAS). The d-CPE procedure was based on forming complexes of elemental ions with complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN), and subsequent entrapping the complexes in nonionic surfactant (Triton X-114). Then the surfactant rich phase containing the metal complexes was treated with aqueous nitric acid solution, and metal ions were back extracted into the aqueous phase, as second cloud point extraction stage, and finally determined by flame atomic absorption spectrometry using conventional nebulization. The multivariate strategy was applied to estimate the optimum values of experimental variables for the recovery of Cu2+ using d-CPE. In optimum experimental conditions, the limit of detection and the enrichment factor were 0.046 μg L-1 and 78, respectively. The validity and accuracy of proposed method were checked by analysis of Cu2+ in certified sample of serum (CRM) by d-CPE and conventional CPE procedure on same CRM. The proposed method was successfully applied to the determination of Cu2+ in serum samples of different viral hepatitis patients and healthy controls.

Graphene oxide-based dispersive micro-solid phase extraction for separation and preconcentration of nicotine from biological and environmental water samples followed by gas chromatography-flame ionization detection.

PubMed

Mahpishanian, Shokouh; Sereshti, Hassan

2014-12-01

Graphene oxide (GO) has showed great potential to use as an adsorbent in sample preparation procedures. In this research, GO was used as an effective adsorbent in a simple GO-based dispersive micro-solid phase extraction (GO-D-µ-SPE) method for isolation and preconcentration of nicotine prior to gas chromatography-flame ionization detection (GC-FID). The prepared GO was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermogravimetric analysis/differential thermal analysis (TGA/DTA), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques. Various experimental parameters affecting the extraction recovery, including the amount of GO, extraction time, pH of the sample solution, salt concentration, and desorption conditions were investigated and optimized. Under the optimized conditions, a linear response was obtained in the concentration range of 5-2000 ng mL(-1) with a determination coefficient of 0.9987. The limit of detection (LOD) of the method at a signal to noise ratio of 3 was 1.5 ng mL(-1). The linearity was in the concentration range of 5-2000 ng mL(-1) with a determination coefficient of 0.9987. Intraday and inter-day precisions were obtained equal to 2.7% and 5.2%, respectively. The method was successfully applied to the nicotine analysis in biological and water samples with the recoveries in the range of 88.7-109.7%. Copyright © 2014 Elsevier B.V. All rights reserved.

Preconcentration and determination of rare-earth elements in iron-rich water samples by extraction chromatography and plasma source mass spectrometry (ICP-MS).

PubMed

Hernández González, Carolina; Cabezas, Alberto J Quejido; Díaz, Marta Fernández

2005-11-15

A 100-fold preconcentration procedure based on rare-earth elements (REEs) separation from water samples with an extraction chromatographic column has been developed. The separation of REEs from matrix elements (mainly Fe, alkaline and alkaline-earth elements) in water samples was performed loading the samples, previously acidified to pH 2.0 with HNO(3), in a 2ml column preconditioned with 20ml 0.01M HNO(3). Subsequently, REEs were quantitatively eluted with 20ml 7M HNO(3). This solution was evaporated to dryness and the final residue was dissolved in 10ml 2% HNO(3) containing 1mugl(-1) of cesium used as internal standard. The solution was directly analysed by inductively coupled plasma mass spectrometry (ICP-MS), using ultrasonic nebulization, obtaining quantification limits ranging from 0.05 to 0.10 ngl(-1). The proposed method has been applied to granitic waters running through fracture fillings coated by iron and manganese oxy-hydroxides in the area of the Ratones (Cáceres, Spain) old uranium mine.

Application of dispersive liquid-liquid microextraction coupled with vortex-assisted hydrophobic magnetic nanoparticles based solid-phase extraction for determination of aflatoxin M1 in milk samples by sensitive micelle enhanced spectrofluorimetry.

PubMed

Amoli-Diva, Mitra; Taherimaslak, Zohreh; Allahyari, Mehdi; Pourghazi, Kamyar; Manafi, Mohammad Hanif

2015-03-01

An efficient, simple and fast low-density solvent based dispersive liquid-liquid microextraction (LDS-DLLME) followed by vortex-assisted dispersive solid phase extraction (VA-D-SPE) has been developed as a new approach for extraction and preconcentration of aflatoxin M1 in milk samples prior to its micelle enhanced spectrofluorimetic determination. In this LDS-DLLME coupled VA-D-SPE method, milk samples were first treated with methanol/water (80:20, v/v) after removing the fat layer. This solvent was directly used as the dispersing solvent in DLLME along with using 1-heptanol (as a low-density solvent with respect to water) as the extracting solvent. In VA-D-SPE approach, hydrophobic oleic acid modified Fe3O4 nanoparticles were used to retrieve the analyte from the DLLME step. It is considerably that the target of VA-D-SPE was 1-heptanol rather than the aflatoxin M1 directly. The main parameters affecting the efficiency of LDS-DLLME and VA-D-SPE procedures and signal enhancement of aflatoxin M1 were investigated and optimized. Under the optimum conditions, the method was linear in the range from 0.02 to 200 µg L(-1) with the correlation coefficient (R(2)) of 0.9989 and detection limit of 13 ng L(-1). The intra-day precision was 2.9 and 4.3% and the inter-day precision was 2.1 and 3.3% for concentration of 2 and 50 µg L(-1) respectively. The developed method was applied for extraction and preconcentration of AFM1 in three commercially available milk samples and the results were compared with the official AOAC method. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation and application of a tyre-based activated carbon solid phase extraction of heavy metals in wastewater samples

NASA Astrophysics Data System (ADS)

Dimpe, K. Mogolodi; Ngila, J. C.; Nomngongo, Philiswa N.

2018-06-01

In this paper, the tyre-based activated carbon solid phase extraction (SPE) method was successfully developed for simultaneous preconcentration of metal ions in the model and real water samples before their determination using flame atomic absorption spectrometry (FAAS). The activation of carbon was achieved by chemical activation and the tyre-based activated carbon was used as a sorbent for solid phase extraction. The prepared activated carbon was characterized using the scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), and Fourier Transform Infrared spectroscopy. Moreover, optimization of the proposed method was performed by the two-level full factorial design (FFD). The FFD was chosen in order to fully investigate the effect of the experimental variables (pH, eluent concentration and sample flow rate) that significantly influence the preconcentration procedure. In this model, individual factors are considered along with their interactions. In addition, modelling of the experiments allowed simultaneous variation of all experimental factors investigated, reduced the required time and number of experimental runs which consequently led to the reduction of the overall required costs. Under optimized conditions, the limits of detection and quantification (LOD and LOQ) ranged 0.66-2.12 μg L-1and 1.78-5.34 μg L-1, respectively and the enrichment factor of 25 was obtained. The developed SPE/FAAS method was validated using CWW-TM-A and CWW-TM-B wastewater standard reference materials (SRMs). The procedure showed to be accurate with satisfactory recoveries ranging from 92 to 99%. The precision (repeatability) was lower than 4% in terms of the relative standard deviation (%RSD). The developed method proved to have the capability to be used in routine analysis of heavy metals in domestic and industrial wastewater samples. In addition, the developed method can be used as a final step (before being discharged to the rivers) in wastewater treatment process in order to keep our water bodies free from toxic metals.

Highly Sensitive Aluminium(III) Ion Sensor Based on a Self-assembled Monolayer on a Gold Nanoparticles Modified Screen-printed Carbon Electrode.

PubMed

See, Wong Pooi; Heng, Lee Yook; Nathan, Sheila

2015-01-01

A new approach for the development of a highly sensitive aluminium(III) ion sensor via the preconcentration of aluminium(III) ion with a self-assembled monolayer on a gold nanoparticles modified screen-printed carbon electrode and current mediation by potassium ferricyanide redox behavior during aluminium(III) ion binding has been attempted. A monolayer of mercaptosuccinic acid served as an effective complexation ligand for the preconcentration of trace aluminium; this led to an enhancement of aluminium(III) ion capture and thus improved the sensitivity of the sensor with a detection limit of down to the ppb level. Under the optimum experimental conditions, the sensor exhibited a wide linear dynamic range from 0.041 to 12.4 μM. The lower detection limit of the developed sensor was 0.037 μM (8.90 ppb) using a 10 min preconcentration time. The sensor showed excellent selectivity towards aluminium(III) ion over other interference ions.

Determination of bentazone, dichlorprop, and MCPA in different soils by sodium hydroxide extraction in combination with solid-phase preconcentration.

PubMed

Thorstensen, C W; Christiansen, A

2001-09-01

A method for the extraction of bentazone, dichlorprop, and MCPA in three selected Norwegian soils of different textures is described. Initially three different extraction methods were tested on one soil type. All methods gave recoveries >80% for the pesticide mixture, but extraction with sodium hydroxide in combination with solid-phase preconcentration was used for further recovery tests with soils of different properties spiked at four herbicide concentration levels (0.001-10 microg/g of wet soil). The method was rapid and easy and required a minimum of organic solvents. The recoveries were in the range of 82-109, 80-123, and 45-91% for the soils containing 1.4 (Hole), 2.5 (Kroer), and 37.8% (Froland) organic carbon, respectively. Limits of quantification using GC-MS were 0.0003 microg/g of wet soil for bentazone and 0.0001 microg/g of wet soil for both dichlorprop and MCPA.

Ionic liquid-based dispersive liquid-liquid microextraction with back-extraction coupled with capillary electrophoresis to determine phenolic compounds.

PubMed

Zhou, Caihong; Tong, Shanshan; Chang, Yunxia; Jia, Qiong; Zhou, Weihong

2012-04-01

Ionic liquid (IL) based dispersive liquid-liquid microextraction (DLLME) with back-extraction coupled with capillary electrophoresis ultraviolet detection was developed to determine four phenolic compounds (bisphenol-A, β-naphthol, α-naphthol, 2, 4-dichlorophenol) in aqueous cosmetics. The developed method was used to preconcentrate and clean up the four phenolic compounds including two steps. The analytes were transferred into room temperature ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate, [C(8) MIM][PF(6) ]) rich-phase in the first step. In the second step, the analytes were back-extracted into the alkaline aqueous phase. The effects of extraction parameters, such as type and volume of extraction solvent, type and volume of disperser, extraction and centrifugal time, sample pH, salt addition, and concentration and volume of NaOH in back-extraction were investigated. Under the optimal experimental conditions, the preconcentration factors were 60.1 for bisphenol-A, 52.7 for β-naphthol, 49.2 for α-naphthol, and 18.0 for 2, 4-dichlorophenol. The limits of detection for bisphenol-A, β-naphthol, α-naphthol and 2, 4-dichlorophenol were 5, 5, 8, and 100 ng mL(-1), respectively. Four kinds of aqueous cosmetics including toner, soften lotion, make-up remover, and perfume were analyzed and yielded recoveries ranging from 81.6% to 119.4%. The main advantages of the proposed method are quick, easy, cheap, and effective. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of metal ions in tea samples using task-specific ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction coupled to liquid chromatography with ultraviolet detection.

PubMed

Werner, Justyna

2016-04-01

Task-specific ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction was used for the preconcentration of cadmium(II), cobalt(II), and lead(II) ions in tea samples, which were subsequently analyzed by liquid chromatography with UV detection. The proposed method of preconcentration is free of volatile organic compounds, which are often used as extractants and dispersing solvents in classic techniques of microextraction. A task-specific ionic liquid trioctylmethylammonium thiosalicylate was used as an extractant and a chelating agent. Ultrasound was used to disperse the ionic liquid. After microextraction, the phases were separated by centrifugation, and the ionic liquid phase was solubilized in methanol and directly injected into the liquid chromatograph. Selected microextraction parameters, such as the volume of ionic liquid, the pH of the sample, the duration of ultrasound treatment, the speed and time of centrifugation, and the effect of ionic strength, were optimized. Under optimal conditions an enrichment factor of 200 was obtained for each analyte. The limits of detection were 0.002 mg/kg for Cd(II), 0.009 mg/kg for Co(II), and 0.013 mg/kg for Pb(II). The accuracy of the proposed method was evaluated by an analysis of the Certified Reference Materials (INCT-TL-1, INCT-MPH-2) with the recovery values in the range of 90-104%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature-controlled ionic liquid-based ultrasound-assisted microextraction for preconcentration of trace quantity of cadmium and nickel by using organic ligand in artificial saliva extract of smokeless tobacco products

NASA Astrophysics Data System (ADS)

Arain, Sadaf Sadia; Kazi, Tasneem Gul; Arain, Asma Jabeen; Afridi, Hassan Imran; Baig, Jameel Ahmed; Brahman, Kapil Dev; Naeemullah; Arain, Salma Aslam

2015-03-01

A new approach was developed for the preconcentration of cadmium (Cd) and nickel (Ni) in artificial saliva extract of dry snuff (brown and black) products using temperature-controlled ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction (TIL-UDLLμE) followed by electrothermal atomic absorption spectrometry (ETAAS). The Cd and Ni were complexed with ammonium pyrrolidinedithiocarbamate (APDC), extracted in ionic liquid drops, 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6]. The multivariate strategy was applied to estimate the optimum values of experimental variables influence the % recovery of analytes by TIL-UDLLμE method. At optimum experimental conditions, the limit of detection (3s) were 0.05 and 0.14 μg L-1 while relative standard deviations (% RSD) were 3.97 and 3.55 for Cd and Ni respectively. After extraction, the enhancement factors (EF) were 87 and 79 for Cd and Ni, respectively. The RSD for six replicates of 10 μg L-1 Cd and Ni were 3.97% and 3.55% respectively. To validate the proposed method, certified reference material (CRM) of Virginia tobacco leaves was analyzed, and the determined values of Cd and Ni were in good agreement with the certified values. The concentration of Cd and Ni in artificial saliva extracts corresponds to 39-52% and 21-32%, respectively, of the total contents of both elements in dry brown and black snuff products.

1-(2-Formamidoethyl)-3-phenylurea functionalized activated carbon for selective solid-phase extraction and preconcentration of metal ions.

PubMed

Tu, Zhifeng; He, Qun; Chang, Xijun; Hu, Zheng; Gao, Ru; Zhang, Lina; Li, Zhenhua

2009-09-07

A novel method that utilizes 1-(2-formamidoethyl)-3-phenylurea-modified activated carbon (AC-1-(2-formamidoethyl)-3-phenylurea) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace levels of Cr(III), Cu(II), Fe(III) and Pb(II) were optimized using batch and column procedures in detail. The optimum pH value for the separation of metal ions simultaneously on the new sorbent was 4. And the adsorbed metal ions could be completely eluted by using 2.0 mL 2.0 mol L(-1) HCl solution. Common coexisting ions did not interfere with the separation and determination of target metal ions. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 39.8, 39.9, 77.8 and 17.3 mg g(-1) for Cr(III), Cu(II), Fe(III) and Pb(II), respectively. The detection limits of the method were found to be 0.15, 0.41, 0.27 and 0.36 ng mL(-1) for Cr(III), Cu(II), Fe(III) and Pb(II), respectively. The relative standard deviation (RSD) of the method was lower than 4.0% (n=8). The method was successfully applied for the preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) in natural and certified samples with satisfactory results.

Analysis of iodinated X-ray contrast agents in water samples by ion chromatography and inductively-coupled plasma mass spectrometry.

PubMed

Sacher, Frank; Raue, Brigitte; Brauch, Heinz-Jürgen

2005-08-26

In this paper, an analytical method for the determination of six iodinated X-ray contrast agents (amidotrizoic acid, iohexol, iomeprol, iopamidol, iopromide, and ioxitalamic acid), iodide, and iodate in water samples is presented. The method is based on a separation of the analytes by ion chromatography (IC) and a subsequent detection by inductively-coupled plasma mass spectrometry (ICP-MS). The method was optimised with respect to separation conditions (column type and eluent composition) and extensively validated. Without pre-concentration of the samples, limits of detection below 0.2 microg/l could be achieved whereby reproducibility was below 6% for all compounds under investigation.

A green and efficient procedure for the preconcentration and determination of cadmium, nickel and zinc from freshwater, hemodialysis solutions and tuna fish samples by cloud point extraction and flame atomic absorption spectrometry.

PubMed

Galbeiro, Rafaela; Garcia, Samara; Gaubeur, Ivanise

2014-04-01

Cloud point extraction (CPE) was used to simultaneously preconcentrate trace-level cadmium, nickel and zinc for determination by flame atomic absorption spectrometry (FAAS). 1-(2-Pyridilazo)-2-naphthol (PAN) was used as a complexing agent, and the metal complexes were extracted from the aqueous phase by the surfactant Triton X-114 ((1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol). Under optimized complexation and extraction conditions, the limits of detection were 0.37μgL(-1) (Cd), 2.6μgL(-1) (Ni) and 2.3μgL(-1) (Zn). This extraction was quantitative with a preconcentration factor of 30 and enrichment factor estimated to be 42, 40 and 43, respectively. The method was applied to different complex samples, and the accuracy was evaluated by analyzing a water standard reference material (NIST SRM 1643e), yielding results in agreement with the certified values. Copyright © 2013 Elsevier GmbH. All rights reserved.

Signal Enhancement in HPLC/Micro-Coil NMR Using Automated Column Trapping

PubMed Central

Djukovic, Danijel; Liu, Shuhui; Henry, Ian; Tobias, Brian; Raftery, Daniel

2008-01-01

A new HPLC-NMR system is described that performs analytical separation, pre-concentration, and NMR spectroscopy in rapid succession. The central component of our method is the online pre-concentration sequence that improves the match between post-column analyte peak volume and the micro-coil NMR detection volume. Separated samples are collected on to a C18 guard column with a mobile phase composed of 90% D2O/10% acetonitrile-D3, and back-flashed to the NMR micro-coil probe with 90% acetonitrile-D3/10% D2O. In order to assess the performance of our unit, we separated a standard mixture of 1 mM ibuprofen, naproxen, and phenylbutazone using a commercially available C18 analytical column. The S/N measurements from the NMR acquisitions indicated that we achieved signal enhancement factors up to 10.4 (±1.2)-fold. Furthermore, we observed that pre-concentration factors increased as the injected amount of analyte decreased. The highest concentration enrichment of 14.7 (±2.2)-fold was attained injecting 100 μL solution of 0.2 mM (~4 μg) ibuprofen. PMID:17037915

Application of chitosan and its N-heterocyclic derivatives for preconcentration of noble metal ions and their determination using atomic absorption spectrometry.

PubMed

Azarova, Yu A; Pestov, A V; Ustinov, A Yu; Bratskaya, S Yu

2015-12-10

Chitosan and its N-heterocyclic derivatives N-2-(2-pyridyl)ethylchitosan (2-PEC), N-2-(4-pyridyl) ethylchitosan (4-PEC), and N-(5-methyl-4-imidazolyl) methylchitosan (IMC) have been applied in group preconcentration of gold, platinum, and palladium for subsequent determination by atomic absorption spectroscopy (AAS) in solutions with high background concentrations of iron and sodium ions. It has been shown that the sorption mechanism, which was elucidated by XPS, significantly influences the sorption capacity of materials, the efficiency of metal ions elution after preconcentration, and, as a result, the accuracy of metal determination by AAS. We have shown that native chitosan was not suitable for preconcentration of Au(III), if the elution step was used as a part of the analysis scheme. The group preconcentration of Au(III), Pd(II), and Pt(IV) with subsequent quantitative elution using 0.1M HCl/1M thiourea solution was possible only on IMC and 4-PEC. Application of IMC for analysis of the national standard quartz ore sample proved that gold could be accurately determined after preconcentration/elution with the recovery above 80%. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparison of Analytical Methods for the Determination of Uranium in Seawater Using Inductively Coupled Plasma Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Jordana R.; Gill, Gary A.; Kuo, Li-Jung

2016-04-20

Trace element determinations in seawater by inductively coupled plasma mass spectrometry are analytically challenging due to the typically very low concentrations of the trace elements and the potential interference of the salt matrix. In this study, we did a comparison for uranium analysis using inductively coupled plasma mass spectrometry (ICP-MS) of Sequim Bay seawater samples and three seawater certified reference materials (SLEW-3, CASS-5 and NASS-6) using seven different analytical approaches. The methods evaluated include: direct analysis, Fe/Pd reductive precipitation, standard addition calibration, online automated dilution using an external calibration with and without matrix matching, and online automated pre-concentration. The methodmore » which produced the most accurate results was the method of standard addition calibration, recovering uranium from a Sequim Bay seawater sample at 101 ± 1.2%. The on-line preconcentration method and the automated dilution with matrix-matched calibration method also performed well. The two least effective methods were the direct analysis and the Fe/Pd reductive precipitation using sodium borohydride« less

Sample preconcentration with chemical derivatization in capillary electrophoresis. Capillary as preconcentrator, microreactor and chiral selector for high-throughput metabolite screening.

PubMed

Ptolemy, Adam S; Britz-McKibbin, Philip

2006-02-17

New strategies for integrating sample pretreatment with chemical analyses under a single format is required for rapid, sensitive and enantioselective analyses of low abundance metabolites in complex biological samples. Capillary electrophoresis (CE) offers a unique environment for controlling analyte/reagent band dispersion and electromigration properties using discontinuous electrolyte systems. Recent work in our laboratory towards developing a high-throughput CE platform for low abundance metabolites via on-line sample preconcentration with chemical derivatization (SPCD) is primarily examined in this review, as there have been surprisingly only a few strategies reported in the literature to date. In-capillary sample preconcentration serves to enhance concentration sensitivity via electrokinetic focusing of long sample injection volumes for lower detection limits, whereas chemical derivatization by zone passing is used to expand detectability and selectivity, notably for enantiomeric resolution of metabolites lacking intrinsic chromophores using nanolitre volumes of reagent. Together, on-line SPCD-CE can provide over a 100-fold improvement in concentration sensitivity, shorter total analysis times, reduced sample handling and improved reliability for a variety of amino acid and amino sugar metabolites, which is also amenable to automated high-throughput screening. This review will highlight basic method development and optimization parameters relevant to SPCD-CE, including applications to bacterial metabolite flux and biomarker analyses. Insight into the mechanism of analyte focusing and labeling by SPCD-CE is also discussed, as well as future directions for continued research.

Potential of sawdust as a green and economical sorbent for simultaneous preconcentration of trace amounts of cadmium, cobalt, and lead from water, biological, food, and herbal samples.

PubMed

Baki, Mostafa Hossein; Shemirani, Farzaneh; Khani, Rouhollah

2013-05-01

Application of treated sawdust with NaOH as a green and economical sorbent for simultaneous preconcentration of trace amounts of Cd(II), Co(II), and Pb(II) ions from liver, lettuce, fish, and water as test samples with complicated matrices was investigated. Various parameters, such as effect of pH and contact time, breakthrough volume, type, and concentration of eluent and interference of ions were studied. The sorption was quantitative in the pH of 5.0 to 7.0 and desorption occurred instantaneously with 5.0 mL of mixed solutions of ethanol and 2.0 mol/L HNO3 -HCl and the amount of ions was measured by using flame atomic absorption spectrometry. Linearity was maintained at 3 to 500 μg/L for cobalt, 5.0 to 800 μg/L for lead, and 2.0 to 300 μg/L for cadmium in the original solution. The relative standard deviation was less than 1.80% (n = 6, with concentration of 0.3 mg/L for cadmium and 0.5 mg/L for lead and cobalt). Detection limits and maximum capacity of the sorbent for Co (II), Cd (II), and Pb (II) in the original solution were 0.86, 0.50, and 1.7 μg/L and 28.5, 30.6, and 47.3 mg/g, respectively. The results for spiked real samples, effect of interfering ions, and adsorption capacity indicated that the applicability of this method for lead preconcentration is better than cadmium and cobalt preconcentration from complicated matrices. Practical Application: Sawdust can be applied as a green and economical sorbent for simultaneous preconcentration and solid-phase extraction of metal ions from food and environmental samples with complicated matrices. © 2013 Institute of Food Technologists®

MODIFYING EPA METHOD 314.0 FOR ANALYSIS OF PERCHLORATE IN AQUEOUS SAMPLES CONTAINING HIGH TOTAL DISSOLVED SOLIDS

EPA Science Inventory

Through the Regional Applied Research Effort (RARE) program, the Chemical Exposure Research Branch and Region 9 personnel in San Francisco, California are collaborating on a project to explore sample pretreatment and preconcentration techniques to lower the method detection limit...

Magnetic scavengers as carriers of analytes for flowing atmospheric pressure afterglow mass spectrometry (FAPA-MS).

PubMed

Cegłowski, Michał; Kurczewska, Joanna; Smoluch, Marek; Reszke, Edward; Silberring, Jerzy; Schroeder, Grzegorz

2015-09-07

In this paper, a procedure for the preconcentration and transport of mixtures of acids, bases, and drug components to a mass spectrometer using magnetic scavengers is presented. Flowing atmospheric pressure afterglow mass spectrometry (FAPA-MS) was used as an analytical method for identification of the compounds by thermal desorption from the scavengers. The proposed procedure is fast and cheap, and does not involve time-consuming purification steps. The developed methodology can be applied for trapping harmful substances in minute quantities, to transport them to specialized, remotely located laboratories.

Chemical analysis of acoustically levitated drops by Raman spectroscopy.

PubMed

Tuckermann, Rudolf; Puskar, Ljiljana; Zavabeti, Mahta; Sekine, Ryo; McNaughton, Don

2009-07-01

An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid-base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension.

Lyotropic liquid crystal preconcentrates for the treatment of periodontal disease.

PubMed

Fehér, A; Urbán, E; Eros, I; Szabó-Révész, P; Csányi, E

2008-06-24

The aim of our study was to develop water-free lyotropic liquid crystalline preconcentrates, which consist of oils and surfactants with good physiological tolerance and spontaneously form lyotropic liquid crystalline phase in aqueous environment. In this way these preconcentrates having low viscosity can be injected into the periodontal pocket, where they are transformed into highly viscous liquid crystalline phase, so that the preparation is prevented from flowing out of the pocket due to its great viscosity, while drug release is controlled by the liquid crystalline texture. In order to follow the structure alteration upon water absorption polarization microscopical and rheological examinations were performed. The water absorption mechanism of the samples was examined by the Enslin-method. Metronidazole-benzoate was used as active agent the release of which was characterized via in vitro investigations performed by means of modified Kirby-Bauer disk diffusion method. On the grounds of the results it can be stated that the 4:1 mixture of the investigated surfactants (Cremophor EL, Cremophor RH40) and oil (Miglyol 810) formed lyotopic liquid crystalline phases upon water addition. Polarization microscopic examinations showed that samples with 10-40% water content possessed anisotropic properties. On the basis of water absorption, rheological and drug release studies it can be concluded that the amount of absorbed water and stiffness of lyotropic structure influenced by the chemical entity of the surfactant exerted major effect on the drug release.

Ultrasonically Modified Amended-Cloud Point Extraction for Simultaneous Pre-Concentration of Neonicotinoid Insecticide Residues.

PubMed

Kachangoon, Rawikan; Vichapong, Jitlada; Burakham, Rodjana; Santaladchaiyakit, Yanawath; Srijaranai, Supalax

2018-05-12

An effective pre-concentration method, namely amended-cloud point extraction (CPE), has been developed for the extraction and pre-concentration of neonicotinoid insecticide residues. The studied analytes including clothianidin, imidacloprid, acetamiprid, thiamethoxam and thiacloprid were chosen as a model compound. The amended-CPE procedure included two cloud point processes. Triton™ X-114 was used to extract neonicotinoid residues into the surfactant-rich phase and then the analytes were transferred into an alkaline solution with the help of ultrasound energy. The extracts were then analyzed by high-performance liquid chromatography (HPLC) coupled with a monolithic column. Several factors influencing the extraction efficiency were studied such as kind and concentration of surfactant, type and content of salts, kind and concentration of back extraction agent, and incubation temperature and time. Enrichment factors (EFs) were found in the range of 20⁻333 folds. The limits of detection of the studied neonicotinoids were in the range of 0.0003⁻0.002 µg mL −1 which are below the maximum residue limits (MRLs) established by the European Union (EU). Good repeatability was obtained with relative standard deviations lower than 1.92% and 4.54% for retention time ( t R ) and peak area, respectively. The developed extraction method was successfully applied for the analysis of water samples. No detectable residues of neonicotinoids in the studied samples were found.

Halloysite nanotubes as a solid sorbent in ultrasound-assisted dispersive micro solid-phase extraction for the determination of bismuth in water samples using high-resolution continuum source graphite-furnace atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Krawczyk-Coda, Magdalena

2017-03-01

In this research, a simple, accurate, and inexpensive preconcentration procedure was developed for the determination of bismuth in water samples, using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS). During the preconcentration step, halloysite nanotubes (HNTs) were used as a solid sorbent in ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE). The influence of the pH of the sample solution, amount of HNTs, and extraction time, as well as of the main parameters of HR CS GFAAS, on absorbance was investigated. The limit of detection was 0.005 μg L- 1. The preconcentration factor achieved for bismuth was 32. The relative standard deviation (RSD) was 4%. The accuracy of this method was validated by analyses of NIST SRM 1643e (Trace elements in water) and TMDA-54.5 (A high level fortified sample for trace elements) certified reference materials. The measured bismuth contents in these certified reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level. The proposed method has been successfully applied to the determination of bismuth in five different real water samples (seawater, lake water, river water, stream water and rain water).

Development of a flow system for the determination of cadmium in fuel alcohol using vermicompost as biosorbent and flame atomic absorption spectrometry.

PubMed

Bianchin, Joyce Nunes; Martendal, Edmar; Mior, Renata; Alves, Vanessa Nunes; Araújo, Cleide Sandra Tavares; Coelho, Nívia Maria Melo; Carasek, Eduardo

2009-04-30

In this study a method for the determination of cadmium in fuel alcohol using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry was developed. The sorbent material used was a vermicompost commonly used as a garden fertilizer. The chemical and flow variables of the on-line preconcentration system were optimized by means of a full factorial design. The selected factors were: sorbent mass, sample pH, buffer concentration and sample flow rate. The optimum extraction conditions were obtained using sample pH in the range of 7.3-8.3 buffered with tris(hydroxymethyl)aminomethane at 50 mmol L(-1), a sample flow rate of 4.5 mL min(-1) and 160 mg of sorbent mass. With the optimized conditions, the preconcentration factor, limit of detection and sample throughput were estimated as 32 (for preconcentration of 10 mL sample), 1.7 microg L(-1) and 20 samples per hour, respectively. The analytical curve was linear from 5 up to at least 50 microg L(-1), with a correlation coefficient of 0.998 and a relative standard deviation of 2.4% (35 microg L(-1), n=7). The developed method was successfully applied to spiked fuel alcohol, and accuracy was assessed through recovery tests, with recovery ranging from 94% to 100%.

Recent Application of Solid Phase Based Techniques for Extraction and Preconcentration of Cyanotoxins in Environmental Matrices.

PubMed

Mashile, Geaneth Pertunia; Nomngongo, Philiswa N

2017-03-04

Cyanotoxins are toxic and are found in eutrophic, municipal, and residential water supplies. For this reason, their occurrence in drinking water systems has become a global concern. Therefore, monitoring, control, risk assessment, and prevention of these contaminants in the environmental bodies are important subjects associated with public health. Thus, rapid, sensitive, selective, simple, and accurate analytical methods for the identification and determination of cyanotoxins are required. In this paper, the sampling methodologies and applications of solid phase-based sample preparation methods for the determination of cyanotoxins in environmental matrices are reviewed. The sample preparation techniques mainly include solid phase micro-extraction (SPME), solid phase extraction (SPE), and solid phase adsorption toxin tracking technology (SPATT). In addition, advantages and disadvantages and future prospects of these methods have been discussed.

Factors governing the pre-concentration of wastewater using forward osmosis for subsequent resource recovery.

PubMed

Ansari, Ashley J; Hai, Faisal I; Guo, Wenshan; Ngo, Hao H; Price, William E; Nghiem, Long D

2016-10-01

This study demonstrated a technique using forward osmosis (FO) to pre-concentrate the organic matter in raw wastewater, thereby transforming low strength wastewater into an anaerobically digestible solution. The chemical oxygen demand (COD) of raw wastewater was concentrated up to approximately eightfold at a water recovery of 90%. Thus, even low strength wastewater could be pre-concentrated by FO to the range suitable for biogas production via anaerobic treatment. Excessive salinity accumulation in pre-concentrated wastewater was successfully mitigated by adopting ionic organic draw solutes, namely, sodium acetate, and EDTA-2Na. These two draw solutes are also expected to benefit the digestibility of the pre-concentrated wastewater compared to the commonly used draw solute sodium chloride. Significant membrane fouling was observed when operating at 90% water recovery using raw wastewater. Nevertheless, membrane fouling was reversible and was effectively controlled by optimising the hydrodynamic conditions of the cross-flow FO system. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Determination of dipyrone in pharmaceutical preparations based on the chemiluminescent reaction of the quinolinic hydrazide-H2O2-vanadium(IV) system and flow-injection analysis.

PubMed

Pradana Pérez, Juan A; Durand Alegría, Jesús S; Hernando, Pilar Fernández; Sierra, Adolfo Narros

2012-01-01

A rapid, economic and sensitive chemiluminescent method involving flow-injection analysis was developed for the determination of dipyrone in pharmaceutical preparations. The method is based on the chemiluminescent reaction between quinolinic hydrazide and hydrogen peroxide in a strongly alkaline medium, in which vanadium(IV) acts as a catalyst. Principal chemical and physical variables involved in the flow-injection system were optimized using a modified simplex method. The variations in the quantum yield observed when dipyrone was present in the reaction medium were used to determine the concentration of this compound. The proposed method requires no preconcentration steps and reliably quantifies dipyrone over the linear range 1-50 µg/mL. In addition, a sample throughput of 85 samples/h is possible. Copyright © 2011 John Wiley & Sons, Ltd.

A new dispersive liquid-liquid microextraction using ionic liquid based microemulsion coupled with cloud point extraction for determination of copper in serum and water samples.

PubMed

Arain, Salma Aslam; Kazi, Tasneem Gul; Afridi, Hassan Imran; Arain, Mariam Shahzadi; Panhwar, Abdul Haleem; Khan, Naeemullah; Baig, Jameel Ahmed; Shah, Faheem

2016-04-01

A simple and rapid dispersive liquid-liquid microextraction procedure based on ionic liquid assisted microemulsion (IL-µE-DLLME) combined with cloud point extraction has been developed for preconcentration copper (Cu(2+)) in drinking water and serum samples of adolescent female hepatitits C (HCV) patients. In this method a ternary system was developed to form microemulsion (µE) by phase inversion method (PIM), using ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and nonionic surfactant, TX-100 (as a stabilizer in aqueous media). The Ionic liquid microemulsion (IL-µE) was evaluated through visual assessment, optical light microscope and spectrophotometrically. The Cu(2+) in real water and aqueous acid digested serum samples were complexed with 8-hydroxyquinoline (oxine) and extracted into IL-µE medium. The phase separation of stable IL-µE was carried out by the micellar cloud point extraction approach. The influence of of different parameters such as pH, oxine concentration, centrifugation time and rate were investigated. At optimized experimental conditions, the limit of detection and enhancement factor were found to be 0.132 µg/L and 70 respectively, with relative standard deviation <5%. In order to validate the developed method, certified reference materials (SLRS-4 Riverine water) and human serum (Sero-M10181) were analyzed. The resulting data indicated a non-significant difference in obtained and certified values of Cu(2+). The developed procedure was successfully applied for the preconcentration and determination of trace levels of Cu(2+) in environmental and biological samples. Copyright © 2015 Elsevier Inc. All rights reserved.

Solid-phase extraction of iridium from soil and water samples by using activated carbon cloth prior to its spectrophotometric determination.

PubMed

Ozkantar, Nebiye; Yilmaz, Erkan; Soylak, Mustafa; Tuzen, Mustafa

2015-08-01

A solid-phase extraction method for separation and preconcentration of Ir(IV) ion by using activated carbon cloth (ACC) has been presented. Ir(IV) as their 1-(2-pyridylazo) 2-naphtol (PAN) chelate was adsorbed on ACC at pH 2.0 and was eluted from ACC with acidic dimethylformamide (DMF). The Ir(IV) concentration was determined at 536 nm as Ir(IV)-PAN complex by using UV-vis spectrophotometer. The analytical parameters including pH, sample and eluent flow rates, amount of PAN, eluent type, concentration, and sample volume were optimized. The effects of foreign ions on the recoveries of iridium were also investigated. The preconcentration factor was calculated as 60. The limit of detection (LOD) and the limit of quantification (LOQ) of the method were found as 0.039 and 0.129 μg L(-1), respectively. The method was applied to soil and water samples for iridium determination.

Preconcentration and Spectrophotometric Determination of a Naphthalene Analog of Medetomidine Using Modified Maghemite Nanoparticles

NASA Astrophysics Data System (ADS)

Maddah, B.; Hosseini, F.; Ahmadi, M.; Rajabi, A. Asghar; Beik-Mohammadlood, Z.

2016-05-01

A novel and sensitive extraction procedure using sodium dodecyl sulfate (SDS) modified maghemite nanoparticles (MNPs) as an efficient solid phase has been developed for removal, preconcentration, and spectrophotometric determination of trace amounts of a naphthalene analog of dexmedetomidine (4-(1-(na phthalene-1-yl)ethyl)-1Himidazole, NMED). The MNPs were obtained by a coprecipitation method, and their surfaces were furthermore modified by SDS. The size and morphological properties of the synthesized MNPs were determined by X-ray diffraction analysis, FT-IR, vibrating sample magnetometry, and scanning electron microscopy. NMED was adsorbed at pH 3.0. The adsorbed drug was then desorbed and determined by spectrophotometry at 280 nm. The calibration graph was linear in the range 1 × 10-6-1 × 10-4 mol/L of NMED with a correlation coefficient of 0.989. The detection limit of the method for NMED determination was 3.7 × 10-7 mol/L. The method was successfully applied to the determination of NMED in human urine samples.

On-line preconcentration of fluorescent derivatives of catecholamines in cerebrospinal fluid using flow-gated capillary electrophoresis.

PubMed

Zhang, Qiyang; Gong, Maojun

2016-06-10

Flow-gated capillary electrophoresis (CE) coupled with microdialysis has become an important tool for in vivo bioanalytical measurements because it is capable of performing rapid and efficient separations of complex biological mixtures thus enabling high temporal resolution in chemical monitoring. However, the limit of detection (LOD) is often limited to a micro- or nano-molar range while many important target analytes have picomolar or sub-nanomolar levels in brain and other tissues. To enhance the capability of flow-gated CE for catecholamine detection, a novel and simple on-line sample preconcentration method was developed exclusively for fluorescent derivatives of catecholamines that were fluorogenically derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide. The effective preconcentration coupled with the sensitive laser-induced fluorescence (LIF) detection lowered the LOD down to 20pM for norepinephrine (NE) and 50pM for dopamine (DA) at 3-fold of S/N ratio, and the signal enhancement was estimated to be over 100-fold relative to normal injection when standard analytes were dissolved in artificial cerebrospinal fluid (aCSF). The basic focusing principle is novel since the sample plug contains borate while the background electrolyte (BGE) is void of borate. This strategy took advantage of the complexation between diols and borate, through which one negative charge was added to the complex entity. The sample derivatization mixture was electrokinetically injected into a capillary via the flow-gated injection, and then NE and DA derivatives were selectively focused to a narrow zone by the reversible complexation. Separation of NE and DA derivatives was executed by incoming surfactants of cholate and deoxycholate mixed in the front BGE plug. This on-line preconcentration method was finally applied to the detection of DA in rat cerebrospinal fluid (CSF) via microdialysis and on-line derivatization. It is anticipated that the method would be valuable for in vivo monitoring of DA and NE in various brain regions of live animals on flow-gated CE or microchip platforms. Published by Elsevier B.V.

Pure-rotational spectrometry: a vintage analytical method applied to modern breath analysis.

PubMed

Hrubesh, Lawrence W; Droege, Michael W

2013-09-01

Pure-rotational spectrometry (PRS) is an established method, typically used to study structures and properties of polar gas-phase molecules, including isotopic and isomeric varieties. PRS has also been used as an analytical tool where it is particularly well suited for detecting or monitoring low-molecular-weight species that are found in exhaled breath. PRS is principally notable for its ultra-high spectral resolution which leads to exceptional specificity to identify molecular compounds in complex mixtures. Recent developments using carbon aerogel for pre-concentrating polar molecules from air samples have extended the sensitivity of PRS into the part-per-billion range. In this paper we describe the principles of PRS and show how it may be configured in several different modes for breath analysis. We discuss the pre-concentration concept and demonstrate its use with the PRS analyzer for alcohols and ammonia sampled directly from the breath.

Separation and preconcentration of the rare-earth elements and yttrium from geological materials by ion-exchange and sequential acid elution

USGS Publications Warehouse

Crock, J.G.; Lichte, F.E.; Riddle, G.O.; Beech, C.L.

1986-01-01

The abundance of rare-earth elements (REE) and yttrium in geological materials is generally low, and most samples contain elements that interfere in the determination of the REE and Y, so a separation and/or preconcentration step is often necessary. This is often achieved by ion-exchange chromatography with either nitric or hydrochloric acid. It is advantageous, however, to use both acids sequentially. The final solution thus obtained contains only the REE and Y, with minor amounts of Al, Ba, Ca, Sc, Sr and Ti. Elements that potentially interfere, such as Be, Co, Cr, Fe, Mn, Th, U, V and Zr, are virtually eliminated. Inductively-coupled argon plasma atomic-emission spectroscopy can then be used for a final precise and accurate measurement. The method can also be used with other instrumental methods of analysis. ?? 1986.

Cloud point extraction and flame atomic absorption spectrometric determination of cadmium and nickel in drinking and wastewater samples.

PubMed

Naeemullah; Kazi, Tasneem G; Shah, Faheem; Afridi, Hassan I; Baig, Jameel Ahmed; Soomro, Abdul Sattar

2013-01-01

A simple method for the preconcentration of cadmium (Cd) and nickel (Ni) in drinking and wastewater samples was developed. Cloud point extraction has been used for the preconcentration of both metals, after formation of complexes with 8-hydroxyquinoline (8-HQ) and extraction with the surfactant octylphenoxypolyethoxyethanol (Triton X-114). Dilution of the surfactant-rich phase with acidified ethanol was performed after phase separation, and the Cd and Ni contents were measured by flame atomic absorption spectrometry. The experimental variables, such as pH, amounts of reagents (8-HQ and Triton X-114), temperature, incubation time, and sample volume, were optimized. After optimization of the complexation and extraction conditions, enhancement factors of 80 and 61, with LOD values of 0.22 and 0.52 microg/L, were obtained for Cd and Ni, respectively. The proposed method was applied satisfactorily for the determination of both elements in drinking and wastewater samples.

Polypyrrole/multi-walled carbon nanotube composite for the solid phase extraction of lead(II) in water samples.

PubMed

Sahmetlioglu, Ertugrul; Yilmaz, Erkan; Aktas, Ece; Soylak, Mustafa

2014-02-01

A multi-walled carbon nanotubes-polypyrrole conducting polymer nanocomposite has been synthesized, characterized and used for the separation and preconcentration of lead at trace levels in water samples prior to its flame atomic absorption spectrometric detection. The analytical parameters like pH, sample volume, eluent, sample flow rate that were affected the retentions of lead(II) on the new nanocomposite were optimized. Matrix effects were also investigated. Limit of detection and preconcentration factors were 1.1 µg L(-1) and 200, respectively. The adsorption capacity of the nanocomposite was 25.0mg lead(II) per gram composite. The validation of the method was checked by using SPS-WW2 Waste water Level 2 certified reference material. The method was applied to the determination of lead in water samples with satisfactory results. © 2013 Elsevier B.V. All rights reserved.

A novel task specific magnetic polymeric ionic liquid for selective preconcentration of potassium in oil samples using centrifuge-less dispersive liquid-liquid microextraction technique and its determination by flame atomic emission spectroscopy.

PubMed

Beiraghi, Asadollah; Shokri, Masood

2018-02-01

In the present study a new centrifuge-less dispersive liquid-liquid microextraction technique based on application of a new task specific magnetic polymeric ionic liquid (TSMPIL) as a chelating and extraction solvent for selective preconcentration of trace amounts of potassium from oil samples is developed, for the first time. After extraction, the fine droplets of TSMPIL were transferred into an eppendorf tube and diluted to 500µL using distilled water. Then, the enriched analyte was determined by flame atomic emission spectroscopy (FAES). Several important factors affecting both the complexation and extraction efficiency including extraction time, rate of vortex agitator, amount of carbonyl iron powder, pH of sample solution, volume of ionic liquid as well as effects of interfering species were investigated and optimized. Under the optimal conditions, the limits of detection (LOD) and quantification (LOQ) were 0.5 and 1.6µgL -1 respectively with the preconcentration factor of 128. The precision (RSD %) for seven replicate determinations at 10µgL -1 of potassium was better than 3.9%. The relative recoveries for the spiked samples were in the acceptable range of 95-104%. The results demonstrated that no remarkable interferences are created by other various ions in the determination of potassium, so that the tolerance limits (W Ion /W K ) of major cations and anions were in the range of 2500-10,000. The purposed method was successfully applied for the analysis of potassium in some oil samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Application of dual-cloud point extraction for the trace levels of copper in serum of different viral hepatitis patients by flame atomic absorption spectrometry: a multivariate study.

PubMed

Arain, Salma Aslam; Kazi, Tasneem G; Afridi, Hassan Imran; Abbasi, Abdul Rasool; Panhwar, Abdul Haleem; Naeemullah; Shanker, Bhawani; Arain, Mohammad Balal

2014-12-10

An efficient, innovative preconcentration method, dual-cloud point extraction (d-CPE) has been developed for the extraction and preconcentration of copper (Cu(2+)) in serum samples of different viral hepatitis patients prior to couple with flame atomic absorption spectrometry (FAAS). The d-CPE procedure was based on forming complexes of elemental ions with complexing reagent 1-(2-pyridylazo)-2-naphthol (PAN), and subsequent entrapping the complexes in nonionic surfactant (Triton X-114). Then the surfactant rich phase containing the metal complexes was treated with aqueous nitric acid solution, and metal ions were back extracted into the aqueous phase, as second cloud point extraction stage, and finally determined by flame atomic absorption spectrometry using conventional nebulization. The multivariate strategy was applied to estimate the optimum values of experimental variables for the recovery of Cu(2+) using d-CPE. In optimum experimental conditions, the limit of detection and the enrichment factor were 0.046μgL(-1) and 78, respectively. The validity and accuracy of proposed method were checked by analysis of Cu(2+) in certified sample of serum (CRM) by d-CPE and conventional CPE procedure on same CRM. The proposed method was successfully applied to the determination of Cu(2+) in serum samples of different viral hepatitis patients and healthy controls. Copyright © 2014 Elsevier B.V. All rights reserved.

Simultaneous speciation and preconcentration of ultra traces of inorganic tellurium and selenium in environmental samples by hollow fiber liquid phase microextraction prior to electrothermal atomic absorption spectroscopy determination.

PubMed

Ghasemi, Ensieh; Najafi, Nahid Mashkouri; Raofie, Farhad; Ghassempour, Alireza

2010-09-15

A simple and effective speciation and preconcentration method based on hollow fiber liquid phase microextraction (HF-LPME) was developed for simultaneous separation of trace inorganic tellurium and selenium in environmental samples prior to electrothermal atomic absorption spectroscopy (ETAAS) determination. The method involves the selective extraction of the Te (IV) and Se (IV) species by HF-LPME with the use of ammonium pyrrolidinecarbodithioate (APDC) as the chelating agent. The complex compounds were extracted into 10 microL of toluene and the solutions were injected into a graphite furnace for the determination of Te (IV) and Se (IV). To determine the total tellurium and selenium in the samples, first Te (VI) and Se (VI) were reduced to Te (IV) and Se (IV), and then the microextraction method was performed. The experimental parameters of HF-LPME were optimized using a central composite design after a 2(n-1) fractional factorial experimental design. Under optimum conditions, enrichment factors of up to 520 and 480 were achieved for Te (IV) and Se (IV), respectively. The detection limits were 4 ng L(-1) with 3.5% RSD (n=5, c=2.0 microg L(-1)) for Te (IV) and 5 ng L(-1) with 3.1% RSD for Se (IV). The applicability of the developed technique was evaluated by application to spiked, environmental water and soil samples. Copyright 2010 Elsevier B.V. All rights reserved.

Dispersive micro-solid phase extraction combined with dispersive liquid-liquid microextraction for speciation analysis of antimony by electrothermal vaporization inductively coupled plasma mass spectrometry

NASA Astrophysics Data System (ADS)

Chen, Shizhong; Zhu, Shengping; Lu, Dengbo

2018-01-01

A method was developed for speciation analysis of antimony by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) after preconcentration/separation using dispersive micro-solid phase extraction (DMSPE) and dispersive liquid-liquid micro-extraction (DLLME). In DMSPE, titanium dioxide nanofibers were used for preconcentration and separation of analytes. The upper aqueous phase and elution solution from DMSPE were used for further preconcentration and separation of Sb(III) and Sb(V) by DLLME without any pre-oxidation or pre-reduction operation, respectively. The extracts from DLLME were used for ETV-ICP-MS determination with APDC as a chemical modifier. Under optimal conditions, the detection limits of this method were 0.019 and 0.025 pg mL- 1 with relative standard deviations of 5.7% and 6.9% for Sb(III) and Sb(V) (c = 1.0 ng mL- 1, n = 9), respectively. This method was applied for speciation analysis of Sb and its distribution in the tea leaves and the tea infusion, including total, suspended, soluble, organic and inorganic Sb as well as Sb(III) and Sb(V). The results showed that the contents of Sb are 62.7, 12.9 and 47.3 ng g- 1 in the tea leaves, tea residue and tea soup, respectively; those of soluble, organic, inorganic, Sb(III) and Sb(V) are 0.41, 0.11, 0.29, 0.21 and 0.07 ng mL- 1 in the tea soup, respectively. A certified reference material of tea leaves (GBW 07605) was analyzed by this method with satisfactory results.

Preconcentration of β-blockers using functionalized ordered mesoporous silica as sorbent for SPE and their determination in waters by chiral CE.

PubMed

Silva, Mariana; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Marina, María Luisa; Sierra, Isabel

2017-08-01

A method for simultaneous separation and determination of four enantiomeric pairs of β-blockers in waters by chiral CE has been developed. Off-line SPE was employed using functionalized ordered mesoporous silica as sorbent. Separation by CE was achieved using a BGE composed by methylated-β-CD (1.25% w/v) dissolved in a 50 mM phosphate buffer (pH 2.5) and 30°C, with good chiral resolution for all enantiomers. Mesoporous silica functionalized with octadecyl groups (denoted SBA15-C18) was prepared by a postsynthesis method and applied for the preconcentration of atenolol, propranolol, metoprolol, and pindolol enantiomers in waters by off-line SPE. Under optimized conditions, a preconcentration factor of 300 was achieved, employing 100 mg of SBA15-C18 as sorbent, with recoveries between 96 and 105% in tap water and good repeatability (% RSD = 7-11%, n = 6). Commercial C18 amorphous silica (ExtraBond R C 18 ) was also tested as sorbent for SPE, but results revealed better extraction capacity with higher recoveries for the SBA15-C18 material. The analytical characteristics of the off-line SPE-chiral CE method were evaluated, showing good precision, linearity, and accuracy with method quantification limits between 5.3 and 13.7 μg/L for all enantiomers. The SBA15-C18 material allowed the extraction of four enantiomeric pairs of β-blockers spiked in tap water, river water, and ground water with recoveries between 58 and 105%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trace elements determination in seawater by ICP-MS with on-line pre-concentration on a Chelex-100 column using a ‘standard’ instrument setup.

PubMed Central

Søndergaard, Jens; Asmund, Gert; Larsen, Martin M.

2015-01-01

Trace element determination in seawater is analytically challenging due to the typically very low concentrations of the trace elements and the potential interference of the salt matrix. A common way to address the challenge is to pre-concentrate the trace elements on a chelating resin, then rinse the matrix elements from the resin and subsequently elute and detect the trace elements using inductively coupled plasma mass spectrometry (ICP-MS). This technique typically involves time-consuming pre-treatment of the samples for ‘off-line’ analyses or complicated sample introduction systems involving several pumps and valves for ‘on-line’ analyses. As an alternative, the following method offers a simple method for ‘on-line’ analyses of seawater by ICP-MS. As opposed to previous methods, excess seawater was pumped through the nebulizer of the ICP-MS during the pre-concentration step but the gas flow was adjusted so that the seawater was pumped out as waste without being sprayed into the instrument. Advantages of the method include: • Simple and convenient analyses of seawater requiring no changes to the ‘standard’ sample introduction system except from a resin-filled micro-column connected to the sample tube. The ‘standard’ sample introduction system refers to that used for routine digest-solution analyses of biota and sediment by ICP-MS using only one peristaltic pump; and • Accurate determination of the elements V, Mn, Co, Ni, Cu, Zn, Cd and Pb in a range of different seawater matrices verified by participation in 6 successive rounds of the international laboratory intercalibration program QUASIMEME. PMID:26258050

Synthesis and characterisation of nano structure lead (II) ion-imprinted polymer as a new sorbent for selective extraction and preconcentration of ultra trace amounts of lead ions from vegetables, rice, and fish samples.

PubMed

Behbahani, Mohammad; Bagheri, Akbar; Taghizadeh, Mohsen; Salarian, Mani; Sadeghi, Omid; Adlnasab, Laleh; Jalali, Kobra

2013-06-01

This paper describes the preparation of new Pb(II)-imprinted polymeric particles using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as the cross-linker, 2,2'- azobisisobutyronitrile as the initiator, diphenylcarbazone as the ligand, acetonitril as the solvent, and Pb(NO(3))(2) as the template ion, through bulk polymerisation technique. The imprinted lead ions were removed from the polymeric matrix using 5 mL of HCl (2 mol.L(-1)) as the eluting solvent. The lead ion concentration was determined by flame atomic absorption spectrometry. Optimum pH for maximum sorption was obtained at 6.0. Sorption and desorption of Pb(II) ions on the IIP particles were quite fast and achieved fully over 5 min. In the proposed method, the maximum sorbent capacity of the ion-imprinted polymer was calculated to be 75.4 mg g(-1). The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 245, 2.1%, and 0.42 ng mL(-1), respectively. The prepared ion-imprinted polymer particles have an increased selectivity toward Pb(II) ions over a range of competing metal ions with the same charge and similar ionic radius. This ion-imprinted polymer is an efficient solid phase for extraction and preconcentration of lead ions in complex matrixes. For proving that the proposed method is reliable, a wide range of food samples with different and complex matrixes was used. Copyright © 2012 Elsevier Ltd. All rights reserved.

Trace determination of antimony by hydride generation atomic absorption spectrometry with analyte preconcentration/atomization in a dielectric barrier discharge atomizer.

PubMed

Zurynková, Pavla; Dědina, Jiří; Kratzer, Jan

2018-06-20

Atomization conditions for antimony hydride in the plasma atomizer based on a dielectric barrier discharge (DBD) with atomic absorption spectrometric detection were optimized. Argon was found as the best discharge gas under a flow rate of 50 mL min - 1 while the DBD power was optimum at 30 W. Analytical figures of merit including interference study of As, Se and Bi have been subsequently investigated and the results compared to those found in an externally heated quartz tube atomizer (QTA). The limit of detection (LOD) reached in DBD (0.15 ng mL -1  Sb) is comparable to that observed in QTA (0.14 ng mL -1  Sb). Finally, possibility of Sb preconcentration by stibane in situ trapping in a DBD atomizer was studied. For trapping time of 300 s, the preconcentration efficiency and LOD, respectively, were 103 ± 2% and 0.02 ng mL -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

Amine-functionalized mesoporous polymer as potential sorbent for nickel preconcentration from electroplating wastewater.

PubMed

Islam, Aminul; Zaidi, Noushi; Ahmad, Hilal; Kumar, Suneel

2015-05-01

In this study, mesoporous glycidyl methacrylate-divinylbenzene-based chelating resin was synthesized and grafted with diethylenetriamine through epoxy ring-opening reaction. The synthesized resin was characterized by elemental analysis, infrared spectroscopy, surface area and pore size analysis, scanning electron microscopy, energy-dispersive spectroscopy, and thermogravimetry. The resin was used for the first time as an effective sorbent for the preconcentration of nickel in electroplating wastewater samples. The analytical variables like pH, flow rate for sorption/desorption, and eluate selection were systematically investigated and optimized. The uniform and monolayer sorption behavior of resin for nickel was proved by an evident fit of the equilibrium data to a Langmuir isotherm model. Under optimized conditions, the resin was observed to show a good sorption capacity of 20.25 mg g(-1) and >96% recovery of nickel even in the presence of a large number of competitive matrix ions. Its ability to extract trace amount of nickel was exhibited by low preconcentration limit (5.9 μg L(-1)). The calibration curve was found to be linear (R(2) = 0.998) in the concentration range of 6.0-400.0 μg L(-1). Coefficient of variation of less than 5 for all the analysis indicated good reproducibility. The reliability was evaluated by the analysis of standard reference material (SRM) and recovery experiments. The applicability of the resin for the systematic preconcentration of nickel is substantiated by the analysis of electroplating wastewater and river water samples. Graphical abstract ᅟ.

Enhancement of the conductivity detection signal in capillary electrophoresis systems using neutral cyclodextrins as sweeping agents.

PubMed

Boublík, Milan; Riesová, Martina; Dubský, Pavel; Gaš, Bohuslav

2018-06-01

Conductivity detection is a universal detection technique often encountered in electrophoretic separation systems, especially in modern chip-electrophoresis based devices. On the other hand, it is sparsely combined with another contemporary trend of enhancing limits of detection by means of various preconcentration strategies. This can be attributed to the fact that a preconcentration experimental setup usually brings about disturbances in a conductivity baseline. Sweeping with a neutral sweeping agent seems a good candidate for overcoming this problem. A neutral sweeping agent does not hinder the conductivity detection while a charged analyte may preconcentrate on its boundary due to a decrease in its effective mobility. This study investigates such sweeping systems theoretically, by means of computer simulations, and experimentally. A formula is provided for the reliable estimation of the preconcentration factor. Additionally, it is demonstrated that the conductivity signal can significantly benefit from slowing down the analyte and thus the overall signal enhancement can easily overweight amplification caused solely by the sweeping process. The overall enhancement factor can be deduced a priori from the linearized theory of electrophoresis implemented in the PeakMaster freeware. Sweeping by neutral cyclodextrin is demonstrated on an amplification of a conductivity signal of flurbiprofen in a real drug sample. Finally, a possible formation of unexpected system peaks in systems with a neutral sweeping agent is revealed by the computer simulation and confirmed experimentally. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aptamer functionalized magnetic nanoparticles for effective extraction of ultratrace amounts of aflatoxin M1 prior its determination by HPLC.

PubMed

Khodadadi, Mohammad; Malekpour, Akbar; Mehrgardi, Masoud A

2018-06-09

Aptamers, due to the inherently high selectivity towards target analytes, are promising candidate for surface modification of the nanoparticles. Therefore, aptamer-functionalized magnetic nanoparticles (AMNPs) was prepared and used to develop a magnetic solid-phase extraction procedure for clean-up of milk and dairy products samples before measuring the aflatoxin M1 (AFM1) contents by the high-performance liquid chromatography. The prepared sorbent was characterized by different instrumental methods such as FT-IR, FESEM, TEM, EDX and AGFM. The AMNPs was used in extraction and pre-concentration of ultratrace amounts AFM1 from local milk samples. The amount of sorbent, elution volume, extraction time, and salt addition were optimized. Based on the results, calibration plot is linear over the 0.3 to 1 ng·L -1 and 5 to 50 ng·L -1 AFM1 concentration ranges. The limits of detection of the developed method were obtained 0.2 ng·L -1 which is the smallest value that has been reported up to now. The results show that this new superior sorbent has a large potential to simplify the complex matrix of the samples and can used for detection, preconcentration and accurate determination of ultratrace amounts of the AFM1 from milk and dairy products. Copyright © 2018 Elsevier B.V. All rights reserved.

Speciation of chromium in environmental samples by dual electromembrane extraction system followed by high performance liquid chromatography.

PubMed

Safari, Meysam; Nojavan, Saeed; Davarani, Saied Saeed Hosseiny; Morteza-Najarian, Amin

2013-07-30

This study proposes the dual electromembrane extraction followed by high performance liquid chromatography for selective separation-preconcentration of Cr(VI) and Cr(III) in different environmental samples. The method was based on the electrokinetic migration of chromium species toward the electrodes with opposite charge into the two different hollow fibers. The extractant was then complexed with ammonium pyrrolidinedithiocarbamate for HPLC analysis. The effects of analytical parameters including pH, type of organic solvent, sample volume, stirring rate, time of extraction and applied voltage were investigated. The results showed that Cr(III) and Cr(VI) could be simultaneously extracted into the two different hollow fibers. Under optimized conditions, the analytes were quantified by HPLC instrument, with acceptable linearity ranging from 20 to 500 μg L(-1) (R(2) values≥0.9979), and repeatability (RSD) ranging between 9.8% and 13.7% (n=5). Also, preconcentration factors of 21.8-33 that corresponded to recoveries ranging from 31.1% to 47.2% were achieved for Cr(III) and Cr(VI), respectively. The estimated detection limits (S/N ratio of 3:1) were less than 5.4 μg L(-1). Finally, the proposed method was successfully applied to determine Cr(III) and Cr(VI) species in some real water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Ionic liquid phase microextraction combined with fluorescence spectrometry for preconcentration and quantitation of carvedilol in pharmaceutical preparations and biological media.

PubMed

Zeeb, Mohsen; Mirza, Behrooz

2015-04-30

Carvedilol belongs to a group of medicines termed non-selective beta-adrenergic blocking agents. In the presented approach, a practical and environmentally friendly microextraction method based on the application of ionic liquids (ILs) was followed by fluorescence spectrometry for trace determination of carvedilol in pharmaceutical and biological media. A rapid and simple ionic liquid phase microextraction was utilized for preconcentration and extraction of carvedilol. A hydrophobic ionic liquid (IL) was applied as a microextraction solvent. In order to disperse the IL through the aqueous media and extract the analyte of interest, IL was injected into the sample solution and a proper temperature was applied and then for aggregating the IL-phase, the sample was cooled in an ice water-bath. The aqueous media was centrifuged and IL-phase collected at the bottom of the test tube was introduced to the micro-cell of spectrofluorimeter, in order to determine the concentration of the enriched analyte. Main parameters affecting the accuracy and precision of the proposed approach were investigated and optimized values were obtained. A linear response range of 10-250 μg I(-1) and a limit of detection (LOD) of 1.7 μg I(-1) were obtained. Finally, the presented method was utilized for trace determination of carvedilol in commercial pharmaceutical preparations and biological media.

Simultaneous derivatisation and preconcentration of parabens in food and other matrices by isobutyl chloroformate and dispersive liquid-liquid microextraction followed by gas chromatographic analysis.

PubMed

Jain, Rajeev; Mudiam, Mohana Krishna Reddy; Chauhan, Abhishek; Ch, Ratnasekhar; Murthy, R C; Khan, Haider A

2013-11-01

A simple, rapid and economical method has been proposed for the quantitative determination of parabens (methyl, ethyl, propyl and butyl paraben) in different samples (food, cosmetics and water) based on isobutyl chloroformate (IBCF) derivatisation and preconcentration using dispersive liquid-liquid microextraction in single step. Under optimum conditions, solid samples were extracted with ethanol (disperser solvent) and 200 μL of this extract along with 50 μL of chloroform (extraction solvent) and 10 μL of IBCF was rapidly injected into 2 mL of ultra-pure water containing 150 μL of pyridine to induce formation of a cloudy state. After centrifugation, 1 μL of the sedimented phase was analysed using gas chromatograph-flame ionisation detector (GC-FID) and the peaks were confirmed using gas chromatograph-positive chemical ionisation-mass spectrometer (GC-PCI-MS). Method was found to be linear over the range of 0.1-10 μg mL(-1) with square of correlation coefficient (R(2)) in the range of 0.9913-0.9992. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.029-0.102 μg mL(-1) and 0.095-0.336 μg mL(-1) with a signal to noise ratio of 3:1 and 10:1, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

Synthesize of silver-nanoparticles by plant extract and its application for preconcentration of cadmium followed by flame atomic absorption spectrometry.

PubMed

Almertaha, Abdul-Hossein; Eftekhari, Mohammad; Chamsaz, Mahmoud; Gheibi, Mohammad

2018-02-02

In this paper, Mentha pulegium leaves extract was used as a green reducing agent for the synthesis of silver-nanoparticles. The synthesized silver-nanoparticles were characterized by UV-VIS spectrophotometry, transmission electron microscopy, X-ray spectroscopy and used as an adsorbent for preconcentration of trace levels of cadmium (ІІ). After the desorption of cadmium (ІІ) in 5 mol L -1 formic acid, the desorbent solution was aspirated into the flame atomic absorption spectrometry for the determination of cadmium. In order to optimize the experimental condition, a response surface methodology based on central composite design was used. The optimum conditions are: pH: 8.6, amounts of adsorbent: 30 mg, 10 min extraction time and desorption time of 2 min. Under the optimum condition, the calibration curve was linear in the range of 5-200 μg L -1 cadmium (ІІ) ion with a correlation coefficient of 0.9995. The limit of detection was 1.1 μg L -1 and the relative standard deviation for 25 μg L -1 cadmium (ІІ) ion was 3.0% (n = 5). In order to check the applicability of the proposed method, different real samples were analyzed. Also, the accuracy of this method was successfully checked by the analysis of certified reference material and spike tests.

Three phases hollow fiber LPME combined with HPLC-UV for extraction, preconcentration and determination of valerenic acid in Valeriana officinalis.

PubMed

Mirzaei, Mohamad; Dinpanah, Hossein

2011-07-01

In the present work, the applicability of hollow fiber-based liquid phase microextraction (HF-LPME) was evaluated for the extraction and preconcentration of valerenic acid prior to its determination by reversed-phase HPLC/UV. The target drug was extracted from 5.0 mL of aqueous solution with pH 3.5 into an organic extracting solvent (dihexyl ether) impregnated in the pores of a hollow fiber and finally back extracted into 10 μ L of aqueous solution with pH 9.5 located inside the lumen of the hollow fiber. In order to obtain high extraction efficiency, the parameters affecting the HF-LPME, including pH of the donor and acceptor phases, type of organic phase, ionic strength, the volume ratio of donor to acceptor phase, stirring rate and extraction time were studied and optimized. Under the optimized conditions, enrichment factor up to 446 was achieved and the relative standard deviation (RSD) of the method was 4.36% (n = 9). The linear range was 7.5-850 μg L⁻¹ with correlation coefficient (r²=0.999), detection limits was 2.5 μg L⁻¹ and the LOQ was 7.5 μg L⁻¹. The proposed method was evaluated by extraction and determination of valerenic acid in some Iranian wild species of Valerianaceae. Copyright © 2011 Elsevier B.V. All rights reserved.

Distribution of pesticides in n-hexane/water and n-hexane/acetonitrile systems and estimation of possibilities of their extraction isolation and preconcentration from various matrices.

PubMed

Zayats, M F; Leschev, S M; Petrashkevich, N V; Zayats, M A; Kadenczki, L; Szitás, R; Szemán Dobrik, H; Keresztény, N

2013-04-24

Distribution of 150 most widely used pesticides of different chemical classes (amides, anilinopirimidines, aromatics, benzenesulfonates, carbamates, dicarboximides, organophosphorus compounds, phenyl esters, phenylureas, pyrazoles, pyrethroids, pyrimidines, strobilurins, sulfamides, triazines, triazoles, etc.) in n-hexane/water and n-hexane/acetonitrile systems was investigated at 25°C. Distribution constants of pesticides (P) have been calculated as ratio of pesticide concentration in n-hexane to its concentration in water or acetonitrile phase. HPLC and GC methods were used for pesticides determination in phases. It was found that the overwhelming majority of pesticides are hydrophobic, i.e. in n-hexane/water system LgP≫0, and the difference in LgP values can reach 9.1 units. Replacement of water for acetonitrile leads to dramatic fall of LgP values reaching 9.5 units. The majority of LgP values in this case are negative and their differences is strongly leveled in comparison with a hexane/water system. Thus, maximal difference in pesticides LgP values for n-hexane/acetonitrile system is 3.2 units. It is shown that n-hexane can be used for selective and efficient extraction and preconcentration of pesticides from water matrices. On the other hand, acetonitrile is effective for the isolation and preconcentration of pesticides from hydrocarbon and vegetable oil matrices. The distribution constants described in the paper may be effectively used for the estimation of possibilities of extraction isolation, preconcentration and separation of pesticides. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis, characterization and application of a new chelating resin for solid phase extraction, preconcentration and determination of trace metals in some dairy samples by flame atomic absorption spectrometry.

PubMed

Daşbaşı, Teslima; Saçmacı, Şerife; Çankaya, Nevin; Soykan, Cengiz

2016-11-15

In this study, a simple and rapid solid phase extraction/preconcentration procedure was developed for determination of Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Pb(II), and Zn(II) trace metals by flame atomic absorption spectrometry (FAAS). A new chelating resin, poly(N-cyclohexylacrylamide-co-divinylbenzene-co-2-acrylamido-2-methyl-1-propanesulfonic acid) (NCA-co-DVB-co-AMPS) (hereafter CDAP) was synthesized and characterized. The influences of the analytical parameters such as pH of the sample solution, type and concentration of eluent, flow rates of the sample and eluent, volume of the sample and eluent, amount of chelating resin, and interference of ions were examined. The limit of detection (LOD) of analytes were found (3s) to be in the range of 0.65-1.90μgL(-1). Preconcentration factor (PF) of 200 and the relative standard deviation (RSD) of ⩽2% were achieved (n=11). The developed method was applied for determination of analytes in some dairy samples and certified reference materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rapid and direct determination of glyphosate, glufosinate, and aminophosphonic acid by online preconcentration CE with contactless conductivity detection.

PubMed

See, Hong Heng; Hauser, Peter C; Ibrahim, Wan Aini Wan; Sanagi, Mohd Marsin

2010-01-01

Rapid and direct online preconcentration followed by CE with capacitively coupled contactless conductivity detection (CE-C(4)D) is evaluated as a new approach for the determination of glyphosate, glufosinate (GLUF), and aminophosphonic acid (AMPA) in drinking water. Two online preconcentration techniques, namely large volume sample stacking without polarity switching and field-enhanced sample injection, coupled with CE-C(4)D were successfully developed and optimized. Under optimized conditions, LODs in the range of 0.01-0.1 microM (1.7-11.1 microg/L) and sensitivity enhancements of 48- to 53-fold were achieved with the large volume sample stacking-CE-C(4)D method. By performing the field-enhanced sample injection-CE-C(4)D procedure, excellent LODs down to 0.0005-0.02 microM (0.1-2.2 microg/L) as well as sensitivity enhancements of up to 245- to 1002-fold were obtained. Both techniques showed satisfactory reproducibility with RSDs of peak height of better than 10%. The newly established approaches were successfully applied to the analysis of glyphosate, glufosinate, and aminophosphonic acid in spiked tap drinking water.

Polyvinylidene Fluoride Micropore Membranes as Solid-Phase Extraction Disk for Preconcentration of Nanoparticulate Silver in Environmental Waters.

PubMed

Zhou, Xiao-Xia; Lai, Yu-Jian; Liu, Rui; Li, Sha-Sha; Xu, Jing-Wen; Liu, Jing-Fu

2017-12-05

Efficient separation and preconcentration of trace nanoparticulate silver (NAg) from large-volume environmental waters is a prerequisite for reliable analysis and therefore understanding the environmental processes of silver nanoparticles (AgNPs). Herein, we report the novel use of polyvinylidene fluoride (PVDF) filter membrane for disk-based solid phase extraction (SPE) of NAg in 1 L of water samples with the disk-based SPE system, which consists of a syringe pump and a syringe filter holder to embed the filter membrane. While the PVDF membrane can selectively adsorb NAg in the presence of Ag + , aqueous solution of 2% (m/v) FL-70 is found to efficiently elute NAg. Analysis of NAg is performed following optimization of filter membrane and elution conditions with an enrichment factor of 1000. Additionally, transmission electron microscopy (TEM), UV-vis spectroscopy, and size-exclusion chromatography coupled with ICP-MS (SEC-ICP-MS) analysis showed that the extraction gives rise to no change in NAg size or shape, making this method attractive for practical applications. Furthermore, feasibility of the protocol is verified by applying it to extract NAg in four real waters with recoveries of 62.2-80.2% at 0.056-0.58 μg/L spiked levels. This work will facilitate robust studies of trace NAg transformation and their hazard assessments in the environment.

Separation of Gd-humic complexes and Gd-based magnetic resonance imaging contrast agent in river water with QAE-Sephadex A-25 for the fractionation analysis.

PubMed

Matsumiya, Hiroaki; Inoue, Hiroto; Hiraide, Masataka

2014-10-01

Gadolinium complexed with naturally occurring, negatively charged humic substances (humic and fulvic acids) was collected from 500 mL of sample solution onto a column packed with 150 mg of a strongly basic anion-exchanger (QAE-Sephadex A-25). A Gd-based magnetic resonance imaging contrast agent (diethylenetriamine-N,N,N',N″,N″-pentaacetato aquo gadolinium(III), Gd-DTPA(2-)) was simultaneously collected on the same column. The Gd-DTPA complex was desorbed by anion-exchange with 50mM tetramethylammonium sulfate, leaving the Gd-humic complexes on the column. The Gd-humic complexes were subsequently dissociated with 1M nitric acid to desorb the humic fraction of Gd. The two-step desorption with small volumes of the eluting agents allowed the 100-fold preconcentration for the fractionation analysis of Gd at low ng L(-1) levels by inductively coupled plasma-mass spectrometry (ICP-MS). On the other hand, Gd(III) neither complexed with humic substances nor DTPA, i.e., free species, was not sorbed on the column. The free Gd in the effluent was preconcentrated 100-fold by a conventional solid-phase extraction with an iminodiacetic acid-type chelating resin and determined by ICP-MS. The proposed analytical fractionation method was applied to river water samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Simultaneous Preconcentration and Determination of Brilliant Blue and Sunset Yellow in Foodstuffs by Solid-Phase Extraction Combined UV-Vis Spectrophotometry.

PubMed

Bişgin, Abdullah Taner

2018-05-29

Background: Brilliant Blue and Sunset Yellow, two highly water-soluble synthetic food dyes, are the most popular food dyes used and consumed. Although they are not highly toxic, some health problems can be observed when excessive amounts of food products containing these dyes are consumed. Objectives: The aim of the study was to develop a simultaneous UV-Vis combined solid-phase extraction method, based on the adsorption onto Amberlite XAD-8 resin, for determination of Brilliant Blue and Sunset Yellow dyes. Methods: Sample solution was poured into the reservoir of the column and permitted to gravitationally pass through the column at 2 mL/min flow rate. Adsorbed dyes were eluted to 5 mL of final volume with 1 mol/L HNO₃ in ethanol solution by applying a 2 mL/min flow rate. Dye concentrations of the solution were determined at 483 and 630 nm for Sunset Yellow and Brilliant Blue, respectively. Results: The detection limits of the method for Brilliant Blue and Sunset Yellow were determined as 0.13 and 0.66 ng/mL, respectively. Preconcentration factor was 80. Brilliant Blue contents of real food samples were found to be between 11 and 240 μg/g. Sunset Yellow concentrations of foodstuffs were determined to be between 19 and 331 μg/g. Conclusions: Economical, effective, and simple simultaneous determination of Brilliant Blue and Sunset Yellow was achieved by using a solid-phase extraction combined UV-Vis spectrometry method. Highlights: The method is applicable and suitable for routine analysis in quality control laboratories without the need for expert personnel and high operational costs because the instrumentation is simple and inexpensive.

The trace analysis of microorganisms in real samples by combination of a filtration microcartridge and capillary isoelectric focusing.

PubMed

Horká, Marie; Horký, Jaroslav; Kubesová, Anna; Zapletalová, Eva; Slais, Karel

2011-07-01

Trace analysis of microorganisms in real biological samples needs very sensitive methods for their detection. Most procedures for detecting and quantifying pathogens require a sample preparation step including concentrating microorganisms from large sample volumes with high and reproducible efficiency. Electromigration techniques have great potential to include the preconcentration, separation, and detection of whole cells and therefore they can rapidly indicate the presence of pathogens. The preconcentration and separation of microorganisms from real suspensions utilising a combination of filtration and capillary isoelectric focusing was developed and the possibility for its application to real samples was verified. For our experiments, spores of Monilinia species and of Penicillium expansum were selected as model bioparticles, as they cause major losses in agrosystems. The isoelectric points of the spores of M. laxa, M. fructigena, M. fruticola, and P. expansum were determined and the method was verified using real samples taken directly from infected apples. The coupling of a filtration cartridge with a separation capillary can improve the detection limit of isoelectric focusing with UV detection by at least 4 orders of magnitude. Spores of M. fructigena and of M. laxa in numbers of hundreds of particles per milliliter were detected on a visually noninfected apple surface which was cross-contaminated during handling and storage. The efficiency of preconcentration and a preliminary identification was verified by the phenotyping technique after cultivation of the spores sampled from the apple surface.

Quantum-Dot-Based Electrochemical Immunoassay for High-Throughput Screening of the Prostate-Specific Antigen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jun; Liu, Guodong; Wu, Hong

2008-01-01

In this paper, we demonstrate an electrochemical high-throughput sensing platform for simple, sensitive detection of PSA based on QD labels. This sensing platform uses a microplate for immunoreactions and disposable screen-printed electrodes (SPE) for electrochemical stripping analysis of metal ions released from QD labels. With the 96-well microplate, capturing antibodies are conveniently immobilized to the well surface, and the process of immunoreaction is easily controlled. The formed sandwich complexes on the well surface are also easily isolated from reaction solutions. In particular, a microplate-based electrochemical assay can make it feasible to conduct a parallel analysis of several samples or multiplemore » protein markers. This assay offers a number of advantages including (1) simplicity, cost-effectiveness, (2) high sensitivity, (3) capability to sense multiple samples or targets in parallel, and (4) a potentially portable device with an SPE array implanted in the microplate. This PSA assay is sensitive because it uses two amplification processes: (1) QDs as a label for enhancing electrical signal since secondary antibodies are linked to QDs that contain a large number of metal atoms and (2) there is inherent signal amplification for electrochemical stripping analysis—preconcentration of metal ion onto the electrode surface for amplifying electrical signals. Therefore, the high sensitivity of this method, stemming from dual signal amplification via QD labels and pre-concentration, allows low concentration levels to be detected while using small sample volumes. Thus, this QD-based electrochemical detection approach offers a simple, rapid, cost-effective, and high throughput assay of PSA.« less

Characterization of semi-solid Self-Emulsifying Drug Delivery Systems (SEDDS) of atorvastatin calcium by Raman image spectroscopy and chemometrics.

PubMed

Breitkreitz, Márcia C; Sabin, Guilherme P; Polla, Griselda; Poppi, Ronei J

2013-01-25

A methodology based on Raman image spectroscopy and chemometrics for homogeneity evaluation of formulations containing atorvastatin calcium in Gelucire(®) 44/14 is presented. In the first part of the work, formulations with high amounts of Gelucire(®) 44/14 (80%) and solvents of different polarities (diethylene glycol monoethyl ether, propyleneglycol, propylene glycol monocaprylate and glyceryl mono/dicaprylate/caprate) were prepared for miscibility screening evaluation by classical least squares (CLS). It was observed that Gelucire(®) 44/14 presented higher affinity for the lipophilic solvents glyceryl mono/dicaprylate/caprate and propylene glycol monocaprylate, whose samples were observed to be homogeneous, and lower affinity for the hydrophilic solvents diethylene glycol monoethyl ether and propyleneglycol, whose samples were heterogeneous. In the second part of the work, the ratio of glyceryl mono/dicaprylate/caprate and Gelucire(®) 44/14 was determined based on studies in water and allowed the selection of the proportions of these two excipients in the preconcentrate that provided supersaturation of atorvastatin upon dilution. The preconcentrate was then evaluated for homogeneity by partial least squares (PLS) and an excellent miscibility was observed in this proportion as well. Therefore, it was possible to select a formulation that presented simultaneously homogeneous preconcentrate and solubility enhancement in water by Raman image spectroscopy and chemometrics. Copyright © 2012 Elsevier B.V. All rights reserved.

A nanosilver-based spectrophotometric method for determination of malachite green in surface water samples.

PubMed

Sahraei, R; Farmany, A; Mortazavi, S S; Noorizadeh, H

2013-07-01

A new spectrophotometric method is reported for the determination of nanomolar level of malachite green in surface water samples. The method is based on the catalytic effect of silver nanoparticles on the oxidation of malachite green by hexacyanoferrate (III) in acetate-acetic acid medium. The absorbance is measured at 610 nm with the fixed-time method. Under the optimum conditions, the linear range was 8.0 × 10(-9)-2.0 × 10(-7) mol L(-1) malachite green with a correlation coefficient of 0.996. The limit of detection (S/N = 3) was 2.0 × 10(-9) mol L(-1). Relative standard deviation for ten replicate determinations of 1.0 × 10(-8) mol L(-1) malachite green was 1.86%. The method is featured with good accuracy and reproducibility for malachite green determination in surface water samples without any pre-concentration and separation step.

RAPID DETERMINATION OF ACTINIDES IN URINE BY INDUCTIVELY-COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY: A HYBRID APPROACH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, S.; Jones, V.

2009-05-27

A new rapid separation method that allows separation and preconcentration of actinides in urine samples was developed for the measurement of longer lived actinides by inductively coupled plasma mass spectrometry (ICP-MS) and short-lived actinides by alpha spectrometry; a hybrid approach. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration, if required, is performed using a streamlined calcium phosphate precipitation. Similar technology has been applied to separate actinides prior to measurement by alpha spectrometry, but this new method has been developed with elution reagents now compatible with ICP-MS as well. Purified solutions are splitmore » between ICP-MS and alpha spectrometry so that long- and short-lived actinide isotopes can be measured successfully. The method allows for simultaneous extraction of 24 samples (including QC samples) in less than 3 h. Simultaneous sample preparation can offer significant time savings over sequential sample preparation. For example, sequential sample preparation of 24 samples taking just 15 min each requires 6 h to complete. The simplicity and speed of this new method makes it attractive for radiological emergency response. If preconcentration is applied, the method is applicable to larger sample aliquots for occupational exposures as well. The chemical recoveries are typically greater than 90%, in contrast to other reported methods using flow injection separation techniques for urine samples where plutonium yields were 70-80%. This method allows measurement of both long-lived and short-lived actinide isotopes. 239Pu, 242Pu, 237Np, 243Am, 234U, 235U and 238U were measured by ICP-MS, while 236Pu, 238Pu, 239Pu, 241Am, 243Am and 244Cm were measured by alpha spectrometry. The method can also be adapted so that the separation of uranium isotopes for assay is not required, if uranium assay by direct dilution of the urine sample is preferred instead. Multiple vacuum box locations may be set-up to supply several ICP-MS units with purified sample fractions such that a high sample throughput may be achieved, while still allowing for rapid measurement of short-lived actinides by alpha spectrometry.« less

Comparison between dispersive solid-phase and dispersive liquid-liquid microextraction combined with spectrophotometric determination of malachite green in water samples based on ultrasound-assisted and preconcentration under multi-variable experimental design optimization.

PubMed

Alipanahpour Dil, Ebrahim; Ghaedi, Mehrorang; Asfaram, Arash; Zare, Fahimeh; Mehrabi, Fatemeh; Sadeghfar, Fardin

2017-11-01

The ultrasound-assisted dispersive solid-phase microextraction (USA-DSPME) and the ultrasound-assisted dispersive liquid-liquid microextraction (USA-DLLME) developed for as an ultra preconcentration and/or technique for the determination of malachite green (MG) in water samples. Central composite design based on analysis of variance and desirability function guide finding best operational conditions and represent dependency of response to variables viz. volume of extraction, eluent and disperser solvent, pH, adsorbent mass and ultrasonication time has significant influence on methods efficiency. Optimum conditions was set for USA-DSPME as: 1mg CNTs/Zn:ZnO@Ni 2 P-NCs; 4min sonication time and 130μL eluent at pH 6.0. Meanwhile optimum point for USA-DLLME conditions were fixed at pH 6.0; 4min sonication time and 130, 650μL and 10mL of extraction solvent (CHCl 3 ), disperser solvent (ethanol) and sample volume, respectively. Under the above specified best operational conditions, the enrichment factors for the USA-DSPME and USA-DLLME were 88.89 and 147.30, respectively. The methods has linear response in the range of 20.0 to 4000.0ngmL -1 with the correlation coefficients (r) between 0.9980 to 0.9995, while its reasonable detection limits viz. 1.386 to 2.348ngmL -1 and good relative standard deviations varied from 1.1% to 2.8% (n=10) candidate this method for successful monitoring of analyte from various media. The relative recoveries of the MG dye from water samples at spiking level of 500ngmL -1 were in the range between 94.50% and 98.86%. The proposed methods has been successfully applied to the analysis of the MG dye in water samples, and a satisfactory result was obtained. Copyright © 2017. Published by Elsevier B.V.

Solvent-stir bar microextraction system using pure tris-(2-ethylhexyl) phosphate as supported liquid membrane: A new and efficient design for the extraction of malondialdehyde from biological fluids.

PubMed

Fashi, Armin; Salarian, Amir Ahmad; Zamani, Abbasali

2018-05-15

A novel and efficient device of solvent stir-bar microextraction (SSBME) system coupled with GC-FID detection was introduced for the pre-concentration and determination of malondialdehyde (MDA) in different biological matrices. In the proposed device, a piece of porous hollow fiber was located on a magnetic rotor by using a stainless steel-wire (as a mechanical support) and the whole device could stir with the magnetic rotor in sample solution cell. The device provided higher pre-concentration factor and better precision in comparison with conventional SBME due to the reproducible, stable and high contact area between the stirred sample and the hollow fiber. Organic solvent type, donor and acceptor phase pH, temperature, electrolyte concentration, agitation speed, extraction time, and sample volume as the effective factors on the SSBME efficiency, were examined and optimized. Pure tris-(2-ethylhexyl) phosphate (TEHP) was examined for the first time as supported liquid membrane (SLM) for the determination of MDA by SSBME method. In contrast to the conventional SLMs of SBME in the literature, the SLM of TEHP was highly stable in contact with biological fluids and provided the highest extraction efficiency. Under optimized extraction conditions, the method provided satisfactory linearity in the range 1-500 ng mL -1 , low LODs (0.3-0.7 ng mL -1 ), good repeatability and reproducibility (RSD% (n = 5) < 4.5) with the pre-concentration factors higher than 130-fold. To verify the accuracy of the proposed method, the traditional spectrophotometric TBA (2-thiobarbituric acid) test was used as a reference method. Finally, the proposed method was successfully applied for the determination and quantification of MDA in biological fluids. Copyright © 2018 Elsevier B.V. All rights reserved.

Chemically-modified activated carbon with ethylenediamine for selective solid-phase extraction and preconcentration of metal ions.

PubMed

Li, Zhenhua; Chang, Xijun; Zou, Xiaojun; Zhu, Xiangbing; Nie, Rong; Hu, Zheng; Li, Ruijun

2009-01-26

A new method that utilizes ethylenediamine-modified activated carbon (AC-EDA) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Fe(III), Hg(II) and Pb(II) prior to the measurement by inductively coupled plasma optical emission spectrometry (ICP-OES). The new sorbent was prepared by oxidative surface modification. Experimental conditions for effective adsorption of trace levels of Cr(III), Fe(III), Hg(II) and Pb(II) were optimized with respect to different experimental parameters using batch and column procedures in detail. The optimum pH value for the separation of metal ions simultaneously on the new sorbent was 4.0. Complete elution of absorbed metal ions from the sorbent surface was carried out using 3.0 mL of 2% (%w/w) thiourea and 0.5 mol L(-1) HCl solution. Common coexisting ions did not interfere with the separation and determination of target metal ions. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 39.4, 28.9, 60.5 and 49.9 mg g(-1) for Cr(III), Fe(III), Hg(II) and Pb(II), respectively. The time for 94% adsorption of target metal ions was less than 2 min. The detection limits of the method was found to be 0.28, 0.22, 0.09 and 0.17 ng mL(-1) for Cr(III), Fe(III), Hg(II) and Pb(II), respectively. The precision (R.S.D.) of the method was lower 4.0% (n=8). The prepared sorbent as solid-phase extractant was successfully applied for the preconcentration of trace Cr(III), Fe(III), Hg(II) and Pb(II) in natural and certified samples with satisfactory results.

Matrix elimination method for the determination of precious metals in ores using electrothermal atomic absorption spectrometry.

PubMed

Salih, Bekir; Celikbiçak, Omür; Döker, Serhat; Doğan, Mehmet

2007-03-28

Poly(N-(hydroxymethyl)methacrylamide)-1-allyl-2-thiourea) hydrogels, poly(NHMMA-ATU), were synthesized by gamma radiation using (60)Co gamma source in the ternary mixture of NHMMA-ATU-H(2)O. These hydrogels were used for the specific gold, silver, platinum and palladium recovery, pre-concentration and matrix elimination from the solutions containing trace amounts of precious metal ions. Elimination of inorganic matrices such as different transition and heavy metal ions, and anions was performed by adjusting the solution pH to 0.5 that was the selective adsorption pH of the precious metal ions. Desorption of the precious metal ions was performed by using 0.8 M thiourea in 3M HCl as the most efficient desorbing agent with recovery values more than 95%. In the desorption medium, thiourea effect on the atomic signal was eliminated by selecting proper pyrolysis and atomization temperatures for all precious metal ions. Precision and the accuracy of the results were improved in the graphite furnace-atomic absorption spectrometer (GFAAS) measurements by applying the developed matrix elimination method performing the adsorption at pH 0.5. Pre-concentration factors of the studied precious metal ions were found to be at least 1000-fold. Detection limits of the precious metal ions were found to be less than 10 ng L(-1) of the all studied precious metal ions by using the proposed pre-concentration method. Determination of trace levels of the precious metals in the sea-water, anode slime, geological samples and photographic fixer solutions were performed using GFAAS clearly after applying the adsorption-desorption cycle onto the poly(NHMMA-UTU) hydrogels.

Determination of methylmercury and inorganic mercury in water samples by slurry sampling cold vapor atomic absorption spectrometry in a flow injection system after preconcentration on silica C(18) modified.

PubMed

Segade, Susana Río; Tyson, Julian F

2007-03-15

A novel method for preconcentration of methylmercury and inorganic mercury from water samples was developed involving the determination of ngl(-1) levels of analytes retained on the silica C(18) solid sorbent, previous complexation with ammonium pyrrolidine dithiocarbamate (APDC), by slurry sampling cold vapor atomic absorption spectrometry (SS-CVAAS) in a flow injection (FI) system. Several variables were optimized affecting either the retention of both mercury species, such as APDC concentration, silica C(18) amount, agitation times, or their determination, including hydrochloric acid concentration in the suspension medium, peristaltic pump speed and argon flow-rate. A Plackett-Burman saturated factorial design permitted to differentiate the influential parameters on the preconcentration efficiency, which were after optimized by the sequential simplex method. The contact time between mercury containing solution and APDC, required to reach an efficient sorption, was decreased from 26 to 3min by the use of sonication stirring instead of magnetic stirring. The use of 1moldm(-3) hydrochloric acid suspension medium and 0.75% (m/v) sodium borohydride reducing agent permitted the selective determination of methylmercury. The combination of 5moldm(-3) hydrochloric acid and 10(-4)% (m/v) sodium borohydride was used for the selective determination of inorganic mercury. The detection limits achieved for methylmercury and inorganic mercury determination under optimum conditions were 0.96 and 0.25ngl(-1), respectively. The reliability of the proposed method for the determination of both mercury species in waters was checked by the analysis of samples spiked with known concentrations of methylmercury and inorganic mercury; quantitative recoveries were obtained.

Pre-concentration technique for reduction in "Analytical instrument requirement and analysis"

NASA Astrophysics Data System (ADS)

Pal, Sangita; Singha, Mousumi; Meena, Sher Singh

2018-04-01

Availability of analytical instruments for a methodical detection of known and unknown effluents imposes a serious hindrance in qualification and quantification. Several analytical instruments such as Elemental analyzer, ICP-MS, ICP-AES, EDXRF, ion chromatography, Electro-analytical instruments which are not only expensive but also time consuming, required maintenance, damaged essential parts replacement which are of serious concern. Move over for field study and instant detection installation of these instruments are not convenient to each and every place. Therefore, technique such as pre-concentration of metal ions especially for lean stream elaborated and justified. Chelation/sequestration is the key of immobilization technique which is simple, user friendly, most effective, least expensive, time efficient; easy to carry (10g - 20g vial) to experimental field/site has been demonstrated.

Determination of ethylenediaminetetraacetic acid in sea water by solid-phase extraction and high-performance liquid chromatography.

PubMed

Kemmei, Tomoko; Kodama, Shuji; Fujishima, Hironori; Yamamoto, Atsushi; Inoue, Yoshinori; Hayakawa, Kazuichi

2012-01-04

The chelating agent EDTA is widely used, and as a result is showing up widely in the aquatic environment. Here we describe a preconcentration procedure for measuring EDTA concentration in sea water samples by HPLC. The procedure consists of forming an Fe(III) complex followed by solid-phase extraction using an activated carbon cartridge. After the preconcentration, EDTA was quantified by HPLC with ultraviolet detection (260 nm). The enrichment permitted the determination of EDTA at concentrations as low as 1 nM. Good recoveries were obtained for both brackish and full-strength sea water with high repeatability (RSD<6%). The method was applied to sea water samples taken from near the mouth of the Oyabe River in Japan. Copyright © 2011 Elsevier B.V. All rights reserved.

Surfactant-enhanced spectrofluorimetric determination of total aflatoxins from wheat samples after magnetic solid-phase extraction using modified Fe3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Manafi, Mohammad Hanif; Allahyari, Mehdi; Pourghazi, Kamyar; Amoli-Diva, Mitra; Taherimaslak, Zohreh

2015-07-01

The extraction and preconcentration of total aflatoxins (including aflatoxin B1, B2, G1, and G2) using magnetic nanoparticles based solid phase extraction (MSPE) followed by surfactant-enhanced spectrofluorimetric detection was proposed. Ethylene glycol bis-mercaptoacetate modified silica coated Fe3O4 nanoparticles as an efficient antibody-free adsorbent was successfully applied to extract aflatoxins from wheat samples. High surface area and strong magnetization properties of magnetic nanoparticles were utilized to achieve high enrichment factor (97), and satisfactory recoveries (92-105%) using only 100 mg of the adsorbent. Furthermore, the fast separation time (less than 10 min) avoids many time-consuming cartridge loading or column-passing procedures accompany with the conventional SPE. In determination step, signal enhancement was performed by formation of Triton X-100 micelles around the analytes in 15% (v/v) acetonitrile-water which dramatically increase the sensitivity of the method. Main factors affecting the extraction efficiency and signal enhancement of the analytes including pH of sample solution, desorption conditions, extraction time, sample volume, adsorbent amount, surfactant concentration and volume and time of micelle formation were evaluated and optimized. Under the optimum conditions, wide linear range of 0.1-50 ng mL-1 with low detection limit of 0.03 ng mL-1 were obtained. The developed method was successfully applied to the extraction and preconcentration of aflatoxins in three commercially available wheat samples and the results were compared with the official AOAC method.

On-line sample cleanup and enrichment chromatographic technique for the determination of ambroxol in human serum.

PubMed

Emara, Samy; Kamal, Maha; Abdel Kawi, Mohamed

2012-02-01

A sensitive and efficient on-line clean up and pre-concentration method has been developed using column-switching technique and protein-coated µ-Bondapak CN silica pre-column for quantification of ambroxol (AM) in human serum. The method is performed by direct injection of serum sample onto a protein-coated µ-Bondapak CN silica pre-column, where AM is pre-concentrated and retained, while proteins and very polar constituents are washed to waste using a phosphate buffer saline (pH 7.4). The retained analyte on the pre-column is directed onto a C(18) analytical column for separation, with a mobile phase consisting of a mixture of methanol and distilled deionized water (containing 1% triethylamine adjusted to pH 3.5 with ortho-phosphoric acid) in the ratio of 50:50 (v/v). Detection is performed at 254 nm. The calibration curve is linear over the concentration range of 12-120 ng/mL (r(2) = 0.9995). The recovery, selectivity, linearity, precision, and accuracy of the method are convenient for pharmacokinetic studies or routine assays.

Monolithic microfluidic concentrators and mixers

DOEpatents

Frechet, Jean M.; Svec, Frantisek; Yu, Cong; Rohr, Thomas

2005-05-03

Microfluidic devices comprising porous monolithic polymer for concentration, extraction or mixing of fluids. A method for in situ preparation of monolithic polymers by in situ initiated polymerization of polymer precursors within microchannels of a microfluidic device and their use for solid phase extraction (SPE), preconcentration, concentration and mixing.

Mechanisms of deterioration of nutrients. [improved quality of freeze-dried foods

NASA Technical Reports Server (NTRS)

Karel, M.; Flink, J. M.

1978-01-01

Methods for improving the quality of freeze-dried foods were investigated. Areas discussed include: (1) microstructure of freeze-dried systems, (2) structural changes in freeze-dried systems, (3) artificial food matrices, and (4) osmotic preconcentration to yield improved freeze-dried products.

Determination of nickel in water, food, and biological samples by electrothermal atomic absorption spectrometry after preconcentration on modified carbon nanotubes.

PubMed

Taher, Mohammad Ali; Mazaheri, Lida; Ashkenani, Hamid; Mohadesi, Alireza; Afzali, Daryoush

2014-01-01

A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained.

Flotation-separation and ICP-AES determination of ultra trace amounts of copper, cadmium, nickel and cobalt using 2-aminocyclopentene-1-dithiocarboxylic acid.

PubMed

Shamsipur, Mojtaba; Hashemi, Omid Reza; Safavi, Afsaneh

2005-09-01

A rapid flotation method for separation and enrichment of ultra trace amounts of copper(II), cadmium(II), nickel(II) and cobalt(II) ions from water samples is established. At pH 6.5 and with sodium dodecylsulfate used as a foaming reagent, Cu2+, Cd2+, Ni2+ and Co2+ were separated simultaneously with 2-aminocyclopentene-1-dithiocarboxylic acid (ACDA) added to 1 l of aqueous solution. The proposed procedure of preconcentration is applied prior to the determination of these four analytes using inductivity coupled plasma-atomic emission spectrometry (ICP-AES). The effects of pH, concentration of ACDA, applicability of different surfactants and foreign ions on the separation efficiency were investigated. The preconcentration factor of the method is 1000 and the detection limits of copper(II), cadmium(II), nickel(II) and cobalt(II) ions are 0.078, 0.075, 0.072 and 0.080 ng ml(-1), respectively.

Environmental monitoring of phenolic pollutants in water by cloud point extraction prior to micellar electrokinetic chromatography.

PubMed

Stege, Patricia W; Sombra, Lorena L; Messina, Germán A; Martinez, Luis D; Silva, María F

2009-05-01

Many aromatic compounds can be found in the environment as a result of anthropogenic activities and some of them are highly toxic. The need to determine low concentrations of pollutants requires analytical methods with high sensitivity, selectivity, and resolution for application to soil, sediment, water, and other environmental samples. Complex sample preparation involving analyte isolation and enrichment is generally necessary before the final analysis. The present paper outlines a novel, simple, low-cost, and environmentally friendly method for the simultaneous determination of p-nitrophenol (PNP), p-aminophenol (PAP), and hydroquinone (HQ) by micellar electrokinetic capillary chromatography after preconcentration by cloud point extraction. Enrichment factors of 180 to 200 were achieved. The limits of detection of the analytes for the preconcentration of 50-ml sample volume were 0.10 microg L(-1) for PNP, 0.20 microg L(-1) for PAP, and 0.16 microg L(-1) for HQ. The optimized procedure was applied to the determination of phenolic pollutants in natural waters from San Luis, Argentina.

Combination of graphene oxide-based solid phase extraction and electro membrane extraction for the preconcentration of chlorophenoxy acid herbicides in environmental samples.

PubMed

Tabani, Hadi; Fakhari, Ali Reza; Shahsavani, Abolfath; Behbahani, Mohammad; Salarian, Mani; Bagheri, Akbar; Nojavan, Saeed

2013-07-26

Combination of different extraction methods is an interesting and debatable work in the field of sample preparation. In the current study, for the first time, solid phase extraction combined with electro membrane extraction (SPE-EME) was developed for ultra-preconcentration and determination of chlorophenoxy acid herbicides in environmental samples using capillary electrophoresis (CE). In the mentioned method, first, a 100mL of chlorophenoxy acid herbicides (2-methyl-4-chlorophenoxyacetic acid (MCPA), 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and 2-(4-chloro-2-methylphenoxy) propanoic acid (MCPP)) was passed through a column of graphene oxide as a solid phase, and then the adsorbed herbicides were eluted by 4.0mL of 8% acetic acid (HOAC) in methanol. Then, the elution solvent was evaporated and the herbicides residue was dissolved in 4.0mL of double distilled water (pH 9.0). Afterwards, the herbicides in 4.0mL of the aqueous solution were transferred to an EME glass vial. In the EME step, the herbicides were extracted from the sample solution into the basic acceptor solution (pH 13.0) under electrical potential, which was held inside the lumen of the fiber with 1-octanol as the supported liquid membrane (SLM). Under the optimized conditions, high enrichment factors were obtained in the range of 1950-2000. The limits of quantification (LOQs) and method detection limits (MDLs) were obtained in the range of 1.0-1.5 and 0.3-0.5ngmL(-1), respectively. Finally, the performance of the present method was evaluated for extraction and determination of chlorophenoxy acid herbicides in environmental samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Fabrication of magnetic microsphere-confined graphene for the preconcentration of some phthalate esters from environmental water and soybean milk samples followed by their determination by HPLC.

PubMed

Wang, Weina; Ma, Ruiyang; Wu, Qiuhua; Wang, Chun; Wang, Zhi

2013-05-15

In this study, a magnetic microsphere-confined graphene (Fe3O4@SiO2-G) was prepared as a novel adsorbent for the preconcentration of some phthalate esters in environmental water and soybean milk samples prior to high performance liquid chromatography analysis. The properties and morphology of the Fe3O4@SiO2-G were characterized by transmission electron microscopy and X-ray diffraction. This novel graphene-based magnetic nanocomposite showed great adsorptive ability toward the analytes. The method, which takes the advantages of both the high adsorption capacity of G and easy phase separation of the magnetic adsorbent from the sample solution, could avoid the time-consuming experimental procedures related to the traditional solid phase extraction. Various experimental parameters that could affect the extraction efficiencies, such as the amount of Fe3O4@SiO2-G, the extraction time, the pH of sample solution and the desorption conditions, were investigated. Under the optimum conditions, the limits of detection (S/N=3) of the method for the compounds were between 0.07 and 0.10 ng mL(-1) in water samples, and between 0.15 and 0.30 ng mL(-1) in soybean milk samples. The relative standard deviations (RSDs) varied from 2.7% to 6.1% (n=5). The recoveries of the method were in the range between 87.2% and 109.0% for environmental water and soybean milk samples. The method is suitable to determine the five phthalate esters (diallyl phthalate, di-n-propyl-phthalate, benzyl butyl phthalate, dicyclohexyl-phthalate and diethyl-hexyl-phthalate) in environmental water and soybean milk samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Solid phase microextraction Arrow for the sampling of volatile amines in wastewater and atmosphere.

PubMed

Helin, Aku; Rönkkö, Tuukka; Parshintsev, Jevgeni; Hartonen, Kari; Schilling, Beat; Läubli, Thomas; Riekkola, Marja-Liisa

2015-12-24

A new method is introduced for the sampling of volatile low molecular weight alkylamines in ambient air and wastewater by utilizing a novel SPME Arrow system, which contains a larger volume of sorbent compared to a standard SPME fiber. Parameters affecting the extraction, such as coating material, need for preconcentration, sample volume, pH, stirring rate, salt addition, extraction time and temperature were carefully optimized. In addition, analysis conditions, including desorption temperature and time as well as gas chromatographic parameters, were optimized. Compared to conventional SPME fiber, the SPME Arrow had better robustness and sensitivity. Average intermediate reproducibility of the method expressed as relative standard deviation was 12% for dimethylamine and 14% for trimethylamine, and their limit of quantification 10μg/L and 0.13μg/L respectively. Working range was from limits of quantification to 500μg/L for dimethylamine and to 130μg/L for trimethylamine. Several alkylamines were qualitatively analyzed in real samples, while target compounds dimethyl- and trimethylamines were quantified. The concentrations in influent and effluent wastewater samples were almost the same (∼80μg/L for dimethylamine, 120μg/L for trimethylamine) meaning that amines pass the water purification process unchanged or they are produced at the same rate as they are removed. For the air samples, preconcentration with phosphoric acid coated denuder was required and the concentration of trimethylamine was found to be around 1ng/m(3). The developed method was compared with optimized method based on conventional SPME and advantages and disadvantages of both approaches are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Preconcentration and determination of vanadium and molybdenum in milk, vegetables and foodstuffs by ultrasonic-thermostatic-assisted cloud point extraction coupled to flame atomic absorption spectrometry.

PubMed

Gürkan, Ramazan; Korkmaz, Sema; Altunay, Nail

2016-08-01

A new ultrasonic-thermostatic-assisted cloud point extraction procedure (UTA-CPE) was developed for preconcentration at the trace levels of vanadium (V) and molybdenum (Mo) in milk, vegetables and foodstuffs prior to determination via flame atomic absorption spectrometry (FAAS). The method is based on the ion-association of stable anionic oxalate complexes of V(V) and Mo(VI) with [9-(diethylamino)benzo[a]phenoxazin-5-ylidene]azanium; sulfate (Nile blue A) at pH 4.5, and then extraction of the formed ion-association complexes into micellar phase of polyoxyethylene(7.5)nonylphenyl ether (PONPE 7.5). The UTA-CPE is greatly simplified and accelerated compared to traditional cloud point extraction (CPE). The analytical parameters optimized are solution pH, the concentrations of complexing reagents (oxalate and Nile blue A), the PONPE 7.5 concentration, electrolyte concentration, sample volume, temperature and ultrasonic power. Under the optimum conditions, the calibration curves for Mo(VI) and V(V) are obtained in the concentration range of 3-340µgL(-1) and 5-250µgL(-1) with high sensitivity enhancement factors (EFs) of 145 and 115, respectively. The limits of detection (LODs) for Mo(VI) and V(V) are 0.86 and 1.55µgL(-1), respectively. The proposed method demonstrated good performances such as relative standard deviations (as RSD %) (≤3.5%) and spiked recoveries (95.7-102.3%). The accuracy of the method was assessed by analysis of two standard reference materials (SRMs) and recoveries of spiked solutions. The method was successfully applied into the determination of trace amounts of Mo(VI) and V(V) in milk, vegetables and foodstuffs with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

Separation and preconcentration of riboflavin from human plasma using polythionine coated magnetite/hydroxyapatite nanocomposite prior to analysis by surfactant-enhanced fluorimetry

NASA Astrophysics Data System (ADS)

Farzin, Leila; Shamsipur, Mojtaba

2017-09-01

The exploration of novel adsorption properties of conductive polymers based on hybridization with biocompatible nanomaterials receives an increasing interest. In this regard, hydroxyapatite (HA) bioceramic is of critical importance mainly owing to its facile synthesis, high surface area, economic and low toxicity in biological environments. In this work, we first prepared and characterized a magnetite/hydroxyapatite (Fe3O4/HA) nanocomposite using the bio-waste chicken eggshell via an attractive green way that involved low cost and irrespective of toxicity. Then, polythionine as a novel class of conductive polymers was in situ coated on the synthesized magnetic bioceramic for the separation and preconcentration of riboflavin (vitamin B2) in human plasma before its fluorimetric determination. Considering the putative role of riboflavin in protecting against cancer and cardiovascular diseases, it is essential to evaluate this vitamin in biological fluids. The described method possesses a linear range of 0.75-262.5 μg L- 1 (R2 = 0.9985) and a detection limit of 0.20 μg L- 1 (signal-to-noise ratio of 3). The relative standard deviations (RSDs) for single-sorbent repeatability and sorbent-to-sorbent reproducibility were less than 4.0% and 7.6% (n = 5), respectively. The respective enrichment factor and extraction recovery of the method found to be 35.7 and 98.4%. The analytical performance of method for riboflavin was characterized by good consistency of the results with those obtained by the enzyme-linked immunosorbent assay (ELISA) conventional method (p-value of < 0.05). The optimized protocol intended for control determinations of riboflavin in human subjects and is addressed to clinical laboratories.

Chromium speciation in environmental samples using a solid phase spectrophotometric method

NASA Astrophysics Data System (ADS)

Amin, Alaa S.; Kassem, Mohammed A.

2012-10-01

A solid phase extraction technique is proposed for preconcentration and speciation of chromium in natural waters using spectrophotometric analysis. The procedure is based on sorption of chromium(III) as 4-(2-benzothiazolylazo)2,2'-biphenyldiol complex on dextran-type anion-exchange gel (Sephadex DEAE A-25). After reduction of Cr(VI) by 0.5 ml of 96% concentrated H2SO4 and ethanol, the system was applied to the total chromium. The concentration of Cr(VI) was calculated as the difference between the total Cr and the Cr(III) content. The influences of some analytical parameters such as: pH of the aqueous solution, amounts of 4-(2-benzothiazolylazo)2,2'-biphenyldiol (BTABD), and sample volumes were investigated. The absorbance of the gel, at 628 and 750 nm, packed in a 1.0 mm cell, is measured directly. The molar absorptivities were found to be 2.11 × 107 and 3.90 × 107 L mol-1 cm-1 for 500 and 1000 ml, respectively. Calibration is linear over the range 0.05-1.45 μg L-1 with RSD of <1.85% (n = 8.0). Using 35 mg exchanger, the detection and quantification limits were 13 and 44 ng L-1 for 500 ml sample, whereas for 1000 ml sample were 8.0 and 27 ng L-1, respectively. Increasing the sample volume can enhance the sensitivity. No considerable interferences have been observed from other investigated anions and cations on the chromium speciation. The proposed method was applied to the speciation of chromium in natural waters and total chromium preconcentration in microwave digested tobacco, coffee, tea, and soil samples. The results were simultaneously compared with those obtained using an ET AAS method, whereby the validity of the method has been tested.

Two-stage preconcentrator for vapor/particle detection

DOEpatents

Linker, Kevin L.; Brusseau, Charles A.

2002-01-01

A device for concentrating particles from a high volume gas stream and delivering the particles for detection in a low volume gas stream includes first and second preconcentrators. The first preconcentrator has a first structure for retaining particles in a first gas flow path through which a first gas flows at a relatively high volume, valves for selectively stopping the first gas flow; and a second gas flow path through which gas flows at an intermediate flow volume for moving particles from the first structure. The second preconcentrator includes a second structure for retaining particles in the second gas flow path; a valve for selectively stopping the second gas flow; and a third gas flow path through which gas flows at a low volume for moving particles from the second structure to a detector. Each of the particle retaining structures is preferably a metal screen that may be resistively heated by application of an electric potential to release the particles.

Recent advances in the development of extraction chromatographic materials for the isolation of radionuclides from biological and environmental samples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dietz, M. L.

1998-11-30

The determination of low levels of radionuclides in environmental and biological samples is often hampered by the complex and variable nature of the samples. One approach to circumventing this problem is to incorporate into the analytical scheme a separation and preconcentration step by which the species of interest can be isolated from the major constituents of the sample. Extraction chromatography (EXC), a form of liquid chromatography in which the stationary phase comprises an extractant or a solution of an extractant in an appropriate diluent coated onto an inert support, provides a simple and efficient means of performing a wide varietymore » of metal ion separations. Recent advances in extractant design, in particular the development of extractants capable of metal ion recognition or of strong complex formation even in acidic media, have substantially improved the utility of the method. For the preconcentration of actinides, for example, an EXC resin consisting of a liquid diphosphonic acid supported on a polymeric substrate has been shown to exhibit extraordinarily strong retention of these elements from acidic chloride media. This resin, together with other related materials, can provide the basis of a number of efficient and flexible schemes for the separation and preconcentration of radionuclides form a variety of samples for subsequent determination.« less

Determination of perchlorate from tea leaves using quaternary ammonium modified magnetic carboxyl-carbon nanotubes followed by liquid chromatography-tandem quadrupole mass spectrometry.

PubMed

Zhao, Yong-Gang; Zhang, Yun; Wang, Feng-Lian; Zhou, Jian; Zhao, Qi-Ming; Zeng, Xiu-Qiong; Hu, Mei-Qin; Jin, Mi-Cong; Zhu, Yan

2018-08-01

The novel quaternary ammonium modified magnetic carboxyl-carbon nanotubes (QA-Mag-CCNTs) have been synthesised and characterized. QA-Mag-CCNTs were applied in magnetic dispersive solid phase extraction (Mag-dSPE) for preconcentration of perchlorate from tea leaves prior to liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) analysis. The Mag-dSPE procedure for preconcentration of perchlorate succeed in overcoming the flaw (containing target analyte randomly) of commercially available SPE cartridge. Under optimal conditions, the results showed higher extraction efficiency of QA-Mag-CCNTs, with recoveries between 85.2% and 107%. And the satisfactory precision with inter-day and intra-day RSD values were lower than 8.0%. Furthermore, QA-Mag-CCNTs were evaluated for reuse up to 20 times. The limit of quantification (LOQ) for perchlorate was 8.21 ng kg -1 . The developed method was successfully applied in tea leaves for food-safety risk monitoring in Zhejiang province, China. The results showed the concentrations of perchlorate in 229 out of 240 collected samples were in the range of 0.082-988 μg kg -1 . It was confirmed that QA-Mag-CCNTs were highly effective materials used for preconcentration of perchlorate. Copyright © 2018 Elsevier B.V. All rights reserved.

On-line separation and preconcentration of lead(II) by solid-phase extraction using activated carbon loaded with xylenol orange and its determination by flame atomic absorption spectrometry.

PubMed

Ensafi, Ali A; Shiraz, A Zendegi

2008-02-11

Activated carbon loaded with xylenol orange in a mini-column was used for the highly selective separation and preconcentration of Pb(II) ions. An on-line system for enrichment and the determination of Pb(II) was carried out on flame atomic absorption spectrometry. The conditions of preconcentration and quantitative recovery of Pb(II) from diluted solution, such as pH of aqueous phase, amount of the sorbent, volume of the solutions and flow variables were studied as well as effect of potential interfering ions. Under the optimum conditions, Pb(II) in an aqueous sample was concentrated about 200-fold and the detection limit was 0.4 ng mL(-1) Pb(II). The adsorption capacity of the solid phase was 0.20mg of lead per one gram of the modified activated carbon. The modified activated carbon is stable for several treatments of sample solutions without the need for using any chemical reagent. The recovery of lead(II) from river water, waste water, tap water, and in the following reference materials: SRM 2711 Montana soil and GBW-07605 tea were obtained in the range of 97-104% by the proposed method.

Reduction of interferences in graphite furnace atomic absorption spectrometry by multiple linear regression modelling

NASA Astrophysics Data System (ADS)

Grotti, Marco; Abelmoschi, Maria Luisa; Soggia, Francesco; Tiberiade, Christian; Frache, Roberto

2000-12-01

The multivariate effects of Na, K, Mg and Ca as nitrates on the electrothermal atomisation of manganese, cadmium and iron were studied by multiple linear regression modelling. Since the models proved to efficiently predict the effects of the considered matrix elements in a wide range of concentrations, they were applied to correct the interferences occurring in the determination of trace elements in seawater after pre-concentration of the analytes. In order to obtain a statistically significant number of samples, a large volume of the certified seawater reference materials CASS-3 and NASS-3 was treated with Chelex-100 resin; then, the chelating resin was separated from the solution, divided into several sub-samples, each of them was eluted with nitric acid and analysed by electrothermal atomic absorption spectrometry (for trace element determinations) and inductively coupled plasma optical emission spectrometry (for matrix element determinations). To minimise any other systematic error besides that due to matrix effects, accuracy of the pre-concentration step and contamination levels of the procedure were checked by inductively coupled plasma mass spectrometric measurements. Analytical results obtained by applying the multiple linear regression models were compared with those obtained with other calibration methods, such as external calibration using acid-based standards, external calibration using matrix-matched standards and the analyte addition technique. Empirical models proved to efficiently reduce interferences occurring in the analysis of real samples, allowing an improvement of accuracy better than for other calibration methods.

Novel amphiphilic polymeric ionic liquid-solid phase micro-extraction membrane for the preconcentration of aniline as degradation product of azo dye Orange G under sonication by liquid chromatography-tandem mass spectrometry.

PubMed

Cai, Mei-Qiang; Wei, Xiao-Qing; Du, Chun-Hui; Ma, Xu-Ming; Jin, Mi-Cong

2014-07-04

A novel amphiphilic polymeric ionic liquid membrane containing a hydrophilic bromide anion and a hydrophobic carbonyl group was synthesized in dimethylformamide (DMF) systems using the ionic liquid 1-butyl-3-vinylimidazolium bromide (BVImBr) and the methylmethacrylate (MMA) as monomers. The prepared amphiphilic ploy-methylmethacrylate-1-butyl-3-vinylimidazolium bromide (MMA-BVImBr) was characterized by a scanning electron microscope and an infrared spectrum instrument. The results of solid-phase micro-extraction membrane (SPMM) experiments showed that the adsorption capacity of membrane was about 0.76μgμg(-1) for aniline. Based on this, a sensitive method for the determination of trace aniline, as a degradation product of azo dye Orange G under sonication, was developed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The calibration curve showed a good linearity ranging from 0.5 to 10.0μgL(-1) with a correlation coefficient value of 0.9998. The limit of quantification was 0.5μgL(-1). The recoveries ranged from 90.6% to 96.1%. The intra- and inter-day relative standard deviations were less than 8.3% and 10.9%. The developed SPMM-LC-MS/MS method was used successfully for preconcentration of trace aniline produced during the sonication of Orange G solution. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of magnetic molecularly imprinted polymers for selective extraction: determination of citrinin in rice samples by liquid chromatography with UV diode array detection.

PubMed

Urraca, Javier L; Huertas-Pérez, José F; Cazorla, Guillermo Aragoneses; Gracia-Mora, Jesus; García-Campaña, Ana M; Moreno-Bondi, María Cruz

2016-04-01

In this work, we report the synthesis of novel magnetic molecularly imprinted polymers (m-MIPs) and their application to the selective extraction of the mycotoxin citrinin (CIT) from food samples. The polymers were prepared by surface imprinting of Fe3O4 nanoparticles, using 2-naphtholic acid (2-NA) as template molecule, N-3,5-bis(trifluoromethyl)phenyl-N'-4-vinylphenyl urea and methacrylamide as functional monomers and ethyleneglycol dimethacrylate as cross-linker. The resulting material was characterized by transmission electron microscopy (TEM), and X-ray diffraction (XRD) and Fourier transform infrared spectroscopies (FT-IR). The polymers were used to develop a solid-phase extraction method (m-MISPE) for the selective recovery of CIT from rice extracts prior to its determination by HPLC with UV diode array detection. The method involves ultrasound-assisted extraction of the mycotoxin from rice samples with (7:3, v/v) methanol/water, followed by sample cleanup and preconcentration with m-MIP. The extraction (washing and elution) conditions were optimized and their optimal values found to provide CIT recoveries of 94-98 % with relative standard deviations (RSD) less than 3.4 % (n = 3) for preconcentrated sample extracts (5 mL) fortified with the analyte at concentrations over the range 25-100 μg kg(-1). Based on the results, the application of the m-MIPs facilitates the accurate and efficient determination of CIT in rice extracts.

Development of magnetic graphene oxide adsorbent for the removal and preconcentration of As(III) and As(V) species from environmental water samples.

PubMed

Rashidi Nodeh, Hamid; Wan Ibrahim, Wan Aini; Ali, Imran; Sanagi, Mohd Marsin

2016-05-01

New-generation adsorbent, Fe3O4@SiO2/GO, was developed by modification of graphene oxide (GO) with silica-coated (SiO2) magnetic nanoparticles (Fe3O4). The synthesized adsorbent was characterized using Fourier transform infrared spectroscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, and field emission scanning electron microscopy. The developed adsorbent was used for the removal and simultaneous preconcentration of As(III) and As(V) from environmental waters prior to ICP-MS analysis. Fe3O4@SiO2/GO provided high adsorption capacities, i.e., 7.51 and 11.46 mg g(-1) for As(III) and As(V), respectively, at pH 4.0. Adsorption isotherm, kinetic, and thermodynamic were investigated for As(III) and As(V) adsorption. Preconcentration of As(III) and As(V) were studied using magnetic solid-phase extraction (MSPE) method at pH 9.0 as the adsorbent showed selective adsorption for As(III) only in pH range 7-10. MSPE using Fe3O4@SiO2/GO was developed with good linearities (0.05-2.0 ng mL(-1)) and high coefficient of determination (R (2) = 0.9992 and 0.9985) for As(III) and As(V), respectively. The limits of detection (LODs) (3× SD/m, n = 3) obtained were 7.9 pg mL(-1) for As(III) and 28.0 pg mL(-1) for As(V). The LOD obtained is 357-1265× lower than the WHO maximum permissible limit of 10.0 ng mL(-1). The developed MSPE method showed good relative recoveries (72.55-109.71 %) and good RSDs (0.1-4.3 %, n = 3) for spring water, lake, river, and tap water samples. The new-generation adsorbent can be used for the removal and simultaneous preconcentration of As(III) and As(V) from water samples successfully. The adsorbent removal for As(III) is better than As(V).

Development of clinical dosage forms for a poorly water-soluble drug II: formulation and characterization of a novel solid microemulsion preconcentrate system for oral delivery of a poorly water-soluble drug.

PubMed

Li, Ping; Hynes, Sara R; Haefele, Thomas F; Pudipeddi, Madhu; Royce, Alan E; Serajuddin, Abu T M

2009-05-01

The solution of a poorly water-soluble drug in a liquid lipid-surfactant mixture, which served as a microemulsion preconcentrate, was converted into a solid form by incorporating it in a solid polyethylene glycol (PEG) matrix. The solid microemulsion preconcentrates thus formed consisted of Capmul PG8 (propylene glycol monocaprylate) as oil, Cremophor EL (polyoxyl 35 castor oil) as surfactant, and hydrophilic polymer PEG 3350 as solid matrix. The drug (aqueous solubility: 0.17 microg/mL at pH 1-8 and 25 degrees C) was dissolved in a melt of the mixture at 65-70 degrees C and then the hot solution was filled into hard gelatin capsules; the liquid gradually solidified upon cooling below 55 degrees C. The solid system was characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), confocal Raman microscopy (CRM), and the dispersion testing in water. It was confirmed that a solid microemulsion preconcentrate is a two-phase system, where clusters of crystalline PEG 3350 formed the solid structure (m.p. 55-60 degrees C) and the liquid microemulsion preconcentrate dispersed in between PEG 3350 crystals as a separate phase. The drug remained dissolved in the liquid phase. In vitro release testing showed that the preconcentrate dispersed readily in water forming a microemulsion with the drug dissolved in the oil particles (<150 nm) and the presence of PEG 3350 did not interfere with the process of self-microemulsification.

Rapid ionic liquid-based ultrasound assisted dual magnetic microextraction to preconcentrate and separate cadmium-4-(2-thiazolylazo)-resorcinol complex from environmental and biological samples.

PubMed

Khan, Sumaira; Kazi, Tasneem Gul; Soylak, Mustafa

2014-04-05

A rapid and innovative microextraction technique named as, ionic liquid-based ultrasound-assisted dual magnetic microextraction (IL-UA-DMME) was developed for the preconcentration and extraction of trace cadmium from environmental and biological samples, prior to analyzed by flame atomic absorption spectrometry (FAAS). The proposed method has many obvious advantages, including evading the use of organic solvents and achieved high extraction yields by the combination of dispersive liquid-liquid microextraction (DLLME) and magnetic mediated-solid phase extraction (MM-SPE). In this approach ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] play an important role to extract the cadmium-4-(2-thiazolylazo)-resorcinol (Cd-TAR) complex from acid digested sample solutions and ultrasonic irradiation was applied to assist emulsification. After then, dispersed small amount of Fe3O4 magnetic nanoparticles (MNPs) in sample solutions to salvaged the IL and complete phase separation was attained. Some analytical parameters that influencing the efficiency of proposed (IL-UA-DMME) method, such as pH, volume of IL, ligand concentration, ultra-sonication time, amount of Fe3O4 MNPs, sample volume and matrix effect were optimized. Limit of detection (LOD) and enrichment factor (EF) of the method under optimal experimental conditions were found to be 0.40μgL(-1) and 100, respectively. The relative standard deviation (RSD) of 50μgL(-1) Cd was 4.29%. The validity and accuracy of proposed method, was assessed to analyzed certified reference materials of fortified lake water TMDA-54.4, SPS-WW2 waste water, spinach leaves 1570a and also checked by standard addition method. The obtained values showed good agreement with the certified values and sufficiently high recovery were found in the range of 98.1-101% for Cd. The proposed method was facile, rapid and successfully applied for the determination of Cd in environmental and different biological samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Determination of phenylurea herbicides in water samples using online sorptive preconcentration and high-performance liquid chromatography with UV or electrospray mass spectrometric detection.

PubMed

Baltussen, E; Snijders, H; Janssen, H G; Sandra, P; Cramers, C A

1998-04-10

A recently developed method for the extraction of organic micropollutants from aqueous samples based on sorptive enrichment in columns packed with 100% polydimethylsiloxane (PDMS) particles was coupled on-line with HPLC analysis. The sorptive enrichment procedure originally developed for relatively nonpolar analytes was used to preconcentrate polar phenylurea herbicides from aqueous samples. PDMS extraction columns of 5, 10 and 25 cm were used to extract the herbicides from distilled, tap and river water samples. A model that allows prediction of retention and breakthrough volumes is presented. Despite the essentially apolar nature of the PDMS material, it is possible to concentrate sample volumes up to 10 ml on PDMS cartridges without losses of the most polar analyte under investigation, fenuron. For less polar analytes significantly larger sample volumes can be applied. Since standard UV detection does not provide adequate selectivity for river water samples, an electrospray (ES)-MS instrument was used to determine phenylurea herbicides in a water sample from the river Dommel. Methoxuron was present at a level of 80 ng/l. The detection limit of the current set-up, using 10 ml water samples and ES-MS detection is 10 ng/l in river water samples. Strategies for further improvement of the detection limits are identified.

Modified Activated Carbon Prepared from Acorn Shells as a New Solid-Phase Extraction Sorbent for the Preconcentration and Determination of Trace Amounts of Nickel in Food Samples Prior to Flame Atomic Absorption Spectrometry.

PubMed

Ebrahimi, Bahram

2017-03-01

A new solid-phase extraction (SPE) sorbent was introduced based on acidic-modified (AM) activated carbon (AC) prepared from acorn shells of native oak trees in Kurdistan. Hydrochloric acid (15%, w/w) and nitric acid (32.5%, w/w) were used to condition and modify AC. The IR spectra of AC and AM-AC showed that AM lead to the formation of increasing numbers of acidic functional groups on AM-AC. AM-AC was used in the SPE method for the extraction and preconcentration of Ni+2 prior to flame atomic absorption spectrometric determination at ng/mL levels in model and real food samples. Effective parameters of the SPE procedure, such as the pH of the solutions, sorbent dosage, extraction time, sample volume, type of eluent, and matrix ions, were considered and optimized. An enrichment factor of 140 was obtained. The calibration curve was linear with an R2 of 0.997 in the concentration range of 1-220 ng/mL. The RSD was 5.67% (for n = 7), the LOD was 0.352 ng/mL, and relative recoveries in vegetable samples ranged from 96.7 to 103.7%.

Nano sponge Mn₂O ₃ as a new adsorbent for the preconcentration of Pd(II) and Rh(III) ions in sea water, wastewater, rock, street sediment and catalytic converter samples prior to FAAS determinations.

PubMed

Yavuz, Emre; Tokalıoğlu, Serife; Sahan, Halil; Patat, Saban

2014-10-01

In this study, a nano sponge Mn2O3 adsorbent was synthesized and was used for the first time. Various parameters affecting the recovery values of Pd(II) and Rh(III) were examined. The tolerance limits (≥ 90 %) for both Pd(II) and Rh(III) ions were found to be 75,000 mg L(-1) Na(I), 75,000 mg L(-1) K(I), 50,000 mg L(-1) Mg(II) and 50,000 mg L(-1) Ca(II). A 30s contact time was enough for both adsorption and elution. A preconcentration factor of 100 was obtained by using 100mg of the nano sponge Mn2O3. The reusability of the adsorbent was 120 times. Adsorption capacities for Pd(II) and Rh(III) were found to be 42 and 6.2 mg g(-1), respectively. The detection limits were 1.0 µg L(-1) for Pd(II) and 0.37 µg L(-1) for Rh(III) and the relative standard deviations (RSD, %) were found to be ≤ 2.5%. The method was validated by analyzing the standard reference material, SRM 2556 (Used Auto Catalyst Pellets) and spiked real samples. The optimized method was applied for the preconcentration of Pd(II) and Rh(III) ions in water (sea water and wastewater), rock, street sediment and catalytic converter samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Carrier mediated hollow fiber liquid phase microextraction combined with HPLC-UV for preconcentration and determination of some tetracycline antibiotics.

PubMed

Shariati, Shahab; Yamini, Yadollah; Esrafili, Ali

2009-02-01

In the present study, a simple and efficient preconcentration method was developed using carrier mediated three phase liquid phase microextraction prior to HPLC-UV for simultaneous extraction and determination of trace amounts of highly hydrophilic tetracycline antibiotics including tetracycline (TCN), oxytetracycline (OTCN) and doxycycline (DCN) in bovine milk, human plasma and water samples. For extraction, 11.0 mL of the aqueous sample containing TCNs and 0.05 M Na(2)HPO(4) (9.10.995). Finally, applicability of the proposed method was successfully confirmed by extraction and determination of the drugs in water and plasma samples as well as in bovine milk samples with low and high fat contents. Comparing to the traditional methods, the proposed method exhibits high sensitivity and high preconcentration factors as well as good precision. The extraction setup is simple and due to active transport of analytes, high cleanup effect and good selectivity are obtained in extraction process.

Biological preconcentrator

DOEpatents

Manginell, Ronald P [Albuquerque, NM; Bunker, Bruce C [Albuquerque, NM; Huber, Dale L [Albuquerque, NM

2008-09-09

A biological preconcentrator comprises a stimulus-responsive active film on a stimulus-producing microfabricated platform. The active film can comprise a thermally switchable polymer film that can be used to selectively absorb and desorb proteins from a protein mixture. The biological microfabricated platform can comprise a thin membrane suspended on a substrate with an integral resistive heater and/or thermoelectric cooler for thermal switching of the active polymer film disposed on the membrane. The active polymer film can comprise hydrogel-like polymers, such as poly(ethylene oxide) or poly(n-isopropylacrylamide), that are tethered to the membrane. The biological preconcentrator can be fabricated with semiconductor materials and technologies.

Sample extraction and injection with a microscale preconcentrator.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Alex Lockwood; Chan, Helena Kai Lun

2007-09-01

This report details the development of a microfabricated preconcentrator that functions as a fully integrated chemical extractor-injector for a microscale gas chromatograph (GC). The device enables parts-per-billion detection and quantitative analysis of volatile organic compounds (VOCs) in indoor air with size and power advantages over macro-scale systems. The 44 mm{sup 3} preconcentrator extracts VOCs using highly adsorptive, granular forms of graphitized carbon black and carbon molecular sieves. The micron-sized silicon cavities have integrated heating and temperature sensing allowing low power, yet rapid heating to thermally desorb the collected VOCs (GC injection). The keys to device construction are a new adsorbent-solventmore » filling technique and solvent-tolerant wafer-level silicon-gold eutectic bonding technology. The product is the first granular adsorbent preconcentrator integrated at the wafer level. Other advantages include exhaustive VOC extraction and injection peak widths an order of magnitude narrower than predecessor prototypes. A mass transfer model, the first for any microscale preconcentrator, is developed to describe both adsorption and desorption behaviors. The physically intuitive model uses implicit and explicit finite differences to numerically solve the required partial differential equations. The model is applied to the adsorption and desorption of decane at various concentrations to extract Langmuir adsorption isotherm parameters from effluent curve measurements where properties are unknown a priori.« less

Preconcentration and Separation of Mixed-Species Samples Near a Nano-Junction in a Convergent Microchannel

PubMed Central

Chiu, Ping-Hsien; Weng, Chen-Hsun; Yang, Ruey-Jen

2015-01-01

A fluidic microchip incorporating a convergent microchannel and a Nafion-nanoporous membrane is proposed for the preconcentration and separation of multi-species samples on a single platform. In the device, sample preconcentration is achieved by means of the ion concentration polarization effect induced at the micro/nano interface under the application of an external electric field, while species separation is achieved by exploiting the different electrophoretic mobilities of the sample components. The experimental results show that the device is capable of detecting C-reactive protein (CRP) with an initial concentration as low as 9.50 × 10−6 mg/L given a sufficient preconcentration time and driving voltage. In addition, it is shown that a mixed-species sample consisting of three negatively-charged components (bovine serum albumin (BSA), tetramethylrhodamine(TAMRA) isothiocyanate-Dextran and fluorescent polymer beads) can be separated and preconcentrated within 20 min given a driving voltage of 100 V across 1 cm microchannel in length. In general, the present results confirm the feasibility of the device for the immunoassay or detection of various multi-species samples under low concentration in the biochemical and biomedical fields. The novel device can therefore improve the detection limit of traditional medical facilities. PMID:26690167

Magnetic ionic liquid-based dispersive liquid-liquid microextraction technique for preconcentration and ultra-trace determination of Cd in honey.

PubMed

Fiorentini, Emiliano F; Escudero, Leticia B; Wuilloud, Rodolfo G

2018-04-19

A simple, highly efficient, batch, and centrifuge-less dispersive liquid-liquid microextraction method based on a magnetic ionic liquid (MIL-DLLME) and electrothermal atomic absorption spectrometry (ETAAS) detection was developed for ultra-trace Cd determination in honey. Initially, Cd(II) was chelated with ammonium diethyldithiophosphate (DDTP) at pH 0.5 followed by its extraction with the MIL trihexyl(tetradecyl)phosphonium tetrachloroferrate(III) ([P 6,6,6,14 ]FeCl 4 ) and acetonitrile as dispersant. The MIL phase containing the analyte was separated from the aqueous phase using only a magnet. A back-extraction procedure was applied to recover Cd from the MIL phase using diluted HNO 3 and this solution was directly injected into the graphite furnace of ETAAS instrument. An extraction efficiency of 93% and a sensitivity enhancement factor of 112 were obtained under optimal experimental conditions. The detection limit (LOD) was 0.4 ng L -1 Cd, while the relative standard deviation (RSD) was 3.8% (at 2 μg L -1 Cd and n = 10), calculated from the peak height of absorbance signals. This work reports the first application of the MIL [P 6,6,6,14 ]FeCl 4 along with the DLLME technique for the successful determination of Cd at trace levels in different honey samples. Graphical abstract Preconcentration of ultratraces of Cd in honey using a magnetic ionic liquid and dispersive liquid-liquid microextraction technique.

Selective ionic liquid ferrofluid based dispersive-solid phase extraction for simultaneous preconcentration/separation of lead and cadmium in milk and biological samples.

PubMed

Fasih Ramandi, Negin; Shemirani, Farzaneh

2015-01-01

For the first time, a selective ionic liquid ferrofluid has been used in dispersive solid phase extraction (IL-FF-D-SPE) for simultaneous preconcentration and separation of lead and cadmium in milk and biological samples combined with flame atomic absorption spectrometry. To improve the selectivity of the ionic liquid ferrofluid, the surface of TiO2 nanoparticles with a magnetic core as sorbent was modified by loading 1-(2-pyridylazo)-2-naphtol. Due to the rapid injection of an appropriate amount of ionic liquid ferrofluid into the aqueous sample by a syringe, extraction can be achieved within a few seconds. In addition, based on the attraction of the ionic liquid ferrofluid to a magnet, no centrifugation step is needed for phase separation. The experimental parameters of IL-FF-D-SPE were optimized using a Box-Behnken design (BBD) after a Plackett-Burman screening design. Under the optimum conditions, the relative standard deviations of 2.2% and 2.4% were obtained for lead and cadmium, respectively (n=7). The limit of detections were 1.21 µg L(-1) for Pb(II) and 0.21 µg L(-1) for Cd(II). The preconcentration factors were 250 for lead and 200 for cadmium and the maximum adsorption capacities of the sorbent were 11.18 and 9.34 mg g(-1) for lead and cadmium, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Simultaneous measurement of volatile sulfur compounds using ascorbic acid for oxidant removal and gas chromatography-flame photometric detection.

PubMed

Inomata, Y; Matsunaga, K; Murai, Y; Osada, K; Iwasaka, Y

1999-12-09

A method for the simultaneous measurement of volatile sulfur compounds (COS, H2S, CS2, CH3SH, DMS) is established with preconcentration and GC-flame photometric detection (FPD). Prior to preconcentration of ambient air, it was necessary to remove SO2, water vapor and atmospheric oxidant. SO2 and water vapor were removed using a glass fiber filter and a cooled PTFE water trap loop, respectively. In order to remove atmospheric oxidant, the efficiency of an ascorbic acid scrubber was examined. It was found that an ascorbic acid scrubber enabled measurement of volatile sulfur compounds without adsorption and reaction loss. The detection limits for COS, H2S, CS2, CH3SH and DMS were 20, 34, 35, 263 and 44 pg of S, respectively.

Simultaneous determination of estrogens and progestogens in honey using high performance liquid chromatography-tandem mass spectrometry

USDA-ARS?s Scientific Manuscript database

This work describes the development and validation of a method for the simultaneous determination of 13 estrogens and progestogens in honey by high performance liquid chromatography-tandem mass spectrometry. The target compounds were preconcentrated by solid phase extraction. Pretreatment variables ...

A STRINGENT COMPARISON OF SAMPLING AND ANALYSIS METHODS FOR VOCS IN AMBIENT AIR

EPA Science Inventory

A carefully designed study was conducted during the summer of 1998 to simultaneously collect samples of ambient air by canisters and compare the analysis results to direct sorbent preconcentration results taken at the time of sample collection. A total of 32 1-h sample sets we...

Determination of Trace Level Triclosan in Water by Online Preconcentration and HPLC-UV Diode Array

EPA Science Inventory

An online high performance liquid chromatography (HPLC) method for the detection and quantification of trace levels of triclosan in water is discussed. Triclosan, an anti-bacterial agent, and related compounds have been shown to reach municipal waste waters through the disposal ...

Analysis of hydroxamate siderophores in soil solution using liquid chromatography with mass spectrometry and tandem mass spectrometry with on-line sample preconcentration.

PubMed

Olofsson, Madelen A; Bylund, Dan

2015-10-01

A liquid chromatography with electrospray ionization mass spectrometry method was developed to quantitatively and qualitatively analyze 13 hydroxamate siderophores (ferrichrome, ferrirubin, ferrirhodin, ferrichrysin, ferricrocin, ferrioxamine B, D1 , E and G, neocoprogen I and II, coprogen and triacetylfusarinine C). Samples were preconcentrated on-line by a switch-valve setup prior to analyte separation on a Kinetex C18 column. Gradient elution was performed using a mixture of an ammonium formate buffer and acetonitrile. Total analysis time including column conditioning was 20.5 min. Analytes were fragmented by applying collision-induced dissociation, enabling structural identification by tandem mass spectrometry. Limit of detection values for the selected ion monitoring method ranged from 71 pM to 1.5 nM with corresponding values of two to nine times higher for the multiple reaction monitoring method. The liquid chromatography with mass spectrometry method resulted in a robust and sensitive quantification of hydroxamate siderophores as indicated by retention time stability, linearity, sensitivity, precision and recovery. The analytical error of the methods, assessed through random-order, duplicate analysis of soil samples extracted with a mixture of 10 mM phosphate buffer and methanol, appears negligible in relation to between-sample variations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of azoxystrobin and chlorothalonil using a methacrylate-based polymer modified with gold nanoparticles as solid-phase extraction sorbent.

PubMed

Catalá-Icardo, Mónica; Gómez-Benito, Carmen; Simó-Alfonso, Ernesto Francisco; Herrero-Martínez, José Manuel

2017-01-01

This paper describes a novel and sensitive method for extraction, preconcentration, and determination of two important widely used fungicides, azoxystrobin, and chlorothalonil. The developed methodology is based on solid-phase extraction (SPE) using a polymeric material functionalized with gold nanoparticles (AuNPs) as sorbent followed by high-performance liquid chromatography (HPLC) with diode array detector (DAD). Several experimental variables that affect the extraction efficiency such as the eluent volume, sample flow rate, and salt addition were optimized. Under the optimal conditions, the sorbent provided satisfactory enrichment efficiency for both fungicides, high selectivity and excellent reusability (>120 re-uses). The proposed method allowed the detection of 0.05 μg L -1 of the fungicides and gave satisfactory recoveries (75-95 %) when it was applied to drinking and environmental water samples (river, well, tap, irrigation, spring, and sea waters).

Large volume preconcentration and determination of nanomolar concentrations of iron in seawater using a renewable cellulose 8-hydroquinoline sorbent microcolumn and universal approach of post-column eluate utilization in a Lab-on-Valve system.

PubMed

Horstkotte, Burkhard; Chocholouš, Petr; Solich, Petr

2016-04-01

We report on a Lab-On-Valve (LOV) configuration for analyte preconcentration from milliliter sample volumes using confluent mixing in the holding coil for in-line addition of loading buffer. The system was applied to the spectrophotometric determination of iron(II) in acidified seawater using 1,10-phenanthroline as color reagent. A cellulose-based chelating sorbent containing 8-hydroxyquinoline was used for the first time in LOV and excellent retention behavior and loading capacity were found. The flow system employs a syringe pump for handling all solutions (sorbent suspension, loading buffer, water, eluent, and color reagent) and a peristaltic pump for sample propulsion and includes a fit-for-purpose 14 cm long detection glass flow cell and a bubble trap for in-line carrier degasification. Advantage was taken of the LOV flow-through port to keep the eluted analytes for re-aspiration for subsequent chromogenic reaction. In effect, a universal analyzer configuration and preconcentration procedure was developed, which is combinable with other analytes, sorbents, and reagents. Among the studied parameters were the compositions, pH, volumes, and flow rates of loading buffer, eluent, and color reagent, as well as the microcolumn size, repeatability, and system stability. Reproducibility of 4.1% RSD over the entire working range, a LOD of down to 5 nmol L(-1), sampling frequency of 12h(-1), and linearity up to 1 µmol L(-1) for 3.3 mL of sample were obtained and applicability to real samples was demonstrated. It was proven that both Fe(III) and Fe(II) were retained and yielded similar recovery and sensitivity values. The method was applied to coastal seawater samples and spiking experiments yielded recovery values close to 100%. Copyright © 2015 Elsevier B.V. All rights reserved.

Fabrication of a novel nanocomposite based on sol-gel process for hollow fiber-solid phase microextraction of aflatoxins: B1 and B2, in cereals combined with high performane liquid chromatography-diode array detection.

PubMed

Es'haghi, Zarrin; Sorayaei, Hoda; Samadi, Fateme; Masrournia, Mahboubeh; Bakherad, Zohreh

2011-10-15

The new pre-concentration technique, hollow fiber-solid phase microextraction based on carbon nanotube reinforced sol-gel and liquid chromatography-photodiode array detection was applied to determination of aflatoxins B(1), B(2) (AFB(1), AFB(2)) in rice, peanut and wheat samples. This research provides an overview of trends related to synthesis of solid phase microextraction (SPME) sorbnents that improves the assay of aflatoxins as the semi-polar compounds in several real samples. It mainly includes summary and a list of the results for a simple carbon nanotube reinforced sol-gel in-fiber device. This device was used for extraction, pre-concentration and determination of aflatoxins B1, B2 in real samples. In this technique carbon nanotube reinforced sol was prepared by the sol-gel method via the reaction of phenyl trimethoxysilane (PTMS) with a basic catalyst (tris hydroxymethyl aminomethan). The influences of microextraction parameters such as pH, ageing time, carbon nanotube contents, desorption conditions, desorption solvent and agitation speed were investigated. Optimal HPLC conditions were: C(18) reversed phase column for separation, water-acetonitril-methanol (35:10:55) as the mobile phase and maximum wavelength for detection was 370 nm. The method was evaluated statistically and under optimized conditions, the detection limits for the analytes were 0.074 and 0.061 ng/mL for B1 and B2 respectively. Limit of quantification for B1 and B2 was 0.1 ng/mL too (n=7). The precisions were in the range of 2.829-2.976% (n=3), and linear ranges were within 0.1 and 400 ng/mL. The method was successfully applied to the analysis of cereals (peanut, wheat, rice) with the relative recoveries from 47.43% to 106.83%. Copyright © 2011 Elsevier B.V. All rights reserved.

Measurement of formaldehyde in clean air

NASA Astrophysics Data System (ADS)

Neitzert, Volker; Seiler, Wolfgang

1981-01-01

A method for the measurement of small amounts of formaldehyde in air has been developed. The method is based on the derivatization of HCHO with 2.4-Dinitrophenylhydrazine, forming 2.4-Dinitrophenylhydrazone, measured with GC-ECD-technique. HCHO is preconcentrated using a cryogenic sampling technique. The detection limit is 0.05 ppbv for a sampling volume of 200 liter. The method has been applied for measurements in continental and marine air masses showing HCHO mixing ratios of 0.4 - 5.0 ppbv and 0.2 - 1.0 ppbv, respectively. HCHO mixing ratios show diurnal variations with maximum values during the early afternoon and minimum values during the early morning. In continental air, HCHO mixing ratios are positively correlated with CO and SO2, indicating anthropogenic HCHO sources which are estimated to be 6-11 × 1012g/year-1 on a global scale.

A kinetic method for the determination of thiourea by its catalytic effect in micellar media

NASA Astrophysics Data System (ADS)

Abbasi, Shahryar; Khani, Hossein; Gholivand, Mohammad Bagher; Naghipour, Ali; Farmany, Abbas; Abbasi, Freshteh

2009-03-01

A highly sensitive, selective and simple kinetic method was developed for the determination of trace levels of thiourea based on its catalytic effect on the oxidation of janus green in phosphoric acid media and presence of Triton X-100 surfactant without any separation and pre-concentration steps. The reaction was monitored spectrophotometrically by tracing the formation of the green-colored oxidized product of janus green at 617 nm within 15 min of mixing the reagents. The effect of some factors on the reaction speed was investigated. Following the recommended procedure, thiourea could be determined with linear calibration graph in 0.03-10.00 μg/ml range. The detection limit of the proposed method is 0.02 μg/ml. Most of foreign species do not interfere with the determination. The high sensitivity and selectivity of the proposed method allowed its successful application to fruit juice and industrial waste water.

TEST AND EVALUATION OF A POLYMER MEMBRANE PRECONCENTRATOR

EPA Science Inventory

The report gives results of an evaluation of the applicability of membrane systems as a preconcentrator and defines operating parameters of a membrane system. Advantages of such a system is a potential reduction in cost for subsequent control systems. The evaluation is part of a ...

Analytical instrument with apparatus for sample concentrating

DOEpatents

Zaromb, Solomon

1989-01-01

A system for analysis of trace concentrations of contaminants in air includes a portable liquid chromatograph and a preconcentrator for the contaminants to be analyzed. The preconcentrator includes a sample bag having an inlet valve and an outlet valve for collecting an air sample. When the sample is collected the sample bag is connected in series with a sorbing apparatus in a recirculation loop. The sorbing apparatus has an inner gas-permeable container containing a sorbent material and an outer gas-impermeable container. The sample is circulated through the outer container and around the inner container for trapping and preconcentrating the contaminants in the sorbent material. The sorbent material may be a liquid having the same composition as the mobile phase of the chromatograph for direct injection thereinto. Alternatively, the sorbent material may be a porous, solid body, to which mobile phase liquid is added after preconcentration of the contaminants for dissolving the contaminants, the liquid solution then being withdrawn for injection into the chromatograph.

Liquid-absorption preconcentrator sampling instrument

DOEpatents

Zaromb, Solomon

1990-01-01

A system for detecting trace concentrations of an analyte in air and includes a preconcentrator for the analyte and an analyte detector. The preconcentrator includes an elongated tubular container in which is disposed a wettable material extending substantially the entire length of the container. One end of the wettable material is continuously wetted with an analyte-sorbing liquid, which flows to the other end of the container. Sample air is flowed through the container in contact with the wetted material for trapping and preconcentrating the traces of analyte in the sorbing liquid, which is then collected at the other end of the container and discharged to the detector. The wetted material may be a wick comprising a bundle of fibers, one end of which is immersed in a reservoir of the analyte-sorbing liquid, or may be a liner disposed on the inner surface of the container, with the sorbing liquid being centrifugally dispersed onto the liner at one end thereof. The container is preferably vertically oriented so that gravity effects the liquid flow.

Liquid-absorption preconcentrator sampling instrument

DOEpatents

Zaromb, S.

1990-12-11

A system is described for detecting trace concentrations of an analyte in air and includes a preconcentrator for the analyte and an analyte detector. The preconcentrator includes an elongated tubular container in which is disposed a wettable material extending substantially the entire length of the container. One end of the wettable material is continuously wetted with an analyte-sorbing liquid, which flows to the other end of the container. Sample air is flowed through the container in contact with the wetted material for trapping and preconcentrating the traces of analyte in the sorbing liquid, which is then collected at the other end of the container and discharged to the detector. The wetted material may be a wick comprising a bundle of fibers, one end of which is immersed in a reservoir of the analyte-sorbing liquid, or may be a liner disposed on the inner surface of the container, with the sorbing liquid being centrifugally dispersed onto the liner at one end thereof. The container is preferably vertically oriented so that gravity effects the liquid flow. 4 figs.

An optimized procedure for preconcentration, determination and on-line recovery of palladium using highly selective diphenyldiketone-monothiosemicarbazone modified silica gel.

PubMed

Sharma, R K; Pandey, Amit; Gulati, Shikha; Adholeya, Alok

2012-03-30

A novel, highly selective, efficient and reusable chelating resin, diphenyldiketone-monothiosemicarbazone modified silica gel, was prepared and applied for the on-line separation and preconcentration of Pd(II) ions in catalytic converter and spiked tap water samples. Several parameters like effect of pH, sample volume, flow rate, type of eluent, and influence of various ionic interferences, etc. were evaluated for effective adsorption of palladium at trace levels. The resin was found to be highly selective for Pd(II) ions in the pH range 4-5 with a very high sorption capacity of 0.73 mmol/g and preconcentration factor of 335. The present environment friendly procedure has also been applied for large-scale extraction by employing the use of newly designed reactor in which on-line separation and preconcentration of Pd can be carried out easily and efficiently in short duration of time. Copyright © 2012 Elsevier B.V. All rights reserved.

A new supramolecular based liquid solid microextraction method for preconcentration and determination of trace bismuth in human blood serum and hair samples by electrothermal atomic absorption spectrometry.

PubMed

Kahe, Hadi; Chamsaz, Mahmoud

2016-11-01

A simple and reliable supramolecule-aggregated liquid solid microextraction method is described for preconcentration and determination of trace amounts of bismuth in water as well as human blood serum and hair samples. Catanionic microstructures of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactants, dissolved in deionized water/propanol, are used as a green solvent to extract bismuth (III)-diethyldithiocarbamate complexes by dispersive microextraction methodology. The extracted solid phase is easily removed and dissolved in 50 μL propanol for subsequent measurement by electrothermal atomic absorption spectrometry (ET-AAS). The procedure benefits the merits of supramolecule aggregates' properties and dispersive microextraction technique using water as the main component of disperser solvent, leading to direct interaction with analyte. Phase separation behavior of extraction solvent and different parameters influencing the extraction efficiency of bismuth ion such as salt concentration, pH, centrifugation time, amount of chelating agent, SDS:CTAB mole ratio, and solvent amounts were thoroughly optimized. Under the optimal experimental conditions, the calibration curve was linear in the range of 0.3-6 μg L -1 Bi (III) with a limit of detection (LOD) of 0.16 μg L -1 (S/N = 3). The relative standard deviations (RSD) of determination were obtained to be 5.1 and 6.2 % for 1 and 3 μg L -1 of Bi (III), respectively. The developed method was successfully applied as a sensitive and accurate technique for determination of bismuth ion in human blood serum, hair samples, and a certified reference material.

Extraction of trace amounts of mercury with sodium dodecyle sulphate-coated magnetite nanoparticles and its determination by flow injection inductively coupled plasma-optical emission spectrometry.

PubMed

Faraji, Mohammad; Yamini, Yadollah; Rezaee, Mohammad

2010-05-15

A new method for solid-phase extraction and preconcentration of trace amounts Hg(II) from environmental samples was developed by using sodium dodecyle sulphate-coated magnetite nanoparticles (SDS-coated Fe(3)O(4) NPs) as a new extractant. The procedure is based on the adsorption of the analyte, as mercury-Michler's thioketone [Hg(2)(TMK)(4)](2+) complex on the negatively charged surface of the SDS-coated Fe(3)O(4) NPs and then elution of the preconcentrated mercury from the surface of the SDS-coated Fe(3)O(4) NPs prior to its determination by flow injection inductively coupled plasma-optical emission spectrometry. The effects of pH, TMK concentration, SDS and Fe(3)O(4) NPs amounts, eluent type, sample volume and interfering ions on the recovery of the analyte were investigated. Under optimized conditions, the calibration curve was linear in the range of 0.2-100ngmL(-1) with r(2)=0.9994 (n=8). The limit of detection for Hg(II) determination was 0.04ngmL(-1). Also, relative standard deviation (R.S.D.) for the determination of 2 and 50ngmL(-1) of Hg(II) was 5.2 and 4.7% (n=6), respectively. Due to the quantitative extraction of Hg(II) from 1000mL of the sample solution an enhancement factor as large as 1230-fold can be obtained. The proposed method has been validated using a certified reference materials, and also the method has been applied successfully for the determination of Hg(II) in aqueous samples.

Preconcentration and determination of ceftazidime in real samples using dispersive liquid-liquid microextraction and high-performance liquid chromatography with the aid of experimental design.

PubMed

Razmi, Rasoul; Shahpari, Behrouz; Pourbasheer, Eslam; Boustanifar, Mohammad Hasan; Azari, Zhila; Ebadi, Amin

2016-11-01

A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid-liquid microextraction followed by high-performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid-liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001-10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Some aspects of analytical chemistry as applied to water quality assurance techniques for reclaimed water: The potential use of X-ray fluorescence spectrometry for automated on-line fast real-time simultaneous multi-component analysis of inorganic pollutants in reclaimed water

NASA Technical Reports Server (NTRS)

Ling, A. C.; Macpherson, L. H.; Rey, M.

1981-01-01

The potential use of isotopically excited energy dispersive X-ray fluorescence (XRF) spectrometry for automated on line fast real time (5 to 15 minutes) simultaneous multicomponent (up to 20) trace (1 to 10 parts per billion) analysis of inorganic pollutants in reclaimed water was examined. Three anionic elements (chromium 6, arsenic and selenium) were studied. The inherent lack of sensitivity of XRF spectrometry for these elements mandates use of a preconcentration technique and various methods were examined, including: several direct and indirect evaporation methods; ion exchange membranes; selective and nonselective precipitation; and complexation processes. It is shown tha XRF spectrometry itself is well suited for automated on line quality assurance, and can provide a nondestructive (and thus sample storage and repeat analysis capabilities) and particularly convenient analytical method. Further, the use of an isotopically excited energy dispersive unit (50 mCi Cd-109 source) coupled with a suitable preconcentration process can provide sufficient sensitivity to achieve the current mandated minimum levels of detection without the need for high power X-ray generating tubes.

Green analytical determination of emerging pollutants in environmental waters using excitation-emission photoinduced fluorescence data and multivariate calibration.

PubMed

Hurtado-Sánchez, María Del Carmen; Lozano, Valeria A; Rodríguez-Cáceres, María Isabel; Durán-Merás, Isabel; Escandar, Graciela M

2015-03-01

An eco-friendly strategy for the simultaneous quantification of three emerging pharmaceutical contaminants is presented. The proposed analytical method, which involves photochemically induced fluorescence matrix data combined with second-order chemometric analysis, was used for the determination of carbamazepine, ofloxacin and piroxicam in water samples of different complexity without the need of chromatographic separation. Excitation-emission photoinduced fluorescence matrices were obtained after UV irradiation, and processed with second-order algorithms. Only one of the tested algorithms was able to overcome the strong spectral overlapping among the studied pollutants and allowed their successful quantitation in very interferent media. The method sensitivity in superficial and underground water samples was enhanced by a simple solid-phase extraction with C18 membranes, which was successful for the extraction/preconcentration of the pollutants at trace levels. Detection limits in preconcentrated (1:125) real water samples ranged from 0.04 to 0.3 ng mL(-1). Relative prediction errors around 10% were achieved. The proposed strategy is significantly simpler and greener than liquid chromatography-mass spectrometry methods, without compromising the analytical quality of the results. Copyright © 2014 Elsevier B.V. All rights reserved.

Selective solid-phase extraction using oxidized activated carbon modified with triethylenetetramine for preconcentration of metal ions

NASA Astrophysics Data System (ADS)

Zhang, Li; Chang, Xijun; Li, Zhenhua; He, Qun

2010-02-01

A new selective solid-phase extractant using activated carbon as matrix which was purified, oxidized and modified by triethylenetetramine (AC-TETA) was prepared and characterized by FT-IR spectroscopy. At pH 4, quantitative extraction of trace Cr(III), Fe(III) and Pb(II) was obtained and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Complete elution of the adsorbed metal ions from the sorbent surface was carried out using 0.5 mol L -1 HCl. The maximum static adsorption capacity of sorbent for Cr(III), Fe(III) and Pb(II) was 34.6, 36.5 and 51.9 mg g -1, respectively. The time of quantitative adsorption was less than 2 min. The detection limits of the method was found to be 0.71, 0.35 and 0.45 ng mL -1 for Cr(III), Fe(III) and Pb(II), and the relative standard deviation (RSD) was 3.7%, 2.2% and 2.5%, respectively. Moreover, the method was free from interference with common coexiting ions. The method was also successfully applied to the preconcentration of trace Cr(III), Fe(III) and Pb(II) in synthetic samples and a real sample with satisfactory results.

Optimisation of the conditions for stripping voltammetric analysis at liquid-liquid interfaces supported at micropore arrays: a computational simulation.

PubMed

Strutwolf, Jörg; Arrigan, Damien W M

2010-10-01

Micropore membranes have been used to form arrays of microinterfaces between immiscible electrolyte solutions (µITIES) as a basis for the sensing of non-redox-active ions. Implementation of stripping voltammetry as a sensing method at these arrays of µITIES was applied recently to detect drugs and biomolecules at low concentrations. The present study uses computational simulation to investigate the optimum conditions for stripping voltammetric sensing at the µITIES array. In this scenario, the diffusion of ions in both the aqueous and the organic phases contributes to the sensing response. The influence of the preconcentration time, the micropore aspect ratio, the location of the microinterface within the pore, the ratio of the diffusion coefficients of the analyte ion in the organic and aqueous phases, and the pore wall angle were investigated. The simulations reveal that the accessibility of the microinterfaces during the preconcentration period should not be hampered by a recessed interface and that diffusional transport in the phase where the analyte ions are preconcentrated should be minimized. This will ensure that the ions are accumulated within the micropores close to the interface and thus be readily available for back transfer during the stripping process. On the basis of the results, an optimal combination of the examined parameters is proposed, which together improve the stripping voltammetric signal and provide an improvement in the detection limit.

Ultrasound-assisted dispersive magnetic solid phase extraction for preconcentration and determination of trace amount of Hg (II) ions from food samples and aqueous solution by magnetic graphene oxide (Fe3O4@GO/2-PTSC): Central composite design optimization.

PubMed

Keramat, Akram; Zare-Dorabei, Rouholah

2017-09-01

In this work, the synthesis of the magnetic graphene oxide modified by 2-pyridinecarboxaldehyde thiosemicarbazone groups (Fe 3 O 4 @GO/2-PTSC) was utilized for preconcentration and determination of mercuric ions in a trace amount by inductively coupled plasma-optical emission spectrometry (ICP-OES). Characterization of the adsorbent was performed using various techniques, such as FT-IR, VSM, SEM and XRD analysis. Central composite design (CCD) under response surface methodology (RSM) was used for obtaining the most important parameters and probable interactions in variables. The variables such as adsorbent dosage, pH, desorption time, and eluent volume was optimized. These values were 8mg, 5.4min, 0.5mL (HCl, 0.1M), respectively. Sonication had an important role in shortening the adsorption time of Hg (II) ions by enhancing the dispersion of adsorbent in solution. Under the optimal conditions, the proposed method presented high enrichment factor of 193, an extraction percentage of 96.5, a detection limit of 0.0079µgL -1 and a relative standard deviation (RSD %) of 1.63%. Finally, the application of the synthesized material was evaluated for preconcentration and determination of mercuric ions from foods and environmental waters samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Chemically modified activated carbon with 1-acylthiosemicarbazide for selective solid-phase extraction and preconcentration of trace Cu(II), Hg(II) and Pb(II) from water samples.

PubMed

Gao, Ru; Hu, Zheng; Chang, Xijun; He, Qun; Zhang, Lijun; Tu, Zhifeng; Shi, Jianping

2009-12-15

A new sorbent 1-acylthiosemicarbazide-modified activated carbon (AC-ATSC) was prepared as a solid-phase extractant and applied for removing of trace Cu(II), Hg(II) and Pb(II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 3, the maximum static adsorption capacity of Cu(II), Hg(II) and Pb(II) onto the AC-ATSC were 78.20, 67.80 and 48.56 mg g(-1), respectively. The adsorbed metal ions were quantitatively eluted by 3.0 mL of 2% CS(NH2)2 and 2.0 mol L(-1) HCl solution. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3sigma) of this method for Cu(II), Hg(II) and Pb(II) were 0.20, 0.12 and 0.45 ng mL(-1), respectively. The relative standard deviation under optimum conditions is less than 4.0% (n=8). The prepared sorbent was applied for the preconcentration of trace Cu(II), Hg(II) and Pb(II) in certified and water samples with satisfactory results.

SELECTIVE TRACE ENRICHMENT BY IMMUNOAFFINITY CAPILLARY ELECTROCHROMATOGRAPHY ON-LINE WITH CAPILLARY ZONE ELECTROPHORESIS - LASER-INDUCED FLUORESCENCE

EPA Science Inventory

Limited by the lack of a sensitive, universal detector, many capillary-based liquid-phase separation techniques might benefit from techniques that overcome modest concentration sensitivity by preconcentrating large injection volumes. The work presented employs selective solid-ph...

Coupling reverse osmosis with electrodialysis to isolate natural organic matter from fresh waters

EPA Science Inventory

This study was undertaken to solve the problem of removal of sulfate and silica from solutions of natural organic matter (NOM) that have been pre-concentrated by reverse osmosis. The goal is the development of a method by which NOM can be concentrated and desalted to obtain a low...

Zeolite based microconcentrators for volatile organic compounds sensing at trace-level: fabrication and performance

NASA Astrophysics Data System (ADS)

Almazán, Fernando; Pellejero, Ismael; Morales, Alberto; Urbiztondo, Miguel A.; Sesé, Javier; Pina, M. Pilar; Santamaría, Jesús

2016-08-01

A novel 6-step microfabrication process is proposed in this work to prepare microfluidic devices with integrated zeolite layers. In particular, microfabricated preconcentrators designed for volatile organic compounds (VOC) sensing applications are fully described. The main novelty of this work is the integration of the pure siliceous MFI type zeolite (silicalite-1) polycrystalline layer, i.e. 4.0  ±  0.5 μm thick, as active phase, within the microfabrication process just before the anodic bonding step. Following this new procedure, Si microdevices with an excellent distribution of the adsorbent material, integrated resistive heaters and Pyrex caps have been obtained. Firstly, the microconcentrator performance has been assessed by means of the normal hexane breakthrough curves as a function of sampling and desorption flowrates, temperature and micropreconcentrator design. In a step further, the best preconcentrator device has been tested in combination with downstream Si based microcantilevers deployed as VOC detectors. Thus, a preliminar evaluation of the improvement on detection sensitivity by silicalite-1 based microconcentrators is presented.

Inorganic selenium speciation analysis in Allium and Brassica vegetables by ionic liquid assisted liquid-liquid microextraction with multivariate optimization.

PubMed

Castro Grijalba, Alexander; Martinis, Estefanía M; Wuilloud, Rodolfo G

2017-03-15

A highly sensitive vortex assisted liquid-liquid microextraction (VA-LLME) method was developed for inorganic Se [Se(IV) and Se(VI)] speciation analysis in Allium and Brassica vegetables. Trihexyl(tetradecyl)phosphonium decanoate phosphonium ionic liquid (IL) was applied for the extraction of Se(IV)-ammonium pyrrolidine dithiocarbamate (APDC) complex followed by Se determination with electrothermal atomic absorption spectrometry. A complete optimization of the graphite furnace temperature program was developed for accurate determination of Se in the IL-enriched extracts and multivariate statistical optimization was performed to define the conditions for the highest extraction efficiency. Significant factors of IL-VA-LLME method were sample volume, extraction pH, extraction time and APDC concentration. High extraction efficiency (90%), a 100-fold preconcentration factor and a detection limit of 5.0ng/L were achieved. The high sensitivity obtained with preconcentration and the non-chromatographic separation of inorganic Se species in complex matrix samples such as garlic, onion, leek, broccoli and cauliflower, are the main advantages of IL-VA-LLME. Copyright © 2016 Elsevier Ltd. All rights reserved.

Automated total and radioactive strontium separation and preconcentration in samples of environmental interest exploiting a lab-on-valve system.

PubMed

Rodríguez, Rogelio; Avivar, Jessica; Ferrer, Laura; Leal, Luz O; Cerdà, Victor

2012-07-15

A novel lab-on-valve system has been developed for strontium determination in environmental samples. Miniaturized lab-on-valve system potentially offers facilities to allow any kind of chemical and physical processes, including fluidic and microcarrier bead control, homogenous reaction and liquid-solid interaction. A rapid, inexpensive and fully automated method for the separation and preconcentration of total and radioactive strontium, using a solid phase extraction material (Sr-Resin), has been developed. Total strontium concentrations are determined by ICP-OES and (90)Sr activities by a low background proportional counter. The method has been successfully applied to different water samples of environmental interest. The proposed system offers minimization of sample handling, drastic reduction of reagent volume, improvement of the reproducibility and sample throughput and attains a significant decrease of both time and cost per analysis. The LLD of the total Sr reached is 1.8ng and the minimum detectable activity for (90)Sr is 0.008Bq. The repeatability of the separation procedure is 1.2% (n=10). Copyright © 2011 Elsevier B.V. All rights reserved.

Vortex-assisted switchable liquid-liquid microextraction for the preconcentration of cadmium in environmental samples prior to its determination with flame atomic absorption spectrometry.

PubMed

Fırat, Merve; Bodur, Süleyman; Tışlı, Büşra; Özlü, Cansu; Chormey, Dotse Selali; Turak, Fatma; Bakırdere, Sezgin

2018-06-12

In this study, a switchable solvent was used to preconcentrate trace amounts of Cd from aqueous solution for its determination by flame atomic absorption spectrometry (FAAS). Protonation of N,N-dimethylbenzylamine by dry ice (solid CO 2 ) made it water soluble, and addition of sodium hydroxide converted it back to its original nonionic state for phase separation and subsequent extraction of Cd. A slotted quartz tube (SQT) was attached to the flame burner head to increase the residence time of Cd atoms in the light path. Under the optimum conditions, limits of detection and quantification were determined as 0.7 and 2.6 μg L -1 , respectively. Low relative standard deviations calculated from seven replicate measurements of the lowest concentration indicated high precision. Accuracy of the developed method was checked by using a standard reference material (SRM 1633c). Spiked recovery tests were also performed on lake water and wastewater samples at different concentrations to check the applicability of the developed method, and the results obtained (90-103%) established high recovery.

Thermophilic Geobacillus galactosidasius sp. nov. loaded γ-Fe2O3 magnetic nanoparticle for the preconcentrations of Pb and Cd.

PubMed

Özdemir, Sadin; Kilinç, Ersin; Okumuş, Veysi; Poli, Annarita; Nicolaus, Barbara; Romano, Ida

2016-02-01

Thermophilic bacteria, Geobacillus galactosidasius sp nov. was loaded on γ-Fe2O3 magnetic nanoparticle for the preconcentrations of Pb and Cd by solid phase extraction before ICP-OES. pH and flow rate of the solution, amounts of biosorbent and magnetic nanoparticle, volume of sample solution, effects of the possible interferic ions were investigated in details. Linear calibration curves were constructed in the concentration ranges of 1.0-60ngmL(-1) for Pb and Cd. The RSDs of the method were lower than 2.8% for Pb and 3.8% for Cd. Certified and standard reference samples of fortified water, wastewater, poplar leaves, and simulated fresh water were used to accurate the method. LOD values were found as 0.07 and 0.06ngmL(-1) respectively for Pb and Cd. The biosorption capacities were found as 34.3mgg(-1) for Pb and 37.1mgg(-1) for Cd. Pb and Cd concentrations in foods were determined. Surface microstructure was investigated by SEM-EDX. Copyright © 2015 Elsevier Ltd. All rights reserved.

Preconcentration and solid phase extraction method for the determination of Co, Cu, Ni, Zn and Cd in environmental and biological samples using activated carbon by FAAS.

PubMed

Kiran, K; Suresh Kumar, K; Suvardhan, K; Janardhanam, K; Chiranjeevi, P

2007-08-17

2-{[1-(2-Hydroxynaphthyl) methylidene] amino} benzoic acid (HNMABA) was synthesized for solid phase extraction (SPE) to the determination of Co, Cu, Ni, Zn and Cd in environmental and biological samples by flame atomic absorption spectrophotometry (FAAS). These metals were sorbed as HNMABA complexes on activated carbon (AC) at the pH range of 5.0+/-0.2 and eluted with 6 ml of 1M HNO3 in acetone. The effects of sample volume, eluent volume and recovery have been investigated to enhance the sensitivity and selectivity of proposed method. The effect of interferences on the sorption of metal ions was studied. The concentration of the metal ions detected after preconcentration was in agreement with the added amount. The detection limits for the metals studied were in the range of 0.75-3.82 microg ml(-1). The proposed system produced satisfactory results for the determination of Co, Cu, Ni, Zn and Cd metals in environmental and biological samples.

Analytical Chemical Sensing in the Submillimeter/terahertz Spectral Range

NASA Astrophysics Data System (ADS)

Moran, Benjamin L.; Fosnight, Alyssa M.; Medvedev, Ivan R.; Neese, Christopher F.

2012-06-01

Highly sensitive and selective Terahertz sensor utilized to quantitatively analyze a complex mixture of Volatile Organic Compounds is reported. To best demonstrate analytical capabilities of THz chemical sensors we chose to perform analytical quantitative analysis of a certified gas mixture using a novel prototype chemical sensor that couples a commercial preconcentration system (Entech 7100A) to a high resolution THz spectrometer. We selected Method TO-14A certified mixture of 39 volatile organic compounds (VOCs) diluted to 1 part per million (ppm) in nitrogen. 26 of the 39 chemicals were identified by us as suitable for THz spectroscopic detection. Entech 7100A system is designed and marketed as an inlet system for Gas Chromatography-Mass Spectrometry (GC-MS) instruments with a specific focus on TO-14 and TO-15 EPA sampling methods. Its preconcentration efficiency is high for the 39 chemicals in the mixture used for this study and our preliminary results confirm this. Here we present the results of this study which serves as basis for our ongoing research in environmental sensing and analysis of exhaled human breath.

Investigation of cloud point extraction for the analysis of metallic nanoparticles in a soil matrix

PubMed Central

Hadri, Hind El; Hackley, Vincent A.

2017-01-01

The characterization of manufactured nanoparticles (MNPs) in environmental samples is necessary to assess their behavior, fate and potential toxicity. Several techniques are available, but the limit of detection (LOD) is often too high for environmentally relevant concentrations. Therefore, pre-concentration of MNPs is an important component in the sample preparation step, in order to apply analytical tools with a LOD higher than the ng kg−1 level. The objective of this study was to explore cloud point extraction (CPE) as a viable method to pre-concentrate gold nanoparticles (AuNPs), as a model MNP, spiked into a soil extract matrix. To that end, different extraction conditions and surface coatings were evaluated in a simple matrix. The CPE method was then applied to soil extract samples spiked with AuNPs. Total gold, determined by inductively coupled plasma mass spectrometry (ICP-MS) following acid digestion, yielded a recovery greater than 90 %. The first known application of single particle ICP-MS and asymmetric flow field-flow fractionation to evaluate the preservation of the AuNP physical state following CPE extraction is demonstrated. PMID:28507763

Integrating preconcentrator heat controller

DOEpatents

Bouchier, Francis A.; Arakaki, Lester H.; Varley, Eric S.

2007-10-16

A method and apparatus for controlling the electric resistance heating of a metallic chemical preconcentrator screen, for example, used in portable trace explosives detectors. The length of the heating time-period is automatically adjusted to compensate for any changes in the voltage driving the heating current across the screen, for example, due to gradual discharge or aging of a battery. The total deposited energy in the screen is proportional to the integral over time of the square of the voltage drop across the screen. Since the net temperature rise, .DELTA.T.sub.s, of the screen, from beginning to end of the heating pulse, is proportional to the total amount of heat energy deposited in the screen during the heating pulse, then this integral can be calculated in real-time and used to terminate the heating current when a pre-set target value has been reached; thereby providing a consistent and reliable screen temperature rise, .DELTA.T.sub.s, from pulse-to-pulse.

Voltammetric analysis of ceftazidime after preconcentration at various mercury and carbon electrodes: application to sub-ppb level determination in urine samples.

PubMed

El-Maali, N A

2000-04-28

The electrochemical behavior of ceftazidime (CFZ) at four different kinds of electrodes viz. static mercury drop electrode (SMDE), controlled growth mercury electrode (CGME), glassy carbon electrode (GCE) and carbon paste electrode (CPE) has been presented. Optimal operational parameters have been selected for the drug preconcentration and determination in aqueous medium. Down to 2x10(-10) M CFZ is achieved as detection limit at the CGME. Modification of the CPE with polyvinyl alcohol (PVA) enhances both the sensitivity and selectivity for the drug accumulation and, therefore, its determination at very low levels. Application of the proposed method for CFZ analysis in spiked urine samples or those taken after metabolism has been easily assessed. Down to 1x10(-9) M CFZ (0.695 ng ml(-1)) could be easily achieved in such samples.

Fast Extraction and Detection of 4-Methylimidazole in Soy Sauce Using Magnetic Molecularly Imprinted Polymer by HPLC.

PubMed

Feng, Zufei; Lu, Yan; Zhao, Yingjuan; Ye, Helin

2017-11-02

On the basis of magnetic molecularly imprinted polymer (MMIP) solid-phase extraction coupled with high performance liquid chromatography, we established a new method for the determination of the 4-methylimidazole (4-MEI) in soy sauce. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to characterize the synthesized MMIPs. To evaluate the polymers, batch rebinding experiments were carried out. The binding strength and capacity were determined from the derived Freundlich isotherm (FI) equation. The selective recognition capability of MMIPs was investigated with a reference compound and a structurally similar compound. As a selective pre-concentration sorbents for 4-methylimidazole in soy sauce, the MMIPs showed a satisfied recoveries rate of spiked samples, ranged from 97% to 105%. As a result, the prepared MMIPs could be applied to selectively pre-concentrate and determine 4-methylimidazole in soy sauce samples.

On chip preconcentration and fluorescence labeling of model proteins by use of monolithic columns: device fabrication, optimization, and automation.

PubMed

Yang, Rui; Pagaduan, Jayson V; Yu, Ming; Woolley, Adam T

2015-01-01

Microfluidic systems with monolithic columns have been developed for preconcentration and on-chip labeling of model proteins. Monoliths were prepared in microchannels by photopolymerization, and their properties were optimized by varying the composition and concentration of the monomers to improve flow and extraction. On-chip labeling of proteins was achieved by driving solutions through the monolith by use of voltage then incubating fluorescent dye with protein retained on the monolith. Subsequently, the labeled proteins were eluted, by applying voltages to reservoirs on the microdevice, and then detected, by monitoring laser-induced fluorescence. Monoliths prepared from octyl methacrylate combine the best protein retention with the possibility of separate elution of unattached fluorescent label with 50% acetonitrile. Finally, automated on-chip extraction and fluorescence labeling of a model protein were successfully demonstrated. This method involves facile sample pretreatment, and therefore has potential for production of integrated bioanalysis microchips.

Parallel-plate wet denuder coupled ion chromatograph for near-real-time detection of trace acidic gases in clean room air.

PubMed

Takeuchi, Masaki; Tsunoda, Hiromichi; Tanaka, Hideji; Shiramizu, Yoshimi

2011-01-01

This paper describes the performance of our automated acidic (CH(3)COOH, HCOOH, HCl, HNO(2), SO(2), and HNO(3)) gases monitor utilizing a parallel-plate wet denuder (PPWD). The PPWD quantitatively collects gaseous contaminants at a high sample flow rate (∼8 dm(3) min(-1)) compared to the conventional methods used in a clean room. Rapid response to any variability in the sample concentration enables near-real-time monitoring. In the developed monitor, the analyte collected with the PPWD is pumped into one of two preconcentration columns for 15 min, and determined by means of ion chromatography. While one preconcentration column is used for chromatographic separation, the other is used for loading the sample solution. The system allows continuous monitoring of the common acidic gases in an advanced semiconductor manufacturing clean room. 2011 © The Japan Society for Analytical Chemistry

Preconcentration and speciation of ultra-trace Se (IV) and Se (VI) in environmental water samples with nano-sized TiO2 colloid and determination by HG-AFS.

PubMed

Fu, Jiaqi; Zhang, Xu; Qian, Shahua; Zhang, Lin

2012-05-30

A united method for speciation analysis of Se (IV) and Se (VI) in environmental water samples was developed using nano-sized TiO(2) colloid as adsorbent and hydride generation atomic fluorescence spectrometry (HG-AFS) as determination means. When the pH values of bulk solution were between 6.0 and 7.0, successful adsorption onto 1 mL nano-sized TiO(2) colloid (0.2%) was achieved for more than 97.0% of Se (IV) while Se (VI) barely got adsorbed. Therefore, the method made it possible to preconcentrate and determine Se (IV) and Se (VI) separately. The precipitated TiO(2) with concentrated selenium was directly converted to colloid without desorption. Selenium in the resulting colloid was then determined by HG-AFS. The detection limits (3σ) and relative standard deviations (R.S.D) of this method were 24 ng/L and 42 ng/L, 7.8% (n=6) and 7.0% (n=6) for Se (IV) and Se (VI), respectively. This simple, sensitive, and united method was successfully applied to the separation and speciation of ultra-trace Se (IV) and Se (VI) in environmental water samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparison between solid phase microextraction (SPME) and hollow fiber liquid phase microextraction (HFLPME) for determination of extractables from post-consumer recycled PET into food simulants.

PubMed

Oliveira, Éder Costa; Echegoyen, Yolanda; Cruz, Sandra Andrea; Nerin, Cristina

2014-09-01

Hollow fiber liquid phase microextraction (HFLPME) and solid phase microextraction (SPME) methods for pre-concentration of contaminants (toluene, benzophenone, tetracosane and chloroform) in food simulants were investigated. For HFLPME 1-heptanol, 2-octanone and dibutyl-ether were studied as extracting solvents. Analysis by gas chromatography coupled to mass spectrometry (GC-MS), flame ionization (GC-FID) and electron capture detectors (GC-ECD) were carried out. In addition, the methods were employed to evaluate the safety in use of a PET material after the recycling process (comprising washing, extrusion and solid state polymerization (SSP)) through extractability studies of the contaminants using 10% (v/v) ethanol in deionized water and 3% (w/v) acetic acid in deionized water as food simulants in different conditions: 10 days at 40°C and 2h at 70°C. The HFLPME preconcentration method provided increased sensitivity when compared to the SPME method and allowed to analyze concentration levels below 10 µg surrogate per kg food simulant. The results of the extractability studies showed considerable reductions after the extrusion and SSP processes and indicated the compliance with regulations for using recycled PET in contact with food. Copyright © 2014 Elsevier B.V. All rights reserved.

Spectrophotometric determination of basic fuchsin from various water samples after vortex assisted solid phase extraction using reduced graphene oxide as an adsorbent.

PubMed

Tokalıoğlu, Şerife; Yavuz, Emre; Aslantaş, Ayşe; Şahan, Halil; Taşkın, Ferhat; Patat, Şaban

2015-01-01

In this study, a fast and simple vortex assisted solid phase extraction method was developed for the separation/preconcentration of basic fuchsin in various water samples. The determination of basic fuchsin was carried out at a wavelength of 554 nm by spectrophotometry. Reduced graphene oxide which was used as a solid phase extractor was synthesized and characterized by X-ray diffraction, scanning electron microscopy and the Brunauer, Emmett and Teller. The optimum conditions are as follows: pH 2, contact times for adsorption and elution of 30 s and 90 s, respectively, 10 mg adsorbent, and eluent (ethanol) volume of 1 mL. The effects of some interfering ions and dyes were investigated. The method was linear in the concentration range of 50-250 μg L(-1). The adsorption capacity was 34.1 mg g(-1). The preconcentration factor, limit of detection and precision (RSD, %) of the method were found to be 400, 0.07 μg L(-1) and 1.2%, respectively. The described method was validated by analyzing basic fuchsin spiked certified reference material (SPS-WW1 Batch 114-Wastewater) and spiked real water samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Molecularly imprinted solid-phase extraction combined with electrochemical oxidation fluorimetry for the determination of methotrexate in human serum and urine

NASA Astrophysics Data System (ADS)

Chen, Suming; Zhang, Zhujun

2008-06-01

The method of synthesis and evaluation of molecularly imprinted polymers was reported. As a selective solid-phase extraction sorbent, the polymers were coupled with electrochemical fluorimetry detection for the efficient determination of methotrexate in serum and urine. Methotrexate was preconcentrated in the molecularly imprinted solid-phase extraction microcolumn packed with molecularly imprinted polymers, and then eluted. The eluate was detected by fluorescence spectrophotometer after electrochemical oxidation. The conditions of preconcentration, elution, electrochemical oxidation and determination were carefully studied. Under the selected experimental conditions, the calibration graph of the fluorescence intensity versus methotrexate concentration was linear from 4 × 10 -9 g mL -1 to 5 × 10 -7 g mL -1, and the detection limit was 8.2 × 10 -10 g mL -1 (3 σ). The relative standard deviation was 3.92% ( n = 7) for 1 × 10 -7 g mL -1 methotrexate. The experiments showed that the selectivity and sensitivity of fluorimetry could be greatly improved by the proposed method. This method has been successfully applied to the determination of methotrexate. At the same time, the binding characteristics of the polymers to the methotrexate were evaluated by batch and dynamic methods.

An analytical method for hydrogeochemical surveys: Inductively coupled plasma-atomic emission spectrometry after using enrichment coprecipitation with cobalt and ammonium pyrrolidine dithiocarbamate

USGS Publications Warehouse

Hopkins, D.M.

1991-01-01

Trace metals that are commonly associated with mineralization were concentrated and separated from natural water by coprecipitation with ammonium pyrollidine dithiocarbamate (APDC) and cobalt and determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The method is useful in hydrogeochemical surveys because it permits preconcentration near the sample sites, and selected metals are preserved shortly after the samples are collected. The procedure is relatively simple: (1) a liter of water is filtered; (2) the pH is adjusted; (3) Co chloride and APDC are added to coprecipitate the trace metals; and (4) later, the precipitate is filtered, dissolved, and diluted to 10 ml for a 100-fold concentration enrichment of the separated metals. Sb(III), As(III), Cd, Cr, Cu, Fe, Pb, Mo, Ni, Ag, V, and Zn can then be determined simultaneously by ICP-AES. In an experiment designed to measure the coprecipitation efficiency, Sb(III), Cd and Ag were recovered at 70 to 75% of their original concentration. The remaining metals were recovered at 85 to 100% of their original concentrations, however. The range for the lower limits of determination for the metals after preconcentration is 0.1 to 3.0 ??g/l. The precision of the method was evaluated by replicate analyses of a Colorado creek water and two simulated water samples. The accuracy of the method was estimated using a water reference standard (SRM 1643a) certified by the U.S. National Bureau of Standards. In addition, the method was evaluated by analyzing groundwater samples collected near a porphyry copper deposit in Arizona and by analyzing meltwater from glacier-covered areas favorable for mineralization in south-central Alaska. The results for the ICP-AES analyses compared favorably with those obtained using the sequential technique of GFAAS on the acidified but unconcentrated water samples. ICP-AES analysis of trace-metal preconcentrates for hydrogeochemical surveys is more efficient than GFAAS because a large suite of metals is simultaneously determined with acceptable analytical accuracy and precision. The proposed analytical technique can provide direct evidence of mineralization and is useful in the exploration for unknown ore deposits. ?? 1991.

Study of 3-Ethylamino-but-2-enoic acid phenylamide as a new ligand for preconcentration of lanthanides from aqueous media by liquid-liquid extraction prior to ICP-MS analysis.

PubMed

Varbanova, Evelina K; Angelov, Plamen A; Stefanova, Violeta M

2016-11-01

In the present work the potential of a new ligand 3-Ethylamino-but-2-enoic acid phenylamide (representing the class of enaminones) for selective preconcentration of lanthanides (La, Ce, Eu, Gd and Er) from aqueous medium is examined. Liquid-liquid extraction parameters, such as pH of the water phase, type and volume of organic solvent, quantity of ligand and reaction time are optimized on model solutions. Recovery of lanthanides by re-extraction with nitric acid makes the LLE procedure compatible with Inductively Coupled Plasma Mass Spectrometry. Spectral and non-spectral interferences are studied. Two isotopes per element are measured (with exception of La) for dynamic evaluation of the potential risk of spectral interference in variable real samples. The selectivity of complex formation reaction towards concomitant alkali and alkali-earth elements eliminates the interferences from sample matrix. Subjecting the standards to the optimized extraction procedure in combination with Re as internal standard is recommended as calibration strategy. The accuracy of developed method is approved by analysis of CRM Bush branches and leaves (NCS DC 73348) and recovery of spiked water and plant samples. The method's limits of detection for both studied objects are in the ranges from 0.2 ((158)Gd) to 3.7 ((139)La) ngl(-1) and 0.02 ((158)Gd) to 0.37((139)La) ngg(-1) for waters and plants respectively. The studied compound is an effective new ligand for preconcentration/separation of lanthanides from aqueous medium by LLE and subsequent determination by ICP-MS. Copyright © 2016 Elsevier B.V. All rights reserved.

The evaluation of different sorbents for the preconcentration of phenoxyacetic acid herbicides and their metabolites from soils.

PubMed

Moret, Sònia; Sánchez, Juan M; Salvadó, Victòria; Hidalgo, Manuela

2005-12-16

A procedure using alkaline extraction, solid-phase extraction (SPE) and HPLC is developed to analyze the polar herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) together with their main metabolites in soils. An ion-pairing HPLC method is used for the determination as it permits the baseline separation of these highly polar herbicides and their main metabolites. The use of a highly cross-linked polystyrene-divinylbenzene sorbent (PS-DVB) gives the best results for the analysis of these compounds. This sorbent allows the direct preconcentration of the analytes at the high pH values obtained after quantitative alkaline extraction of the herbicides from soil samples. Different parameters are evaluated for the SPE preconcentration step. The high polarity of the main analytes of interest (2,4-D and MCPA) makes it necessary to work at low flow rates (< or =0.5 mL min(-1)) in order for these compounds to be retained by the PS-DVB sorbent. A two stage desorption from the SPE sorbent is required to obtain the analytes in solvents that are appropriate for HPLC determination. A first desorption with a 50:50 methanol:water mixture elutes the most polar analytes (2,4-D, MCPA and 2CP). The second elution step with methanol permits the analysis of the other phenol derivatives. The humic and fulvic substances present in the soil are not efficiently retained by PS-DVB sorbents at alkaline pH's and so do not interfere in the analysis. This method has been successfully applied in the analysis of soil samples from a golf course treated with a commercial product containing esters of 2,4-D and MCPA as the active components.

Solid-Phase Extraction Coupled to a Paper-Based Technique for Trace Copper Detection in Drinking Water.

PubMed

Quinn, Casey W; Cate, David M; Miller-Lionberg, Daniel D; Reilly, Thomas; Volckens, John; Henry, Charles S

2018-03-20

Metal contamination of natural and drinking water systems poses hazards to public and environmental health. Quantifying metal concentrations in water typically requires sample collection in the field followed by expensive laboratory analysis that can take days to weeks to obtain results. The objective of this work was to develop a low-cost, field-deployable method to quantify trace levels of copper in drinking water by coupling solid-phase extraction/preconcentration with a microfluidic paper-based analytical device. This method has the advantages of being hand-powered (instrument-free) and using a simple "read by eye" quantification motif (based on color distance). Tap water samples collected across Fort Collins, CO, were tested with this method and validated against ICP-MS. We demonstrate the ability to quantify the copper content of tap water within 30% of a reference technique at levels ranging from 20 to 500 000 ppb. The application of this technology, which should be sufficient as a rapid screening tool, can lead to faster, more cost-effective detection of soluble metals in water systems.

Application of dispersive liquid-liquid microextraction for the preconcentration of eight parabens in real samples and their determination by high-performance liquid chromatography.

PubMed

Shen, Xiong; Liang, Jian; Zheng, Luxia; Lv, Qianzhou; Wang, Hong

2017-11-01

A simple and sensitive method for the simultaneous determination of eight parabens in human plasma and urine samples was developed. The samples were preconcentrated using dispersive liquid-liquid microextraction based on the solidification of floating organic drops and determined by high-performance liquid chromatography with ultraviolet detection. The influence of variables affecting the extraction efficiency was investigated and optimized using Placket-Burman design and Box-Behnken design. The optimized values were: 58 μL of 1-decanol (as extraction solvent), 0.65 mL methanol (as disperser solvent), 1.5% w/v NaCl in 5.0 mL of sample solution, pH 10.6, and 4.0 min centrifugation at 4000 rpm. The extract was injected into the high-performance liquid chromatography system for analysis. Under the optimum conditions, the linear ranges for eight parabens in plasma and urine were 1.0-1000 ng/mL, with correlation coefficients above 0.994. The limit of detection was 0.2-0.4 and 0.1-0.4 ng/mL for plasma and urine samples, respectively. Relative recoveries were between 80.3 and 110.7%, while relative standard deviations were less than 5.4%. Finally, the method was applied to analyze the parabens in 98 patients of primary breast cancer. Results showed that parabens existed widely, at least one paraben detected in 96.9% (95/98) of plasma samples and 98.0% (96/98) of urine samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic ionic liquid aqueous two-phase system coupled with high performance liquid chromatography: A rapid approach for determination of chloramphenicol in water environment.

PubMed

Yao, Tian; Yao, Shun

2017-01-20

A novel organic magnetic ionic liquid based on guanidinium cation was synthesized and characterized. A new method of magnetic ionic liquid aqueous two-phase system (MILATPs) coupled with high-performance liquid chromatography (HPLC) was established to preconcentrate and determine trace amount of chloramphenicol (CAP) in water environment for the first time. In the absence of volatile organic solvents, MILATPs not only has the excellent properties of rapid extraction, but also exhibits a response to an external magnetic field which can be applied to assist phase separation. The phase behavior of MILATPs was investigated and phase equilibrium data were correlated by Merchuk equation. Various influencing factors on CAP recovery were systematically investigated and optimized. Under the optimal conditions, the preconcentration factor was 147.2 with the precision values (RSD%) of 2.42% and 4.45% for intra-day (n=6) and inter-day (n=6), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.14ngmL -1 and 0.42ngmL -1 , respectively. Fine linear range of 12.25ngmL -1 -2200ngmL -1 was obtained. Finally, the validated method was successfully applied for the analysis of CAP in some environmental waters with the recoveries for the spiked samples in the acceptable range of 94.6%-99.72%. Hopefully, MILATPs is showing great potential to promote new development in the field of extraction, separation and pretreatment of various biochemical samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Optimization of multiwalled carbon nanotubes reinforced hollow-fiber solid-liquid-phase microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples using experimental design.

PubMed

Hamedi, Raheleh; Hadjmohammadi, Mohammad Reza

2017-09-01

A novel design of hollow-fiber liquid-phase microextraction containing multiwalled carbon nanotubes as a solid sorbent, which is immobilized in the pore and lumen of hollow fiber by the sol-gel technique, was developed for the pre-concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples. The proposed method utilized both solid- and liquid-phase microextraction media. Parameters that affect the extraction of polycyclic aromatic hydrocarbons were optimized in two successive steps as follows. Firstly, a methodology based on a quarter factorial design was used to choose the significant variables. Then, these significant factors were optimized utilizing central composite design. Under the optimized condition (extraction time = 25 min, amount of multiwalled carbon nanotubes = 78 mg, sample volume = 8 mL, and desorption time = 5 min), the calibration curves showed high linearity (R 2  = 0.99) in the range of 0.01-500 ng/mL and the limits of detection were in the range of 0.007-1.47 ng/mL. The obtained extraction recoveries for 10 ng/mL of polycyclic aromatic hydrocarbons standard solution were in the range of 85-92%. Replicating the experiment under these conditions five times gave relative standard deviations lower than 6%. Finally, the method was successfully applied for pre-concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Grafting 3-mercaptopropyl trimethoxysilane on multi-walled carbon nanotubes surface for improving on-line cadmium(II) preconcentration from water samples.

PubMed

Corazza, Marcela Zanetti; Somera, Bruna Fabrin; Segatelli, Mariana Gava; Tarley, Cesar Ricardo Teixeira

2012-12-01

In the present study, the performance of multi-walled carbon nanotubes (MWCNTs) grafted with 3-mercaptopropyltrimethoxysilane (3-MPTMS), used as a solid phase extractor for Cd(2+) preconcentration in a flow injection system coupled to flame atomic absorption spectrometry (FAAS), was evaluated. The procedure involved the preconcentration of 20.0 mL of Cd(2+) solution at pH 7.5 (0.1 mol L(-1) buffer phosphate) through 70 mg of 3-MPTMS-grafted MWCNTs packed into a minicolumn at 6.0 mL min(-1). The elution step was carried out with 1.0 mol L(-1) HCl. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to estimate the extent of the MWCNT chemical modification. The 3-MPTMS-grafted MWCNTs provided a 1.68 times improvement in the sensitivity of the Cd(2+) FAAS determination compared to the unsilanized oxidized MWCNTs. The following parameters were obtained: preconcentration factor of 31.5, consumptive index of 0.635 mL, sample throughput of 14 h(-1), and concentration efficiency of 9.46 min(-1). The analytical curve was constructed in the range of 1.0-60.0 μg L(-1) (r=0.9988), and the detection and quantification limits were found to be 0.15 μg L(-1) and 0.62 μg L(-1), respectively. Different types of water samples and cigarette sample were successfully analyzed, and the results were compared using electrothermal atomic absorption spectrometry (ETAAS) as reference technique. In addition, the accuracy of proposed method was also checked by analysis of certified reference material NIST SRM 1573a (tomato leaves) and standard reference material NIST SRM 1643e (trace elements in natural waters). Copyright © 2012 Elsevier B.V. All rights reserved.

Ion Imprinted Polymer for Preconcentration and Determination of Ultra-Trace Cadmium, Employing Flow Injection Analysis with Thermo Spray Flame Furnace Atomic Absorption Spectrometry.

PubMed

do Lago, Ayla Campos; Marchioni, Camila; Mendes, Tássia Venga; Wisniewski, Célio; Fadini, Pedro Sergio; Luccas, Pedro Orival

2016-11-01

This work proposes a preconcentration method using an ion imprinted polymer (IIP) for determination of cadmium, in several samples, employing a mini-column filled with the polymer coupled into a flow injection analysis system with detection by thermospray flame furnace atomic absorption spectrometry (FIA-TS-FF-AAS). The polymer was synthesized via bulk using methacrylic acid and vinylimidazole as a functional monomer. For the FIA system initial assessment, the variables: pH, eluent concentration and buffer concentration were studied, employing a 23 full factorial design. To obtain the optimum values for each significant variable, a Doehlert matrix was employed. After the optimization conditions as: pH 5.8, eluent (HNO3) concentration of 0.48 mol L -1 and buffer concentration of 0.01 mol L -1 , were adopted. The proposed method showed a linear response in the range of 0.081-10.0 μg L -1 , limits detection and quantification of 0.024 and 0.081 μg L -1 , respectively; preconcentration factor of 165, consumptive index of 0.06 mL, concentration efficiency 132 min -1 , and frequency of readings equal to 26 readings h -1 The accuracy was checked by analysis of certified reference materials for trace metals and recovery tests. The obtained results were in agreement with 95% confidence level (t-test). The method was adequate to apply in samples of: jewelry (earrings) (2.38 ± 0.28 μg kg -1 ), black tea (1.09 ± 0.15 μg kg -1 ), green tea (3.85 ± 0.13 μg kg -1 ), cigarette tobacco (38.27 ± 0.22 μg kg -1 ), and hair (0.35 ± 0.02 μg kg -1 ). © The Author(s) 2016.

Mixed hemimicelle solid-phase extraction based on magnetic halloysite nanotubes and ionic liquids for the determination and extraction of azo dyes in environmental water samples.

PubMed

Liu, Wei; Fizir, Meriem; Hu, Fan; Li, Ang; Hui, Xuanhong; Zha, Jun; He, Hua

2018-05-25

An effective and greener mixed hemimicelles magnetic solid phase extraction (MHMSPE) based on magnetic halloysite nanotubes (MHNTs) and ionic liquid (IL) is developed for the simultaneous enrichment and determination of anionic azo dyes in a spiked environmental water sample. In this MHMSPE, the formation of C 16 mimBr with mixed hemimicelles on the surface of MHNTs leads to the retention of analytes by strong hydrophobic, p-p and electrostatic interactions. This MHMSPE technique combines the advantages of MHNTs and mixed hemimicelles. Zeta potential data demonstrated that mixed hemimicelles were formed in [C 16 mimBr]/[MHNTs] ratios of the range from 0.15 to 1.33. Different important factors affecting the preconcentration of analytes were investigated and optimized by response surface methodology and one variable at a time. Under the optimum conditions, the limits of detection (LOD) for methyl red and methyl orange (MR and MO) were 0.042 and 0.050 μg L -1 in samples, respectively. The accuracy of the method was assessed by recovery measurements on a spiked sample, and good recoveries 85-87% for MR and 89-93% for MO, with preconcentration factors of 481 and 524, respectively. The low relative standard deviations from 1.6-3.1% for tap water and 2.5-5.4% for lake water was achieved. So far as we know, this is the first development of a mixed hemimicelles SPE based on MHNTs and IL for the extraction of trace anionic azo dyes in environment water samples. Copyright © 2018 Elsevier B.V. All rights reserved.

On-line preconcentration system for lead(II) determination in waste water by atomic absorption spectrometry using active carbon loaded with Pyrogallol Red.

PubMed

Ensafi, Ali A; Khayamian, Taghi; Karbasi, Mohammad H

2003-06-01

An on-line system for enrichment and determination of lead(II) is presented. It is based on the adsorption of lead(II) ions on a minicolumn packed with active carbon loaded with Pyrogallol Red. After preconcentration step, the metal ions are eluted automatically by 5.0 ml of 0.50 M nitric acid solution and the lead ion contents were determined by atomic absorption spectrometry. The influence of chemicals, pH and flow variables were studied as well as effect of potential interfering ions. Under the optimum conditions, the lead ions in aqueous samples were concentrated about 100 fold by the column. The detection limit was 0.001 microg ml(-1). The recovery percent of spliced lead(II) was in the range of 98%-103%.

Rapid and highly sensitive determination of low-molecular-weight carbonyl compounds in drinking water and natural water by preconcentration HPLC with 2,4-dinitrophenylhydrazine.

PubMed

Takeda, Kazuhiko; Katoh, Shinya; Nakatani, Nobutake; Sakugawa, Hiroshi

2006-12-01

The aim of this research was to develop a simple procedure for a highly sensitive determination of low-molecular-weight (LMW) carbonyl compounds in drinking water and natural water. We employed a preconcentration HPLC system with 2,4-dinitrophenylhydrazine (DNPH) for the determination of LMW carbonyl compounds. A C-18 reverse-phase preconcentration column was used instead of a sample loop at the sample injection valve. A 0.1 - 5.0 mL portion of the derivatized sample solution was injected with a gas-tight syringe, and a 15% acetonitrile aqueous solution was pushed through the preconcentration column to remove the unreacted excess DNPH, which caused serious interference in the determination of formaldehyde. The detection limits were 1 - 3 nM with a relative standard deviation of 2 - 5% for 20 nM standard solutions (n = 5). The calibration curves were essentially unaffected by coexisting sea salts. Applications to commercial mineral water, tap water, river water, pond water and seawater are presented.

Selection of forward osmosis draw solutes for subsequent integration with anaerobic treatment to facilitate resource recovery from wastewater.

PubMed

Ansari, Ashley J; Hai, Faisal I; Guo, Wenshan; Ngo, Hao H; Price, William E; Nghiem, Long D

2015-09-01

Forward osmosis (FO) can be used to extract clean water and pre-concentrate municipal wastewater to make it amenable to anaerobic treatment. A protocol was developed to assess the suitability of FO draw solutes for pre-concentrating wastewater for potential integration with anaerobic treatment to facilitate resource recovery from wastewater. Draw solutes were evaluated in terms of their ability to induce osmotic pressure, water flux, and reverse solute flux. The compatibility of each draw solute with subsequent anaerobic treatment was assessed by biomethane potential analysis. The effect of each draw solute (at concentrations corresponding to the reverse solute flux at ten-fold pre-concentration of wastewater) on methane production was also evaluated. The results show that ionic organic draw solutes (e.g., sodium acetate) were most suitable for FO application and subsequent anaerobic treatment. On the other hand, the reverse solute flux of inorganic draw solutions could inhibit methane production from FO pre-concentrated wastewater. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Development of a selective and sensitive flotation method for determination of trace amounts of cobalt, nickel, copper and iron in environmental samples.

PubMed

Karimi, H; Ghaedi, M; Shokrollahi, A; Rajabi, H R; Soylak, M; Karami, B

2008-02-28

A simple, selective and rapid flotation method for the separation-preconcentration of trace amounts of cobalt, nickel, iron and copper ions using phenyl 2-pyridyl ketone oxime (PPKO) has been developed prior to their flame atomic absorption spectrometric determinations. The influence of pH, amount of PPKO as collector, type and amount of eluting agent, type and amount of surfactant as floating agent and ionic strength was evaluated on the recoveries of analytes. The influences of the concomitant ions on the recoveries of the analyte ions were also examined. The enrichment factor was 93. The detection limits based on 3 sigma for Cu, Ni, Co and Fe were 0.7, 0.7, 0.8, and 0.7 ng mL(-1), respectively. The method has been successfully applied for determination of trace amounts of ions in various real samples.

Potential application of microsensor technology in radioactive waste management with emphasis on headspace gas detection.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Chad Edward; Thomas, Michael Loren; Wright, Jerome L.

2004-09-01

Waste characterization is probably the most costly part of radioactive waste management. An important part of this characterization is the measurements of headspace gas in waste containers in order to demonstrate the compliance with Resource Conservation and Recovery Act (RCRA) or transportation requirements. The traditional chemical analysis methods, which include all steps of gas sampling, sample shipment and laboratory analysis, are expensive and time-consuming as well as increasing worker's exposure to hazardous environments. Therefore, an alternative technique that can provide quick, in-situ, and real-time detections of headspace gas compositions is highly desirable. This report summarizes the results obtained from amore » Laboratory Directed Research & Development (LDRD) project entitled 'Potential Application of Microsensor Technology in Radioactive Waste Management with Emphasis on Headspace Gas Detection'. The objective of this project is to bridge the technical gap between the current status of microsensor development and the intended applications of these sensors in nuclear waste management. The major results are summarized below: {sm_bullet} A literature review was conducted on the regulatory requirements for headspace gas sampling/analysis in waste characterization and monitoring. The most relevant gaseous species and the related physiochemical environments were identified. It was found that preconcentrators might be needed in order for chemiresistor sensors to meet desired detection {sm_bullet} A long-term stability test was conducted for a polymer-based chemresistor sensor array. Significant drifts were observed over the time duration of one month. Such drifts should be taken into account for long-term in-situ monitoring. {sm_bullet} Several techniques were explored to improve the performance of sensor polymers. It has been demonstrated that freeze deposition of black carbon (CB)-polymer composite can effectively eliminate the so-called 'coffee ring' effect and lead to a desirable uniform distribution of CB particles in sensing polymer films. The optimal ratio of CB/polymer has been determined. UV irradiation has been shown to improve sensor sensitivity. {sm_bullet} From a large set of commercially available polymers, five polymers were selected to form a sensor array that was able to provide optimal responses to six target-volatile organic compounds (VOCs). A series of tests on the response of sensor array to various VOC concentrations have been performed. Linear sensor responses have been observed over the tested concentration ranges, although the responses over a whole concentration range are generally nonlinear. {sm_bullet} Inverse models have been developed for identifying individual VOCs based on sensor array responses. A linear solvation energy model is particularly promising for identifying an unknown VOC in a single-component system. It has been demonstrated that a sensor array as such we developed is able to discriminate waste containers for their total VOC concentrations and therefore can be used as screening tool for reducing the existing headspace gas sampling rate. {sm_bullet} Various VOC preconcentrators have been fabricated using Carboxen 1000 as an absorbent. Extensive tests have been conducted in order to obtain optimal configurations and parameter ranges for preconcentrator performance. It has been shown that use of preconcentrators can reduce the detection limits of chemiresistors by two orders of magnitude. The life span of preconcentrators under various physiochemical conditions has also been evaluated. {sm_bullet} The performance of Pd film-based H2 sensors in the presence of VOCs has been evaluated. The interference of sensor readings by VOC has been observed, which can be attributed to the interference of VOC with the H2-O2 reaction on the Pd alloy surface. This interference can be eliminated by coating a layer of silicon dioxide on sensing film surface. Our work has demonstrated a wide range of applications of gas microsensors in radioactive waste management. Such applications can potentially lead to a significant cost saving and risk reduction for waste characterization.« less

Nickel (II) Preconcentration and Speciation Analysis During Transport from Aqueous Solutions Using a Hollow-fiber Permeation Liquid Membrane (HFPLM) Device.

PubMed

Bautista-Flores, Ana Nelly; De San Miguel, Eduardo Rodríguez; Gyves, Josefina de; Jönsson, Jan Åke

2011-08-18

Nickel (II) preconcentration and speciation analysis using a hollow fiber supported liquid membrane (HFSLM) device was studied. A counterflow of protons coupled to complexation with formate provided the driving force of the process, while Kelex 100 was employed as carrier. The influence of variables related to module configuration (acceptor pH and carrier concentration) and to the sample properties (donor pH) on the preconcentration factor, E, was simultaneously studied and optimized using a 3 factor Doehlert matrix response surface methodology. The effect of metal concentration was studied as well. Preconcentration factors as high as 4240 were observed  depending on the values of the different variables. The effects of the presence of inorganic anions (NO2-, SO42-, Cl-, NO3-, CO32-, CN-) and dissolved organic matter (DOM) in the form of humic acids were additionally considered in order to carry out a speciation analysis study. Nickel preconcentration was observed to be independent of both effects, except when cyanide was present in the donor phase. A characterization of the transport regime was performed through the analysis of the dependence of E on the temperature. E increases with the increase in temperature according to the equation E(K) = -8617.3 + 30.5T with an activation energy of 56.7 kJ mol-1 suggesting a kinetic-controlled regime. Sample depletion ranged from 12 to 1.2% depending on the volume of the donor phase (100 to 1000 mL, respectively).

Coupling of solvent-based de-emulsification dispersive liquid-liquid microextraction with high performance liquid chromatography for simultaneous simple and rapid trace monitoring of 2,4-dichlorophenoxyacetic acid and 2-methyl-4-chlorophenoxyacetic acid.

PubMed

Behbahani, Mohammad; Najafi, Fatemeh; Bagheri, Saman; Bojdi, Majid Kalate; Hassanlou, Parmoon Ghareh; Bagheri, Akbar

2014-04-01

A simple, rapid, and efficient sample pretreatment technique, based on solvent-based de-emulsification dispersive liquid-liquid microextraction (SD-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for simultaneous preconcentration and trace detection of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in water and urine samples. Some parameters such as acidity of solution, the amount of salt, type, and volume of extraction solvents, type of disperser/de-emulsifier solvent, and its volume were investigated and optimized. Under optimum extraction conditions, the limits of detections (LODs) of this method for MCPA and 2,4-D were 0.2 and 0.6 μg L(-1) (based on 3S(b)/m) in water and 0.4 and 1.6 μg L(-1) in urine, respectively. Furthermore, dynamic linear range of this method for MCPA and 2,4-D was 1-300 and 2-400 μg L(-1), repectively. Finally, the applicability of the proposed method was evaluated by extraction and determination of the herbicides in urine and different water samples.

Development and optimization of an analytical system for volatile organic compound analysis coming from the heating of interstellar/cometary ice analogues.

PubMed

Abou Mrad, Ninette; Duvernay, Fabrice; Theulé, Patrice; Chiavassa, Thierry; Danger, Grégoire

2014-08-19

This contribution presents an original analytical system for studying volatile organic compounds (VOC) coming from the heating and/or irradiation of interstellar/cometary ice analogues (VAHIIA system) through laboratory experiments. The VAHIIA system brings solutions to three analytical constraints regarding chromatography analysis: the low desorption kinetics of VOC (many hours) in the vacuum chamber during laboratory experiments, the low pressure under which they sublime (10(-9) mbar), and the presence of water in ice analogues. The VAHIIA system which we developed, calibrated, and optimized is composed of two units. The first is a preconcentration unit providing the VOC recovery. This unit is based on a cryogenic trapping which allows VOC preconcentration and provides an adequate pressure allowing their subsequent transfer to an injection unit. The latter is a gaseous injection unit allowing the direct injection into the GC-MS of the VOC previously transferred from the preconcentration unit. The feasibility of the online transfer through this interface is demonstrated. Nanomoles of VOC can be detected with the VAHIIA system, and the variability in replicate measurements is lower than 13%. The advantages of the GC-MS in comparison to infrared spectroscopy are pointed out, the GC-MS allowing an unambiguous identification of compounds coming from complex mixtures. Beyond the application to astrophysical subjects, these analytical developments can be used for all systems requiring vacuum/cryogenic environments.

Simultaneous preconcentration and determination of copper, nickel, cobalt and lead ions content by flame atomic absorption spectrometry.

PubMed

Ghaedi, Mehrorang; Ahmadi, Farshid; Shokrollahi, Ardeshir

2007-04-02

A sensitive and simple method for the simultaneous preconcentration of nutritionally important minerals in real samples has been reported. The method is based on the formation of metal complexes by 4,6-dihydroxy-2-mercaptopyrimidine (DHMP) loaded on activated carbon. The metals content on the complexes are then eluted using 5 mL 2M HNO(3) in acetone, which are detected by AAS at resonance line. In this procedure, minerals such as Cu, Ni, Pb and Co could be analyzed in one run by caring out the simultaneous separation and quantification of them. At optimum condition the response are linear over concentration range of 0.04-1.1 microg mL(-1) for Ni(2+) and 0.04-1.0 microg mL(-1) for Cu(2+), Pb(2+) and Co(2+). The detection limits of each element are expressed as the amount of analytes in ng mL(-1) giving a signal to noise ratio of 3 are equal to 3.5, 3.4, 2.9 and 8.4 for Ni(2+), Co(2+), Cu(2+) and Pb(2+). The sorption capacity was determined by saturating 0.5 g solid phase. The loading capacity are 0.54, 0.53, 0.63 and 0.45 mg g(-1) for Ni(2+), Co(2+), Cu(2+) and Pb(2+). The ability of method for repeatable recovery of trace ion are 99.0, 98.9, 99.2 and 98.8 with R.S.D. of 1.4, 1.3, 1.2 and 1.4 for Ni(2+), Co(2+), Cu(2+) and Pb(2+). The low detection limits of these elements in this technique make it a superior alternative to UV-vis and in several applications, also an alternative to ICP-MS techniques. The method has been successfully applied for these metals content evaluation in some real samples including natural water, leaves of spinach and cow liver.

Chromium speciation in environmental samples using a solid phase spectrophotometric method.

PubMed

Amin, Alaa S; Kassem, Mohammed A

2012-10-01

A solid phase extraction technique is proposed for preconcentration and speciation of chromium in natural waters using spectrophotometric analysis. The procedure is based on sorption of chromium(III) as 4-(2-benzothiazolylazo)2,2'-biphenyldiol complex on dextran-type anion-exchange gel (Sephadex DEAE A-25). After reduction of Cr(VI) by 0.5 ml of 96% concentrated H(2)SO(4) and ethanol, the system was applied to the total chromium. The concentration of Cr(VI) was calculated as the difference between the total Cr and the Cr(III) content. The influences of some analytical parameters such as: pH of the aqueous solution, amounts of 4-(2-benzothiazolylazo)2,2'-biphenyldiol (BTABD), and sample volumes were investigated. The absorbance of the gel, at 628 and 750 nm, packed in a 1.0 mm cell, is measured directly. The molar absorptivities were found to be 2.11×10(7) and 3.90×10(7) L mol(-1)cm(-1) for 500 and 1000 ml, respectively. Calibration is linear over the range 0.05-1.45 μg L(-1) with RSD of <1.85% (n=8.0). Using 35 mg exchanger, the detection and quantification limits were 13 and 44 ng L(-1) for 500 ml sample, whereas for 1000 ml sample were 8.0 and 27 ng L(-1), respectively. Increasing the sample volume can enhance the sensitivity. No considerable interferences have been observed from other investigated anions and cations on the chromium speciation. The proposed method was applied to the speciation of chromium in natural waters and total chromium preconcentration in microwave digested tobacco, coffee, tea, and soil samples. The results were simultaneously compared with those obtained using an ET AAS method, whereby the validity of the method has been tested. Copyright © 2012 Elsevier B.V. All rights reserved.

A versatile, refrigerant- and cryogen-free cryofocusing-thermodesorption unit for preconcentration of traces gases in air

NASA Astrophysics Data System (ADS)

Obersteiner, Florian; Bönisch, Harald; Keber, Timo; O'Doherty, Simon; Engel, Andreas

2016-10-01

We present a compact and versatile cryofocusing-thermodesorption unit, which we developed for quantitative analysis of halogenated trace gases in ambient air. Possible applications include aircraft-based in situ measurements, in situ monitoring and laboratory operation for the analysis of flask samples. Analytes are trapped on adsorptive material cooled by a Stirling cooler to low temperatures (e.g. -80 °C) and subsequently desorbed by rapid heating of the adsorptive material (e.g. +200 °C). The set-up involves neither the exchange of adsorption tubes nor any further condensation or refocusing steps. No moving parts are used that would require vacuum insulation. This allows for a simple and robust design. Reliable operation is ensured by the Stirling cooler, which neither contains a liquid refrigerant nor requires refilling a cryogen. At the same time, it allows for significantly lower adsorption temperatures compared to commonly used Peltier elements. We use gas chromatography - mass spectrometry (GC-MS) for separation and detection of the preconcentrated analytes after splitless injection. A substance boiling point range of approximately -80 to +150 °C and a substance mixing ratio range of less than 1 ppt (pmol mol-1) to more than 500 ppt in preconcentrated sample volumes of 0.1 to 10 L of ambient air is covered, depending on the application and its analytical demands. We present the instrumental design of the preconcentration unit and demonstrate capabilities and performance through the examination of analyte breakthrough during adsorption, repeatability of desorption and analyte residues in blank tests. Examples of application are taken from the analysis of flask samples collected at Mace Head Atmospheric Research Station in Ireland using our laboratory GC-MS instruments and by data obtained during a research flight with our in situ aircraft instrument GhOST-MS (Gas chromatograph for the Observation of Tracers - coupled with a Mass Spectrometer).

Methodology Measuring Rare Earth Elements in High TDS Reservoir Brines Application as Natural Tracers in CCUS Studies

NASA Astrophysics Data System (ADS)

Smith, W.; Mcling, T. L.; Smith, R. W.; Neupane, H.

2013-12-01

In recent years rare earth elements (REE) have been demonstrated to be useful natural tracers for geochemical processes in aqueous environments. The application of REE's to carbon dioxide utilization and storage (CCUS) could provide researchers with a sensitive, inexpensive tool for tracking the movement of CO2 and displaced formation brines. By definition, geologic reservoirs that have been deemed suitable for carbon capture and storage contain formation brine with total dissolved solids (TDS) greater than 10,000 ppm and often these formation brines exceed 75,000 ppm TDS. This high TDS water makes it very difficult to measure REE, which typically occur at part per trillion concentrations. Critical to the use of REE for CCUS studies is the development of a procedure, which allows for the pre-concentration of REE's across a wide range of water quality. Additionally, due to the large number of samples that will need analysis, any developed procedure must be inexpensive, reproducible, and quick to implement. As part of the Big Sky Carbon Sequestration Project the INL's Center for Advance Energy Studies is developing REE pre-concentration procedures based on methods reported in the literature. While there are many REE pre-concentration procedures in the literature, our tests have shown these methods have difficulty at TDS greater than seawater (roughly 35,000 ppm TDS). Therefore, the ability to quantitatively measure REE's in formation brines with very high TDS has required the modification of an already developed procedure. After careful consideration and testing we selected methods modified after those described by Kingston et al., 1978 and Strachan et al., 1989 utilizing chelating media for very high TDS waters and ion-exchange media as detailed by Crock et al., 1984; Robinson et al., 1985; and Stetzenbach et al., 1994 for low TDS (<10,000 ppm TDS) waters. These modified procedures have been successfully tested in our laboratory and have proven effective in greatly reducing interfering monovalent and divalent cation concentrations (e.g. Ba) and enriching the REE up to 100X for analysis. The procedures are straightforward, inexpensive, and require little infrastructure, using only single chromatography columns with inexpensive, reusable, commercially available resins and wash chemicals. The procedures have been tested with synthetic brines and waters (up to 250,000 ppm TDS) and field water samples (up to 5,000 ppm TDS). Testing has produced data with REE capture efficiency exceeding 95%, while reducing interfering elements by more than 93%. Further method development and testing continues in preparation for brine analysis of waters from the Big Sky Carbon Sequestration Partnership's Kevin Dome Pilot Study and the University of Wyoming's Carbon Institutes Rock Springs Uplift.

Application of mercapto-silica polymerized high internal phase emulsions for the solid-phase extraction and preconcentration of trace lead(II).

PubMed

Su, Rihui; Ruan, Guihua; Chen, Zhengyi; Du, Fuyou; Li, Jianping

2015-12-01

A new class of solid-phase extraction column prepared with grafted mercapto-silica polymerized high internal phase emulsion particles was used for the preconcentration of trace lead. First, mercapto-silica polymerized high internal phase emulsion particles were synthesized by using high internal phase emulsion polymerization and carefully assembled in a polyethylene syringe column. The influences of various parameters including adsorption pH value, adsorption and desorption solvents, flow rate of the adsorption and desorption procedure were optimized, respectively, and the suitable uploading sample volumes, adsorption capacity, and reusability of solid phase extraction column were also investigated. Under the optimum conditions, Pb(2+) could be preconcentrated quantitatively over a wide pH range (2.0-5.0). In the presence of foreign ions, such as Na(+) , K(+) , Ca(2+) , Zn(2+) , Mg(2+) , Cu(2+) , Fe(2+) , Cd(2+) , Cl(-) and NO3 (-) , Pb(2+) could be recovered successfully. The prepared solid-phase extraction column performed with high stability and desirable durability, which allowed more than 100 replicate extractions without measurable changes of performance. The feasibility of the developed method was further validated by the extraction of Pb(2+) in rice samples. At three spiked levels of 40.0, 200 and 800 μg/kg, the average recoveries for Pb(2+) in rice samples ranged from 87.3 to 105.2%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of copper ions in environmental water samples.

PubMed

Roushani, Mahmoud; Abbasi, Shahryar; Khani, Hossein

2015-04-01

Novel Cu(II) ion-imprinted polymers (Cu-IIP) nanoparticles were prepared by using Cu(II) ion-thiosemicarbazide complex as the template molecule and methacrylic acid, ethylene glycol dimethacrylate (EGDMA), and 2,2'azobisisobutyronitrile (AIBN) as the functional monomer, cross-linker, and the radical initiator, respectively. The synthesized polymer nanoparticles were characterized by using infrared spectroscopy (IR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopic (SEM) techniques. Some parameters such as pH, weight of the polymer, adsorption time, elution time, eluent type, and eluent volume which affect the extraction efficiency of the polymer were studied. In the proposed method, the maximum sorbent capacity of the ion-imprinted polymer was calculated to be 38.8 mg g(-1). The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 80, 1.7%, and 0.003 μg mL(-1), respectively. The prepared ion-imprinted polymer nanoparticles have an increased selectivity toward Cu(II) ions over a range of competing metal ions with the same charge and similar ionic radius. The method was applied to the determination of ultra trace levels of Cu2+ in environmental water samples with satisfactory results.

A dispersive liquid--liquid microextraction methodology for copper (II) in environmental samples prior to determination using microsample injection flame atomic absorption spectrometry.

PubMed

Alothman, Zeid A; Habila, Mohamed; Yilmaz, Erkan; Soylak, Mustafa

2013-01-01

A simple, environmentally friendly, and efficient dispersive liquid-liquid microextraction method combined with microsample injection flame atomic absorption spectrometry was developed for the separation and preconcentration of Cu(II). 2-(5-Bromo-2-pyridylazo)-5-(diethylamino)phenol (5-Br-PADAP) was used to form a hydrophobic complex of Cu(II) ions in the aqueous phase before extraction. To extract the Cu(II)-5-Br-PADAP complex from the aqueous phase to the organic phase, 2.0 mL of acetone as a disperser solvent and 200 microL of chloroform as an extraction solvent were used. The influences of important analytical parameters, such as the pH, types and volumes of the extraction and disperser solvents, amount of chelating agent, sample volume, and matrix effects, on the microextraction procedure were evaluated and optimized. Using the optimal conditions, the LOD, LOQ, preconcentration factor, and RSD were determined to be 1.4 microg/L, 4.7 microg/L, 120, and 6.5%, respectively. The accuracy of the proposed method was investigated using standard addition/recovery tests. The analysis of certified reference materials produced satisfactory analytical results. The developed method was applied for the determination of Cu in real samples.

Polyaniline-coated cigarette filters as a solid-phase extraction sorbent for the extraction and enrichment of polycyclic aromatic hydrocarbon in water samples.

PubMed

Bunkoed, Opas; Rueankaew, Thanaschaphorn; Nurerk, Piyaluk; Kanatharana, Proespichaya

2016-06-01

Polyaniline coated cigarette filters were successfully synthesized and used as a solid-phase extraction sorbent for the extraction and preconcentration of polycyclic aromatic hydrocarbons in water samples. The polyaniline helped to enhance the adsorption ability of polycyclic aromatic hydrocarbons on the sorbent through π-π interactions. The high porosity and large surface area of the cigarette filters helped to reduce backpressure and can be operated with high sample flow rate without loss of extraction efficiency. The developed sorbent was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters that affected the extraction efficiencies, i.e. polymerization time, type of desorption solvent and its volume, sample flow rate, sample volume, sample pH, ionic strength, and organic modifier were investigated. Under the optimal conditions, the method was linear over the range of 0.5-10 μg/L and a detection limit of 0.5 ng/L. This simple, rapid, and cost-effective method was successfully applied to the preconcentration of polycyclic aromatic hydrocarbons from water samples. The developed method provided a high enrichment factor with good extraction efficiency (85-98%) and a relative standard deviation <10%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for separation and preconcentration of radium from water

DOEpatents

Dietz, Mark; Horwitz, E. Philip; Chiarizia, Renato; Bartsch, Richard A.

1999-01-01

A process for preconcentrating and separating radium from a contaminated solution containing at least water and radium includes the steps of adding a quantity of a water-soluble macrocyclic polyether to the contaminated solution to form a combined solution. An acid is added to the combined solution to form an acidic combined solution having an ›H.sup.+ ! concentration of about 0.5M. The acidic combined solution is contacted with a sulfonic acid-based strong acid cation exchange medium or a organophilic sulfonic acid medium having a plurality of binding sites thereon to bind the radium thereto and to form a radium-depleted solution. The radium-depleted solution is separated from the strong acid cation exchange medium or organophilic sulfonic acid medium. The radium remaining bound to the exchange medium or organophilic reagent is then stripped from the exchange medium or organophilic medium and the activity of the radium is measured.

Process for separation and preconcentration of radium from water

DOEpatents

Dietz, M.; Horwitz, E.P.; Chiarizia, R.; Bartsch, R.A.

1999-01-26

A process for preconcentrating and separating radium from a contaminated solution containing at least water and radium includes the steps of adding a quantity of a water-soluble macrocyclic polyether to the contaminated solution to form a combined solution. An acid is added to the combined solution to form an acidic combined solution having an [H{sup +}] concentration of about 0.5M. The acidic combined solution is contacted with a sulfonic acid-based strong acid cation exchange medium or a organophilic sulfonic acid medium having a plurality of binding sites thereon to bind the radium thereto and to form a radium-depleted solution. The radium-depleted solution is separated from the strong acid cation exchange medium or organophilic sulfonic acid medium. The radium remaining bound to the exchange medium or organophilic reagent is then stripped from the exchange medium or organophilic medium and the activity of the radium is measured. 24 figs.

Quantification of trace metals in water using complexation and filter concentration.

PubMed

Dolgin, Bella; Bulatov, Valery; Japarov, Julia; Elish, Eyal; Edri, Elad; Schechter, Israel

2010-06-15

Various metals undergo complexation with organic reagents, resulting in colored products. In practice, their molar absorptivities allow for quantification in the ppm range. However, a proper pre-concentration of the colored complex on paper filter lowers the quantification limit to the low ppb range. In this study, several pre-concentration techniques have been examined and compared: filtering the already complexed mixture, complexation on filter, and dipping of dye-covered filter in solution. The best quantification has been based on the ratio of filter reflectance at a certain wavelength to that at zero metal concentration. The studied complex formations (Ni ions with TAN and Cd ions with PAN) involve production of nanoparticle suspensions, which are associated with complicated kinetics. The kinetics of the complexation of Ni ions with TAN has been investigated and optimum timing could be found. Kinetic optimization in regard to some interferences has also been suggested.

Utilization of an ionic liquid in situ preconcentration method for the determination of the 15 + 1 European Union polycyclic aromatic hydrocarbons in drinking water and fruit-tea infusions.

PubMed

Germán-Hernández, Mónica; Crespo-Llabrés, Pilar; Pino, Verónica; Ayala, Juan H; Afonso, Ana M

2013-08-01

An ionic liquid (IL) in situ preconcentration method was optimized and applied to the monitoring of the 15 + 1 European Union polycyclic aromatic hydrocarbons in water and fruit-tea infusions. The optimized method utilizes 10 mL of water (or infusion) containing 38 μL of the IL 1-butyl-3-methylimidazolium chloride and a content of 36.1 g/L NaCl, which are mixed with Li-NTf2 (340 μL, 0.2 g/mL), followed by vortex (4 min) and centrifugation (5 min). The obtained microdroplet containing hydrocarbons is diluted with acetonitrile and injected into an HPLC with UV/Vis and fluorescence detection. The method presented average enrichment factors of 127 for water (tap water and bottled water) and 27 for two fruit-tea infusions; with average relative recoveries of 86.7 and 106% for water and fruit-tea infusions, respectively. The method was sensitive, with detection limits ranging from 0.001 to 0.050 ng/mL in water, and from 0.010 to 0.600 ng/mL in fruit-tea infusions, for the fluorescent hydrocarbons. Real extraction efficiencies ranged from 12.7 to 58.7% for water, and from 20.2 to 117% for the infusions. The method was also fast (~12 min) and free of organic solvents in the extraction step. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Method validation for high resolution sector field inductively coupled plasma mass spectrometry determination of the emerging contaminants in the open ocean: Rare earth elements as a case study

NASA Astrophysics Data System (ADS)

Wysocka, Irena; Vassileva, Emilia

2017-02-01

Analytical procedure for the determination of fourteen rare earth elements (REEs) in the seawater samples has been developed and validated. The elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) at ultra-trace level were measured by high resolution sector field inductively coupled plasma mass spectrometry (HR ICP-SFMS) after off-line analytes pre-concentration and matrix separation. The sample pre-treatment was carried out by commercially available automated system seaFAST-pico™, which is a low-pressure ion chromatography technique, based on solid phase extraction principles. Efficient elimination of seawater matrix and up to 50-fold pre-concentration of REEs enabled their accurate and precise quantification at ng L- 1 level. A validation approach in line with the requirements of ISO/IEC 17025 standard and Eurachem guidelines were followed. With this in mind, selectivity, working range, linearity, recovery (from 92% to 102%), repeatability (1%-4%), intermediate precision (2%-6%), limits of detection (0.001-0.08 ng L- 1) were systematically assessed. The total uncertainty associated to each result was estimated and the main sources of uncertainty sorted out. All major contributions to the combined uncertainty of the obtained results were identified and propagated together, following the ISO/GUM guidelines. The relative expanded uncertainty was estimated at range from 10.4% to 11.6% (k = 2). Demonstration of traceability of measurement results was also presented. Due to the low limits of detection, this method enables the determination of ultra-low levels of REEs in the open seawater as well as small variations in their concentrations. The potential of the proposed analytical procedure, based on combination of seaFAST-pico™ for sample preparation and HR ICP-SFMS, was demonstrated by direct analysis of seawater form different regions of the world.

Molecularly imprinted polymer coupled with dispersive liquid-liquid microextraction and injector port silylation: a novel approach for the determination of 3-phenoxybenzoic acid in complex biological samples using gas chromatography-tandem mass spectrometry.

PubMed

Mudiam, Mohana Krishna Reddy; Chauhan, Abhishek; Jain, Rajeev; Dhuriya, Yogesh Kumar; Saxena, Prem Narain; Khanna, Vinay Kumar

2014-01-15

A novel analytical approach based on molecularly imprinted solid phase extraction (MISPE) coupled with dispersive liquid-liquid microextraction (DLLME), and injector port silylation (IPS) has been developed for the selective preconcentration, derivatization and analysis of 3-phenoxybenzoic acid (3-PBA) using gas chromatography-tandem mass spectrometry (GC-MS/MS) in complex biological samples such as rat blood and liver. Factors affecting the synthesis of MIP were evaluated and the best monomer and cross-linker were selected based on binding affinity studies. Various parameters of MISPE, DLLME and IPS were optimized for the selective preconcentration and derivatization of 3-PBA. The developed method offers a good linearity over the calibration range of 0.02-2.5ngmg(-1) and 7.5-2000ngmL(-1) for liver and blood respectively. Under optimized conditions, the recovery of 3-PBA in liver and blood samples were found to be in the range of 83-91%. The detection limit was found to be 0.0045ngmg(-1) and 1.82ngmL(-1) in liver and blood respectively. SRM transition of 271→227 and 271→197 has been selected as quantifier and qualifier transition for 3-PBA derivative. Intra and inter-day precision for five replicates in a day and for five, successive days was found to be less than 8%. The method developed was successfully applied to real samples, i.e. rat blood and tissue for quantitative evaluation of 3-PBA. The analytical approach developed is rapid, economic, simple, eco-friendly and possess immense utility for the analysis of analytes with polar functional groups in complex biological samples by GC-MS/MS. Copyright © 2013 Elsevier B.V. All rights reserved.

Nickel (II) Preconcentration and Speciation Analysis During Transport from Aqueous Solutions Using a Hollow-fiber Permeation Liquid Membrane (HFPLM) Device

PubMed Central

Bautista-Flores, Ana Nelly; de San Miguel, Eduardo Rodríguez; de Gyves, Josefina; Jönsson, Jan Åke

2011-01-01

Nickel (II) preconcentration and speciation analysis using a hollow fiber supported liquid membrane (HFSLM) device was studied. A counterflow of protons coupled to complexation with formate provided the driving force of the process, while Kelex 100 was employed as carrier. The influence of variables related to module configuration (acceptor pH and carrier concentration) and to the sample properties (donor pH) on the preconcentration factor, E, was simultaneously studied and optimized using a 3 factor Doehlert matrix response surface methodology. The effect of metal concentration was studied as well. Preconcentration factors as high as 4240 were observed depending on the values of the different variables. The effects of the presence of inorganic anions (NO2−, SO42−, Cl−, NO3−, CO32−, CN−) and dissolved organic matter (DOM) in the form of humic acids were additionally considered in order to carry out a speciation analysis study. Nickel preconcentration was observed to be independent of both effects, except when cyanide was present in the donor phase. A characterization of the transport regime was performed through the analysis of the dependence of E on the temperature. E increases with the increase in temperature according to the equation E(K) = −8617.3 + 30.5T with an activation energy of 56.7 kJ mol−1 suggesting a kinetic-controlled regime. Sample depletion ranged from 12 to 1.2% depending on the volume of the donor phase (100 to 1000 mL, respectively). PMID:24957733

Capillary-driven microfluidic paper-based analytical devices for lab on a chip screening of explosive residues in soil.

PubMed

Ueland, Maiken; Blanes, Lucas; Taudte, Regina V; Stuart, Barbara H; Cole, Nerida; Willis, Peter; Roux, Claude; Doble, Philip

2016-03-04

A novel microfluidic paper-based analytical device (μPAD) was designed to filter, extract, and pre-concentrate explosives from soil for direct analysis by a lab on a chip (LOC) device. The explosives were extracted via immersion of wax-printed μPADs directly into methanol soil suspensions for 10min, whereby dissolved explosives travelled upwards into the μPAD circular sampling reservoir. A chad was punched from the sampling reservoir and inserted into a LOC well containing the separation buffer for direct analysis, avoiding any further extraction step. Eight target explosives were separated and identified by fluorescence quenching. The minimum detectable amounts for all eight explosives were between 1.4 and 5.6ng with recoveries ranging from 53-82% from the paper chad, and 12-40% from soil. This method provides a robust and simple extraction method for rapid identification of explosives in complex soil samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Simultaneous pre-concentration and separation on simple paper-based analytical device for protein analysis.

PubMed

Niu, Ji-Cheng; Zhou, Ting; Niu, Li-Li; Xie, Zhen-Sheng; Fang, Fang; Yang, Fu-Quan; Wu, Zhi-Yong

2018-02-01

In this work, fast isoelectric focusing (IEF) was successfully implemented on an open paper fluidic channel for simultaneous concentration and separation of proteins from complex matrix. With this simple device, IEF can be finished in 10 min with a resolution of 0.03 pH units and concentration factor of 10, as estimated by color model proteins by smartphone-based colorimetric detection. Fast detection of albumin from human serum and glycated hemoglobin (HBA1c) from blood cell was demonstrated. In addition, off-line identification of the model proteins from the IEF fractions with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was also shown. This PAD IEF is potentially useful either for point of care test (POCT) or biomarker analysis as a cost-effective sample pretreatment method.

Preconcentration determination of arsenic species by sorption of As(V) on Amberlite IRA-410 coupled with fluorescence quenching of L-cysteine capped CdS nanoparticles.

PubMed

Hosseini, Mohammad Saeid; Nazemi, Sahar

2013-10-07

A simple and accurate method for arsenic speciation analysis in natural and drinking water samples is described in which preconcentration of arsenic as As(V) was coupled with spectrofluorometric determination. The extracted As(V) species with a column containing Amberlite IRA-410 were subjected to L-cysteine capped CdS quantum dots (QDs) and the fluorescence quenching of the QDs due to reduction of As(V) by L-cysteine was considered as a signal relevant to As(V) concentration. The As(III) species were also determined after oxidation of As(III) ions to As(V) with H2O2 and measurement of the total arsenic content. In treatment with 400 mL portions of water samples containing 30 μg L(-1) As(V), the relative standard deviation was 2.8%. The detection limit of arsenic was also found to be 0.75 μg L(-1) (1 × 10(-8) M). The reliability of proposed method was confirmed using certified reference materials. The trace amounts of arsenic species were then determined in different water samples, satisfactorily.

Separation, preconcentration and inductively coupled plasma-mass spectrometric (ICP-MS) determination of thorium(IV), titanium(IV), iron(III), lead(II) and chromium(III) on 2-nitroso-1-naphthol impregnated MCI GEL CHP20P resin.

PubMed

Aydin, Funda Armagan; Soylak, Mustafa

2010-01-15

A simple and effective method is presented for the separation and preconcentration of Th(IV), Ti(IV), Fe(III), Pb(II) and Cr(III) by solid phase extraction on 2-nitroso-1-naphthol impregnated MCI GEL CHP20P resin prior to their inductively coupled plasma-mass spectrometric determinations. The influence of analytical parameters including pH of the aqueous solution, flow rates of sample and eluent solutions and sample volume on the quantitative recoveries of analyte ions was investigated. Matrix effects caused by the presence of alkali, earth alkali and some metal ions in the analyzed solutions were investigated. The presented solid phase extraction method was applied to BCR-144R Sewage Sludge (domestic origin), BCR-141R Calcareous Loam Soil, NIST 1568a Rice Flour and NIST 1577b Bovine Liver certified reference materials (CRMs) for the determination of analyte ions and the results were in good agreement with the certified values. The separation procedure presented was also applied to the various natural water samples collected from Turkey with satisfactory results.

[Study on extracting and separating curcuminoids from Curcuma longa rhizome using ultrasound strengthen by microemulsion].

PubMed

Yue, Chun-Hua; Zheng, Li-Tao; Guo, Qi-Ming; Li, Kun-Ping

2014-05-01

To establish a new method for the extraction and separation of curcuminoids from Curcuma longa rhizome by cloud-point preconcentration using microemulsions as solvent. The spectrophotometry was used to detect the solubility of curcumin in different oil phase, emulsifier and auxiliary emulsifier, and the microemulsion prescription was used for false three-phase figure optimization. The extraction process was optimized by uniform experiment design. The curcuminoids were separated from microemulsion extract by cloud-point preconcentration. Oil phase was oleic acid ethyl ester; Emulsifier was OP emulsifier; Auxiliary emulsifier was polyethylene glycol(peg) 400; The quantity of emulsifier to auxiliary emulsifier was the ratio of 5: 1; Microemulsion prescription was water-oleic acid ethyl ester-mixed emulsifier (0.45:0.1:0.45). The optimum extraction process was: time for 12.5 min, temperature of 52 degrees C, power of 360 W, frequency of 400 kHz, and the liquid-solid ratio of 40:1. The extraction rate of curcuminoids was 92.17% and 86.85% in microemulsion and oil phase, respectively. Curcuminoids is soluble in this microemulsion prescription with good extraction rate. This method is simple and suitable for curcuminoids extraction from Curcuma longa rhizome.

[Separation/preconcentration of trace rare earth elements in Tricholoma giganteum by micro-column with nanometer A1203 and their determination by ICP-AES].

PubMed

Liu, Hong-gao; Wang, Yuan-zhong

2010-01-01

Using a micro-column packed with immobilized 1-phenyl-3-methyl-4-bonzoil-5-pyrazone(PMBP) on nanometer Al2O3 powder as the adsorption material, the adsorption and elution behaviors of rare earth ions (Sc3+, Y3+ and La3+) on the above material under dynamic conditions were studied with inductively coupled plasma-atomic emission spectrometry. The conditions for preconcentration of rare earth ions were optimized, and the results show that the studied ions can be adsorbed quantitatively on the above material at pH 4.5 and the analytes adsorbed on the column can be eluted with 0.5 mol x L(-1) HCl solution. The detection limits of the method for Sc, Y and La were 0.15, 0.18 and 0.34 microg x L(-1), respectively, and the relative standard deviations were 2.5%, 3.0% and 1.7%, respectively (n=12, c = 0.5 mg x L(-1)). The proposed method was applied to the determination of trace amount of Sc, Y and La in Tricholoma giganteum with satisfactory results.

Determination of cadmium and lead in table salt by sequential multi-element flame atomic absorption spectrometry.

PubMed

Amorim, Fábio A C; Ferreira, Sérgio L C

2005-02-28

In the present paper, a simultaneous pre-concentration procedure for the sequential determination of cadmium and lead in table salt samples using flame atomic absorption spectrometry is proposed. This method is based on the liquid-liquid extraction of cadmium(II) and lead(II) ions as dithizone complexes and direct aspiration of the organic phase for the spectrometer. The sequential determination of cadmium and lead is possible using a computer program. The optimization step was performed by a two-level fractional factorial design involving the variables: pH, dithizone mass, shaking time after addition of dithizone and shaking time after addition of solvent. In the studied levels these variables are not significant. The experimental conditions established propose a sample volume of 250mL and the extraction process using 4.0mL of methyl isobutyl ketone. This way, the procedure allows determination of cadmium and lead in table salt samples with a pre-concentration factor higher than 80, and detection limits of 0.3ngg(-1) for cadmium and 4.2ngg(-1) for lead. The precision expressed as relative standard deviation (n = 10) were 5.6 and 2.6% for cadmium concentration of 2 and 20ngg(-1), respectively, and of 3.2 and 1.1% for lead concentration of 20 and 200ngg(-1), respectively. Recoveries of cadmium and lead in several samples, measured by standard addition technique, proved also that this procedure is not affected by the matrix and can be applied satisfactorily for the determination of cadmium and lead in saline samples. The method was applied for the evaluation of the concentration of cadmium and lead in table salt samples consumed in Salvador City, Bahia, Brazil.

Preconcentration of trace lead and iron on activated carbon functionalized by o-Anisic acid derivatives prior to their determination in environmental samples.

PubMed

Tian, Hua; Hu, Zheng; He, Qun; Liu, Xueliang; Zhang, Li; Chang, Xijun

2012-07-01

Two solid-phase adsorbents (phase I and phase II) were synthesized successfully that o-Anisic acid derivatives were evenly functionalized on the surface of activated carbon. It was certified that the two adsorbents were applied to preconcentrate and separate trace levels of Pb(II) and Fe(III) from natural liquid samples with satisfactory results. It can be found that the adsorption capacity of the ions adsorbed on phase I and phase II was 48.3 and 85.7 mg g(-1) for Pb(II), 39.5 and 72.5 mg g(-1) for Fe(III), respectively. The detection limit (3σ) of the method separated on phase I and phase II was 0.12 and 0.09 ng mL(-1) for Pb(II), 0.23 and 0.17 ng mL(-1) for Fe(III), respectively. The relative standard deviation (R.S.D.) of the method was lower than 3.0%. The adsorption and desorption property of two kinds of adsorbents was comparatively studied, respectively. The adsorption selectivity of heavy metal ions at certain pH, the adsorption kinetics, the condition of complete elution, the effect of coexisting ions, the adsorption capacity and adsorption isotherm modes were examined. Based on the experimental datum determined by inductively coupled plasma optical emission spectrometry (ICP-OES), it was certified that the adsorption on the surface of adsorbents was in strict accordance with the monolayer adsorption principle. The structural features of series of multidentate ligand modified on adsorption matrix had been obtained. These conclusions can provide reference for synthesizing an efficient adsorbent which is specific to remove a particular kind of contaminant. Copyright © 2012 Elsevier B.V. All rights reserved.

A new magnetic nanodiamond/graphene oxide hybrid (Fe3O4@ND@GO) material for pre-concentration and sensitive determination of sildenafil in alleged herbal aphrodisiacs by HPLC-DAD system.

PubMed

Yilmaz, Erkan; Ulusoy, Halil İbrahim; Demir, Özge; Soylak, Mustafa

2018-05-01

A sensitive analytical methodology was investigated to concentrate and determine of sildenafil citrate (SLC) present at trace level in herbal supplementary products. The proposed method is based on simple and sensitive pre-concentration of SLC by using magnetic solid phase extraction with new developed magnetic nanodiamond/graphene oxide hybrid (Fe 3 O 4 @ND@GO) material as a sorbent. Experimental variables affecting the extraction efficiency of SLC like; pH, sample volume, eluent type and volume, extraction time and amount of adsorbent were studied and optimized in detail. Determination of sildenafil citrate after magnetic solid phase extraction (MSPE) was carried out by HPLC-DAD system. The morphology, composition, and properties of the synthesized hybrid material was characterized by Fourier transform infrared spectrometry (FT-IR), Raman spectrometry (Raman), X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM), mapping photographs, zeta potential analyzer, and BET surface area analysis. Under optimized conditions, linear range was ranged from 5.00 to 250.00 ng mL -1 with R 2 of 0.9952. The limit of detection (LOD) was 1.49 ng mL -1 and the recoveries at two spiked levels were ranged from 94.0 to 104.1% with the relative standard deviation (RSD) < 7.1% (n = 5). The enhancement factor (EF) was 86.9. The results show that the combination MSPE with HPLC-DAD is a suitable and sensitive method for the determination of SLC in real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Sensitive spectrophotometric determination of Co(II) using dispersive liquid-liquid micro-extraction method in soil samples.

PubMed

Hasanpour, Foroozan; Hadadzadeh, Hassan; Taei, Masoumeh; Nekouei, Mohsen; Mozafari, Elmira

2016-05-01

Analytical performance of conventional spectrophotometer was developed by coupling of effective dispersive liquid-liquid micro-extraction method with spectrophotometric determination for ultra-trace determination of cobalt. The method was based on the formation of Co(II)-alpha-benzoin oxime complex and its extraction using a dispersive liquid-liquid micro-extraction technique. During the present work, several important variables such as pH, ligand concentration, amount and type of dispersive, and extracting solvent were optimized. It was found that the crucial factor for the Co(II)-alpha benzoin oxime complex formation is the pH of the alkaline alcoholic medium. Under the optimized condition, the calibration graph was linear in the ranges of 1.0-110 μg L(-1) with the detection limit (S/N = 3) of 0.5 μg L(-1). The preconcentration operation of 25 mL of sample gave enhancement factor of 75. The proposed method was applied for determination of Co(II) in soil samples.

A double-stage tube furnace--acid-trapping protocol for the pre-concentration of mercury from solid samples for isotopic analysis.

PubMed

Sun, Ruoyu; Enrico, Maxime; Heimbürger, Lars-Eric; Scott, Clint; Sonke, Jeroen E

2013-08-01

High-precision mercury (Hg) stable isotopic analysis requires relatively large amounts of Hg (>10 ng). Consequently, the extraction of Hg from natural samples with low Hg concentrations (<1-20 ng/g) by wet chemistry is challenging. Combustion-trapping techniques have been shown to be an appropriate alternative. Here, we detail a modified off-line Hg pre-concentration protocol that is based on combustion and trapping. Hg in solid samples is thermally reduced and volatilized in a pure O2 stream using a temperature-programmed combustion furnace. A second furnace, kept at 1,000 °C, decomposes combustion products into H2O, CO2, SO2, etc. The O2 carrier gas, including combustion products and elemental Hg, is then purged into a 40% (v/v) acid-trapping solution. The method was optimized by assessing the variations of Hg pre-concentration efficiency and Hg isotopic compositions as a function of acid ratio, gas flow rate, and temperature ramp rate for two certified reference materials of bituminous coals. Acid ratios of 2HNO3/1HCl (v/v), 25 mL/min O2 flow rate, and a dynamic temperature ramp rate (15 °C/min for 25-150 and 600-900 °C; 2.5 °C/min for 150-600 °C) were found to give optimal results. Hg step-release experiments indicated that significant Hg isotopic fractionation occurred during sample combustion. However, no systematic dependence of Hg isotopic compositions on Hg recovery (81-102%) was observed. The tested 340 samples including coal, coal-associated rocks, fly ash, bottom ash, peat, and black shale sediments with Hg concentrations varying from <5 ng/g to 10 μg/g showed that most Hg recoveries were within the acceptable range of 80-120%. This protocol has the advantages of a short sample processing time (∼3.5 h) and limited transfer of residual sample matrix into the Hg trapping solution. This in turn limits matrix interferences on the Hg reduction efficiency of the cold vapor generator used for Hg isotopic analysis.

UV-vis spectrophotometric determination of trinitrotoluene (TNT) with trioctylmethylammonium chloride as ion pair assisted and disperser agent after dispersive liquid-liquid microextraction.

PubMed

Larki, Arash; Nasrabadi, Mehdi Rahimi; Pourreza, Nahid

2015-06-01

In the present study, a simple, fast and inexpensive method based on dispersive liquid-liquid microextraction (DLLME) prior to microvolume UV-vis spectrophotometry was developed for the preconcentration and determination of trinitrotoluene (TNT). The procedure is based on the color reaction of TNT in alkaline medium and extraction into CCl4 as an ion pair assisted by trioctylmethylammonium chloride, which also acts as a disperser agent. Experimental parameters affecting the DLLME method such as pH, concentration of sodium hydroxide, amount of trioctylmethylammonium chloride, type and volume of extraction solvent were investigated and optimized. Under the optimum conditions, the limit of detection (LOD) was 0.9ng/mL and the calibration curve was linear in the range of 3-200ng/mL. The relative standard deviation for 25 and 100ng/mL of TNT were 3.7% and 1.5% (n=6), respectively. The developed DLLME method was applied for the determination of TNT in different water and soil samples. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

An innovative method for analysis of Pb (II) in rice, milk and water samples based on TiO2 reinforced caprylic acid hollow fiber solid/liquid phase microextraction.

PubMed

Bahar, Shahriyar; Es'haghi, Zarrin; Nezhadali, Azizollah; Banaei, Alireza; Bohlooli, Shahab

2017-04-15

In the present study, nano-sized titanium oxides were applied for preconcentration and determination of Pb(II) in aqueous samples using hollow fiber based solid-liquid phase microextraction (HF-SLPME) combined with flame atomic absorption spectrometry (FAAS). In this work, the nanoparticles dispersed in caprylic acid as an extraction solvent was placed into a polypropylene porous hollow fiber segment supported by capillary forces and sonification. This membrane was in direct contact with solutions containing Pb (II). The effect of experimental conditions on the extraction, such as pH, stirring rate, sample volume, and extraction time were optimized. Under the optimal conditions, the performance of the proposed method was investigated for the determination of Pb (II) in food and water samples. The method was linear in the range of 0.6-3000μgmL -1 . The relative standard deviations and relative recovery of Pb (II) was 4.9% and 99.3%, respectively (n=5). Copyright © 2016 Elsevier Ltd. All rights reserved.

Assessment of strobilurin fungicides' content in soya-based drinks by liquid micro-extraction and liquid chromatography with tandem mass spectrometry.

PubMed

Campillo, Natalia; Iniesta, María Jesús; Viñas, Pilar; Hernández-Córdoba, Manuel

2015-01-01

Seven strobilurin fungicides were pre-concentrated from soya-based drinks using dispersive liquid-liquid micro-extraction (DLLME) with a prior protein precipitation step in acid medium. The enriched phase was analysed by liquid chromatography (LC) with dual detection, using diode array detection (DAD) and electrospray-ion trap tandem mass spectrometry (ESI-IT-MS/MS). After selecting 1-undecanol and methanol as the extractant and disperser solvents, respectively, for DLLME, the Taguchi experimental method, an orthogonal array design, was applied to select the optimal solvent volumes and salt concentration in the aqueous phase. The matrix effect was evaluated and quantification was carried out using external aqueous calibration for DAD and matrix-matched calibration method for MS/MS. Detection limits in the 4-130 and 0.8-4.5 ng g(-1) ranges were obtained for DAD and MS/MS, respectively. The DLLME-LC-DAD-MS method was applied to the analysis of 10 different samples, none of which was found to contain residues of the studied fungicides.

Centrifugeless dispersive liquid-liquid microextraction based on salting-out phenomenon followed by high performance liquid chromatography for determination of Sudan dyes in different species.

PubMed

Bazregar, Mohammad; Rajabi, Maryam; Yamini, Yadollah; Arghavani-Beydokhti, Somayeh; Asghari, Alireza

2018-04-01

In this work, a novel method, namely centrifugeless dispersive liquid-liquid microextraction, is introduced for the efficient extraction of banned Sudan dyes from foodstuff and water samples. In this method, which is based upon the salting-out phenomenon, in order to accelerate the extraction process, the extraction solvent (1-undecanol, 75 μL) is dispersed into the sample solution. Then the mixture is passed through a small column filled with 5 g sodium chloride, used as a separating reagent. In this condition, fine droplets of the extraction solvent are floated on the mixture, and the phase separation is simply achieved. This method is environmentally friendly, simple, and very fast, so that the overall extraction time is only 7 min. Under the optimal experimental conditions, the preconcentration factors in the range of 90-121 were obtained for the analytes. Also good linearities were obtained in the range of 2.5-1200 ng mL -1 (r 2  ≥ 0.993). Copyright © 2017 Elsevier Ltd. All rights reserved.

Simultaneous determination of heavy metal ions in water using near-infrared spectroscopy with preconcentration by nano-hydroxyapatite.

PubMed

Ning, Yu; Li, Jihui; Cai, Wensheng; Shao, Xueguang

2012-10-01

A method for simultaneous determination of metal ions in river water was developed by using preconcentration and near-infrared diffuse reflectance spectroscopy (NIRDRS). An inorganic biomaterial, nano-hydroxyapatite (HAP) was used as a high-efficient adsorbent for gathering the ions from water samples. After adsorbing the analytes onto the adsorbent, NIRDRS was measured and partial least squares (PLS) models were established for fast and simultaneous quantitative prediction. With the samples prepared by river water, determination of Pb(2+), Zn(2+), Cu(2+), Cd(2+) and Cr(3+) was investigated. The calibration models of Cu(2+), Cr(3+) and total content were proven to be efficient enough for precise prediction. The determination coefficients (R(2)) of the independent validation were found as high as 0.9924, 0.9869 and 0.9273 for Cu(2+), Cr(3+) and total content, respectively. Therefore, the feasibility of NIRDRS for microanalysis of heavy metal ions in waste water was demonstrated. Copyright © 2012 Elsevier B.V. All rights reserved.

Functionalization of silica-gel with polyamidoamine and 2-mercaptobenzothiazole and its adsorption property for lead

NASA Astrophysics Data System (ADS)

Wu, X. Z.; Liu, Y.; Luo, L. L.; Chen, Z. Y.

2018-01-01

Adsorbents PAMAM-n.0MBTSG (n=1-4) have been prepared by immobilizing polyamidoamine (PAMAM) and 2-mercaptobenzothiazole (MBT) on silica-gel. Characterized with FTIR, SEM, TGA, the preconcentration of Pb2+ with PAMAM-n.0MBTSG(n=1-4) has been investigated by graphite furnace atomic absorption spectroscopy (GFAAS). SEM showed that the surface morphology of adsorbent changed with the generation increase of PAMAM. Adsorption capacity of PAMAM-n.0MBTSG for Pb2+ (n=1-4) reached 16.22, 19.84, 22.92 and 27.56 mg g-1 respectively. Pb2+ (1.0 ng mL-1) in 2000 mL solution could be quantitatively absorbed with PAMAM-4.0MBTSG and eluted to obtain a preconcentration factor (PF) of 200. GFAAS method for analysis of Pb2+ with PAMAM-4.0MBTSG as adsorbent was proposed and successfully applied to analysis of Pb2+ of standard reference material, sea water and squid sample.

Novel magnetic hollow zein nanoparticles for preconcentration of chlorpyrifos from water and soil samples prior to analysis via high-performance liquid chromatography (HPLC).

PubMed

Rahimi Moghadam, Mojtaba; Zargar, Behrooz; Rastegarzadeh, Saadat

2018-04-30

Herein, magnetically hollow zein nanoparticles were synthesized and used as a magnetic sorbent for the preconcentration of chlorpyrifos and its analysis by high-performance liquid chromatography (HPLC). Morphology of the sorbent was characterized by transmission electron microscopy (TEM). In this study, the effects of important parameters such as pH of the solution, adsorption and desorption time, type and volume of desorption solvent, and salt addition were investigated. Under optimized experimental conditions, the linear range was from 50 to 2000 μg mL-1, and an LOD of 25 μg L-1 was calculated. The relative standard deviations (RSD) varied from 3.8 to 5.1% (n = 5). The enrichment factors for 50 and 100 μg L-1 samples were calculated as 187 and 210, respectively. The developed method was successfully applied in soil and water samples and showed good extraction recoveries.

Method for remote detection of trace contaminants

DOEpatents

Simonson, Robert J.; Hance, Bradley G.

2003-09-09

A method for remote detection of trace contaminants in a target area comprises applying sensor particles that preconcentrate the trace contaminant to the target area and detecting the contaminant-sensitive fluorescence from the sensor particles. The sensor particles can have contaminant-sensitive and contaminant-insensitive fluorescent compounds to enable the determination of the amount of trace contaminant present in the target are by relative comparison of the emission of the fluorescent compounds by a local or remote fluorescence detector. The method can be used to remotely detect buried minefields.

Determination of inorganic arsenic species in natural waters--benefits of separation and preconcentration on ion exchange and hybrid resins.

PubMed

Ben Issa, Nureddin; Rajaković-Ognjanović, Vladana N; Jovanović, Branislava M; Rajaković, Ljubinka V

2010-07-19

A simple method for the separation and determination of inorganic arsenic (iAs) species in natural and drinking water was developed. Procedures for sample preparation, separation of As(III) and As(V) species and preconcentration of the total iAs on fixed bed columns were defined. Two resins, a strong base anion exchange (SBAE) resin and a hybrid (HY) resin were utilized. The inductively-coupled plasma-mass spectrometry method was applied as the analytical method for the determination of the arsenic concentration in water. The governing factors for the ion exchange/sorption of arsenic on resins in a batch and a fixed bed flow system were analyzed and compared. Acidity of the water, which plays an important role in the control of the ionic or molecular forms of arsenic species, was beneficial for the separation; by adjusting the pH values to less than 8.00, the SBAE resin separated As(V) from As(III) in water by retaining As(V) and allowing As(III) to pass through. The sorption activity of the hydrated iron oxide particles integrated into the HY resin was beneficial for bonding of all iAs species over a wide range of pH values from 5.00 to 11.00. The resin capacities were calculated according to the breakthrough points in a fixed bed flow system. At pH 7.50, the SBAE resin bound more than 370 microg g(-1) of As(V) while the HY resin bound more than 4150 microg g(-1) of As(III) and more than 3500 microg g(-1) of As(V). The high capacities and selectivity of the resins were considered as advantageous for the development and application of two procedures, one for the separation and determination of As(III) (with SBAE) and the other for the preconcentration and determination of the total arsenic (with HY resin). Methods were established through basic analytical procedures (with external standards, certified reference materials and the standard addition method) and by the parallel analysis of some samples using the atomic absorption spectrometry-hydride generation technique. The analytical properties of both procedures were similar: the limit of detection was 0.24 microg L(-1), the limit of quantification was 0.80 microg L(-1) and the relative standard deviations for samples with a content of arsenic from 10.00 to 300.0 microg L(-1) ranged from 1.1 to 5.8%. The interference effects of anions commonly found in water and some organic species which can be present in water were found to be negligible. Verification with certified reference materials proved that the experimental concentrations found for model solutions and real samples were in agreement with the certified values. 2010 Elsevier B.V. All rights reserved.

An Aptamer-based Biosensor for Troponin I Detection in Diagnosis of Myocardial Infarction.

PubMed

Negahdary, M; Behjati-Ardakani, M; Sattarahmady, N; Heli, H

2018-06-01

Acute myocardial infarction (MI) accounts for one third of deaths. Cardiac troponin I (TnI) is a reliable biomarker of cardiac muscle tissue injury and is employed in the early diagnosis of MI. In this study, a molecular method is introduced to early diagnosis of MI by rapid detection of TnI. The detection method was based on electrochemical aptasensing, being developed using different methods and evaluation steps. A gold electrode was used as a transducer to successful immobilize 76base aptamer to fabricate a TnI biosensor. The designed aptasensor could detect TnI in a range of 0.03 to 2.0 ng mL-1 without using any label, pre-concentration or amplification steps. The limit of detection was attained as 10 pg mL-1 without significant trouble of interfering species. The TnI biosensor demonestrated a stable, regenerative and reproducible function. 89 human samples were used to evaluate the performance of the TnI biosensor, and it represented 100% and 81%, diagnostic sensitivity and specificity, respectively. This aptasensor may be used as an applicable tool in the future of early medical diagnosis of MI.

Method of trivalent chromium concentration determination by atomic spectrometry

DOEpatents

Reheulishvili, Aleksandre N [Tbilisi, 0183, GE; Tsibakhashvili, Neli Ya [Tbilisi, 0101, GE

2006-12-12

A method is disclosed for determining the concentration of trivalent chromium Cr(III) in a sample. The addition of perchloric acid has been found to increase the atomic chromium spectrometric signal due to Cr(III), while leaving the signal due to hexavalent chromium Cr(VI) unchanged. This enables determination of the Cr(III) concentration without pre-concentration or pre-separation from chromium of other valences. The Cr(III) concentration may be measured using atomic absorption spectrometry, atomic emission spectrometry or atomic fluorescence spectrometry.

Microfluidic Isoelectric Focusing of Amyloid Beta Peptides Followed by Micropillar-Matrix-Assisted Laser Desorption Ionization-Mass Spectrometry.

PubMed

Mikkonen, Saara; Jacksén, Johan; Roeraade, Johan; Thormann, Wolfgang; Emmer, Åsa

2016-10-18

A novel method for preconcentration and purification of the Alzheimer's disease related amyloid beta (Aβ) peptides by isoelectric focusing (IEF) in 75 nL microchannels combined with their analysis by micropillar-matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) is presented. A semiopen chip-based setup, consisting of open microchannels covered by a lid of a liquid fluorocarbon, was used. IEF was performed in a mixture of four small and chemically well-defined amphoteric carriers, glutamic acid, aspartyl-histidine (Asp-His), cycloserine (cSer), and arginine, which provided a stepwise pH gradient tailored for focusing of the C-terminal Aβ peptides with a pI of 5.3 in the boundary between cSer and Asp-His. Information about the focusing dynamics and location of the foci of Aβ peptides and other compounds was obtained using computer simulation and by performing MALDI-MS analysis directly from the open microchannel. With the established configuration, detection was performed by direct sampling of a nanoliter volume containing the focused Aβ peptides from the microchannel, followed by deposition of this volume onto a chip with micropillar MALDI targets. In addition to purification, IEF preconcentration provides at least a 10-fold increase of the MALDI-MS-signal. After immunoprecipitation and concentration of the eluate in the microchannel, IEF-micropillar-MALDI-MS is demonstrated to be a suitable platform for detection of Aβ peptides in human cerebrospinal fluid as well as in blood plasma.

Electrochemical detection of methylated DNA on a microfluidic chip with nanoelectrokinetic pre-concentration.

PubMed

Hong, Sung A; Kim, Yong-June; Kim, Sung Jae; Yang, Sung

2018-06-01

DNA methylation is considered to be a promising marker for the early diagnosis and prognosis of cancer. However, direct detection of the methylated DNAs in clinically relevant samples is still challenging because of its extremely low concentration (~fM). Here, an integrated microfluidic chip is reported, which is capable of pre-concentrating the methylated DNAs using ion concentration polarization (ICP) and electrochemically detecting the pre-concentrated DNAs on a single chip. The proposed chip is the first demonstration of an electrochemical detection of both level and concentration of the methylated DNAs by integrating a DNA pre-concentration unit without gene amplification. Using the proposed chip, 500 fM to 500 nM of methylated DNAs is pre-concentrated by almost 100-fold in 10 min, resulting in a drastic improvement of the electrochemical detection threshold down to the fM level. The proposed chip is able to measure not only the DNA concentration, but also the level of methylation using human urine sample by performing a consecutive electrochemical sensing on a chip. For clinical application, the level as well as the concentration of methylation of glutathione-S transferase-P1 (GSTP1) and EGF-containing fibulin-like extracellular matrix protein 1 (EFEMP1), which are known to be closely associated with prostate cancer diagnosis, are electrochemically detected in human urine spiked with these genes. The developed chip shows a limit of detection (LoD) of 7.9 pM for GSTP1 and 11.8 pM for EFEMP1 and is able to detect the level of methylation in a wide range from 10% to 100% with the concentration variation from 50 pM to 500 nM. Copyright © 2018 Elsevier B.V. All rights reserved.

A highly selective and sensitive ultrasonic assisted dispersive liquid phase microextraction based on deep eutectic solvent for determination of cadmium in food and water samples prior to electrothermal atomic absorption spectrometry.

PubMed

Zounr, Rizwan Ali; Tuzen, Mustafa; Deligonul, Nihal; Khuhawar, Muhammad Yar

2018-07-01

A simple, fast, green, sensitive and selective ultrasonic assisted deep eutectic solvent liquid-phase microextraction technique was used for preconcentration and extraction of cadmium (Cd) in water and food samples by electrothermal atomic absorption spectrometry (ETAAS). In this technique, a synthesized reagent (Z)-N-(3,5-diphenyl-1H-pyrrol-2-yl)-3,5-diphenyl-2H-pyrrol-2-imine (Azo) was used as a complexing agent for Cd. The main factors effecting the pre-concentration and extraction of Cd such as effect of pH, type and composition of deep eutectic solvent (DES), volume of DES, volume of complexing agent, volume of tetrahydrofuran (THF) and ultrasonication time have been examined in detail. At optimum conditions the value of pH and molar ratio of DES were found to be 6.0 and 1:4 (ChCl:Ph), respectively. The detection limit (LOD), limit of quantification (LOQ), relative standard deviation (RSD) and preconcentration factor (PF) were observed as 0.023 ng L -1 , 0.161 ng L -1 , 3.1% and 100, correspondingly. Validation of the developed technique was observed by extraction of Cd in certified reference materials (CRMs) and observed results were successfully compared with certified values. The developed procedure was practiced to various food, beverage and water samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Optofluidic analysis system for amplification-free, direct detection of Ebola infection

NASA Astrophysics Data System (ADS)

Cai, H.; Parks, J. W.; Wall, T. A.; Stott, M. A.; Stambaugh, A.; Alfson, K.; Griffiths, A.; Mathies, R. A.; Carrion, R.; Patterson, J. L.; Hawkins, A. R.; Schmidt, H.

2015-09-01

The massive outbreak of highly lethal Ebola hemorrhagic fever in West Africa illustrates the urgent need for diagnostic instruments that can identify and quantify infections rapidly, accurately, and with low complexity. Here, we report on-chip sample preparation, amplification-free detection and quantification of Ebola virus on clinical samples using hybrid optofluidic integration. Sample preparation and target preconcentration are implemented on a PDMS-based microfluidic chip (automaton), followed by single nucleic acid fluorescence detection in liquid-core optical waveguides on a silicon chip in under ten minutes. We demonstrate excellent specificity, a limit of detection of 0.2 pfu/mL and a dynamic range of thirteen orders of magnitude, far outperforming other amplification-free methods. This chip-scale approach and reduced complexity compared to gold standard RT-PCR methods is ideal for portable instruments that can provide immediate diagnosis and continued monitoring of infectious diseases at the point-of-care.

Optimization of β-cyclodextrin cross-linked polymer for monitoring of quercetin

NASA Astrophysics Data System (ADS)

Zhu, Xiashi; Ping, Wenhui

2014-11-01

A novel method for the separation/analysis of quercetin was described, which was based on the investigation of the inclusion interactions of β-cyclodextrin cross-linked polymer (β-CDCP) with quercetin (Qu) and the adsorption behavior of Qu on β-CDCP. The inclusion interaction of β-CDCP with Qu was studied through FTIR, TGA and 13C NMR. Under the optimum conditions, the preconcentration factor of the proposed method was approximately 8.8, the β-CDCP could be used repeatedly for 30 times and offered better recovery. The linear range, limit of detection (LOD) and the relative standard deviation (RSD) was found to be 0.10-12.0 μg mL-1, 4.6 ng mL-1 and 3.10% (n = 3, c = 2.0 μg mL-1) respectively. This technique had been successfully applied to the determination of Qu in real samples.

Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates.

PubMed

Pena-Pereira, Francisco; Duarte, Regina M B O; Trindade, Tito; Duarte, Armando C

2013-07-19

The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica-magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10-C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10-C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8-1.9μgL(-1) for C10-C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N=6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Quantification of Alkyl Nitrates in Ambient Air by Thermal Dissociation Cavity Ring-Down Spectroscopy with Preconcentration

NASA Astrophysics Data System (ADS)

Ye, C. Z.; Osthoff, H. D.; Taha, Y. M.; Pak, J. K.; Saowapon, M. T.

2015-12-01

Alkyl nitrates (AN, molecular formula RONO2) play a crucial role in the troposphere as temporary reservoirs of nitrogen oxides (NOx =NO +NO2) and by acting as chain terminators in the photochemical production of ozone. Mixing ratios of AN in ambient air are commonly quantified by gas chromatography with electron capture or mass spectrometric detection (GC-ECD or GC-MS) coupled to purge-and-trap preconcentration, usually on Tenax sorbent, to improve the detection limits. The analysis, however, is quite laborious as there are many alkyl nitrates that are low in individual abundance (often less than 1 parts-per-trillion by volume, pptv) and that exhibit different instrumental response factors. An alternative method is to determine alkyl nitrates as a sum (ΣAN) by thermal dissociation (TD) to a common fragment (NO2), which can then be quantified with a uniform response factor by optical absorption, for example by cavity ring-down spectroscopy (CRDS). However, the determination of ΣAN by TD-CRDS is hampered by its relatively high detection limits (several 100 pptv) and secondary chemistry following TD that results in both negative and positive interferences and depends on the composition of the ambient air sampled. In this work, a TD-CRDS equipped with a Tenax preconcentration unit is described. Matrix effects are minimized by desorbing the samples from the Tenax in a background of nitrogen. The performance of the instrument, in particular the recovery from the Tenax sorbent, was evaluated by sampling laboratory-generated mixtures of alkyl and peroxyacyl nitrates. Field data from a coastal site collected during the Ozone-depleting reactions in a coastal atmosphere (ORCA) campaign, which took place at the Amphitrite Point Observatory in Ucluelet, BC, from July 6 - 31, 2015, are presented. Advantages and disadvantages of the new method are discussed.

DIRECT MERCURY ANALYSIS IN ENVIRONMENTAL SOLIDS BY ICPMS WITH ON-LINE SAMPLE ASHING AND MERCURY PRE-CONCENTRATION USING THE DIRECT MERCURY ANALYZER

EPA Science Inventory

A Direct Mercury Analyzer based on sample combustion and mercury concentration by gold amalgamation, followed by atomic absorption determination, was interfaced with a quadrupole and a magnet sector ICPMS. In this paper, we discuss design and operating parameters and eval...

Determination of Cd in urine by cloud point extraction-tungsten coil atomic absorption spectrometry.

PubMed

Donati, George L; Pharr, Kathryn E; Calloway, Clifton P; Nóbrega, Joaquim A; Jones, Bradley T

2008-09-15

Cadmium concentrations in human urine are typically at or below the 1 microgL(-1) level, so only a handful of techniques may be appropriate for this application. These include sophisticated methods such as graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry. While tungsten coil atomic absorption spectrometry is a simpler and less expensive technique, its practical detection limits often prohibit the detection of Cd in normal urine samples. In addition, the nature of the urine matrix often necessitates accurate background correction techniques, which would add expense and complexity to the tungsten coil instrument. This manuscript describes a cloud point extraction method that reduces matrix interference while preconcentrating Cd by a factor of 15. Ammonium pyrrolidinedithiocarbamate and Triton X-114 are used as complexing agent and surfactant, respectively, in the extraction procedure. Triton X-114 forms an extractant coacervate surfactant-rich phase that is denser than water, so the aqueous supernatant is easily removed leaving the metal-containing surfactant layer intact. A 25 microL aliquot of this preconcentrated sample is placed directly onto the tungsten coil for analysis. The cloud point extraction procedure allows for simple background correction based either on the measurement of absorption at a nearby wavelength, or measurement of absorption at a time in the atomization step immediately prior to the onset of the Cd signal. Seven human urine samples are analyzed by this technique and the results are compared to those found by the inductively coupled plasma mass spectrometry analysis of the same samples performed at a different institution. The limit of detection for Cd in urine is 5 ngL(-1) for cloud point extraction tungsten coil atomic absorption spectrometry. The accuracy of the method is determined with a standard reference material (toxic metals in freeze-dried urine) and the determined values agree with the reported levels at the 95% confidence level.

Tracing the pathogen Staphylococcus aureus on laboratory ants using physical preconcentration coupled ZnO nanoparticle assisted MALDI-TOF MS.

PubMed

Gopal, Judy; Wu, Hui-Fen; Lee, Chia-Hsun; Manikandan, Muthu

2012-01-21

Ants and humans coexist closely and for the most part happily. We consider ants to be harmless, small beings--we have no problem picking them out of our tea cups or sugar jars, throwing them away and continuing to consume the food. This paper is an eye-opener that these ants are not as harmless as they may seem. In particular, our relationship with those present in bacteria-rich environments (e.g. a microbiological lab) need to be reconsidered. From an analytical point of view we have applied the physical preconcentration coupled ZnO NPs assisted MALDI-MS (PP-MALDI-MS) as a novel and sensitive technique for detecting bacteria on the surface of a species of ant present in our laboratory. The preconcentration methods consist of simple techniques comprising of vortex combined with centrifugation or ultrasonication resulting in increasing sample concentration up to the MALDI-MS detection limit. ZnO NPs were used to further enhance the bacterial signals for culture free rapid analysis using MALDI-MS. The importance of a vortex-combined centrifugation approach, using a large number of samples (large number of ants) and decreasing the suspension volume and addition of sample to ZnO NPs (3.5g L(-1)) were found to be crucial prerequisites for increasing MALDI-MS detection of bacteria on ants. We were able to identify the pathogenic clinically important Staphylococcus aureus on the surface of the ants. The bacterial identification was validated using ClinPro 2.1.

Impregnated multiwalled carbon nanotubes as efficient sorbent for the solid phase extraction of trace amounts of heavy metal ions in food and water samples.

PubMed

Gouda, Ayman A; Al Ghannam, Sheikha M

2016-07-01

A new, sensitive and simple solid phase extraction (SPE), separation and preconcentration method of some heavy metal ions, Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) at trace levels using multiwalled carbon nanotubes (MWCNTs) impregnated with 2-(2-benzothiazolylazo)orcinol (BTAO) from food and water samples were investigated. The effect of analytical parameters was examined. The metals retained on the nanotubes at pH 7.0 were eluted by 5.0mL HNO3 (2.0molL(-1)). The influence of matrix ions on the proposed method was evaluated. The preconcentration factor was calculated and found to be 100. The detection limits (LODs) for Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) were found at 0.70, 1.2, 0.80, 2.6 and 2.2μgL(-1), respectively. The relative standard deviation (RSD) and the recoveries of the standard addition method were lower than 5.0% and 95-102%, respectively. The new procedure was successfully applied to the determination of trace amounts of the studied metal ions in various food and water samples and validated using certified reference materials SRM 1570A (spinach leaves) with satisfactory and compatible results. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ionic Liquid Dispersive Liquid-Liquid Microextraction Method for the Determination of Irinotecan, an Anticancer Drug, in Water and Urine Samples Using UV-Vis Spectrophotometry.

PubMed

Uysal, Deniz; Karadaş, Cennet; Kara, Derya

2017-05-01

A new, simple, efficient, and environmentally friendly ionic liquid dispersive liquid-liquid microextraction method was developed for the determination of irinotecan, an anticancer drug, in water and urine samples using UV-Vis spectrophotometry. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate was used as the extraction solvent, and ethanol was used as the disperser solvent. The main parameters affecting the extraction efficiency, including sample pH, volume of the ionic liquid, choice of the dispersive solvent and its volume, concentration of NaCl, and extraction and centrifugation times, were investigated and optimized. The effect of interfering species on the recovery of irinotecan was also examined. Under optimal conditions, the LOD (3σ) was 48.7 μg/L without any preconcentration. Because the urine sample was diluted 10-fold, the LOD for urine would be 487 μg/L. However, this could be improved 16-fold if preconcentration using a 40 mL aliquot of the sample is used. The proposed method was successfully applied to the determination of irinotecan in tap water, river water, and urine samples spiked with 10.20 mg/L for the water samples and 8.32 mg/L for the urine sample. The average recovery values of irinotecan determined were 99.1% for tap water, 109.4% for river water, and 96.1% for urine.

Development and application of a microwave-assisted extraction and LC/MS/MS methodology to the determination of antifouling booster biocides in sea mullets (Mugil cephalus) organisms.

PubMed

Franco-Barrios, Alejandro; Torres-Padrón, María Esther; Sosa-Ferrera, Zoraida; Santana-Rodríguez, José Juan

2014-01-01

A method is presented for the extraction, preconcentration, and determination of two commonly used booster biocides, Irgarol 1051 and diuron, in samples of muscle and liver tissues from Mugil cephalus by microwave-assisted extraction (MAE) followed by SPE for the preconcentration and cleanup step, coupled with LC/MS/MS. The optimum conditions for MAE were established as power 200 W and irradiation time 4 min. Using these conditions, the LOD was 0.13 ng/g for diuron and 0.10 ng/g for Irgarol 1051. The recoveries calculated at three concentration levels (0.5, 5, and 50 ng/g) were greater than 74%. Repeatability was less than 7.5% and reproducibility less than 12.7%. The optimized method was used to monitor these compounds in M. cephalus from different harbors of Gran Canaria Island. The samples were collected bimonthly and processed following the optimized method. High levels of Irgarol 1051 (6.9 +/- 1.03 ng/g) were found in the liver, while diuron was undetected. However, diuron was found in the muscle (1.41 +/- 0.45 ng/g). The proposed sentinel organism could be used in tropical and subtropical regions to continuously biomonitor for booster biocides over long periods of time. This technique could be a useful tool for improving the management of ocean and coastal waters.

Application of methyl silane coated iron oxide magnetic nanoparticles for solid-phase extraction and determination of fat-soluble vitamins by high performance liquid chromatography.

PubMed

Momenbeik, Fariborz; Yazdani, Elham

2015-01-01

Methyl silane coated Fe3O4 magnetic nanoparticles were used for simultaneous extraction of the fat-soluble vitamins (FSVs). The amounts of extracted vitamins were determined by HPLC. The synthesized Fe3O4 nanoparticles were coated with silica and then modified with trimethoxymethylsilane (TMMS). The prepared particles were characterized by different methods. The best amounts of silica and TMMS in sorbent synthesis were 1.2 and 0.5 mL, respectively. The optimum pH values for the sample solution and washing buffer were 5 and 3, respectively. Application of 100 mg sorbent, 700 μL tetrahydrofuran, 5-fold dilution of the sample solution, and 1 min for sorption and desorption times were among the best conditions. At the optimum conditions, the calibration plots for each vitamin were obtained with good linearity (R(2) >0.9992) and suitable linear ranges. This method has a low LOD (<76.1 μg/mL), acceptable repeatability (RSD <5.63%) and reproducibility (RSD <4.71%), and good accuracy (recovery >90.3%). Preconcentration of low concentrations of vitamin D3 was performed, and results showed 3.7 times greater sensitivity after preconcentration. Finally, the amounts of the FSVs in pharmaceutical formulations were determined using the proposed method, and results showed good agreement with those reported by manufacturers.

Monitoring the enrichment of virgin olive oil with natural antioxidants by using a new capillary electrophoresis method.

PubMed

Nevado, Juan José Berzas; Robledo, Virginia Rodríguez; Callado, Carolina Sánchez-Carnerero

2012-07-15

The enrichment of virgin olive oil (VOO) with natural antioxidants contained in various herbs (rosemary, thyme and oregano) was studied. Three different enrichment procedures were used for the solid-liquid extraction of antioxidants present in the herbs to VOO. One involved simply bringing the herbs into contact with the VOO for 190 days; another keeping the herb-VOO mixture under stirring at room temperature (25°C) for 11 days; and the third stirring at temperatures above room level (35-40°C). The efficiency of each procedure was assessed by using a reproducible, efficient, reliable analytical capillary zone electrophoresis (CZE) method to separate and determine selected phenolic compounds (rosmarinic and caffeic acid) in the oil. Prior to electrophoretic separation, the studied antioxidants were isolated from the VOO matrix by using an optimised preconcentration procedure based on solid phase extraction (SPE). The CZE method was optimised and validated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Solvent microextraction-flame atomic absorption spectrometry (SME-FAAS) for determination of ultratrace amounts of cadmium in meat and fish samples.

PubMed

Goudarzi, Nasser

2009-02-11

A simple, low cost and highly sensitive method based on solvent microextraction (SME) for separation/preconcentration and flame atomic absorption spectrometry (FAAS) was proposed for the determination of ultratrace amounts of cadmium in meat and fish samples. The analytical procedure involved the formation of a hydrophobic complex by mixing the analyte solution with an ammonium pyrrolidinedithiocarbamate (APDC) solution. In suitable conditions, the complex of cadmium-APDC entered the micro organic phase, and thus, separation of the analyte from the matrix was achieved. Under optimal chemical and instrumental conditions, a detection limit (3 sigma) of 0.8 ng L(-1) and an enrichment factor of 93 were achieved. The relative standard deviation for the method was found to be 2.2% for Cd. The interference effects of some anions and cations were also investigated. The developed method has been applied to the determination of trace Cd in meat and fish samples.

Determination of trace metals in drinking water using solid-phase extraction disks and X-ray fluorescence spectrometry.

PubMed

Hou, Xiandeng; Peters, Heather L; Yang, Zheng; Wagner, Karl A; Batchelor, James D; Daniel, Meredith M; Jones, Bradley T

2003-03-01

A convenient method is described for monitoring Cd, Ni, Cu, and Pb at trace levels in drinking water samples. These metals are preconcentrated on a chelating solid-phase extraction disk and then determined by X-ray fluorescence spectrometry. The method tolerates a wide pH range (pH 6-14) and a large amount of alkaline and alkaline earth elements. The preconcentration factor is well over 1600, assuming a 1 L water sample volume. The limits of detection for Cd, Ni, Cu, and Pb are 3.8, 0.6, 0.4, and 0.3 ng/mL, respectively. These are well below the federal maximum contaminant level values, which are 5, 100, 1300, and 15 ng/mL, respectively. The proposed method has many advantages including ease of operation, multielement capability, nondestructiveness, high sensitivity, and relative cost efficiency. The solid-phase extraction step can be conducted in the field and then the disks can be mailed to a laboratory for the analysis, eliminating the cost of transporting large volumes of water samples. Furthermore, the color of the used extraction disk provides an initial estimate of the degree of contamination for some transition metals (for example, Ni and Cu). Thus, the overall cost for analysis of metals in drinking water can be minimized by implementing the method, and small water supply companies with limited budgets will be better able to comply with the Safe Drinking Water Act.

[Study on the determination of trace Cu and Mn in foodstuff preconcentration by precipitate flotation and FAAS].

PubMed

Li, Chun-xiang; Chen, Ting-yu; Yan, Yong-sheng

2007-10-01

In the present paper, the use of 8-hydroxyquinoline(oxine, HQ) complexs in precipitate flotation to separate and preconcentrate Cu and Mn, using SDBS as collector, followed by AAS spectrophotometric determination is proposed. The optimum conditions of precipitate flotation were studied. The effects of several parameters of flotation processes condition on single metal ions precipitation-flotation and multi-metal ions coprecipitation-flotation of Cu and Mn at pH 9 were investigated. The experimental results show that the flotation rate of Cu is supreme with pH 9. Under the condition of pH 9 and changing the ratio of concentration, when Mn/Cu> or =8, the recovery rate of Cu is less than 90%. This method is simple, rapid, accurate, sensitive and precise and avoids using the virulent organic solvent. The linear range of Cu is 0.5-5.0 microg x mL(-1) with the correlative coefficient of 0.9996, detection limit of this method was found to be 1.59 x 10(-3) microg x mL(-1), the linear range of Mn is 0.5-5.0 microg x mL(-1) with the correlative coefficient of 0.9987, and the detection limit of this method was found to be 3.52 x 10(-3) microg x mL(-1). The method was applied to the determination of Cu and Mn in foodstuff, and the recovery is 87.6%-100.7%. The result was satisfactory.

Graphene oxide/Fe3O4 as sorbent for magnetic solid-phase extraction coupled with liquid chromatography to determine 2,4,6-trinitrotoluene in water samples.

PubMed

Costa Dos Reis, Luciana; Vidal, Lorena; Canals, Antonio

2017-04-01

A fast, simple, economical, and environmentally friendly magnetic solid-phase extraction (MSPE) procedure has been developed to preconcentrate 2,4,6-trinitrotoluene (TNT) from water samples prior to determination by liquid chromatography-UV-Vis employing graphene oxide/Fe 3 O 4 nanocomposite as sorbent. The nanocomposite synthesis was investigated, and the MSPE was optimized by a multivariate approach. The optimum MSPE conditions were 40 mg of nanocomposite, 10 min of vortex extraction, 1 mL of acetonitrile as eluent, and 6 min of desorption in an ultrasonic bath. Under the optimized experimental conditions, the method was evaluated to obtain a preconcentration factor of 153. The linearity of the method was studied from 1 to 100 μg L -1 (N = 5), obtaining a correlation coefficient of 0.994. The relative standard deviation and limit of detection were found to be 12% (n = 6, 10 μg L -1 ) and 0.3 μg L -1 , respectively. The applicability of the method was investigated, analyzing three types of water samples (i.e., reservoir and drinking water and effluent wastewater) and recovery values ranged between 87 and 120% (50 μg L -1 spiking level), showing that the matrix had a negligible effect upon extraction. Finally, the semiquantitative Eco-Scale metrics confirmed the greenness of the developed method.

U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads

NASA Astrophysics Data System (ADS)

Bischoff, James L.; Wooden, Joe; Murphy, Fred; Williams, Ross W.

2005-04-01

We present a new analytical method for U-series isotopes using the SHRIMP RG (Sensitive High mass Resolution Ion MicroProbe) mass spectrometer that utilizes the preconcentration of the U-series isotopes from a sample onto a single ion-exchange bead. Ion-microprobe mass spectrometry is capable of producing Th ionization efficiencies in excess of 2%. Analytical precision is typically better than alpha spectroscopy, but not as good as thermal ionization mass spectroscopy (TIMS) and inductively coupled plasma multicollector mass spectrometry (ICP-MS). Like TIMS and ICP-MS the method allows analysis of small samples sizes, but also adds the advantage of rapidity of analysis. A major advantage of ion-microprobe analysis is that U and Th isotopes are analyzed in the same bead, simplifying the process of chemical separation. Analytical time on the instrument is ˜60 min per sample, and a single instrument-loading can accommodate 15-20 samples to be analyzed in a 24-h day. An additional advantage is that the method allows multiple reanalyses of the same bead and that samples can be archived for reanalysis at a later time. Because the ion beam excavates a pit only a few μm deep, the mount can later be repolished and reanalyzed numerous times. The method described of preconcentrating a low concentration sample onto a small conductive substrate to allow ion-microprobe mass spectrometry is potentially applicable to many other systems.

Solid phase extraction of rare earth elements in seawater and estuarine water with 4-(2-thiazolylazo) resorcinol immobilized Chromosorb 106 for determination by inductively coupled plasma mass spectrometry

PubMed Central

Zereen, Fahmida; Yilmaz, Vedat; Arslan, Zikri

2013-01-01

A solid phase preconcentration method has been developed using new chelating resin prepared by immobilization of 4-(2-thiazolylazo) resorcinol (TAR) on Chromosorb 106. The method was optimized for determination of rare earth elements (REEs) in seawater and estuarine water samples by inductively coupled plasma mass spectrometry (ICP-MS). The effects of various experimental parameters, such as load pH, eluent concentration, sample and eluent flow rates were examined to find the optimum operating conditions. The REEs were quantitatively retained from saline solutions on a minicolumn Chromosorb 106-TAR resin at pH 5.0 and then eluted with 1.0 mL of 1% (v/v) HNO3. The resin possesses large sorption capacity for REEs ranging from 81.1 µmol g−1 for Lu and 108 µmol g−1 for Nd. Detection limits (3s) varied between 0.06 ng L−1 for Pr to 0.31 for Ce for preconcentration of 5.0 mL blank solutions (pH 5.0). The relative standard deviation for triplicate measurements was less than 5% at 0.1 µg L−1 level. The method was validated by analysis Nearshore seawater certified reference material (CASS–4). The elemental results were comparable with the values reported in literature. The method was verified by analysis of spiked and unspiked coastal seawater and estuarine water samples. PMID:24000264

U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads

USGS Publications Warehouse

Bischoff, J.L.; Wooden, J.; Murphy, F.; Williams, Ross W.

2005-01-01

We present a new analytical method for U-series isotopes using the SHRIMP RG (Sensitive High mass Resolution Ion MicroProbe) mass spectrometer that utilizes the preconcentration of the U-series isotopes from a sample onto a single ion-exchange bead. Ion-microprobe mass spectrometry is capable of producing Th ionization efficiencies in excess of 2%. Analytical precision is typically better than alpha spectroscopy, but not as good as thermal ionization mass spectroscopy (TIMS) and inductively coupled plasma multicollector mass spectrometry (ICP-MS). Like TIMS and ICP-MS the method allows analysis of small samples sizes, but also adds the advantage of rapidity of analysis. A major advantage of ion-microprobe analysis is that U and Th isotopes are analyzed in the same bead, simplifying the process of chemical separation. Analytical time on the instrument is ???60 min per sample, and a single instrument-loading can accommodate 15-20 samples to be analyzed in a 24-h day. An additional advantage is that the method allows multiple reanalyses of the same bead and that samples can be archived for reanalysis at a later time. Because the ion beam excavates a pit only a few ??m deep, the mount can later be repolished and reanalyzed numerous times. The method described of preconcentrating a low concentration sample onto a small conductive substrate to allow ion-microprobe mass spectrometry is potentially applicable to many other systems. Copyright ?? 2005 Elsevier Ltd.

Solid phase extraction of rare earth elements in seawater and estuarine water with 4-(2-thiazolylazo) resorcinol immobilized Chromosorb 106 for determination by inductively coupled plasma mass spectrometry.

PubMed

Zereen, Fahmida; Yilmaz, Vedat; Arslan, Zikri

2013-09-01

A solid phase preconcentration method has been developed using new chelating resin prepared by immobilization of 4-(2-thiazolylazo) resorcinol (TAR) on Chromosorb 106. The method was optimized for determination of rare earth elements (REEs) in seawater and estuarine water samples by inductively coupled plasma mass spectrometry (ICP-MS). The effects of various experimental parameters, such as load pH, eluent concentration, sample and eluent flow rates were examined to find the optimum operating conditions. The REEs were quantitatively retained from saline solutions on a minicolumn Chromosorb 106-TAR resin at pH 5.0 and then eluted with 1.0 mL of 1% (v/v) HNO 3 . The resin possesses large sorption capacity for REEs ranging from 81.1 µmol g -1 for Lu and 108 µmol g -1 for Nd. Detection limits (3s) varied between 0.06 ng L -1 for Pr to 0.31 for Ce for preconcentration of 5.0 mL blank solutions (pH 5.0). The relative standard deviation for triplicate measurements was less than 5% at 0.1 µg L -1 level. The method was validated by analysis Nearshore seawater certified reference material (CASS-4). The elemental results were comparable with the values reported in literature. The method was verified by analysis of spiked and unspiked coastal seawater and estuarine water samples.

Capillary electrochromatography and preconcentration of neutral compounds on poly(dimethylsiloxane) microchips.

PubMed

Ro, Kyung Won; Chang, Woo-Jin; Kim, Ho; Koo, Yoon-Mo; Hahn, Jong Hoon

2003-09-01

Capillary electrochromatography (CEC) and preconcentration of neutral compounds have been realized on poly(dimethylsiloxane) (PDMS) microchips. The channels are coated with polyelectrolyte multilayers to avoid absorption of hydrophobic analytes into PDMS. The structures of a microchip include an injector and a bead chamber with integrated frits, where the particles of the stationary phase are completely retained. Dimensions of the frit structures are 25 micro mx20 micro m, and the space between the structures is 3 micro m. A neutral compound, BODIPY, that is strongly absorbed into native PDMS, is successfully and selectively retained on octadecylsilane-coated silica beads in the bead chamber with a concentration enhancement of up to 100 times and eluted with elution buffer solution containing 70% acetonitrile. Preconcentrations and CEC separations of coumarins have been conducted with the same device and achieved complete separations in less than 50 s.

The quality of our drinking water: aluminium determination with an acoustic wave sensor.

PubMed

Veríssimo, Marta I S; Gomes, M Teresa S R

2008-06-09

A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100. The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07 mg L(-1). Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV-vis spectrophotometry. Results obtained with both methodologies were not statistically different (alpha=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.

Solid supports for extraction and preconcentration of proteins and peptides in microfluidic devices: A review.

PubMed

Dziomba, Szymon; Araya-Farias, Monica; Smadja, Claire; Taverna, Myriam; Carbonnier, Benjamin; Tran, N Thuy

2017-02-22

Determination of proteins and peptides is among the main challenges of today's bioanalytical chemistry. The application of microchip technology in this field is an exhaustively developed concept that aims to create integrated and fully automated analytical devices able to quantify or detect one or several proteins from a complex matrix. Selective extraction and preconcentration of targeted proteins and peptides especially from biological fluids is of the highest importance for a successful realization of these microsystems. Incorporation of solid structures or supports is a convenient solution employed to face these demands. This review presents a critical view on the latest achievements in sample processing techniques for protein determination using solid supports in microfluidics. The study covers the period from 2006 to 2015 and focuses mainly on the strategies based on microbeads, monolithic materials and membranes. Less common approaches are also briefly discussed. The reviewed literature suggests future trends which are discussed in the concluding remarks. Copyright © 2016 Elsevier B.V. All rights reserved.

Real-time analysis of δ13C- and δD-CH4 in ambient air with laser spectroscopy: method development and first intercomparison results

NASA Astrophysics Data System (ADS)

Eyer, S.; Tuzson, B.; Popa, M. E.; van der Veen, C.; Röckmann, T.; Rothe, M.; Brand, W. A.; Fisher, R.; Lowry, D.; Nisbet, E. G.; Brennwald, M. S.; Harris, E.; Zellweger, C.; Emmenegger, L.; Fischer, H.; Mohn, J.

2015-08-01

In situ and simultaneous measurement of the three most abundant isotopologues of methane using mid-infrared laser absorption spectroscopy is demonstrated. A field-deployable, autonomous platform is realized by coupling a compact quantum cascade laser absorption spectrometer (QCLAS) to a preconcentration unit, called TRace gas EXtractor (TREX). This unit enhances CH4 mole fractions by a factor of up to 500 above ambient levels and quantitatively separates interfering trace gases such as N2O and CO2. The analytical precision of the QCLAS isotope measurement on the preconcentrated (750 ppm, parts-per-million, μmole/mole) methane is 0.1 and 0.5 ‰ for δ13C- and δD-CH4 at 10 min averaging time. Based on replicate measurements of compressed air during a two-week intercomparison campaign, the repeatability of the TREX-QCLAS was determined to be 0.19 and 1.9 ‰ for δ13C and δD-CH4, respectively. In this intercomparison campaign the new in situ technique is compared to isotope-ratio mass-spectrometry (IRMS) based on glass flask and bag sampling and real time CH4 isotope analysis by two commercially available laser spectrometers. Both laser-based analyzers were limited to methane mole fraction and δ13C-CH4 analysis, and only one of them, a cavity ring down spectrometer, was capable to deliver meaningful data for the isotopic composition. After correcting for scale offsets, the average difference between TREX-QCLAS data and bag/flask sampling-IRMS values are within the extended WMO compatibility goals of 0.2 and 5 ‰ for δ13C- and δD-CH4, respectively. Thus, the intercomparison also reveals the need for reference air samples with accurately determined isotopic composition of CH4 to further improve the interlaboratory compatibility.

Separation and Enrichment of Gold in Water, Geological and Environmental Samples by Solid Phase Extraction on Multiwalled Carbon Nanotubes Prior to its Determination by Flame Atomic Absorption Spectrometry.

PubMed

Duran, Ali; Tuzen, Mustafa; Soylak, Mustafa

2015-01-01

This study proposes the application of multi-walled carbon nanotubes as a solid sorbent for the preconcentration of gold prior to its flame atomic absorption spectrometry determination. Extraction was achieved by using a glass column (15.0 cm in length and 1.0 cm in diameter). Quantitative recoveries were obtained in the pH range of 2.5-4.0; the elution step was carried out with 5.0 ml of 1.0 mol/L HNO3 in acetone. In the ligand-free study, variables such as pH, eluent type, sample volume, flow rates, and matrix effect were examined for the optimum recovery of gold ions. The gold ions were able to be pre-concentrated by a factor of 150 and their LOD was determined to be 1.71 μg/L. In order to evaluate the accuracy of the developed method, addition-recovery tests were applied for the tap water, mineral water, and sea water samples. Gold recovery studies were implemented using a wet digestion technique for mine and soil samples taken from various media, and this method was also applied for anodic slime samples taken from the factories located in the Kayseri Industrial Zone of Turkey.

Solid phase extraction of metal ions in environmental samples on 1-(2-pyridylazo)-2-naphthol impregnated activated carbon cloth.

PubMed

Alothman, Zeid A; Yilmaz, Erkan; Habila, Mohamed; Soylak, Mustafa

2015-02-01

1-(2-Pyridylazo)-2-naphthol impregnated activated carbon cloth (PAN-imp-ACC) was prepared as a solid phase sorbent and, for the first time, was used for the simultaneous separation and preconcentration of trace amounts of lead, cadmium and nickel in water, soil and sewage sludge samples prior to determination by flame atomic absorption spectrometry (FAAS). The parameters governing the efficiency of the method were optimized, including the pH, the eluent type and volume, the sample and eluent flow rates, diverse ions effects and the sample volume. A preconcentration factor of 100 was achieved for all the metal ions, with detection limits of 0.1-2.8 µg L(-1) and relative standard deviations below 6.3%. The adsorption capacity of the PAN-imp-ACC for Pb(II), Cd(II) and Ni(II) ions was found to be 45.0 mg g(-1), 45.0 mg g(-1) and 43.2 mg g(-1), respectively. The method was validated by the analysis of the certified reference materials TMDA-64.2 fortified Lake Ontario water and BCR-146R Sewage Sludge Amended Soil (Industrial Origin). The procedure was applied to determine the analytes content in real samples. Copyright © 2014 Elsevier Inc. All rights reserved.

Ultrasound-assisted combined with nano-sized molecularly imprinted polymer for selective extraction and pre-concentration of amitriptyline in human plasma with gas chromatography-flame detection.

PubMed

Khanahmadzadeh, Salah; Tarigh, Ahmad

2014-12-01

A new process was developed for the selective extraction and pre-concentration of amitriptyline (AT) from human plasma using nano-sized molecularly imprinted polymer (MIP) with ultrasound-assisted extraction (UAE). The nano-sized AT imprinted polymer particles were synthesized using suspension polymerization in silicon oil and characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscope (SEM) methods. With the application of optimized values, linearity values in the ranges of 20-200μgmL(-1) and 35-200μgmL(-1) were obtained for AT with the correlation of determination values (r(2)) 0.998 and 0.995 in water and plasma, respectively. The limits of detections (S/N=3) for AT were found to be 0.7 and 1.2μgmL(-1) in water and plasma, respectively. The enrichment factors of AT in water and plasma were 52 and 40, respectively. The inter-day precisions (%) were in the range of 5.8-9.2%. Relative recovery rates ranged from 82.4% to 92.3%. The method was successfully applied to determine AT in the human plasma samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Solving matrix effects exploiting the second-order advantage in the resolution and determination of eight tetracycline antibiotics in effluent wastewater by modelling liquid chromatography data with multivariate curve resolution-alternating least squares and unfolded-partial least squares followed by residual bilinearization algorithms II. Prediction and figures of merit.

PubMed

García, M D Gil; Culzoni, M J; De Zan, M M; Valverde, R Santiago; Galera, M Martínez; Goicoechea, H C

2008-02-01

A new powerful algorithm (unfolded-partial least squares followed by residual bilinearization (U-PLS/RBL)) was applied for first time on second-order liquid chromatography with diode array detection (LC-DAD) data and compared with a well-known established method (multivariate curve resolution-alternating least squares (MCR-ALS)) for the simultaneous determination of eight tetracyclines (tetracycline, oxytetracycline, meclocycline, minocycline, metacycline, chlortetracycline, demeclocycline and doxycycline) in wastewaters. Tetracyclines were pre-concentrated using Oasis Max C18 cartridges and then separated on a Thermo Aquasil C18 (150 mm x 4.6mm, 5 microm) column. The whole method was validated using Milli-Q water samples and both univariate and multivariate analytical figures of merit were obtained. Additionally, two data pre-treatment were applied (baseline correction and piecewise direct standardization), which allowed to correct the effect of breakthrough and to reduce the total interferences retained after pre-concentration of wastewaters. The results showed that the eight tetracycline antibiotics can be successfully determined in wastewaters, the drawbacks due to matrix interferences being adequately handled and overcome by using U-PSL/RBL.

Monitoring of trace amounts of heavy metals in different food and water samples by flame atomic absorption spectrophotometer after preconcentration by amine-functionalized graphene nanosheet.

PubMed

Behbahani, Mohammad; Tapeh, Nasim Akbari Ghareh; Mahyari, Mojtaba; Pourali, Ali Reza; Amin, Bahareh Golrokh; Shaabani, Ahmad

2014-11-01

We are introducing graphene oxide modified with amine groups as a new solid phase for extraction of heavy metal ions including cadmium(II), copper(II), nickel(II), zinc(II), and lead(II). Effects of pH value, flow rates, type, concentration, and volume of the eluent, breakthrough volume, and the effect of potentially interfering ions were studied. Under optimized conditions, the extraction efficiency is >97 %, the limit of detections are 0.03, 0.05, 0.2, 0.1, and 1 μg L(-1) for the ions of cadmium, copper, nickel, zinc, and lead, respectively, and the adsorption capacities for these ions are 178, 142, 110, 125, and 210 mg g(-1). The amino-functionalized graphene oxide was characterized by thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectrometry. The proposed method was successfully applied in the analysis of environmental water and food samples. Good spiked recoveries over the range of 95.8-100.0 % were obtained. This work not only proposes a useful method for sample preconcentration but also reveals the great potential of modified graphene as an excellent sorbent material in analytical processes.

Simultaneous detection of antibacterial sulfonamides in a microfluidic device with amperometry.

PubMed

Won, So-Young; Chandra, Pranjal; Hee, Tak Seong; Shim, Yoon-Bo

2013-01-15

A highly sensitive and robust method for simultaneous detection of five sulfonamide drugs is developed by integrating the preconcentration and separation steps in a microfluidic device. An ampetrometry is performed for the selective detection of sulfonamides using an aluminum oxide-gold nanoparticle (Al(2)O(3)-AuNPs) modified carbon paste (CP) electrode at the end of separation channel. The preconcentration capacity of the channel is enhanced by using the field amplified sample stacking and the field amplified sample injection techniques. The experimental parameters affecting the analytical performances, such as pH, % of Al(2)O(3), volume of AuNPs, buffer concentration, and water plug length are optimized. A reproducible response is observed during the multiple injections of samples with RSDs<4%. The calibration plots are linear with the correlation coefficient between 0.991 and 0.997 over the range between 0.01 and 2025pM. The detection limits of five drugs are determined to be between 0.91 (±0.03) and 2.21 (±0.09)fM. The interference effects of common biological compounds are also investigated and the applicability of the method to the direct analysis of sulfonamides in real meat samples is successfully demonstrated. Long term stability of the modified electrode was also investigated. Copyright © 2012 Elsevier B.V. All rights reserved.

UPLC-MS/MS determination of ptaquiloside and pterosin B in preserved natural water.

PubMed

Clauson-Kaas, Frederik; Hansen, Hans Christian Bruun; Strobel, Bjarne W

2016-11-01

The naturally occurring carcinogen ptaquiloside and its degradation product pterosin B are found in water leaching from bracken stands. The objective of this work is to present a new sample preservation method and a fast UPLC-MS/MS method for quantification of ptaquiloside and pterosin B in environmental water samples, employing a novel internal standard. A faster, reliable, and efficient method was developed for isolation of high purity ptaquiloside and pterosin B from plant material for use as analytical standards, with purity verified by 1 H-NMR. The chemical analysis was performed by cleanup and preconcentration of samples with solid phase extraction, before analyte quantification with UPLC-MS/MS. By including gradient elution and optimizing the liquid chromatography mobile phase buffer system, a total run cycle of 5 min was achieved, with method detection limits, including preconcentration, of 8 and 4 ng/L for ptaquiloside and pterosin B, respectively. The use of loganin as internal standard improved repeatability of the determination of both analytes, though it could not be employed for sample preparation. Buffering raw water samples in situ with ammonium acetate to pH ∼5.5 decisively increased sample integrity at realistic transportation and storing conditions prior to extraction. Groundwater samples collected in November 2015 at the shallow water table below a Danish bracken stand were preserved and analyzed using the above methods, and PTA concentrations of 3.8 ± 0.24 μg/L (±sd, n = 3) were found, much higher than previously reported. Graphical abstract Workflow overview of ptaquiloside determination.

Preconcentration of Trace Neonicotinoid Insecticide Residues Using Vortex-Assisted Dispersive Micro Solid-Phase Extraction with Montmorillonite as an Efficient Sorbent.

PubMed

Moyakao, Khwankaew; Santaladchaiyakit, Yanawath; Srijaranai, Supalax; Vichapong, Jitlada

2018-04-11

In this work, we investigated montmorillonite for adsorption of neonicotinoid insecticides in vortex-assisted dispersive micro-solid phase extraction (VA-d-μ-SPE). High-performance liquid chromatography with photodiode array detection was used for quantification and determination of neonicotinoid insecticide residues, including thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid. In this method, the solid sorbent was dispersed into the aqueous sample solution and vortex agitation was performed to accelerate the extraction process. Finally, the solution was filtered from the solid sorbent with a membrane filter. The parameters affecting the extraction efficiency of the proposed method were optimized, such as amount of sorbent, sample volume, salt addition, type and volume of extraction solvent, and vortex time. The adsorbing results show that montmorillonite could be reused at least 4 times and be used as an effective adsorbent for rapid extraction/preconcentration of neonicotinoid insecticide residues. Under optimum conditions, linear dynamic ranges were achieved between 0.5 and 1000 ng mL -1 with a correlation of determination ( R² ) greater than 0.99. Limit of detection (LOD) ranged from 0.005 to 0.065 ng mL -1 , while limit of quantification (LOQ) ranged from 0.008 to 0.263 ng mL -1 . The enrichment factor (EF) ranged from 8 to 176-fold. The results demonstrated that the proposed method not only provided a more simple and sensitive method, but also can be used as a powerful alternative method for the simultaneous determination of insecticide residues in natural surface water and fruit juice samples.

Validation of an ultra-high-performance liquid chromatography-tandem mass spectrometry method to quantify illicit drug and pharmaceutical residues in wastewater using accuracy profile approach.

PubMed

Hubert, Cécile; Roosen, Martin; Levi, Yves; Karolak, Sara

2017-06-02

The analysis of biomarkers in wastewater has become a common approach to assess community behavior. This method is an interesting way to estimate illicit drug consumption in a given population: by using a back calculation method, it is therefore possible to quantify the amount of a specific drug used in a community and to assess the consumption variation at different times and locations. Such a method needs reliable analytical data since the determination of a concentration in the ngL -1 range in a complex matrix is difficult and not easily reproducible. The best analytical method is liquid chromatography - mass spectrometry coupling after solid-phase extraction or on-line pre-concentration. Quality criteria are not specially defined for this kind of determination. In this context, it was decided to develop an UHPLC-MS/MS method to analyze 10 illicit drugs and pharmaceuticals in wastewater treatment plant influent or effluent using a pre-concentration on-line system. A validation process was then carried out using the accuracy profile concept as an innovative tool to estimate the probability of getting prospective results within specified acceptance limits. Influent and effluent samples were spiked with known amounts of the 10 compounds and analyzed three times a day for three days in order to estimate intra-day and inter-day variations. The matrix effect was estimated for each compound. The developed method can provide at least 80% of results within ±25% limits except for compounds that are degraded in influent. Copyright © 2017 Elsevier B.V. All rights reserved.

Rapid and sensitive analysis of polychlorinated biphenyls and acrylamide in food samples using ionic liquid-based in situ dispersive liquid-liquid microextraction coupled to headspace gas chromatography.

PubMed

Zhang, Cheng; Cagliero, Cecilia; Pierson, Stephen A; Anderson, Jared L

2017-01-20

A simple and rapid ionic liquid (IL)-based in situ dispersive liquid-liquid microextraction (DLLME) method was developed and coupled to headspace gas chromatography (HS-GC) employing electron capture (ECD) and mass spectrometry (MS) detection for the analysis of polychlorinated biphenyls (PCBs) and acrylamide at trace levels from milk and coffee samples. The chemical structures of the halide-based ILs were tailored by introducing various functional groups to the cations to evaluate the effect of different structural features on the extraction efficiency of the target analytes. Extraction parameters including the molar ratio of IL to metathesis reagent and IL mass were optimized. The effects of HS oven temperature and the HS sample vial volume on the analyte response were also evaluated. The optimized in situ DLLME method exhibited good analytical precision, good linearity, and provided detection limits down to the low ppt level for PCBs and the low ppb level for acrylamide in aqueous samples. The matrix-compatibility of the developed method was also established by quantifying acrylamide in brewed coffee samples. This method is much simpler and faster compared to previously reported GC-MS methods using solid-phase microextraction (SPME) for the extraction/preconcentration of PCBs and acrylamide from complex food samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Recent Advances in On-Line Methods Based on Extraction for Speciation Analysis of Chromium in Environmental Matrices.

PubMed

Trzonkowska, Laura; Leśniewska, Barbara; Godlewska-Żyłkiewicz, Beata

2016-07-03

The biological activity of Cr(III) and Cr(VI) species, their chemical behavior, and toxic effects are dissimilar. The speciation analysis of Cr(III) and Cr(VI) in environmental matrices is then of great importance and much research has been devoted to this area. This review presents recent developments in on-line speciation analysis of chromium in such samples. Flow systems have proved to be excellent tools for automation of sample pretreatment, separation/preconcentration of chromium species, and their detection by various instrumental techniques. Analytical strategies used in chromium speciation analysis discussed in this review are divided into categories based on selective extraction/separation of chromium species on solid sorbents and liquid-liquid extraction of chromium species. The most popular strategy is that based on solid-phase extraction. Therefore, this review shows the potential of novel materials designed and used for selective binding of chromium species. The progress in miniaturization of measurement systems is also presented.

Assessment of Metaborate Fusion for the Rapid Dissolution of Solid Samples: Suitability with the Northstar ARSIIe

DTIC Science & Technology

2016-07-01

goal of this project was to develop a rapid dissolution methodology for solid environmental samples and a crude pre- concentration of actinides ...environmental solid samples needed to be removed from the samples prior to actinide separation on the ARSIIe system. As a result of this project, two...procedures were developed, one applicable to the pre-concentration of the actinides only and a second for the pre-concentration of both actinides and

Fused silica capillaries with two segments of different internal diameters and inner surface roughnesses prepared by etching with supercritical water and used for volume coupling electrophoresis.

PubMed

Horká, Marie; Karásek, Pavel; Roth, Michal; Šlais, Karel

2017-05-01

In this work, single-piece fused silica capillaries with two different internal diameter segments featuring different inner surface roughness were prepared by new etching technology with supercritical water and used for volume coupling electrophoresis. The concept of separation and online pre-concentration of analytes in high conductivity matrix is based on the online large-volume sample pre-concentration by the combination of transient isotachophoretic stacking and sweeping of charged proteins in micellar electrokinetic chromatography using non-ionogenic surfactant. The modified surface roughness step helped to the significant narrowing of the zones of examined analytes. The sweeping and separating steps were accomplished simultaneously by the use of phosphate buffer (pH 7) containing ethanol, non-ionogenic surfactant Brij 35, and polyethylene glycol (PEG 10000) after sample injection. Sample solution of a large volume (maximum 3.7 μL) dissolved in physiological saline solution was injected into the wider end of capillary with inlet inner diameter from 150, 185 or 218 μm. The calibration plots were linear (R 2 ∼ 0.9993) over a 0.060-1 μg/mL range for the proteins used, albumin and cytochrome c. The peak area RSDs from at least 20 independent measuremens were below 3.2%. This online pre-concentration technique produced a more than 196-fold increase in sensitivity, and it can be applied for detection of, e.g. the presence of albumin in urine (0.060 μg/mL). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid method to determine actinides and 89/90Sr in limestone and marble samples

DOE PAGES

Maxwell, Sherrod L.; Culligan, Brian; Hutchison, Jay B.; ...

2016-04-12

A new method for the determination of actinides and radiostrontium in limestone and marble samples has been developed that utilizes a rapid sodium hydroxide fusion to digest the sample. Following rapid pre-concentration steps to remove sample matrix interferences, the actinides and 89/90Sr are separated using extraction chromatographic resins and measured radiometrically. The advantages of sodium hydroxide fusion versus other fusion techniques will be discussed. Lastly, this approach has a sample preparation time for limestone and marble samples of <4 hours.

Preconcentration of Zr, Hf, Nb, Ta and W in seawater using solid-phase extraction on TSK-8-hydroxyquinoline resin and determination by inductively coupled plasma-mass spectrometry.

PubMed

Firdaus, M Lutfi; Norisuye, Kazuhiro; Sato, Taishi; Urushihara, Shouhei; Nakagawa, Yusuke; Umetani, Shigeo; Sohrin, Yoshiki

2007-02-05

Here, we present the first simultaneous preconcentration and determination of ultratrace (pmol kg(-1) level) Zr, Hf, Nb, Ta and W in seawater, both in the form of dissolved and acid-dissolvable species. 8-Hydroxyquinoline (8HQ) bonded covalently to a vinyl polymer resin, TSK-8HQ, was used in a chelating adsorbent column to concentrate the metals. The greatest advantage of this resin is its endurance to 5M HF, since this is an effective eluent for all five metals. The analytes were successfully concentrated from 250 mL seawater with a 50-fold concentration factor through the column extraction and evaporation. The detection limit was 0.009-0.15 pmol kg(-1). The procedure blank determined using ultra pure water as a sample was 0.005-0.37 pmol kg(-1). The five metals were quantitatively recovered from seawater with good precision (2-4%). The effect of sample pH, sample flow rate, eluent composition and sample pretreatment were carefully studied. This method was applied to seawater.

Solid Phase Extraction and Preconcentration of Trace Gallium, Indium, and Thallium Using New Modified Amino Silica.

PubMed

Hassanien, Mohamed M; Mortada, Wael I; Kenawy, Ibrahim M; El-Daly, Heba

2017-02-01

Amino silica gel functionalized with 2-hydroxy-5 -(2-hydroxybenzylideneamino)benzoic acid was synthesized, characterized and used as adsorbent for the removal of Ga 3+ , In 3+ and Tl 3+ from aqueous solution prior to their determination by flame atomic absorption spectrometry. Experimental parameters that affect the separation process were investigated in both batch and column modes. The maximum adsorption capacities of the sorbent are 61.7 mg g -1 , 81.3 mg g -1 and 133.0 mg g -1 for Ga 3+ , In 3+ and Tl 3+ , respectively. The preconcentration factor is 200 and the limits of detection of Ga 3+ , In 3+ and Tl 3+ are 4.10 μg L -1 , 1.55 μg L -1 and 1.21 μg L -1 , respectively. Interference by Al 3+ can be masked by the addition of F - ; and that of Fe 3+ by its reduction to Fe 2+ using 10% ascorbic acid. The method was successfully applied for the determination of these ions in water, sediments and liquid crystal display samples.

Simultaneous trace multielement determination by ICP-OES after solid phase extraction with modified octadecyl silica gel.

PubMed

Karbasi, Mohamad-Hadi; Jahanparast, Babak; Shamsipur, Mojtaba; Hassan, Jalal

2009-10-15

Multielement simultaneous determination of 35 trace elements in environmental samples was carried out by inductively coupled plasma emission spectrometry (ICP-OES) after preconcentration with octadecyl silicagel, modified with aurin tricarboxylic acid (Aluminon). Optimal experimental conditions including pH of sample solution, sample volume, sample and eluent flow rate, type, concentration and volume of eluent and foreign ions effect were investigated and established. Trace element ions in aqueous solution were quantitatively adsorbed onto octadecyl silicagel modified with aurin tricarboxylic acid at pH 8.0 with a flow rate of 11.0 mL min(-1). The adsorbed element ions were eluted with 3-5 mL of 0.5 mol L(-1) HNO(3) at a flow rate of 10.0 mL min(-1) and analyzed by ICP-OES simultaneously. The proposed method has at least preconcentration factor of 100 in water samples, which results high sensitive detection of ultra-trace and trace analysis. The present methodology gave recoveries better than 70% and RSD less than 16%.

Simultaneous diamagnetic and magnetic particle trapping in ferrofluid microflows via a single permanent magnet

PubMed Central

Zhou, Yilong; Kumar, Dhileep Thanjavur; Lu, Xinyu; Kale, Akshay; DuBose, John; Song, Yongxin; Wang, Junsheng; Li, Dongqing; Xuan, Xiangchun

2015-01-01

Trapping and preconcentrating particles and cells for enhanced detection and analysis are often essential in many chemical and biological applications. Existing methods for diamagnetic particle trapping require the placement of one or multiple pairs of magnets nearby the particle flowing channel. The strong attractive or repulsive force between the magnets makes it difficult to align and place them close enough to the channel, which not only complicates the device fabrication but also restricts the particle trapping performance. This work demonstrates for the first time the use of a single permanent magnet to simultaneously trap diamagnetic and magnetic particles in ferrofluid flows through a T-shaped microchannel. The two types of particles are preconcentrated to distinct locations of the T-junction due to the induced negative and positive magnetophoretic motions, respectively. Moreover, they can be sequentially released from their respective trapping spots by simply increasing the ferrofluid flow rate. In addition, a three-dimensional numerical model is developed, which predicts with a reasonable agreement the trajectories of diamagnetic and magnetic particles as well as the buildup of ferrofluid nanoparticles. PMID:26221197

Simultaneous diamagnetic and magnetic particle trapping in ferrofluid microflows via a single permanent magnet.

PubMed

Zhou, Yilong; Kumar, Dhileep Thanjavur; Lu, Xinyu; Kale, Akshay; DuBose, John; Song, Yongxin; Wang, Junsheng; Li, Dongqing; Xuan, Xiangchun

2015-07-01

Trapping and preconcentrating particles and cells for enhanced detection and analysis are often essential in many chemical and biological applications. Existing methods for diamagnetic particle trapping require the placement of one or multiple pairs of magnets nearby the particle flowing channel. The strong attractive or repulsive force between the magnets makes it difficult to align and place them close enough to the channel, which not only complicates the device fabrication but also restricts the particle trapping performance. This work demonstrates for the first time the use of a single permanent magnet to simultaneously trap diamagnetic and magnetic particles in ferrofluid flows through a T-shaped microchannel. The two types of particles are preconcentrated to distinct locations of the T-junction due to the induced negative and positive magnetophoretic motions, respectively. Moreover, they can be sequentially released from their respective trapping spots by simply increasing the ferrofluid flow rate. In addition, a three-dimensional numerical model is developed, which predicts with a reasonable agreement the trajectories of diamagnetic and magnetic particles as well as the buildup of ferrofluid nanoparticles.

Preparation of Ion Exchange Films for Solid-Phase Spectrophotometry and Solid-Phase Fluorometry

NASA Technical Reports Server (NTRS)

Hill, Carol M.; Street, Kenneth W.; Tanner, Stephen P.; Philipp, Warren H.

2000-01-01

Atomic spectroscopy has dominated the field of trace inorganic analysis because of its high sensitivity and selectivity. The advantages gained by the atomic spectroscopies come with the disadvantage of expensive and often complicated instrumentation. Solid-phase spectroscopy, in which the analyte is preconcentrated on a solid medium followed by conventional spectrophotometry or fluorometry, requires less expensive instrumentation and has considerable sensitivity and selectivity. The sensitivity gains come from preconcentration and the use of chromophore (or fluorophore) developers and the selectivity is achieved by use of ion exchange conditions that favor the analyte in combination with speciative chromophores. Little work has been done to optimize the ion exchange medium (IEM) associated with these techniques. In this report we present a method for making ion exchange polymer films, which considerably simplify the solid-phase spectroscopic techniques. The polymer consists of formaldehyde-crosslinked polyvinyl alcohol with polyacrylic acid entrapped therein. The films are a carboxylate weak cation exchanger in the calcium form. They are mechanically sturdy and optically transparent in the ultraviolet and visible portion of the spectrum, which makes them suitable for spectrophotometry and fluorometry.

Interference modelling, experimental design and pre-concentration steps in validation of the Fenton's reagent for pesticides determination.

PubMed

Ostra, Miren; Ubide, Carlos; Zuriarrain, Juan

2007-02-12

The determination of atrazine in real samples (commercial pesticide preparations and water matrices) shows how the Fenton's reagent can be used with analytical purposes when kinetic methodology and multivariate calibration methods are applied. Also, binary mixtures of atrazine-alachlor and atrazine-bentazone in pesticide preparations have been resolved. The work shows the way in which interferences and the matrix effect can be modelled. Experimental design has been used to optimize experimental conditions, including the effect of solvent (methanol) used for extraction of atrazine from the sample. The determination of pesticides in commercial preparations was accomplished without any pre-treatment of sample apart from evaporation of solvent; the calibration model was developed for concentration ranges between 0.46 and 11.6 x 10(-5) mol L(-1) with mean relative errors under 4%. Solid-phase extraction is used for pre-concentration of atrazine in water samples through C(18) disks, and the concentration range for determination was established between 4 and 115 microg L(-1) approximately. Satisfactory results for recuperation of atrazine were always obtained.

Determination of total selenium in food samples by d-CPE and HG-AFS.

PubMed

Wang, Mei; Zhong, Yizhou; Qin, Jinpeng; Zhang, Zehua; Li, Shan; Yang, Bingyi

2017-07-15

A dual-cloud point extraction (d-CPE) procedure was developed for the simultaneous preconcentration and determination of trace level Se in food samples by hydride generation-atomic fluorescence spectrometry (HG-AFS). The Se(IV) was complexed with ammonium pyrrolidinedithiocarbamate (APDC) in a Triton X-114 surfactant-rich phase, which was then treated with a mixture of 16% (v/v) HCl and 20% (v/v) H 2 O 2 . This converted the Se(IV)-APDC into free Se(IV), which was back extracted into an aqueous phase at the second cloud point extraction stage. This aqueous phase was analyzed directly by HG-AFS. Optimization of the experimental conditions gave a limit of detection of 0.023μgL -1 with an enhancement factor of 11.8 when 50mL of sample solution was preconcentrated to 3mL. The relative standard deviation was 4.04% (c=6.0μgL -1 , n=10). The proposed method was applied to determine the Se contents in twelve food samples with satisfactory recoveries of 95.6-105.2%. Copyright © 2016 Elsevier Ltd. All rights reserved.

A fully automated and fast method using direct sample injection combined with fused-core column on-line SPE-HPLC for determination of ochratoxin A and citrinin in lager beers.

PubMed

Lhotská, Ivona; Šatínský, Dalibor; Havlíková, Lucie; Solich, Petr

2016-05-01

A new fast and sensitive method based on on-line solid-phase extraction on a fused-core precolumn coupled to liquid chromatography with fluorescence detection has been developed for ochratoxin A (OTA) and citrinin (CIT) determination in lager beer samples. Direct injection of 100 μL filtered beer samples into an on-line SPE-HPLC system enabled fast and effective sample extraction including separation in less than 6 min. Preconcentration of OTA and CIT from beer samples was performed on an Ascentis Express RP C18 guard column (5 × 4.6 mm), particle size 2.7 μm, with a mobile phase of methanol/0.5% aqueous acetic acid pH 2.8 (30:70, v/v) at a flow rate of 2.0 mL min(-1). The flow switch from extraction column to analytical column in back-flush mode was set at 2.0 min and the separation was performed on the fused-core column Ascentis Express Phenyl-Hexyl (100 × 4.6 mm), particle size 2.7 μm, with a mobile phase acetonitrile/0.5% aqueous acetic acid pH 2.8 in a gradient elution at a flow rate of 1.0 mL min(-1) and temperature of 50 °C. Fluorescence excitation/emission detection wavelengths were set at 335/497 nm. The accuracy of the method, defined as the mean recoveries of OTA and CIT from light and dark beer samples, was in the range 98.3-102.1%. The method showed high sensitivity owing to on-line preconcentration; LOQ values were found to be 10 and 20 ng L(-1) for OTA and CIT, respectively. The found values of OTA and CIT in all tested light, dark and wheat beer samples were significantly below the maximum tolerable limits (3.0 μg kg(-1) for OTA and 2000 μg kg(-1) for CIT) set by the European Union.

Solid Phase Extraction of Trace Elements in Waterand Tissue Samples on a Mini Column with Diphenylcarbazone Impregnated Nano-TiO2 and Their Determination by Inductively Coupled Plasma Optical Emission Spectrometry

PubMed Central

Baytak, Sıtkı; Arslan, Zikri

2015-01-01

This study presents a simple, robust and environmentally friendly solid phase preconcentration procedure for multielement determination by inductively coupled plasma optical emission spectrometry (ICP-OES) using diphenylcarbazone (DPC) impregnated TiO2 nanopowder (n-TiO2). DPC was successfully impregnated onto n-TiO2 in colloidal solution. A number of elements, including Co(II), Cr(III), Cu(II), Fe(III), Mn(II) and Zn(II) were quantitatively preconcentrated from aqueous solutions between pH 8 and 8.5 at a flow rate of 2 mL min−1, and then eluted with 2 mL of 5% (v/v) HNO3. A mini-column packed with 0.12 g DPC impregnated n-TiO2 retained all elements quantitatively from up to 250 mL multielement solution (2.5 μg per analyte) affording an enrichment factor of 125. The limits of detection (LOD) for preconcentration of 50 mL blank solutions (n = 12) were 0.28, 0.15, 0.25, 0.22, 0.12, and 0.10 μg L−1 for Co, Cr, Cu, Fe, Mn, and Zn, respectively. The relative standard deviation (RSD) for five replicate determinations was 0.8, 3.4, 2.6, 2.2, 1.2 and 3.3% for Co, Cr, Cu, Fe, Mn and Zn, respectively, at 5 μg L−1 level. The method was validated with analysis of Freshwater (SRM 1643e) and Lobster hepatopancreas (TORT-2) certified reference materials, and then applied to the determination of the elements from tap water and lake water samples by ICP-OES. PMID:26236403

Speciation of chromium using reversed phase-high performance liquid chromatography coupled to different spectrometric detection methods

NASA Astrophysics Data System (ADS)

Andrle, C. M.; Jakubowski, N.; Broekaert, J. A. C.

1997-02-01

Speciation of Cr(III) and Cr(VI) based on the formation of different complexes with ammonium-pyrrolidinedithioate (APDC) in a continuous flow technique and their preconcentration using solid phase extraction (SPE) have been elaborated and applied to the analysis of waste waters from the galvanic industry. The Cr complexes were separated and determined using reversed phase-high performance liquid chromatography (RP-HPLC) coupled to different detection methods, namely UV-detection, graphite furnace-atomic absorption spectrometry (GF-AAS) and inductively coupled plasma mass spectrometry with hydraulic high pressure nebulization (HHPN/ICP-MS). After optimization the detection limits for Cr(III) and Cr(VI) of all methods are at the μg 1 -1 level and the precision in terms of RSD is 5% ( cCr = 100 μg 1 -1, N = 10). The procedure was applied to the determination of Cr(III) and Cr(VI) at the μg 1 -1 level in galvanic waste waters, and its accuracy was approved by comparing the results with those of independent methods.

Simplified transient isotachophoresis/capillary gel electrophoresis method for highly sensitive analysis of polymerase chain reaction samples on a microchip with laser-induced fluorescence detection.

PubMed

Liu, Dayu; Ou, Ziyou; Xu, Mingfei; Wang, Lihui

2008-12-19

We present a sensitive, simple and robust on-chip transient isotachophoresis/capillary gel electrophoresis (tITP/CGE) method for the analysis of polymerase chain reaction (PCR) samples. Using chloride ions in the PCR buffer and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) in the background electrolyte, respectively, as the leading and terminating electrolytes, the tITP preconcentration was coupled with CGE separation with double-T shaped channel network. The tITP/CGE separation was carried out with a single running buffer. The separation process involved only two steps that were performed continuously with the sequential switching of four voltage outputs. The tITP/CGE method showed an analysis time and a separation efficiency comparable to those of standard CGE, while the signal intensity was enhanced by factors of over 20. The limit of detection of the chip-based tITP/CGE method was estimated to be 1.1 ng/mL of DNA in 1x PCR buffer using confocal fluorescence detection following 473 nm laser excitation.

Confocal Raman Microscopy for pH-Gradient Preconcentration and Quantitative Analyte Detection in Optically Trapped Phospholipid Vesicles.

PubMed

Hardcastle, Chris D; Harris, Joel M

2015-08-04

The ability of a vesicle membrane to preserve a pH gradient, while allowing for diffusion of neutral molecules across the phospholipid bilayer, can provide the isolation and preconcentration of ionizable compounds within the vesicle interior. In this work, confocal Raman microscopy is used to observe (in situ) the pH-gradient preconcentration of compounds into individual optically trapped vesicles that provide sub-femtoliter collectors for small-volume samples. The concentration of analyte accumulated in the vesicle interior is determined relative to a perchlorate-ion internal standard, preloaded into the vesicle along with a high-concentration buffer. As a guide to the experiments, a model for the transfer of analyte into the vesicle based on acid-base equilibria is developed to predict the concentration enrichment as a function of source-phase pH and analyte concentration. To test the concept, the accumulation of benzyldimethylamine (BDMA) was measured within individual 1 μm phospholipid vesicles having a stable initial pH that is 7 units lower than the source phase. For low analyte concentrations in the source phase (100 nM), a concentration enrichment into the vesicle interior of (5.2 ± 0.4) × 10(5) was observed, in agreement with the model predictions. Detection of BDMA from a 25 nM source-phase sample was demonstrated, a noteworthy result for an unenhanced Raman scattering measurement. The developed model accurately predicts the falloff of enrichment (and measurement sensitivity) at higher analyte concentrations, where the transfer of greater amounts of BDMA into the vesicle titrates the internal buffer and decreases the pH gradient. The predictable calibration response over 4 orders of magnitude in source-phase concentration makes it suitable for quantitative analysis of ionizable compounds from small-volume samples. The kinetics of analyte accumulation are relatively fast (∼15 min) and are consistent with the rate of transfer of a polar aromatic molecule across a gel-phase phospholipid membrane.

Carbon-Based Fe₃O₄ Nanocomposites Derived from Waste Pomelo Peels for Magnetic Solid-Phase Extraction of 11 Triazole Fungicides in Fruit Samples.

PubMed

Ren, Keyu; Zhang, Wenlin; Cao, Shurui; Wang, Guomin; Zhou, Zhiqin

2018-05-06

Carbon-based Fe₃O₄ nanocomposites (C/Fe₃O₄ NCs) were synthesized by a simple one-step hydrothermal method using waste pomelo peels as the carbon precursors. The characterization results showed that they had good structures and physicochemical properties. The prepared C/Fe₃O₄ NCs could be applied as excellent and recyclable adsorbents for magnetic solid phase extraction (MSPE) of 11 triazole fungicides in fruit samples. In the MSPE procedure, several parameters including the amount of adsorbents, extraction time, the type and volume of desorption solvent, and desorption time were optimized in detail. Under the optimized conditions, the good linearity ( R ² > 0.9916), the limits of detection (LOD), and quantification (LOQ) were obtained in the range of 1⁻100, 0.12⁻0.55, and 0.39⁻1.85 μg/kg for 11 pesticides, respectively. Lastly, the proposed MSPE method was successfully applied to analyze triazole fungicides in real apple, pear, orange, peach, and banana samples with recoveries in the range of 82.1% to 109.9% and relative standard deviations (RSDs) below 8.4%. Therefore, the C/Fe₃O₄ NCs based MSPE method has a great potential for isolating and pre-concentrating trace levels of triazole fungicides in fruits.

Extraction and preconcentration of trace Al and Cr from vegetable samples by vortex-assisted ionic liquid-based dispersive liquid-liquid microextraction prior to atomic absorption spectrometric determination.

PubMed

Altunay, Nail; Yıldırım, Emre; Gürkan, Ramazan

2018-04-15

In the study, a simple, and efficient microextraction approach, which is termed as vortex-assisted ionic liquid-based dispersive liquid-liquid microextraction (VA-IL-DLLME), was developed for flame atomic absorption spectrometric analysis of aluminum (Al) and chromium (Cr) in vegetables. The method is based on the formation of anionic chelate complexes of Al(III) and Cr(VI) with o-hydroxy azo dye, at pH 6.5, and then extraction of the hydrophobic ternary complexes formed in presence of cetyltrimethylammonium bromide (CTAB) into a 125 μL volume of 1-butyl-3-methylimidazolium bis(trifluorosulfonyl)imide [C 4 mim][Tf 2 N]) as extraction solvent. Under optimum conditions, the detection limits were 0.02 µg L -1 in linear working range of 0.07-100 µg L -1 for Al(III), and 0.05 µg L -1 in linear working range of 0.2-80 µg L -1 for Cr(VI). After the validation by analysis of a certified reference material (CRM), the method was successfully applied to the determination of Al and Cr in vegetables using standard addition method. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction and derivatization of sulfonamides in river water, honey, milk, and animal plasma.

PubMed

Xu, Xu; Su, Rui; Zhao, Xin; Liu, Zhuang; Zhang, Yupu; Li, Dan; Li, Xueyuan; Zhang, Hanqi; Wang, Ziming

2011-11-30

The ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction (IL-based MADLLME) and derivatization was applied for the pretreatment of six sulfonamides (SAs) prior to the determination by high-performance liquid chromatography (HPLC). By adding methanol (disperser), fluorescamine solution (derivatization reagent) and ionic liquid (extraction solvent) into sample, extraction, derivatization, and preconcentration were continuously performed. Several experimental parameters, such as the type and volume of extraction solvent, the type and volume of disperser, amount of derivatization reagent, microwave power, microwave irradiation time, pH of sample solution, and ionic strength were investigated and optimized. When the microwave power was 240 W, the analytes could be derivatized and extracted simultaneously within 90 s. The proposed method was applied to the analysis of river water, honey, milk, and pig plasma samples, and the recoveries of analytes obtained were in the range of 95.0-110.8, 95.4-106.3, 95.0-108.3, and 95.7-107.7, respectively. The relative standard deviations varied between 1.5% and 7.3% (n=5). The results showed that the proposed method was a rapid, convenient and feasible method for the determination of SAs in liquid samples. Copyright © 2011 Elsevier B.V. All rights reserved.

Determination of neonicotinoid insecticides in environmental samples by micellar electrokinetic chromatography using solid-phase treatments.

PubMed

Ettiene, Gretty; Bauza, Roberto; Plata, María R; Contento, Ana M; Ríos, Angel

2012-10-01

A sensitive and reliable method based on MEKC has been developed and validated for trace determination of neonicotinoid insecticides (thiamethoxam, acetamiprid, and imidacloprid) and the metabolite 6-chloronicotinic acid in water and soil matrices. Optimum separation of the neonicotinoid insecticides was obtained on a 58 cm long capillary (75 μm id) using as the running electrolyte 40 mM SDS, 5 mM borate (pH 10.4), and 5% (v/v) methanol at a temperature of 25°C, a voltage of 25 kV and with hydrodynamic injection (10 s). The analysis time was less than 7 min. Prior to MEKC determination, the samples were purified and enriched by carrying out extraction-preconcentration steps. For aqueous samples, off-line SPE with a sorptive material such as Strata-X (polymeric hydrophobic sorbent) and octadecylsilane (C₁₈) was carried out to clean up and preconcentrate the insecticides. However, for soil samples, matrix solid-phase dispersion (MSPD) was applied with C₁₈ used as the dispersant. Good linearity, accuracy, and precision were obtained and the detection limits were in the range between 0.01 and 0.07 μg mL⁻¹ for river water and 0.17 and 0.37 μg g⁻¹ for soil samples. Recovery levels reached greater than 92% for all of the assayed neonicotinoids in river water samples with Strata-X. In soil matrices, the best recoveries (63-99%) were obtained with MSPD. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Binary electrokinetic separation of target DNA from background DNA primers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

James, Conrad D.; Derzon, Mark Steven

2005-10-01

This report contains the summary of LDRD project 91312, titled ''Binary Electrokinetic Separation of Target DNA from Background DNA Primers''. This work is the first product of a collaboration with Columbia University and the Northeast BioDefense Center of Excellence. In conjunction with Ian Lipkin's lab, we are developing a technique to reduce false positive events, due to the detection of unhybridized reporter molecules, in a sensitive and multiplexed detection scheme for nucleic acids developed by the Lipkin lab. This is the most significant problem in the operation of their capability. As they are developing the tools for rapidly detecting themore » entire panel of hemorrhagic fevers this technology will immediately serve an important national need. The goal of this work was to attempt to separate nucleic acid from a preprocessed sample. We demonstrated the preconcentration of kilobase-pair length double-stranded DNA targets, and observed little preconcentration of 60 base-pair length single-stranded DNA probes. These objectives were accomplished in microdevice formats that are compatible with larger detection systems for sample pre-processing. Combined with Columbia's expertise, this technology would enable a unique, fast, and potentially compact method for detecting/identifying genetically-modified organisms and multiplexed rapid nucleic acid identification. Another competing approach is the DARPA funded IRIS Pharmaceutical TIGER platform which requires many hours for operation, and an 800k$ piece of equipment that fills a room. The Columbia/SNL system could provide a result in 30 minutes, at the cost of a few thousand dollars for the platform, and would be the size of a shoebox or smaller.« less

Evaluation of needle trap micro-extraction and solid-phase micro-extraction: Obtaining comprehensive information on volatile emissions from in vitro cultures.

PubMed

Oertel, Peter; Bergmann, Andreas; Fischer, Sina; Trefz, Phillip; Küntzel, Anne; Reinhold, Petra; Köhler, Heike; Schubert, Jochen K; Miekisch, Wolfram

2018-05-14

Volatile organic compounds (VOCs) emitted from in vitro cultures may reveal information on species and metabolism. Owing to low nmol L -1 concentration ranges, pre-concentration techniques are required for gas chromatography-mass spectrometry (GC-MS) based analyses. This study was intended to compare the efficiency of established micro-extraction techniques - solid-phase micro-extraction (SPME) and needle-trap micro-extraction (NTME) - for the analysis of complex VOC patterns. For SPME, a 75 μm Carboxen®/polydimethylsiloxane fiber was used. The NTME needle was packed with divinylbenzene, Carbopack X and Carboxen 1000. The headspace was sampled bi-directionally. Seventy-two VOCs were calibrated by reference standard mixtures in the range of 0.041-62.24 nmol L -1 by means of GC-MS. Both pre-concentration methods were applied to profile VOCs from cultures of Mycobacterium avium ssp. paratuberculosis. Limits of detection ranged from 0.004 to 3.93 nmol L -1 (median = 0.030 nmol L -1 ) for NTME and from 0.001 to 5.684 nmol L -1 (median = 0.043 nmol L -1 ) for SPME. NTME showed advantages in assessing polar compounds such as alcohols. SPME showed advantages in reproducibility but disadvantages in sensitivity for N-containing compounds. Micro-extraction techniques such as SPME and NTME are well suited for trace VOC profiling over cultures if the limitations of each technique is taken into account. Copyright © 2018 John Wiley & Sons, Ltd.

Synthesis and application of Amberlite xad-4 functionalized with alizarin red-s for preconcentration and adsorption of rhodium (III)

PubMed Central

2012-01-01

A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = –1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich–Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%). PMID:23369526

Synthesis and application of Amberlite xad-4 functionalized with alizarin red-s for preconcentration and adsorption of rhodium (III).

PubMed

Sid Kalal, Hossein; Panahi, Homayon Ahmad; Hoveidi, Hassan; Taghiof, Mohammad; Menderjani, Mahnaz Taheri

2012-09-18

A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = -1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich-Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%).

Offline solid-phase extraction for preconcentration of pharmaceuticals and personal care products in environmental water and their simultaneous determination using the reversed phase high-performance liquid chromatography method.

PubMed

G Archana; Dhodapkar, Rita; Kumar, Anupama

2016-09-01

The present study reports a precise and simple offline solid-phase extraction (SPE) coupled with reversed-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous determination of five representative and commonly present pharmaceuticals and personal care products (PPCPs), a new class of emerging pollutants in the aquatic environment. The target list of analytes including ciprofloxacin, acetaminophen, caffeine benzophenone and irgasan were separated by a simple HPLC method. The column used was a reversed-phase C18 column, and the mobile phase was 1 % acetic acid and methanol (20:80 v/v) under isocratic conditions, at a flow rate of 1 mL min(-1). The analytes were separated and detected within 15 min using the photodiode array detector (PDA). The linearity of the calibration curves were obtained with correlation coefficients 0.98-0.99.The limit of detection (LOD), limit of quantification (LOQ), precision, accuracy and ruggedness demonstrated the reproducibility, specificity and sensitivity of the developed method. Prior to the analysis, the SPE was performed using a C18 cartridge to preconcentrate the targeted analytes from the environmental water samples. The developed method was applied to evaluate and fingerprint PPCPs in sewage collected from a residential engineering college campus, polluted water bodies such as Nag river and Pili river and the influent and effluent samples from a sewage treatment plant (STP) situated at Nagpur city, in the peak summer season. This method is useful for estimation of pollutants present in microquantities in the surface water bodies and treated sewage as compared to nanolevel pollutants detected by mass spectrometry (MS) detectors.

Needle Trap Device as a New Sampling and Preconcentration Approach for Volatile Organic Compounds of Herbal Medicines and its Application to the Analysis of Volatile Components in Viola tianschanica.

PubMed

Qin, Yan; Pang, Yingming; Cheng, Zhihong

2016-11-01

The needle trap device (NTD) technique is a new microextraction method for sampling and preconcentration of volatile organic compounds (VOCs). Previous NTD studies predominantly focused on analysis of environmental volatile compounds in the gaseous and liquid phases. Little work has been done on its potential application in biological samples and no work has been reported on analysis of bioactive compounds in essential oils from herbal medicines. The main purpose of the present study is to develop a NTD sampling method for profiling VOCs in biological samples using herbal medicines as a case study. A combined method of NTD sample preparation and gas chromatography-mass spectrometry was developed for qualitative analysis of VOCs in Viola tianschanica. A 22-gauge stainless steel, triple-bed needle packed with Tenax, Carbopack X and Carboxen 1000 sorbents was used for analysis of VOCs in the herb. Furthermore, different parameters affecting the extraction efficiency and capacity were studied. The peak capacity obtained by NTDs was 104, more efficient than those of the static headspace (46) and hydrodistillation (93). This NTD method shows potential to trap a wide range of VOCs including the lower and higher volatile components, while the static headspace and hydrodistillation only detects lower volatile components, and semi-volatile and higher volatile components, respectively. The developed NTD sample preparation method is a more rapid, simpler, convenient, and sensitive extraction/desorption technique for analysis of VOCs in herbal medicines than the conventional methods such as static headspace and hydrodistillation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Simultaneous in situ derivatization and ultrasound-assisted dispersive magnetic solid phase extraction for thiamine determination by spectrofluorimetry.

PubMed

Tarigh, Ghazale Daneshvar; Shemirani, Farzaneh

2014-06-01

A simple and rapid method for the simultaneous in situ derivatizaion, preconcentration and extraction of thiamine (vitamin B1) as a model analyte was developed by a novel quantitative method, namely ultrasound-assisted dispersive magnetic solid phase extraction spectrofluorimetry (USA-DMSPE-FL) from different real samples. This method consists of sample preparation, in situ derivatization, exhaustive extraction and clean up by a single process. High extraction efficiency and in situ derivatization in a short period of time is the main advantages of this procedure. For this purpose, the reusable magnetic multi-wall carbon nanotube (MMWCNT) nanocomposite was used as an adsorbent for preconcentration and determination of thiamine. Thiamine was, simultaneously, in situ derivatized as thiochrome by potassium hexacyanoferrate (III) and adsorbed on MMWCNT in an ultrasonic water bath. The MMWCNTs were then collected using an external magnetic field. Subsequently, the extracted thiochrome was washed from the surface of the adsorbent and determined by spectrofluorimetry. The developed method, which has been analytically characterized under its optimal operating conditions, allows the detection of the analyte in the samples with method detection limits of 0.37 µg L(-1). The repeatability of the method, expressed as the relative standard deviation (RSD, n=6), varies between 2.0% and 4.8% in different real samples, while the enhancement factor is 197. The proposed procedure has been applied for the determination of thiamine in biological (serum and urine), pharmaceutical (multivitamin tablet and B complex syrup) and foodstuff samples (cereal, wheat flour, banana and honey) with the good recoveries in the range from 90% to 105%. Copyright © 2014 Elsevier B.V. All rights reserved.

Cold column trapping-cloud point extraction coupled to high performance liquid chromatography for preconcentration and determination of curcumin in human urine.

PubMed

Rahimi, Marzieh; Hashemi, Payman; Nazari, Fariba

2014-05-15

A cold column trapping-cloud point extraction (CCT-CPE) method coupled to high performance liquid chromatography (HPLC) was developed for preconcentration and determination of curcumin in human urine. A nonionic surfactant, Triton X-100, was used as the extraction medium. In the proposed method, a low surfactant concentration of 0.4% v/v and a short heating time of only 2min at 70°C were sufficient for quantitative extraction of the analyte. For the separation of the extraction phase, the resulted cloudy solution was passed through a packed trapping column that was cooled to 0 °C. The temperature of the CCT column was then increased to 25°C and the surfactant rich phase was desorbed with 400μL ethanol to be directly injected into HPLC for the analysis. The effects of different variables such as pH, surfactant concentration, cloud point temperature and time were investigated and optimum conditions were established by a central composite design (response surface) method. A limit of detection of 0.066mgL(-1) curcumin and a linear range of 0.22-100mgL(-1) with a determination coefficient of 0.9998 were obtained for the method. The average recovery and relative standard deviation for six replicated analysis were 101.0% and 2.77%, respectively. The CCT-CPE technique was faster than a conventional CPE method requiring a lower concentration of the surfactant and lower temperatures with no need for the centrifugation. The proposed method was successfully applied to the analysis of curcumin in human urine samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimization of Antibody-Conjugated Magnetic Nanoparticles for Target Preconcentration and Immunoassays

DTIC Science & Technology

2010-01-01

protein, AlexaFluor647– chicken IgG (Alexa647–chick IgG). Antibody-labeled MNPs (Alexa647– chick–MNPs) were used to preconcentrate the target via magnetic...separation and as the tracer to dem- onstrate binding to slides modified with anti- chicken IgG as a capture agent. A full optimization study of the...magnetically assisted transport evanescent field fluoroimmunoassay; Alexa647–chick–MNPs, MNPs functionalized with fluorescently labeled target chicken IgG

From carbon nanostructures to high-performance sorbents for chromatographic separation and preconcentration

NASA Astrophysics Data System (ADS)

Postnov, V. N.; Rodinkov, O. V.; Moskvin, L. N.; Novikov, A. G.; Bugaichenko, A. S.; Krokhina, O. A.

2016-02-01

Information on carbon nanostructures (fullerenes, nanotubes, graphene, nanodiamond and nanodispersed active carbon) used to develop high-performance sorbents of organics and heavy metal ions from aqueous solutions is collected and analyzed. The advantages in the synthesis of hybrid carbon nanostructures and the possibilities of surface modification of these systems in order to carry out fast sorption pre-concentration are considered. Prospects for application of these materials in sorption technologies and analytical chemistry are discussed. The bibliography includes 364 references.

Displacement-dispersive liquid-liquid microextraction based on solidification of floating organic drop of trace amounts of palladium in water and road dust samples prior to graphite furnace atomic absorption spectrometry determination.

PubMed

Ghanbarian, Maryam; Afzali, Daryoush; Mostafavi, Ali; Fathirad, Fariba

2013-01-01

A new displacement-dispersive liquid-liquid microextraction method based on the solidification of floating organic drop was developed for separation and preconcentration of Pd(ll) in road dust and aqueous samples. This method involves two steps of dispersive liquid-liquid microextraction based on solidification. In Step 1, Cu ions react with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex, which is extracted by dispersive liquid-liquid microextraction based on a solidification procedure using 1-undecanol (extraction solvent) and ethanol (dispersive solvent). In Step 2, the extracted complex is first dispersed using ethanol in a sample solution containing Pd ions, then a dispersive liquid-liquid microextraction based on a solidification procedure is performed creating an organic drop. In this step, Pd(ll) replaces Cu(ll) from the pre-extracted Cu-DDTC complex and goes into the extraction solvent phase. Finally, the Pd(ll)-containing drop is introduced into a graphite furnace using a microsyringe, and Pd(ll) is determined using atomic absorption spectrometry. Several factors that influence the extraction efficiency of Pd and its subsequent determination, such as extraction and dispersive solvent type and volume, pH of sample solution, centrifugation time, and concentration of DDTC, are optimized.

Preconcentration of DNA using magnetic ionic liquids that are compatible with real-time PCR for rapid nucleic acid quantification.

PubMed

Emaus, Miranda N; Clark, Kevin D; Hinners, Paige; Anderson, Jared L

2018-04-28

Nucleic acid extraction and purification represents a major bottleneck in DNA analysis. Traditional methods for DNA purification often require reagents that may inhibit quantitative polymerase chain reaction (qPCR) if not sufficiently removed from the sample. Approaches that employ magnetic beads may exhibit lower extraction efficiencies due to sedimentation and aggregation. In this study, four hydrophobic magnetic ionic liquids (MILs) were investigated as DNA extraction solvents with the goal of improving DNA enrichment factors and compatibility with downstream bioanalytical techniques. By designing custom qPCR buffers, we directly incorporated DNA-enriched MILs including trihexyl(tetradecyl)phosphonium tris(hexafluoroacetylaceto)nickelate(II) ([P 6,6,6,14 + ][Ni(hfacac) 3 - ]), [P 6,6,6,14 + ] tris(hexafluoroacetylaceto)colbaltate(II) ([Co(hfacac) 3 - ]), [P 6,6,6,14 + ] tris(hexafluoroacetylaceto)manganate(II) ([Mn(hfacac) 3 - ]), or [P 6,6,6,14 + ] tetrakis(hexafluoroacetylaceto)dysprosate(III) ([Dy(hfacac) 4 - ]) into reaction systems, thereby circumventing the need for time-consuming DNA recovery steps. Incorporating MILs into the reaction buffer did not significantly impact the amplification efficiency of the reaction (91.1%). High enrichment factors were achieved using the [P 6,6,6,14 + ][Ni(hfacac) 3 - ] MIL for the extraction of single-stranded and double-stranded DNA with extraction times as short as 2 min. When compared to a commercial magnetic bead-based platform, the [P 6,6,6,14 + ][Ni(hfacac) 3 - ] MIL was capable of producing higher enrichment factors for single-stranded DNA and similar enrichment factors for double-stranded DNA. The MIL-based method was applied for the extraction and direct qPCR amplification of mutation prone-KRAS oncogene fragment in plasma samples. Graphical abstract Magnetic ionic liquid solvents are shown to preconcentrate sufficient KRAS DNA template from an aqueous solution in as short as 2 min without using chaotropic salts or toxic organic solvents. By using custom-designed qPCR buffers, DNA can be directly amplified and quantified from four MILs examined in this study.

Identification of trace levels of selenomethionine and related organic selenium species in high-ionic-strength waters.

PubMed

LeBlanc, Kelly L; Ruzicka, Josef; Wallschläger, Dirk

2016-02-01

A new anion-exchange chromatographic separation method was used for the simultaneous speciation analysis of selenoamino acids and the more ubiquitous inorganic selenium oxyanions, selenite and selenate. For quantification, this separation was coupled to inductively coupled plasma-mass spectrometry to achieve an instrumental detection limit of 5 ng Se L(-1) for all species. This chromatographic method was also coupled to electrospray tandem mass spectrometry to observe the negative ion mode fragmentation of selenomethionine and one of its oxidation products. Low detection limits were achieved, which were similar to those obtained using inductively coupled plasma-mass spectrometry. An extensive preconcentration and cleanup procedure using cation-exchange solid-phase extraction was developed for the identification and quantification of trace levels of selenomethionine in environmental samples. Preconcentration factors of up to five were observed for selenomethionine, which in addition to the removal of high concentrations of sulphate and chloride from industrial process waters, allowed for an unambiguous analysis that would have been impossible otherwise. Following these methods, selenomethionine was identified at an original concentration of 3.2 ng Se L(-1) in samples of effluent collected at a coal-fired power plant's biological remediation site. It is the first time that this species has been identified in the environment, outside of a biological entity. Additionally, oxidation products of selenomethionine were identified in river water and laboratory algal culture samples. High-resolution mass spectrometry was employed to postulate the chemical structures of these species.

Determination of ultratrace elements in natural waters by solid-phase extraction and atomic spectrometry methods.

PubMed

Grotti, Marco; Abelmoschi, Maria Luisa; Soggia, Francesco; Frache, Roberto

2003-01-01

A study was carried out on the preconcentration of ultratrace amounts of cadmium, lead, manganese, copper and iron from high-salinity aqueous samples and determination by atomic spectrometry methods. Sample volume, amount of resin, loading flow rate, and elution volume were optimized in order to obtain the simultaneous preconcentration of all the analytes. Quantitative recoveries were obtained by using 200 mg of iminodiacetic resin with a loading flow rate of 2 mL min(-1), elution volume of 3 mL and sample volume of 50-450 mL. Only copper in seawater samples was not completely retained by the resin (60-70% recovery), due to unfavorable competition of iminodiacetic-active groups with organically bound metal.To quantify the metals in the eluates, two atomic spectrometry techniques were compared: electrothermal atomization atomic absorption spectrometry (ETAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) with simultaneous CCD detection system. Both techniques are suitable for sample analysis with detection limits of 1.0, 4.7, 3.3, 6.8, and 53 ng L(-1) using ETAAS and 12, 122, 3.4, 17, and 21 ng L(-1) using ICP-OES for Cd, Pb, Mn, Cu, and Fe, respectively. Relative standard deviations of the procedures ranged from 1.7 to 14% at the sub-microg L(-1) concentration level. The accuracy of both methods was verified by analyzing various certified reference materials (river water, estuarine water, coastal and off-shore seawater).

The cooperative effect of reduced graphene oxide and Triton X-114 on the electromembrane microextraction efficiency of Pramipexole as a model analyte in urine samples.

PubMed

Fashi, Armin; Khanban, Fatemeh; Yaftian, Mohammad Reza; Zamani, Abbasali

2017-01-01

A new design of electromembrane microextraction coupled with high-performance liquid chromatography was developed for the determination of Pramipexole as a model analyte in urine samples. The presence of reduced graphene oxide in the membrane and Triton X-114 in the donor phase augments the extraction efficiency of Pramipexole by the proposed method. Dispersed reduced graphene oxide in the organic solvent was held in the pores of the fiber wall by capillary forces and sonication. It is possible that the immobilized reduced graphene oxide acts as a sorbent, affording an additional pathway for analyte transportation. Besides, the presence of Triton X-114 in the donor phase promotes effective migration of ionic analytes across the membrane. The parameters influencing the extraction procedure, such as type and concentration of surfactant, type of organic solvent, amount of reduced graphene oxide, sonication time, applied voltage, extraction time, ionic strength, pH of the donor and acceptor solutions, and stirring rate were optimized. The linear working ranges of the method for preconcentration- determination of Pramipexole in water and urine samples were found to be 0.13-1000 and 0.47-1000ngmL -1 with corresponding detection limits of 0.04 and 0.14ngmL -1 , respectively. The proposed method allows achieving enrichment factors of 301 and 265 for preconcentration of the analyte in water and urine samples, respectively. The method was successfully applied for the determination of Pramipexole in the urine samples. Copyright © 2016 Elsevier B.V. All rights reserved.

A solid-phase extraction method using Transcarpathian clinoptilolite for preconcentration of trace amounts of terbium in water samples.

PubMed

Vasylechko, Volodymyr O; Gryshchouk, Galyna V; Zakordonskiy, Victor P; Vyviurska, Olga; Pashuk, Andriy V

2015-01-01

In spite of the fact that terbium is one of the rarest elements in the Earth's crust, it is frequently used for the production of high technological materials. At the result, an effective combination of sample preparation procedure and detection method for terbium ions in different matrices is highly required. The solid-phase extraction procedure with natural Transcarpathian clinoptilolite thermally activated at 350 °C was used to preconcentrate trace amounts of terbium ions in aqueous solutions for a final spectrophotometric determination with arsenazo III. Thermogravimetric investigations confirmed the existence of relations between changes that appeared during dehydratation of calcined zeolite and its sorption affinity. Since the maximum of sorption capacity towards terbium was observed at pH 8.25, a borate buffer medium (2.5 · 10(-4) М) was used to maintain ionic force and solution acidity. Terbium was quantitatively removed from the solid-phase extraction column with a 1.0 M solution of sodium chloride (pH 2.5). The linearity of the proposed method was evaluated in the range of 2.5-200 ng · mL(-1) with detection limit 0.75 ng · mL(-1). Due to acceptable recoveries (93.3-102.0 %) and RSD values (6-7.1) from spiked tap water, the developed method can be successfully applied for the determination of trace amounts of terbium ions in the presence of major components of water. Graphical abstractSorption of terbium(III) ions on clinoptilolite.

Chemical preconcentrator

DOEpatents

Manginell, Ronald P.; Frye-Mason, Gregory C.

2001-01-01

A chemical preconcentrator is disclosed with applications to chemical sensing and analysis. The preconcentrator can be formed by depositing a resistive heating element (e.g. platinum) over a membrane (e.g. silicon nitride) suspended above a substrate. A coating of a sorptive material (e.g. a microporous hydrophobic sol-gel coating or a polymer coating) is formed on the suspended membrane proximate to the heating element to selective sorb one or more chemical species of interest over a time period, thereby concentrating the chemical species in the sorptive material. Upon heating the sorptive material with the resistive heating element, the sorbed chemical species are released for detection and analysis in a relatively high concentration and over a relatively short time period. The sorptive material can be made to selectively sorb particular chemical species of interest while not substantially sorbing other chemical species not of interest. The present invention has applications for use in forming high-sensitivity, rapid-response miniaturized chemical analysis systems (e.g. a "chem lab on a chip").

Permeation absorption sampler with multiple detection

DOEpatents

Zaromb, Solomon

1990-01-01

A system for detecting analytes in air or aqueous systems includes a permeation absorption preconcentrator sampler for the analytes and analyte detectors. The preconcentrator has an inner fluid-permeable container into which a charge of analyte-sorbing liquid is intermittently injected, and a fluid-impermeable outer container. The sample is passed through the outer container and around the inner container for trapping and preconcentrating the analyte in the sorbing liquid. The analyte can be detected photometrically by injecting with the sorbing material a reagent which reacts with the analyte to produce a characteristic color or fluorescence which is detected by illuminating the contents of the inner container with a light source and measuring the absorbed or emitted light, or by producing a characteristic chemiluminescence which can be detected by a suitable light sensor. The analyte can also be detected amperometrically. Multiple inner containers may be provided into which a plurality of sorbing liquids are respectively introduced for simultaneously detecting different analytes. Baffles may be provided in the outer container. A calibration technique is disclosed.

Detection biomarkers of lung cancer using mini-GC-PID system integrated with micro GC column and micro pre-concentrator

PubMed Central

2014-01-01

The survival rate of lung cancer can be significantly improved by monitoring biomarkers in exhaled air that indicate diseases in early stage, so it is very important to develop micro analytical systems which can offer a fast, on-site, real-time detecting biomarkers in exhaled air. In this paper, a mini-gas chromatography (GC)-photo-ionization detector (PID) system integrated with a micro GC column and a micro pre-concentrator was developed for forming an inexpensive, fast, and non-invasive diagnostic tool for lung cancer. This system has very strong concentrate ability owing to its integrated micro pre-concentrator, which make the detection of trace components in exhaled air very easy. In addition, the integrated micro GC column can separate complex mixtures, which overcome low resolution and poor anti-interference ability of other instruments. The results indicated that the mini-GC-PID system can effectively separate and detect the biomarkers at parts-per-billion (ppb) level. PMID:25339856

The mercury isotope composition of Arctic coastal seawater

NASA Astrophysics Data System (ADS)

Štrok, Marko; Baya, Pascale Anabelle; Hintelmann, Holger

2015-11-01

For the first time, Hg isotope composition of seawater in the Canadian Arctic Archipelago is reported. Hg was pre-concentrated from large volumes of seawater sampling using anion exchange resins onboard the research vessel immediately after collection. Elution of Hg was performed in laboratory followed by isotope composition determination by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). For comparison, seawater from two stations was shipped to the laboratory and processed within it. Results showed negative mass-dependent fractionation in the range from -2.85 to -1.10‰ for δ202Hg, as well as slightly positive mass-independent fractionation of odd Hg isotopes. Positive mass-independent fractionation of 200Hg was also observed. Samples that were pre-concentrated in the laboratory showed different Hg isotope signatures and this is most probably due to the abiotic reduction of Hg in the dark by organic matter during storage and shipment after sampling. This emphasizes the need for immediate onboard pre-concentration.

Determination of volatile components of green, black, oolong and white tea by optimized ultrasound-assisted extraction-dispersive liquid-liquid microextraction coupled with gas chromatography.

PubMed

Sereshti, Hassan; Samadi, Soheila; Jalali-Heravi, Mehdi

2013-03-08

Ultrasound assisted extraction (UAE) followed by dispersive liquid-liquid microextraction (DLLME) was used for extraction and preconcentration of volatile constituents of six tea plants. The preconcentrated compounds were analyzed by gas chromatography-mass spectrometry (GC-MS). Totally, 42 compounds were identified and caffeine was quantitatively determined. The main parameters (factors) of the extraction process were optimized by using a central composite design (CCD). Methanol and chloroform were selected as the extraction solvent and preconcentration solvent, respectively .The optimal conditions were obtained as 21 in for sonication time; 32°C for temperature; 27 L for volume of extraction solvent and 7.4% for salt concentration (NaCl/H(2)O). The determination coefficient (R(2)) was 0.9988. The relative standard deviation (RSD %) was 4.8 (n=5), and the enhancement factors (EFs) were 4.0-42.6. Copyright © 2013 Elsevier B.V. All rights reserved.

An evaluation of the bioaccessibility of arsenic in corn and rice samples based on cloud point extraction and hydride generation coupled to atomic fluorescence spectrometry.

PubMed

Castor, José Martín Rosas; Portugal, Lindomar; Ferrer, Laura; Hinojosa-Reyes, Laura; Guzmán-Mar, Jorge Luis; Hernández-Ramírez, Aracely; Cerdà, Víctor

2016-08-01

A simple, inexpensive and rapid method was proposed for the determination of bioaccessible arsenic in corn and rice samples using an in vitro bioaccessibility assay. The method was based on the preconcentration of arsenic by cloud point extraction (CPE) using o,o-diethyldithiophosphate (DDTP) complex, which was generated from an in vitro extract using polyethylene glycol tert-octylphenyl ether (Triton X-114) as a surfactant prior to its detection by atomic fluorescence spectrometry with a hydride generation system (HG-AFS). The CPE method was optimized by a multivariate approach (two-level full factorial and Doehlert designs). A photo-oxidation step of the organic species prior to HG-AFS detection was included for the accurate quantification of the total As. The limit of detection was 1.34μgkg(-1) and 1.90μgkg(-1) for rice and corn samples, respectively. The accuracy of the method was confirmed by analyzing certified reference material ERM BC-211 (rice powder). The corn and rice samples that were analyzed showed a high bioaccessible arsenic content (72-88% and 54-96%, respectively), indicating a potential human health risk. Copyright © 2016 Elsevier Ltd. All rights reserved.

Factorial design optimization of experimental variables in the on-line separation/preconcentration of copper in water samples using solid phase extraction and ICP-OES determination.

PubMed

Escudero, Luis A; Cerutti, S; Olsina, R A; Salonia, J A; Gasquez, J A

2010-11-15

An on-line preconcentration procedure using solid phase extraction (SPE) for the determination of copper in different water samples by inductively coupled plasma optical emission spectrometry (ICP-OES) is proposed. The copper was retained on a minicolumn filled with ethyl vinyl acetate (EVA) at pH 8.0 without using any complexing reagent. The experimental optimization step was performed using a two-level full factorial design. The results showed that pH, sample loading flow rate, and their interaction (at the tested levels) were statistically significant. In order to determine the best conditions for preconcentration and determination of copper, a final optimization of the significant factors was carried out using a central composite design (CCD). The calibration graph was linear with a regression coefficient of 0.995 at levels near the detection limit up to at least 300 μg L(-1). An enrichment factor (EF) of 54 with a preconcentration time of 187.5 s was obtained. The limit of detection (3σ) was 0.26 μg L(-1). The sampling frequency for the developed methodology was about 15 samples/h. The relative standard deviation (RSD) for six replicates containing 50 μg L(-1) of copper was 3.76%. The methodology was successfully applied to the determination of Cu in tap, mineral, river water samples, and in a certified VKI standard reference material. Copyright © 2010 Elsevier B.V. All rights reserved.

Method for making electro-fluidic connections in microfluidic devices

DOEpatents

Frye-Mason, Gregory C.; Martinez, David; Manginell, Ronald P.; Heller, Edwin J.; Chanchani, Rajen

2004-08-10

A method for forming electro-fluidic interconnections in microfluidic devices comprises forming an electrical connection between matching bond pads on a die containing an active electrical element and a microfluidic substrate and forming a fluidic seal ring that circumscribes the active electrical element and a fluidic feedthrough. Preferably, the electrical connection and the seal ring are formed in a single bonding step. The simple method is particularly useful for chemical microanalytical systems wherein a plurality of microanalytical components, such as a chemical preconcentrator, a gas chromatography column, and a surface acoustic wave detector, are fluidically interconnected on a hybrid microfluidic substrate having electrical connection to external support electronics.

An ICP-MS procedure to determine Cd, Co, Cu, Ni, Pb and Zn in oceanic waters using in-line flow-injection with solid-phase extraction for preconcentration.

PubMed

O'Sullivan, Jeanette E; Watson, Roslyn J; Butler, Edward C V

2013-10-15

An automated procedure including both in-line preconcentration and multi-element determination by an inductively coupled plasma mass spectrometer (ICP-MS) has been developed for the determination of Cd, Co, Cu, Ni, Pb and Zn in open-ocean samples. The method relies on flow injection of the sample through a minicolumn of chelating (iminodiacetate) sorbent to preconcentrate the trace metals, while simultaneously eliminating the major cations and anions of seawater. The effectiveness of this step is tested and reliability in results are secured with a rigorous process of quality assurance comprising 36 calibration and reference samples in a run for analysis of 24 oceanic seawaters in a 6-h program. The in-line configuration and procedures presented minimise analyst operations and exposure to contamination. Seawater samples are used for calibration providing a true matrix match. The continuous automated pH measurement registers that chelation occurs within a selected narrow pH range and monitors the consistency of the entire analytical sequence. The eluent (0.8M HNO3) is sufficiently strong to elute the six metals in 39 s at a flow rate of 2.0 mL/min, while being compatible for prolonged use with the mass spectrometer. Throughput is one sample of 7 mL every 6 min. Detection limits were Co 3.2 pM, Ni 23 pM, Cu 46 pM, Zn 71 pM, Cd 2.7 pM and Pb 1.5 pM with coefficients of variation ranging from 3.4% to 8.6% (n=14) and linearity of calibration established beyond the observed concentration range of each trace metal in ocean waters. Recoveries were Co 96.7%, Ni 102%, Cu 102%, Zn 98.1%, Cd 92.2% and Pb 97.6%. The method has been used to analyse ~800 samples from three voyages in the Southern Ocean and Tasman Sea. It has the potential to be extended to other trace elements in ocean waters. © 2013 Elsevier B.V. All rights reserved.

Preparation of a zeolite-modified polymer monolith for identification of synthetic colorants in lipsticks

NASA Astrophysics Data System (ADS)

Wang, Huiqi; Li, Zheng; Niu, Qian; Ma, Jiutong; Jia, Qiong

2015-10-01

A novel zeolite-modified poly(methacrylic acid-ethylenedimethacrylate) (zeolite@poly(MAA-EDMA)) monolithic column was prepared with the in situ polymerization method and employed in polymer monolith microextraction for the separation and preconcentration of synthetic colorants combined with high performance liquid chromatography. The polymer was characterized by scanning electronmicroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermo-gravimetric analysis. Various parameters affecting the extraction efficiency were investigated and optimized. Under the optimum experimental conditions, we obtained acceptable linearities, low limits of detection, and good intra-day/inter-day relative standard deviations. The method was applied to the determination of synthetic colorants in lipsticks with recoveries ranged from 70.7% to 109.7%. Compared with conventional methacrylic acid-based monoliths, the developed monolith exhibited high enrichment capacity because of the introduction of zeolites into the preparation process. The extraction efficiency followed the order: zeolite@poly(MAA-EDMA) > poly(MAA-EDMA) > direct HPLC analysis.

NEW COLUMN SEPARATION METHOD FOR EMERGENCY URINE SAMPLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, S; Brian Culligan, B

2007-08-28

The Savannah River Site Environmental Bioassay Lab participated in the 2007 NRIP Emergency Response program administered by the National Institute for Standards and Technology (NIST) in May, 2007. A new rapid column separation method was applied directly to the NRIP 2007 emergency urine samples, with only minimal sample preparation to reduce preparation time. Calcium phosphate precipitation, previously used to pre-concentrate actinides and Sr-90 in NRIP 2006 urine and water samples, was not used for the NRIP 2007 urine samples. Instead, the raw urine was acidified and passed directly through the stacked resin columns (TEVA+TRU+SR Resins) to separate the actinides andmore » strontium from the NRIP urine samples more quickly. This improvement reduced sample preparation time for the NRIP 2007 emergency urine analyses significantly. This approach works well for small volume urine samples expected during an emergency response event. Based on initial feedback from NIST, the SRS Environmental Bioassay Lab had the most rapid analysis times for actinides and strontium-90 analyses for NRIP 2007 urine samples.« less

Ionic Liquid-Hybrid Molecularly Imprinted Material-Filter Solid-Phase Extraction Coupled with HPLC for Determination of 6-Benzyladenine and 4-Chlorophenoxyacetic Acid in Bean Sprouts.

PubMed

Han, Yehong; Yang, Chunliu; Zhou, Yang; Han, Dandan; Yan, Hongyuan

2017-03-01

A new method involving ionic liquid-hybrid molecularly imprinted material-filter solid-phase extraction coupled to high-performance liquid chromatography (IL-HIM-FSPE-HPLC) was developed for the simultaneous isolation and determination of 6-benzyladenine (6-BA) and 4-chlorophenoxyacetic acid (4-CPA) in bean sprouts. Sample preconcentration was performed using a modified filter, with the new IL-HIM as the adsorbent, which shows double adsorption. The first adsorption involves special recognition of molecular imprinting, and the second involves ion exchange and electrostatic attraction caused by the ionic liquid. This method combines the advantages of ionic liquids, hybrid materials, and molecularly imprinted polymers and was successfully applied to determine 6-BA and 4-CPA in bean sprouts. The adsorption of 6-BA to IL-HIM is based on selective imprinted recognition, whereas the adsorption of 4-CPA is mainly dependent on ion-exchange interactions.

Ion mobility spectrometry as a detector for molecular imprinted polymer separation and metronidazole determination in pharmaceutical and human serum samples.

PubMed

Jafari, M T; Rezaei, B; Zaker, B

2009-05-01

Application of ion mobility spectrometry (IMS) as the detection technique for a separation method based on molecular imprinted polymer (MIP) was investigated and evaluated for the first time. On the basis of the results obtained in this work, the MIP-IMS system can be used as a powerful technique for separation, preconcentration, and detection of the metronidazole drug in pharmaceutical and human serum samples. The method is exhaustively validated in terms of sensitivity, selectivity, recovery, reproducibility, and column capacity. The linear dynamic range of 0.05-70.00 microg/mL was obtained for the determination of metronidazole with IMS. The recovery of analyzed drug was calculated to be above 89%, and the relative standard deviation (RSD) was lower than 6% for all experiments. Various real samples were analyzed with the coupled techniques, and the results obtained revealed the efficient cleanup of the samples using MIP separation before the analysis by IMS as a detection technique.

Surface-enhanced Raman spectroscopy detection of polybrominated diphenylethers using a portable Raman spectrometer.

PubMed

Jiang, Xiaohong; Lai, Yongchao; Wang, Wei; Jiang, Wei; Zhan, Jinhua

2013-11-15

Polybrominated diphenylethers (PBDEs), one of the most common brominated flame retardants, are toxic and persistent, generally detected by the chromatographic method. In this work, qualitative and quantitative detection of PBDEs were explored based on surface-enhanced Raman spectroscopy (SERS) technique using a portable Raman spectrometer. Alkanethiol modified silver nanoparticle aggregates were used as the substrate and PBDEs could be pre-concentrated close to the substrate surface through their hydrophobic interactions with alkanethiol. The effect of alkanethiols with different chain length on the SERS detection of PBDEs was evaluated. It was shown that 1-hexanethiol (HT) modified substrate has higher sensitivity, good stability and reusability. Qualitative and quantitative SERS detection of PBDEs in real sea water was accomplished, with the measured detection limits at 1.2×10(2) μg L(-1). These results illustrate SERS could be used as an effective method for the detection of PBDEs. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrochemical luminescence determination of hyperin using a sol-gel@graphene luminescent composite film modified electrode for solid phase microextraction

NASA Astrophysics Data System (ADS)

Zou, Xiaojun; Shang, Fang; Wang, Sui

2017-02-01

In this paper, a novel electrochemiluminescence (ECL) sensor of sol-gel@graphene luminescent composite film modified electrode for hyperin determination was prepared using graphene (G) as solid-phase microextraction (SPME) material, based on selective preconcentration of target onto an electrode and followed by luminol ECL detection. Hyperin was firstly extracted from aqueous solution through the modified GCE. Hydrogel, electrogenerated chemiluminescence reagents, pH of working solution, extraction time and temperature and scan rate were discussed. Under the optimum conditions, the change of ECL intensity was in proportion to the concentration of hyperin in the range of 0.02-0.24 μg/mL with a detection limit of 0.01 μg/mL. This method showed good performance in stability, reproducibility and precision for the determination of hyperin.

Extraction or adsorption? Voltammetric assessment of protamine transfer at ionophore-based polymeric membranes.

PubMed

Garada, Mohammed B; Kabagambe, Benjamin; Amemiya, Shigeru

2015-01-01

Cation-exchange extraction of polypeptide protamine from water into an ionophore-based polymeric membrane has been hypothesized as the origin of a potentiometric sensor response to this important heparin antidote. Here, we apply ion-transfer voltammetry not only to confirm protamine extraction into ionophore-doped polymeric membranes but also to reveal protamine adsorption at the membrane/water interface. Protamine adsorption is thermodynamically more favorable than protamine extraction as shown by cyclic voltammetry at plasticized poly(vinyl chloride) membranes containing dinonylnaphthalenesulfonate as a protamine-selective ionophore. Reversible adsorption of protamine at low concentrations down to 0.038 μg/mL is demonstrated by stripping voltammetry. Adsorptive preconcentration of protamine at the membrane/water interface is quantitatively modeled by using the Frumkin adsorption isotherm. We apply this model to ensure that stripping voltammograms are based on desorption of all protamine molecules that are transferred across the interface during a preconcentration step. In comparison to adsorption, voltammetric extraction of protamine requires ∼0.2 V more negative potentials, where a potentiometric super-Nernstian response to protamine is also observed. This agreement confirms that the potentiometric protamine response is based on protamine extraction. The voltammetrically reversible protamine extraction results in an apparently irreversible potentiometric response to protamine because back-extraction of protamine from the membrane extremely slows down at the mixed potential based on cation-exchange extraction of protamine. Significantly, this study demonstrates the advantages of ion-transfer voltammetry over potentiometry to quantitatively and mechanistically assess protamine transfer at ionophore-based polymeric membranes as foundation for reversible, selective, and sensitive detection of protamine.

Multiplexed electrokinetic sample fractionation, preconcentration and elution for proteomics.

PubMed

Hua, Yujuan; Jemere, Abebaw B; Dragoljic, Jelena; Harrison, D Jed

2013-07-07

Both 6 and 8-channel integrated microfluidic sample pretreatment devices capable of performing "in space" sample fractionation, collection, preconcentration and elution of captured analytes via sheath flow assisted electrokinetic pumping are described. Coatings and monolithic polymer beds were developed for the glass devices to provide cationic surface charge and anodal electroosmotic flow for delivery to an electrospray emitter tip. A mixed cationic ([2-(methacryloyloxy)ethyl] trimethylammonium chloride) (META) and hydrophobic butyl methacrylate-based monolithic porous polymer, photopolymerized in the 6- or 8-fractionation channels, was used to capture and preconcentrate samples. A 0.45 wt% META loaded bed generated comparable anodic electroosmotic flow to the cationic polymer PolyE-323 coated channel segments in the device. The balanced electroosmotic flow allowed stable electrokinetic sheath flow to prevent cross contamination of separated protein fractions, while reducing protein/peptide adsorption on the channel walls. Sequential elution of analytes trapped in the SPE beds revealed that the monolithic columns could be efficiently used to provide sheath flow during elution of analytes, as demonstrated for neutral carboxy SNARF (residual signal, 0.08% RSD, n = 40) and charged fluorescein (residual signal, 2.5% n = 40). Elution from monolithic columns showed reproducible performance with peak area reproducibility of ~8% (n = 6 columns) in a single sequential elution and the run-to-run reproducibility was 2.4-6.7% RSD (n = 4) for elution from the same bed. The demonstrated ability of this device design and operation to elute from multiple fractionation beds into a single exit channel for sample analysis by fluorescence or electrospray mass spectrometry is a crucial component of an integrated fractionation and assay system for proteomics.

Fe3O4/hydroxyapatite/graphene quantum dots as a novel nano-sorbent for preconcentration of copper residue in Thai food ingredients: Optimization of ultrasound-assisted magnetic solid phase extraction.

PubMed

Sricharoen, Phitchan; Limchoowong, Nunticha; Areerob, Yonrapach; Nuengmatcha, Prawit; Techawongstien, Suchila; Chanthai, Saksit

2017-07-01

Fe 3 O 4 /hydroxyapatite/graphene quantum dots (Fe 3 O 4 /HAP/GQDs) nanocomposite was synthesized and used as a novel magnetic adsorbent. This nanocomposite was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetization property. The Fe 3 O 4 /HAP/GQDs was applied to pre-concentrate copper residues in Thai food ingredients (so-called "Tom Yum Kung") prior to determination by inductively coupled plasma-atomic emission spectrometry. Based on ultrasound-assisted extraction optimization, various parameters affecting the magnetic solid-phase extraction, such as solution pH, amount of magnetic nanoparticles, adsorption and desorption time, and type of elution solvent and its concentration were evaluated. Under optimal conditions, the linear range was 0.05-1500ngmL -1 (R 2 >0.999), limit of detection was 0.58ngmL -1 , and limit of quantification was 1.94ngmL -1 . The precision, expressed as the relative standard deviation of the calibration curve slope (n=5), for intra-day and inter-day analyses was 0.87% and 4.47%, respectively. The recovery study of Cu for real samples was ranged between 83.5% and 104.8%. This approach gave the enrichment factor of 39.2, which guarantees trace analysis of Cu residues. Therefore, Fe 3 O 4 /HAP/GQDs can be a potential and suitable candidate for the pre-concentration and separation of Cu from food samples. It can easily be reused after treatment with deionized water. Copyright © 2017 Elsevier B.V. All rights reserved.