Dielectrophoretic concentration of particles under electrokinetic flow

DOEpatents

Miles, Robin R.; Bettencourt, Kerry A.; Fuller, Christopher K.

2004-09-07

The use of dielectrophoresis to collect particles under the conditions of electrokinetically-driven flow. Dielectrophortic concentration of particles under electrokinetic flow is accomplished by interdigitated electrodes patterned on an inner surface of a microfluid channel, a DC voltage is applied across the ends to the channel, and an AC voltage is applied across the electrodes, and particles swept down the channel electrokinetically are trapped within the field established by the electrodes. The particles can be released when the voltage to the electrodes is released.

REMOVAL OF RADIONUCLIDES BY ELECTROKINETIC SOIL PROCESSING

EPA Science Inventory

Electrokinetics promises to be an innovative treatment process for in-situ treatment of soils and groundwater contaminated with heavy metals and radionuclides. Electrokinetics refers to the movement of ionic liquids and charged particles relative to one another under the action ...

Microscale electrokinetic transport and stability

NASA Astrophysics Data System (ADS)

Chen, Chuan-Hua

Electrokinetics is a leading mechanism for transport and separation of biochemical samples in microdevices due to its favorable scaling at small scales. However, electrokinetic systems can become highly unstable, and this instability adversely affects key processes such as sample stacking and electrophoretic separation. This dissertation deals with two major topics: a novel planar micropump exploiting the favorable scaling of electroosmosis at the microscale, and a fundamental study of electrokinetic flow instabilities induced by electrical conductivity gradients. Electroosmotic micropumps use field-induced ion drag to drive liquids and achieve high pressures in a compact design with no moving parts. An analytical model applicable to planar, etched-structure micropumps was developed to guide the geometrical design and working fluid selection. Standard microlithography and wet etching techniques were used to fabricate a pump 1 mm long along the flow direction and 0.9 mum by 38 mm in cross section. The pump produced a maximum pressure of 0.33 atm and a maximum flow rate of 15 mul/min at 1 kV applied potential with deionized water as working fluid. The pump performance agreed well with the theoretical model. Electrokinetic flow instabilities occur under high electric field in the presence of electrical conductivity gradients. In a microfluidic T-junction 11 mum by 155 mum in cross section, aqueous electrolytes of 10:1 conductivity ratio were electrokinetically driven into a common mixing channel. Convectively unstable waves were observed at 0.5 kV/cm, and upstream propagating waves at 1.5 kV/cm. A physical model for this instability has been developed. A linear stability analysis of the governing equations in the thin-layer limit predicts both qualitative trends and quantitative features that agree well with experimental data. Briggs-Bers criteria were applied to select physically unstable modes and determine the nature of instability. Conductivity gradients and bulk

Pseudo 1-D Micro/Nanofluidic Device for Exact Electrokinetic Responses.

PubMed

Kim, Junsuk; Kim, Ho-Young; Lee, Hyomin; Kim, Sung Jae

2016-06-28

Conventionally, a 1-D micro/nanofluidic device, whose nanochannel bridged two microchannels, was widely chosen in the fundamental electrokinetic studies; however, the configuration had intrinsic limitations of the time-consuming and labor intensive tasks of filling and flushing the microchannel due to the high fluidic resistance of the nanochannel bridge. In this work, a pseudo 1-D micro/nanofluidic device incorporating air valves at each microchannel was proposed for mitigating these limitations. High Laplace pressure formed at liquid/air interface inside the microchannels played as a virtual valve only when the electrokinetic operations were conducted. The identical electrokinetic behaviors of the propagation of ion concentration polarization layer and current-voltage responses were obtained in comparison with the conventional 1-D micro/nanofluidic device by both experiments and numerical simulations. Therefore, the suggested pseudo 1-D micro/nanofluidic device owned not only experimental conveniences but also exact electrokinetic responses.

A Novel Micellar Electrokinetic Chromatographic Method for Separation of Metal-DDTC Complexes

PubMed Central

Mallah, Arfana; Memon, Saima Q.; Solangi, Amber R.; Memon, Najma; Abbassi, Kulsoom; Khuhawar, Muhammad Yar

2012-01-01

Micellar electrokinetic chromatography (MEKC) was examined for the separation and determination of Mo(VI), Cr(VI), Ni(II), Pd(II), and Co(III) as diethyl dithiocarbamate (DDTC) chelates. The separation was achieved from fused silica capillary (52 cm × 75 μm id) with effective length 40 cm, background electrolyte (BGE) borate buffer pH 9.1 (25 mM), CTAB 30% (100 mM), and 1% butanol in methanol (70 : 30 : 5 v/v/v) with applied voltage of −10 kV using reverse polarity. The photodiode array detection was achieved at 225 nm. The linear calibration for each of the element was obtained within 0.16–10 μg/mL with a limit of detection (LOD) 0.005–0.0167 μg/mL. The separation and determination was repeatable with relative standard deviation (RSD) within 2.4–3.3% (n = 4) in terms of migration time and peak height/peak area. The method was applied for the determination of Mo(VI) from potatoes and almond, Ni(II) from hydrogenated vegetable oil, and Co(III) from pharmaceutical preparations with RSD within 3.9%. The results obtained were checked by standard addition and rechecked by atomic absorption spectrometry. PMID:22649320

Marble protection: An inorganic electrokinetic approach

NASA Astrophysics Data System (ADS)

Meloni, Paola; Manca, Francesco; Carcangiu, Gianfranco

2013-05-01

The influence of an electric potential difference in an aqueous solution was studied as a method for depositing a calcium oxalate coating over a weathered carbonatic stone. Samples of weathered Carrara white marble were treated at 15 and 50 °C for 5 h in an electrokinetic cell, specifically conceived for this study, containing a solution of ammonium oxalate (4% by weight), and were subsequently characterised by scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis and mercury intrusion porosimetry. The electrokinetic treatment proved to be a cost effective and time saving process, able to produce a thick and homogeneous calcium oxalate coating over the stone surface that improves its chemical and physical resistance in low pH environments, and is able to protect the stone from the by-products of urban pollution.

Electrokinetically controlled fluid injection into unicellular microalgae.

PubMed

Zhou, Xuewen; Zhang, Xixi; Boualavong, Jonathan; Durney, Andrew R; Wang, Tonghui; Kirschner, Scott; Wentz, Michaela; Mukaibo, Hitomi

2017-10-01

Electrokinetically controlled microinjection is reported as an effective transport mechanism for microinjection into the wild-type strain of the widely studied model microalga Chlamydomonas reinhardtii. A microinjection system using glass capillary pipettes was developed to capture and impale the motile cells. To apply an electric field and induce electrokinetic flow (e.g., electrophoresis and electroosmosis), an electrode was inserted directly into the solution inside the impaling injection pipette and another electrode was inserted into the external cell media. The viability of the impaled cells was confirmed for more than an hour under 0.01 V using the fluorescein diacetate/propidium iodide dual fluorescent dye based assay. The viability was also found to increase almost logarithmically with decreasing voltage and to depend strongly on the solution within the injection pipette. Successful electrokinetic microinjection into cells was confirmed by both an increase in cell volume under an applied voltage and electric field dependent delivery of fluorescent fluorescein molecules into an impaled cell. Our study offers novel opportunities for quantitative delivery of biomolecules into microalgae and advancing the research and development of these organisms as biosynthetic factories. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability and electrokinetic potential of silicon carbide suspensions in aqueous organic media

NASA Technical Reports Server (NTRS)

Yeremenko, B. V.; Lyubchenko, I. N.; Skobets, I. Y.

1984-01-01

The method of electroosmosis was used to study the dependence of the electrokinetic potential of silicon carbide suspensions in mixtures of water -n. alcohol. The reasons for the dependence of the electrokinetic potential on the composition of the intermicellar liquid are discussed.

Pilot scale study on the ex situ electrokinetic removal of heavy metals from municipal wastewater sludges.

PubMed

Kim, Soon-Oh; Moon, Seung-Hyeon; Kim, Kyoung-Woong; Yun, Seong-Taek

2002-11-01

In order to remove toxic heavy metals from municipal wastewater sludges, the ex situ electrokinetic technique was studied at pilot scale. This study focused on the feasibility of the electrokinetic removal of heavy metals from sludge and the effectiveness of this technique on the variations of abiotic (physicochemical) and biotic (intracellular and extracellular) speciations of heavy metals using several analytical methods. Even though the sludge used was taken from a municipal wastewater treatment plant, the sludge contained relatively high concentrations of target metal contaminants (Cd = 6.8 mg/kg, Cr = 115.6 mg/kg, Cu = 338.7 mg/kg, and Pb = 62.8 mg/kg). The removal efficiencies of heavy metals were significantly dependent on their speciations in the sludge matrices. The electrokinetic removal efficiencies of abiotic heavy metals exceeded 70% for the mobile and weakly bound fractions, such as, the exchangeable and carbonate fractions and were lower than 35% for the strongly bound fractions, such as, the organic/sulfide and residual fractions. In the case of the biotic heavy metals, the removal efficiencies of the extracellular fractions were slightly higher than those of the intracellular fractions.

Electrokinetic Stabilisation Method of Soft Clay in Pure System using Electrokinetic Geosynthetic Electrode

NASA Astrophysics Data System (ADS)

Azhar, A. T. S.; Jefferson, I.; Madun, A.; Abidin, M. H. Z.; Rogers, C. D. F.

2018-04-01

Electrokinetic stabilisation (EKS) method has the ability to solve the problems of soft highly compressibility soil. This study will present the results from an experimental study of EKS on soft soils using inactive kaolinite clay, inert electrode and distilled water (DW) as a pure system mechanism before any chemical stabilisers being used in this research. Therefore, this will provide a baseline study to improve the efficiency of EKS approach. The test model was using inert electrode of Electrokinetic Geosythentic (EKG) developed at the Newcastle University to apply a constant voltage gradient of 50 V/m across a soil sample approximately 400 mm. Distilled water was used at the pore electrolyte fluid compartments supplied under zero hydraulic gradient conditions for the periods of 3, 7 and 14 days. Throughout the monitoring, physical and chemical characteristics were measured. Results from the monitoring data, physical and chemical properties of the pure system showed the development of pH gradient, the changes of electrical conductivity and chemical concentrations with regards to the distance from anode and treatment periods due to the electrochemical effects even though there was no chemical stabilisers were introduced or released from the degradation of electrodes.

Electrokinetic high pressure hydraulic system

DOEpatents

Paul, Phillip H.; Rakestraw, David J.

2000-01-01

A compact high pressure hydraulic pump having no moving mechanical parts for converting electric potential to hydraulic force. The electrokinetic pump, which can generate hydraulic pressures greater than 2500 psi, can be employed to compress a fluid, either liquid or gas, and manipulate fluid flow. The pump is particularly useful for capillary-base systems. By combining the electrokinetic pump with a housing having chambers separated by a flexible member, fluid flow, including high pressure fluids, is controlled by the application of an electric potential, that can vary with time.

Electrokinetic remediation of fluorine-contaminated soil and its impact on soil fertility.

PubMed

Zhou, Ming; Wang, Hui; Zhu, Shufa; Liu, Yana; Xu, Jingming

2015-11-01

Compared to soil pollution by heavy metals and organic pollutants, soil pollution by fluorides is usually ignored in China. Actually, fluorine-contaminated soil has an unfavorable influence on human, animals, plants, and surrounding environment. This study reports on electrokinetic remediation of fluorine-contaminated soil and the effects of this remediation technology on soil fertility. Experimental results showed that electrokinetic remediation using NaOH as the anolyte was a considerable choice to eliminate fluorine in contaminated soils. Under the experimental conditions, the removal efficiency of fluorine by the electrokinetic remediation method was 70.35%. However, the electrokinetic remediation had a significant impact on the distribution and concentrations of soil native compounds. After the electrokinetic experiment, in the treated soil, the average value of available nitrogen was raised from 69.53 to 74.23 mg/kg, the average value of available phosphorus and potassium were reduced from 20.05 to 10.39 mg/kg and from 61.31 to 51.58 mg/kg, respectively. Meanwhile, the contents of soil available nitrogen and phosphorus in the anode regions were higher than those in the cathode regions, but the distribution of soil available potassium was just the opposite. In soil organic matter, there was no significant change. These experiment results suggested that some steps should be taken to offset the impacts, after electrokinetic treatment.

Fate of zinc in an electroplating sludge during electrokinetic treatments.

PubMed

Liu, Shou-Heng; Wang, H Paul

2008-08-01

Chemical structure of zinc in the electrokinetic treatments of an electroplating sludge has been studied by in situ extended X-ray absorption fine structural (EXAFS) and X-ray absorption near edge structural (XANES) spectroscopies in the present work. The least-square fitted XANES spectra indicate that the main zinc compounds in the sludge were ZnCO(3) (75%), ZnOSiO(2) (17%) and Zn(OH)(2) (7%). Zinc in the sludge possessed a Zn-O bond distance of 2.07 A with a coordination number (CN) of 5. In the second shells, the bond distance of Zn-(O)-Si was 3.05 A (CN=2). An increase of Zn-(O)-Si (0.05 A) with a decrease of its CN (from 5 to <1) was found in the early stage of the electrokinetic treatment. Prolong the electrokinetic treatment time to 180 min, about 34% of Zn(II) was dissolved into the aqueous phase and about 68% of Zn(II) in the sludge (or 23% of total zinc) was migrated to the cathode under the electric field (5 V cm(-1)). The dissolution and electromigration rates of Zn(II) in the sludge were 1.0 and 0.6 mmol h(-1)g(-1) sludge, respectively during the electrokinetic treatment. This work also exemplifies the utilization of in situ EXAFS and XANES for revealing speciation and possible reaction pathways during the course of zinc recycling from the sludge by electrokinetic treatments.

Integrating Electrokinetic and Bioremediation Process for Treating Oil Contaminated Low Permeability Soil

NASA Astrophysics Data System (ADS)

Ramadan, Bimastyaji Surya; Effendi, Agus Jatnika; Helmy, Qomarudin

2018-02-01

Traditional oil mining activities always ignores environmental regulation which may cause contamination in soil and environment. Crude oil contamination in low-permeability soil complicates recovery process because it requires substantial energy for excavating and crushing the soil. Electrokinetic technology can be used as an alternative technology to treat contaminated soil and improve bioremediation process (biostimulation) through transfer of ions and nutrient that support microorganism growth. This study was conducted using a combination of electrokinetic and bioremediation processes. Result shows that the application of electrokinetic and bioremediation in low permeability soils can provide hydrocarbon removal efficiency up to 46,3% in 7 days operation. The highest amount of microorganism can be found in 3-days operation, which is 2x108 CFU/ml using surfactant as flushing fluid for solubilizing hydrocarbon molecules. Enhancing bioremediation using electrokinetic process is very potential to recover oil contaminated low permeability soil in the future.

Potential Electrokinetic Remediation Technologies of Laboratory Scale into Field Application- Methodology Overview

NASA Astrophysics Data System (ADS)

Ayuni Suied, Anis; Tajudin, Saiful Azhar Ahmad; Nizam Zakaria, Muhammad; Madun, Aziman

2018-04-01

Heavy metal in soil possesses high contribution towards soil contamination which causes to unbalance ecosystem. There are many ways and procedures to make the electrokinetic remediation (EKR) method to be efficient, effective, and potential as a low cost soil treatment. Electrode compartment for electrolyte is expected to treat the contaminated soil through electromigration and enhance metal ions movement. The electrokinetic is applicable for many approaches such as electrokinetic remediation (EKR), electrokinetic stabilization (EKS), electrokinetic bioremediation and many more. This paper presents a critical review on comparison of laboratory scale between EKR, EKS and EK bioremediation treatment by removing the heavy metal contaminants. It is expected to propose one framework of contaminated soil mapping. Electrical Resistivity Method (ERM) is one of famous indirect geophysical tools for surface mapping and subsurface profiling. Hence, ERM is used to mapping the migration of heavy metal ions by electrokinetic.

FEASIBILITY OF ELECTROKINETIC SOIL REMEDIATION IN HORIZONTAL LASAGNA CELLS

EPA Science Inventory

An integrated soil remediation technology called Lasagna has been developed that combines electrokinetics with treatment zones for use in low permeability soils where the rates of hydraulic and electrokinetic transport are too low to be useful for remediation of contaminants. The...

Acoustically and Electrokinetically Driven Transport in Microfluidic Devices

NASA Astrophysics Data System (ADS)

Sayar, Ersin

Electrokinetically driven flows are widely employed as a primary method for liquid pumping in micro-electromechanical systems. Mixing of analytes and reagents is limited in microfluidic devices due to the low Reynolds number of the flows. Acoustic excitations have recently been suggested to promote mixing in the microscale flow systems. Electrokinetic flows through straight microchannels were investigated using the Poisson-Boltzmann and Nernst-Planck models. The acoustic wave/fluid flow interactions in a microchannel were investigated via the development of two and three-dimensional dynamic predictive models for flows with field couplings of the electrical, mechanical and fluid flow quantities. The effectiveness and applicability of electrokinetic augmentation in flexural plate wave micropumps for enhanced capabilities were explored. The proposed concept can be exploited to integrate micropumps into complex microfluidic chips improving the portability of micro-total-analysis systems along with the capabilities of actively controlling acoustics and electrokinetics for micro-mixer applications. Acoustically excited flows in microchannels consisting of flexural plate wave devices and thin film resonators were considered. Compressible flow fields were considered to accommodate the acoustic excitations produced by a vibrating wall. The velocity and pressure profiles for different parameters including frequency, channel height, wave amplitude and length were investigated. Coupled electrokinetics and acoustics cases were investigated while the electric field intensity of the electrokinetic body forces and actuation frequency of acoustic excitations were varied. Multifield analysis of a piezoelectrically actuated valveless micropump was also presented. The effect of voltage and frequency on membrane deflection and flow rate were investigated. Detailed fluid/solid deformation coupled simulations of piezoelectric valveless micropump have been conducted to predict the

Application of Electrokinetic Stabilisation (EKS) Method for Soft Soil: A Review

NASA Astrophysics Data System (ADS)

Azhar, ATS; Azim, MAM; Syakeera, NN; Jefferson, IF; Rogers, CDF

2017-08-01

Soil properties such as low shear strength, excessive compression, collapsing behavior, high swell potential are some of the undesirable properties of soils in geotechnical engineering and those properties would cause severe distress to the structures. To solve these, an innovative stabilization of Electrokinetic (EKS) has been introduced. Electrokinetic is an applicable technique to transport charged particles and fluid in an electric potential. The EKS demonstrates changes in soil pH due to electrolysis reactions, water flow between the electrodes and migration of ions towards the cathode. This treatment has proven its efficiency in consolidating organic, peat and clayey silt as well as less expensive than other methods. Otherwise, this method also gives advantage by not disturbing site. The primary objective of this review is to discuss the application of electrokinetic and to investigate the current knowledge of electrokinetic in geotechnical application through a literature search and review, including consideration of certain aspects related to the soft soil application that may be relevant to the future study and at the same time addressing some key issues and their implications on soil behaviors.

Electrokinetic focusing injection methods on microfluidic devices.

PubMed

Fu, Lung-Ming; Yang, Ruey-Jen; Lee, Gwo-Bin

2003-04-15

This paper presents an experimental and numerical investigation into electrokinetic focusing injection on microfluidic chips. The valving characteristics on microfluidic devices are controlled through appropriate manipulations of the electric potential strengths during the sample loading and dispensing steps. The present study also addresses the design and testing of various injection systems used to deliver a sample plug. A novel double-cross injection microfluidic chip is fabricated, which employs electrokinetic focusing to deliver sample plugs of variable volume. The proposed design combines several functions of traditional sample plug injection systems on a single microfluidic chip. The injection technique uses an unique sequence of loading steps with different electric potential distributions and magnitudes within the various channels to effectuate a virtual valve.

Applications and theory of electrokinetic enrichment in micro-nanofluidic chips.

PubMed

Chen, Xueye; Zhang, Shuai; Zhang, Lei; Yao, Zhen; Chen, Xiaodong; Zheng, Yue; Liu, Yanlin

2017-09-01

This review reports the progress on the recent development of electrokinetic enrichment in micro-nanofluidic chips. The governing equations of electrokinetic enrichment in micro-nanofluidic chips are given. Various enrichment applications including protein analysis, DNA analysis, bacteria analysis, viruses analysis and cell analysis are illustrated and discussed. The advantages and difficulties of each enrichment method are expatiated. This paper will provide a particularly convenient and valuable reference to those who intend to research the electrokinetic enrichment based on micro-nanofluidic chips.

Pb2+ ions mobility perturbation by iron particles during electrokinetic remediation of contaminated soil.

PubMed

Zulfiqar, Waqas; Iqbal, Muhammad Asad; Butt, Mehwish Khalid

2017-02-01

Electrokinetic (EK) remediation is one of the most useful approaches for de-contamination of soils. However, it is unclear that how and when the electrokinetic remediation gives advantages over other remediation techniques in soil. This study was designed to find the influence of Fe 2+ particles on the mobility of Pb 2+ ions, during electrokinetic remediation, in soil contaminated purposely by lead nitrate Pb(NO 3 ) 2 . Two types of electrokinetic experiments were performed, by using iron and graphite electrodes. The Fe 2+ ions from the iron electrodes, produced due to acidic environment in anode compartment, affected the mobility of lead particles by precipitating as Fe(OH) 2 . Fe 2+ ions enhance the adsorption of lead ions in soil. The results show Fe 2+ ions of lower ionic conductivity decreased mobility of other particles in soil. Electrokinetic remediation for up to 120 h with iron electrodes is shown to be less effective for removal of lead. In contrast, graphite electrodes were 15 times more effective in lead removal from soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

A review of combinations of electrokinetic applications.

PubMed

Moghadam, Mohamad Jamali; Moayedi, Hossein; Sadeghi, Masoud Mirmohamad; Hajiannia, Alborz

2016-12-01

Anthropogenic activities contaminate many lands and underground waters with dangerous materials. Although polluted soils occupy small parts of the land, the risk they pose to plants, animals, humans, and groundwater is too high. Remediation technologies have been used for many years in order to mitigate pollution or remove pollutants from soils. However, there are some deficiencies in the remediation in complex site conditions such as low permeability and complex composition of some clays or heterogeneous subsurface conditions. Electrokinetic is an effective method in which electrodes are embedded in polluted soil, usually vertically but in some cases horizontally, and a low direct current voltage gradient is applied between the electrodes. The electric gradient initiates movement of contaminants by electromigration (charged chemical movement), electro-osmosis (movement of fluid), electrolysis (chemical reactions due to the electric field), and diffusion. However, sites that are contaminated with heavy metals or mixed contaminants (e.g. a combination of organic compounds with heavy metals and/or radionuclides) are difficult to remediate. There is no technology that can achieve the best results, but combining electrokinetic with other remediation methods, such as bioremediation and geosynthetics, promises to be the most effective method so far. This review focuses on the factors that affect electrokinetic remediation and the state-of-the-art methods that can be combined with electrokinetic.

Electrokinetics of the silica and aqueous electrolyte solution interface: Viscoelectric effects.

PubMed

Hsu, Wei-Lun; Daiguji, Hirofumi; Dunstan, David E; Davidson, Malcolm R; Harvie, Dalton J E

2016-08-01

The manipulation of biomolecules, fluid and ionic current in a new breed of integrated nanofluidic devices requires a quantitative understanding of electrokinetics at the silica/water interface. The conventional capacitor-based electrokinetic Electric Double Layer (EDL) models for this interface have some known shortcomings, as evidenced by a lack of consistency within the literature for the (i) equilibrium constants of surface silanol groups, (ii) Stern layer capacitance, (iii) zeta (ζ) potential measured by various electrokinetic methods, and (iv) surface conductivity. In this study, we consider how the experimentally observable viscoelectric effect - that is, the increase of the local viscosity due to the polarisation of polar solvents - affects electrokinetcs at the silica/water interface. Specifically we consider how a model that considers viscoelectric effects (the VE model) performs against two conventional electrokinetic models, namely the Gouy-Chapman (GC) and Basic Stern capacitance (BS) models, in predicting four fundamental electrokinetic phenomena: electrophoresis, electroosmosis, streaming current and streaming potential. It is found that at moderate to high salt concentrations (>5×10(-3)M) predictions from the VE model are in quantitative agreement with experimental electrokinetic measurements when the sole additional adjustable parameter, the viscoelectric coefficient, is set equal to a value given by a previous independent measurement. In contrast neither the GS nor BS models is able to reproduce all experimental data over the same concentration range using a single, robust set of parameters. Significantly, we also show that the streaming current and potential in the moderate to high surface charge range are insensitive to surface charge behaviour (including capacitances) when viscoelectric effects are considered, in difference to models that do not consider these effects. This strongly questions the validity of using pressure based

Lead (II) removal from natural soils by enhanced electrokinetic remediation.

PubMed

Altin, Ahmet; Degirmenci, Mustafa

2005-01-20

Electrokinetic remediation is a very effective method to remove metal from fine-grained soils having low adsorption and buffering capacity. However, remediation of soil having high alkali and adsorption capacity via the electrokinetic method is a very difficult process. Therefore, enhancement techniques are required for use in these soil types. In this study, the effect of the presence of minerals having high alkali and cation exchange capacity in natural soil polluted with lead (II) was investigated by means of the efficiency of electrokinetic remediation method. Natural soil samples containing clinoptilolite, gypsum and calcite minerals were used in experimental studies. Moreover, a sample containing kaolinite minerals was studied to compare with the results obtained from other samples. Best results for soils bearing alkali and high sorption capacity minerals were obtained upon addition of 3 mol AcH and application of 20 V constant potential after a remediation period of 220 h. In these test conditions, lead (II) removal efficiencies for these samples varied between 60% and 70% up to 0.55 normalized distance. Under the same conditions, removal efficiencies in kaolinite sample varied between 50% and 95% up to 0.9 normalized distance.

Method for eliminating gas blocking in electrokinetic pumping systems

DOEpatents

Arnold, Don W.; Paul, Phillip H.; Schoeniger, Joseph S.

2001-09-11

A method for eliminating gas bubble blockage of current flow during operation of an electrokinetic pump. By making use of the ability to modify the surface charge on the porous dielectric medium used in electrokinetic pumps, it becomes possible to place electrodes away from the pressurized region of the electrokinetic pump. While gas is still generated at the electrodes they are situated such that the generated gas can escape into a larger buffer reservoir and not into the high pressure region of the pump where the gas bubbles can interrupt current flow. Various combinations of porous dielectric materials and ionic conductors can be used to create pumps that have desirable electrical, material handling, and flow attributes.

Electrokinetic energy conversion in a finite length superhydrophobic microchannel

NASA Astrophysics Data System (ADS)

Malekidelarestaqi, M.; Mansouri, A.; Chini, S. F.

2018-07-01

We investigated the effect of superhydrophobic walls on electrokinetics phenomena in a finite-length microchannel with superhydrophobic walls (in both transient and steady-state). We implemented the effect of superhydrophobicity using Navier's slip-length. To include the importance of the electric double-layer, we scaled the slip-length with respect to Debye-length (κ-1). By increasing the slip-length from 0 to 144 nm (1.5κ-1), streaming-current, streaming-potential, flow-rate and electrokinetic energy conversion increased by 2.55, 2.44, 1.8, and 3.4 folds, accordingly. The electrokinetic energy conversion of each microchannel was in the order of picowatt. To produce more energy, an array of microchannels should be used.

Electrokinetic ion breakdown in a nanochannel

NASA Astrophysics Data System (ADS)

Wang, Jun-yao; Xu, Zheng

2016-07-01

In this paper, the electrokinetic ion breakdown in a nanochannel is investigated. The Poisson-Nernst-Planck equations are employed to simulate the influence of the voltage on the concentration. Both theoretical research and experiments show that increasing the voltage can promote the ion concentration, but high voltage will break up the repulsion effect of the electric double layer and bring the concentration down. For a given micro-nanochannel, the ion concentration has a peak value corresponding with a peak voltage. Narrowing the width of a nanochannel improves the peak voltage and the peak concentration. The results will be beneficial to research the internal discipline of electrokinetic concentration.

Direct numerical simulations of three-dimensional electrokinetic flows

NASA Astrophysics Data System (ADS)

Chiam, Keng-Hwee

2006-11-01

We discuss direct numerical simulations of three-dimensional electrokinetic flows in microfluidic devices. In particular, we focus on the study of the electrokinetic instability that develops when two solutions with different electrical conductivities are coupled to an external electric field. We characterize this ``mixing'' instability as a function of the parameters of the model, namely the Reynolds number of the flow, the electric Peclet number of the electrolyte solution, and the ratio of the electroosmotic to the electroviscous time scales. Finally, we describe how this model breaks down when the length scale of the device approaches the nanoscale, where the width of the electric Debye layer is comparable to the width of the channel, and discuss solutions to overcome this.

Removal of fluorine from contaminated soil by electrokinetic treatment driven by solar energy.

PubMed

Zhou, Ming; Zhu, Shufa; Liu, Yana; Wang, Xuejian

2013-08-01

Instead of direct current power supply, a series of electrokinetic remediation experiments driven by solar energy on fluorine-contaminated soil were conducted in a self-made electrolyzer, in order to reduce energy expenditure of electrokinetic remediation. After the 12-day electrokinetic remediation driven by solar energy, the removal efficiency of fluorine was 22.3%, and electrokinetic treatment had an impact on changes in partitioning of fluorine in soil. It proved that the combination of electrokinetics and solar energy was feasible and effective to some extent for the remediation of fluorine-contaminated soil. Meanwhile, the experimental results also indicated that the electromigration was a more dominant transport mechanism for the removal of fluorine from contaminated soil than electroosmosis, and the weather condition was the important factor in affecting the removal efficiency.

Electrokinetic high pressure hydraulic system

DOEpatents

Paul, Phillip H.; Rakestraw, David J.; Arnold, Don W.; Hencken, Kenneth R.; Schoeniger, Joseph S.; Neyer, David W.

2001-01-01

An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based systems. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (Microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

Electrokinetic high pressure hydraulic system

DOEpatents

Paul, Phillip H.; Rakestraw, David J.; Arnold, Don W.; Hencken, Kenneth R.; Schoeniger, Joseph S.; Neyer, David W.

2003-06-03

An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based system. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

Electrokinetic dispersion in microfluidic separation systems

NASA Astrophysics Data System (ADS)

Molho, Joshua Irving

Numerous efforts have focused on engineering miniaturized chemical analysis devices that are faster, more portable and consume smaller volumes of expensive reagents than their macroscale counterparts. Many of these analysis devices employ electrokinetic effects to transport picoliter volumes of liquids and to separate chemical species from an initially mixed sample volume. In these microfluidic separation systems, dispersion must be minimized to obtain the highest resolution separation possible. This work focuses on modeling, simulation and experimental measurement of two electrokinetic dispersion mechanisms that can reduce the effectiveness of microfluidic separation systems: dispersion resulting from non-uniform wall zeta-potential, and dispersion caused by microchannel turns. When the surface of a microchannel has non-uniform zeta-potential (e.g., if the surface charge varies along the length of the microchannel), an applied electric field creates both electroosmotic and pressure-driven flow. A caged-fluorescence imaging technique was used to visualize the dispersion caused by this electrokinetically induced pressure-driven flow. A simple model for a single channel with an axially varying surface charge is presented and compared to experimental measurements. Microchannel turns have been shown to create dispersion of electrokinetically transported analyte bands. Using a method of moments analysis, a model is developed that quantifies this dispersion and identifies the conditions under which turn dispersion limits the resolution of a microfluidic separation system. Measurements using the caged-fluorescence visualization technique were used to verify this model. New turn geometries are presented and were optimized using both a reduced parameter technique as well as a more generalized, numerical shape optimization approach. These improved turn designs were manufactured using two fabrication techniques and then tested experimentally. The turn optimization approaches

Evaluation of the suitability of chromatographic systems to predict human skin permeation of neutral compounds.

PubMed

Hidalgo-Rodríguez, Marta; Soriano-Meseguer, Sara; Fuguet, Elisabet; Ràfols, Clara; Rosés, Martí

2013-12-18

Several chromatographic systems (three systems of high-performance liquid chromatography and two micellar electrokinetic chromatography systems) besides the reference octanol-water partition system are evaluated by a systematic procedure previously proposed in order to know their ability to model human skin permeation. The precision achieved when skin-water permeability coefficients are correlated against chromatographic retention factors is predicted within the framework of the solvation parameter model. It consists in estimating the contribution of error due to the biological and chromatographic data, as well as the error coming from the dissimilarity between the human skin permeation and the chromatographic systems. Both predictions and experimental tests show that all correlations are greatly affected by the considerable uncertainty of the skin permeability data and the error associated to the dissimilarity between the systems. Correlations with much better predictive abilities are achieved when the volume of the solute is used as additional variable, which illustrates the main roles of both lipophilicity and size of the solute to penetrate through the skin. In this way, the considered systems are able to give precise estimations of human skin permeability coefficients. In particular, the HPLC systems with common C18 columns provide the best performances in emulating the permeation of neutral compounds from aqueous solution through the human skin. As a result, a methodology based on easy, fast, and economical HPLC measurements in a common C18 column has been developed. After a validation based on training and test sets, the method has been applied with good results to the estimation of skin permeation of several hormones and pesticides. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrokinetic-enhanced bioremediation of organic contaminants: a review of processes and environmental applications.

PubMed

Gill, R T; Harbottle, M J; Smith, J W N; Thornton, S F

2014-07-01

There is current interest in finding sustainable remediation technologies for the removal of contaminants from soil and groundwater. This review focuses on the combination of electrokinetics, the use of an electric potential to move organic and inorganic compounds, or charged particles/organisms in the subsurface independent of hydraulic conductivity; and bioremediation, the destruction of organic contaminants or attenuation of inorganic compounds by the activity of microorganisms in situ or ex situ. The objective of the review is to examine the state of knowledge on electrokinetic bioremediation and critically evaluate factors which affect the up-scaling of laboratory and bench-scale research to field-scale application. It discusses the mechanisms of electrokinetic bioremediation in the subsurface environment at different micro and macroscales, the influence of environmental processes on electrokinetic phenomena and the design options available for application to the field scale. The review also presents results from a modelling exercise to illustrate the effectiveness of electrokinetics on the supply electron acceptors to a plume scale scenario where these are limiting. Current research needs include analysis of electrokinetic bioremediation in more representative environmental settings, such as those in physically heterogeneous systems in order to gain a greater understanding of the controlling mechanisms on both electrokinetics and bioremediation in those scenarios. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Numerical framework for the modeling of electrokinetic flows

NASA Astrophysics Data System (ADS)

Deshpande, Manish; Ghaddar, Chahid; Gilbert, John R.; St. John, Pamela M.; Woudenberg, Timothy M.; Connell, Charles R.; Molho, Joshua; Herr, Amy; Mungal, Godfrey; Kenny, Thomas W.

1998-09-01

This paper presents a numerical framework for design-based analyses of electrokinetic flow in interconnects. Electrokinetic effects, which can be broadly divided into electrophoresis and electroosmosis, are of importance in providing a transport mechanism in microfluidic devices for both pumping and separation. Models for the electrokinetic effects can be derived and coupled to the fluid dynamic equations through appropriate source terms. In the design of practical microdevices, however, accurate coupling of the electrokinetic effects requires the knowledge of several material and physical parameters, such as the diffusivity and the mobility of the solute in the solvent. Additionally wall-based effects such as chemical binding sites might exist that affect the flow patterns. In this paper, we address some of these issues by describing a synergistic numerical/experimental process to extract the parameters required. Experiments were conducted to provide the numerical simulations with a mechanism to extract these parameters based on quantitative comparisons with each other. These parameters were then applied in predicting further experiments to validate the process. As part of this research, we have created NetFlow, a tool for micro-fluid analyses. The tool can be validated and applied in existing technologies by first creating test structures to extract representations of the physical phenomena in the device, and then applying them in the design analyses to predict correct behavior.

An overview of electrokinetic soil flushing and its effect on bioremediation of hydrocarbon contaminated soil.

PubMed

Ramadan, Bimastyaji Surya; Sari, Gina Lova; Rosmalina, Raden Tina; Effendi, Agus Jatnika; Hadrah

2018-07-15

Combination of electrokinetic soil flushing and bioremediation (EKSF-Bio) technology has attracted many researchers attention in the last few decades. Electrokinetic is used to increase biodegradation rate of microorganisms in soil pores. Therefore, it is necessary to use solubilizing agents such as surfactants that can improve biodegradation process. This paper describes the basic understanding and recent development associated with electrokinetic soil flushing, bioremediation, and its combination as innovative hybrid solution for treating hydrocarbon contaminated soil. Surfactant has been widely used in many studies and practical applications in remediation of hydrocarbon contaminant, but specific review about those combination technology cannot be found. Surfactants and other flushing/solubilizing agents have significant effects to increase hydrocarbon remediation efficiency. Thus, this paper is expected to provide clear information about fundamental interaction between electrokinetic, flushing agents and bioremediation, principal factors, and an inspiration for ongoing and future research benefit. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of Stern layer conductance on electrokinetic energy conversion in nanofluidic channels.

PubMed

Davidson, Christian; Xuan, Xiangchun

2008-03-01

A thermo-electro-hydro-dynamic model is developed to analytically account for the effects of Stern layer conductance on electrokinetic energy conversion in nanofluidic channels. The optimum electrokinetic devices performance is dependent on a figure of merit, in which the Stern layer conductance appears as a nondimensional Dukhin number. Such surface conductance is found to significantly reduce the figure of merit and thus the efficiency and power output. This finding may explain why the recently measured electrokinetic devices performances are far below the theoretical predictions where the effects of Stern layer conductance have been ignored.

Microbial fuel cell driving electrokinetic remediation of toxic metal contaminated soils.

PubMed

Habibul, Nuzahat; Hu, Yi; Sheng, Guo-Ping

2016-11-15

An investigation of the feasibility of in-situ electrokinetic remediation for toxic metal contaminated soil driven by microbial fuel cell (MFC) is presented. Results revealed that the weak electricity generated from MFC could power the electrokinetic remediation effectively. The metal removal efficiency and its influence on soil physiological properties were also investigated. With the electricity generated through the oxidation of organics in soils by microorganisms, the metals in the soils would mitigate from the anode to the cathode. The concentrations of Cd and Pb in the soils increased gradually through the anode to the cathode regions after remediation. After about 143days and 108 days' operation, the removal efficiencies of 31.0% and 44.1% for Cd and Pb at the anode region could be achieved, respectively. Soil properties such as pH and soil conductivity were also significantly redistributed from the anode to the cathode regions. The study shows that the MFC driving electrokinetic remediation technology is cost-effective and environmental friendly, with a promising application in soil remediation. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemometric strategy for automatic chromatographic peak detection and background drift correction in chromatographic data.

PubMed

Yu, Yong-Jie; Xia, Qiao-Ling; Wang, Sheng; Wang, Bing; Xie, Fu-Wei; Zhang, Xiao-Bing; Ma, Yun-Ming; Wu, Hai-Long

2014-09-12

Peak detection and background drift correction (BDC) are the key stages in using chemometric methods to analyze chromatographic fingerprints of complex samples. This study developed a novel chemometric strategy for simultaneous automatic chromatographic peak detection and BDC. A robust statistical method was used for intelligent estimation of instrumental noise level coupled with first-order derivative of chromatographic signal to automatically extract chromatographic peaks in the data. A local curve-fitting strategy was then employed for BDC. Simulated and real liquid chromatographic data were designed with various kinds of background drift and degree of overlapped chromatographic peaks to verify the performance of the proposed strategy. The underlying chromatographic peaks can be automatically detected and reasonably integrated by this strategy. Meanwhile, chromatograms with BDC can be precisely obtained. The proposed method was used to analyze a complex gas chromatography dataset that monitored quality changes in plant extracts during storage procedure. Copyright © 2014 Elsevier B.V. All rights reserved.

Remediation of 137Cs contaminated concrete using electrokinetic phenomena and ionic salt washes in nuclear energy contexts.

PubMed

Parker, Andrew J; Joyce, Malcolm J; Boxall, Colin

2017-10-15

This work describes the first known the use of electrokinetic treatments and ionic salt washes to remediate concrete contaminated with 137 Cs. A series of experiments were performed on concrete samples, contaminated with K + and 137 Cs, using a bespoke migration cell and an applied electric field (60V potential gradient and current limit of 35mA). Additionally, two samples were treated with an ionic salt wash (≤400molm -3 of KCl) alongside the electrokinetic treatment. The results show that the combined treatment produces removal efficiencies three times higher (>60%) than the electrokinetic treatment alone and that the decontamination efficiency appears to be proportional to the initial degree of contamination. Furthermore, the decontamination efficiencies are equivalent to previous electrokinetic studies that utilised hazardous chemical enhancement agents demonstrating the potential of the technique for use on nuclear licensed site. The results highlight the relationship between the initial contamination concentration within the concrete and achievable removal efficiency of electrokinetic treatment and other treatments. This information would be useful when selecting the most appropriate decontamination techniques for particular contamination scenarios. Copyright © 2017 Elsevier B.V. All rights reserved.

Downhole Measurements of Electrokinetic Potential to Monitor Flow in Oilfields

NASA Astrophysics Data System (ADS)

Saunders, J.; Jackson, M.; Pain, C.; Addiego-Guevara, E.

2005-12-01

Oil companies currently produce an average of three barrels of water for each barrel of oil, which is expensive and environmentally unfriendly: the produced water is contaminated and must be treated and disposed of carefully. Ideally, water production would be prevented or minimised by monitoring its movement within the reservoir and responding appropriately. We suggest that measurements of electrokinetic (or ' streaming') potential during oil production, using permanently installed downhole electrodes, could be used to monitor water encroachment towards a well before water breakthrough occurs. Electrokinetic potentials are generated when fluids flow through rock, and although they are increasingly being used in other areas of earth science to monitor subsurface flows, there has been little investigation of their utility in hydrocarbon reservoirs. We have used a new numerical model to simulate the electrokinetic potential measured at a well during oil production, with reservoir pressure maintained by water injection or aquifer influx. Our results suggest that encroaching water causes changes in the electrokinetic potential at the well which could be resolved above background electrical noise; indeed, water approaching the well could be monitored several 10s to 100s of metres away. Our results differ from those obtained previously, because we include the results of recent laboratory experiments which provide new insight into the nature of the coupling between fluid and electrokinetic potentials as the oil saturation changes. Moreover, we investigate a range of production rates which are more appropriate for modern offshore developments, and simulate the potential measured at electrodes installed at the producing well rather than at a nearby monitoring well or at the surface. Electrodes mounted downhole on insulated casing have been successfully applied in subsurface resistivity surveys during oil production, and similar technology could be used to measure

Electrokinetic Microstrirring to Enhance Immunoassays

NASA Astrophysics Data System (ADS)

Feldman, Hope; Sigurdson, Marin; Meinhart, Carl

2006-11-01

Electrokinetic microstirring is used to improve the sensitivity of microfluidic heterogeneous immuno-sensors by enhancing the transport in diffusion-limited reactions. The AC electrokinetic force, Electrothermal Flow, is exploited to create a circular stirring fluid motion, thereby providing more binding opportunities between suspended and wall-immobilized molecules. This process can significantly reduce test times, important for both field-portable biosensors and for lab-based assays. A 2-D numerical simulation model is used to predict the effect of electrothermal flow on a heterogeneous immunoassay resulting from an AC potential applied to two parallel electrodes. The binding is increased by a factor of 7 for an applied voltage of 10 Vrms. The effect was investigated experimentally using a high affinity biotin-streptavidin reaction. Microstirred reaction rates were compared with passive reactions. The measurements show on average an order of magnitude increase in binding between immobilized biotin and fluorescently-labeled streptavidin after 5 minutes. Therefore, this technique shows significant promise for reducing incubation time and enhancing the sensitivity of immunoassays.

Electrokinetic Stringency Control in Self-Assembled Monolayer-based Biosensors for Multiplex Urinary Tract Infection Diagnosis

PubMed Central

Liu, Tingting; Sin, Mandy L. Y.; Pyne, Jeff D.; Gau, Vincent; Liao, Joseph C.; Wong, Pak Kin

2013-01-01

Rapid detection of bacterial pathogens is critical toward judicious management of infectious diseases. Herein, we demonstrate an in situ electrokinetic stringency control approach for a self-assembled monolayer-based electrochemical biosensor toward urinary tract infection diagnosis. The in situ electrokinetic stringency control technique generates Joule heating induced temperature rise and electrothermal fluid motion directly on the sensor to improve its performance for detecting bacterial 16S rRNA, a phylogenetic biomarker. The dependence of the hybridization efficiency reveals that in situ electrokinetic stringency control is capable of discriminating single-base mismatches. With electrokinetic stringency control, the background noise due to the matrix effects of clinical urine samples can be reduced by 60%. The applicability of the system is demonstrated by multiplex detection of three uropathogenic clinical isolates with similar 16S rRNA sequences. The results demonstrate that electrokinetic stringency control can significantly improve the signal-to-noise ratio of the biosensor for multiplex urinary tract infection diagnosis. PMID:23891989

Simulation of electrokinetic flow in microfluidic channels

NASA Astrophysics Data System (ADS)

Sabur, Romena; Matin, M.

2005-08-01

Electrokinetic phenomena become an increasingly efficient fluid transport mechanism in micro- and nano-fluidic fields. These phenomena have also been applied successfully in microfluidic devices to achieve particle separation, pre-concentration and mixing. Electrokinetic is the flow produced by the action of an electric field on a fluid with a net charge, where the charged ions of fluid are able to drag the whole solution through the channels in the microfluidic device from one analyzing point to the other. We will present the simulation results of electrokinetic transports of fluid in various typical micro-channel geometries such as T-channel, Y-channel, cross channel and straight channel. In practice, high-speed micro-PIV technique is used to measure transient fluidic phenomena in a microfluidic channel. Particle Image Velocimetry (PIV) systems provide two- or three-dimensional velocity maps in flows using whole field techniques based on imaging the light scattered by small particles in the flow illuminated by a laser light sheet. The system generally consists of an epifluorescent microscope, CW laser and a high-speed CMOS of CCD camera. The flow of a liquid, (water for example), containing fluorescent particle is then analyzed in a counter microchannel by the highly accurate PIV method. One can then compare the simulated and experimental microfluidic flow due to electroosmotic effect.

Electrokinetic instability micromixing.

PubMed

Oddy, M H; Santiago, J G; Mikkelsen, J C

2001-12-15

We have developed an electrokinetic process to rapidly stir micro- and nanoliter volume solutions for microfluidic bioanalytical applications. We rapidly stir microflow streams by initiating a flow instability, which we have observed in sinusoidally oscillating, electroosmotic channel flows. As the effect occurs within an oscillating electroosmotic flow, we refer to it here as an electrokinetic instability (EKI). The rapid stretching and folding of material lines associated with this instability can be used to stir fluid streams with Reynolds numbers of order unity, based on channel depth and rms electroosmotic velocity. This paper presents a preliminary description of the EKI and the design and fabrication of two micromixing devices capable of rapidly stirring two fluid streams using this flow phenomenon. A high-resolution CCD camera is used to record the stirring and diffusion of fluorescein from an initially unmixed configuration. Integration of fluorescence intensity over measurement volumes (voxels) provides a measure of the degree to which two streams are mixed to within the length scales of the voxels. Ensemble-averaged probability density functions and power spectra of the instantaneous spatial intensity profiles are used to quantify the mixing processes. Two-dimensional spectral bandwidths of the mixing images are initially anisotropic for the unmixed configuration, broaden as the stirring associated with the EKI rapidly stretches and folds material lines (adding high spatial frequencies to the concentration field), and then narrow to a relatively isotropic spectrum at the well-mixed conditions.

Electrokinetically pumped high pressure sprays

DOEpatents

Schoeniger, Joseph S [Oakland, CA; Paul, Phillip H [Livermore, CA; Schoeniger, Luke [Pittsford, NY

2005-11-01

An electrokinetic pump capable of producing high pressure is combined with a nozzle having a submicron orifice to provide a high pressure spray device. Because of its small size, the device can be contained within medical devices such as an endoscope for delivering biological materials such as DNA, chemo therapeutic agents, or vaccines to tissues and cells.

Electrokinetically pumped high pressure sprays

DOEpatents

Schoeniger, Joseph S.; Paul, Phillip H.; Schoeniger, Luke

2002-01-01

An electrokinetic pump capable of producing high pressure is combined with a nozzle having a submicron orifice to provide a high pressure spray device. Because of its small size, the device can be contained within medical devices such as an endoscope for delivering biological materials such as DNA, chemo therapeutic agents, or vaccines to tissues and cells.

Assessment of electrokinetic removal of heavy metals from soils by sequential extraction analysis.

PubMed

Reddy, K R; Xu, C Y; Chinthamreddy, S

2001-06-29

Electrokinetic remediation of metal-contaminated soils is strongly affected by soil-type and chemical species of contaminants. This paper investigates the speciation and extent of migration of heavy metals in soils during electrokinetic remediation. Laboratory electrokinetic experiments were conducted using two diverse soils, kaolin and glacial till, contaminated with chromium as either Cr(III) or Cr(VI). Initial total chromium concentrations were maintained at 1000mg/kg. In addition, Ni(II) and Cd(II) were used in concentrations of 500 and 250mg/kg, respectively. The contaminated soils were subjected to a voltage gradient of 1 VDC/cm for over 200h. The extent of migration of contaminants after the electric potential application was determined. Sequential extractions were performed on the contaminated soils before and after electrokinetic treatment to provide an understanding of the distribution of the contaminants in the soils. The initial speciation of contaminants was found to depend on the soil composition as well as the type and amounts of different contaminants present. When the initial form of chromium was Cr(III), exchangeable and soluble fractions of Cr, Ni, and Cd ranged from 10 to 65% in kaolin; however, these fractions ranged from 0 to 4% in glacial till. When the initial form of chromium was Cr(VI), the exchangeable and soluble fractions of Cr, Ni and Cd ranged from 66 to 80% in kaolin. In glacial till, however, the exchangeable and soluble fraction for Cr was 38% and Ni and Cd fractions were 2 and 10%, respectively. The remainder of the contaminants existed as the complex and precipitate fractions. During electrokinetic remediation, Cr(VI) migrated towards the anode, whereas Cr(III), Ni(II) and Cd(II) migrated towards the cathode. The speciation of contaminants after electrokinetic treatment showed that significant change in exchangeable and soluble fractions occurred. In kaolin, exchangeable and soluble Cr(III), Ni(II), and Cd(II) decreased near the

Citric-acid preacidification enhanced electrokinetic remediation for removal of chromium from chromium-residue-contaminated soil.

PubMed

Meng, Fansheng; Xue, Hao; Wang, Yeyao; Zheng, Binghui; Wang, Juling

2018-02-01

Electrokinetic experiments were conducted on chromium-residue-contaminated soils collected from a chemical plant in China. Acidification-electrokinetic remediation technology was proposed in order to solve the problem of removing inefficient with ordinary electrokinetic. The results showed that electrokinetic remediation removal efficiency of chromium from chromium-contaminated soil was significantly enhanced with acidizing pretreatment. The total chromium [Cr(T)] and hexavalent chromium [Cr(VI)] removal rate of the group acidized by citric acid (0.9 mol/L) for 5 days was increased from 6.23% and 19.01% in the acid-free experiments to 26.97% and 77.66% in the acidification-treated experiments, respectively. In addition, part of chromium with the state of carbonate-combined will be converted into water-soluble state through acidification to improve the removal efficiency. Within the appropriate concentration range, the higher concentration of acid was, the more chromium was released. So the removal efficiency of chromium depended on the acid concentration. The citric acid is also a kind of complexing agent, which produced complexation with Cr that was released by the electrokinetic treatment and then enhanced the removal efficiency. The major speciation of chromium that was removed from soils by acidification-electrokinetics remediation was acid-soluble speciation, revivification speciation and oxidation speciation, which reduced biological availability of chromium.

Modeling Electrokinetic Flows by the Smoothed Profile Method

PubMed Central

Luo, Xian; Beskok, Ali; Karniadakis, George Em

2010-01-01

We propose an efficient modeling method for electrokinetic flows based on the Smoothed Profile Method (SPM) [1–4] and spectral element discretizations. The new method allows for arbitrary differences in the electrical conductivities between the charged surfaces and the the surrounding electrolyte solution. The electrokinetic forces are included into the flow equations so that the Poisson-Boltzmann and electric charge continuity equations are cast into forms suitable for SPM. The method is validated by benchmark problems of electroosmotic flow in straight channels and electrophoresis of charged cylinders. We also present simulation results of electrophoresis of charged microtubules, and show that the simulated electrophoretic mobility and anisotropy agree with the experimental values. PMID:20352076

Optimization of an electrokinetic mixer for microfluidic applications.

PubMed

Bockelmann, Hendryk; Heuveline, Vincent; Barz, Dominik P J

2012-06-01

This work is concerned with the investigation of the concentration fields in an electrokinetic micromixer and its optimization in order to achieve high mixing rates. The mixing concept is based on the combination of an alternating electrical excitation applied to a pressure-driven base flow in a meandering microchannel geometry. The electrical excitation induces a secondary electrokinetic velocity component, which results in a complex flow field within the meander bends. A mathematical model describing the physicochemical phenomena present within the micromixer is implemented in an in-house finite-element-method code. We first perform simulations comparable to experiments concerned with the investigation of the flow field in the bends. The comparison of the complex flow topology found in simulation and experiment reveals excellent agreement. Hence, the validated model and numerical schemes are employed for a numerical optimization of the micromixer performance. In detail, we optimize the secondary electrokinetic flow by finding the best electrical excitation parameters, i.e., frequency and amplitude, for a given waveform. Two optimized electrical excitations featuring a discrete and a continuous waveform are discussed with respect to characteristic time scales of our mixing problem. The results demonstrate that the micromixer is able to achieve high mixing degrees very rapidly.

Optimization of an electrokinetic mixer for microfluidic applications

PubMed Central

Bockelmann, Hendryk; Heuveline, Vincent; Barz, Dominik P. J.

2012-01-01

This work is concerned with the investigation of the concentration fields in an electrokinetic micromixer and its optimization in order to achieve high mixing rates. The mixing concept is based on the combination of an alternating electrical excitation applied to a pressure-driven base flow in a meandering microchannel geometry. The electrical excitation induces a secondary electrokinetic velocity component, which results in a complex flow field within the meander bends. A mathematical model describing the physicochemical phenomena present within the micromixer is implemented in an in-house finite-element-method code. We first perform simulations comparable to experiments concerned with the investigation of the flow field in the bends. The comparison of the complex flow topology found in simulation and experiment reveals excellent agreement. Hence, the validated model and numerical schemes are employed for a numerical optimization of the micromixer performance. In detail, we optimize the secondary electrokinetic flow by finding the best electrical excitation parameters, i.e., frequency and amplitude, for a given waveform. Two optimized electrical excitations featuring a discrete and a continuous waveform are discussed with respect to characteristic time scales of our mixing problem. The results demonstrate that the micromixer is able to achieve high mixing degrees very rapidly. PMID:22712034

Effect of various electrokinetic treatment regimes on solids surface properties and thermal behavior of oil sediments.

PubMed

Kariminezhad, Esmaeel; Elektorowicz, Maria

2018-04-10

The electrokinetic process has shown its ability to separate the different material phases. However, not much is known about the effect of the electric fields on the surface properties of solids in the oil sediments and their behavior under different electrical regimes. In this study, the effect of four different types of electrical current on the surface properties of oil sediments was investigated, namely constant direct current (CDC), pulsed direct current (PDC), incremental direct current (IDC) and decremental direct current (DDC). X-ray photoelectron spectroscopy (XPS) analyses showed a decrease in the concentration of carbon from 99% in centrifuged samples to 63% on the surface of the solids in the PDC-treated oil sediment. Wettability alteration and contact angle studies showed an enhance in hydrophilicity of the solids following electrokinetic treatment. A significant change in carbon and oxygen-containing functionalities at the surface solids of the DDC-treated sediment was also observed. Thermogravimetric analyses (TGA) confirmed the ability of electrokinetic treatment in separating the phases by shifting the thermogram profiles towards lower temperatures. The findings showed that the electrokinetic process exerts its effect by altering the surface properties of the sediment solids and destabilizing water-in-oil emulsions to facilitate phase separation of this complex waste. Copyright © 2018 Elsevier B.V. All rights reserved.

Enhanced electrokinetic remediation of lead-contaminated soil by complexing agents and approaching anodes.

PubMed

Zhang, Tao; Zou, Hua; Ji, Minhui; Li, Xiaolin; Li, Liqiao; Tang, Tang

2014-02-01

Optimizing process parameters that affect the remediation time and power consumption can improve the treatment efficiency of the electrokinetic remediation as well as determine the cost of a remediation action. Lab-scale electrokinetic remediation of Pb-contaminated soils was investigated for the effect of complexant ethylenediaminetetraacetic acid (EDTA) and acetic acid and approaching anode on the removal efficiency of Pb. When EDTA was added to the catholyte, EDTA dissolved insoluble Pb in soils to form soluble Pb-EDTA complexes, increasing Pb mobility and accordingly removal efficiency. The removal efficiency was enhanced from 47.8 to 61.5 % when the EDTA concentration was increased from 0.1 to 0.2 M, showing that EDTA played an important role in remediation. And the migration rate of Pb was increased to 72.3 % when both EDTA and acetic acid were used in the catholyte. The "approaching anode electrokinetic remediation" process in the presence of both EDTA and acetic acid had a higher Pb-removal efficiency with an average efficiency of 83.8 %. The efficiency of electrokinetic remediation was closely related to Pb speciation. Exchangeable and carbonate-bounded Pb were likely the forms which could be removed. All results indicate that the approaching anode method in the presence of EDTA and acetic acid is an advisable choice for electrokinetic remediation of Pb-contaminated soil.

Uncertainty Quantification of Nonlinear Electrokinetic Response in a Microchannel-Membrane Junction

NASA Astrophysics Data System (ADS)

Alizadeh, Shima; Iaccarino, Gianluca; Mani, Ali

2015-11-01

We have conducted uncertainty quantification (UQ) for electrokinetic transport of ionic species through a hybrid microfluidic system using different probabilistic techniques. The system of interest is an H-configuration consisting of two parallel microchannels that are connected via a nafion junction. This system is commonly used for ion preconcentration and stacking by utilizing a nonlinear response at the channel-nafion junction that leads to deionization shocks. In this work, the nafion medium is modeled as many parallel nano-pores where, the nano-pore diameter, nafion porosity, and surface charge density are independent random variables. We evaluated the resulting uncertainty on the ion concentration fields as well as the deionization shock location. The UQ methods predicted consistent statistics for the outputs and the results revealed that the shock location is weakly sensitive to the nano-pore surface charge and primarily driven by nano-pore diameters. The present study can inform the design of electrokinetic networks with increased robustness to natural manufacturing variability. Applications include water desalination and lab-on-a-chip systems. Shima is a graduate student in the department of Mechanical Engineering at Stanford University. She received her Master's degree from Stanford in 2011. Her research interests include Electrokinetics in porous structures and high performance computing.

The transport behavior of As, Cu, Pb, and Zn during electrokinetic remediation of a contaminated soil using electrolyte conditioning

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

Yang, Jung-Seok; Kwon, Man Jae; Choi, Jaeyoung

2014-12-01

Electrokinetic remediation (also known as electrokinetics) is a promising technology for removing metals from fine-grained soils. However, few studies have been conducted regarding the transport behavior of multi-metals during electrokinetics. We investigated the transport of As, Cu, Pb, and Zn from soils during electrokinetics, the metal fractionation before and after electrokinetics, the relationships between metal transport and fractionation, and the effects of electrolyte conditioning. The main transport mechanisms of the metals were electroosmosis and electromigration during the first two weeks and electromigration during the following weeks. The direction of electroosmotic flow was from the anode to the cathode, and themore » metals in the dissolved and reducible-oxides fractions were transported to the anode or cathode by electromigration according to the chemical speciation of the metal ions in the pore water. Moreover, a portion of the metals that were initially in the residual fraction transitioned to the reducible and soluble fractions during electrokinetic treatment. However, this alteration was slow and resulted in decreasing metal removal rates as the electrokinetic treatment progressed. In addition, the use of NaOH, H3PO4, and Na2SO4 as electrolytes resulted in conditions that favored the precipitation of metal hydroxides, phosphates, and sulfates in the soil. These results demonstrated that metal removal was affected by the initial metal fractionation, metal speciation in the pore solution, and the physical–chemical parameters of the electrolytes, such as pH and electrolyte composition. Therefore, the treatment time, use of chemicals, and energy consumption could be reduced by optimizing pretreatment and by choosing appropriate electrolytes for the target metals.« less

Remediating ethylbenzene-contaminated clayey soil by a surfactant-aided electrokinetic (SAEK) process.

PubMed

Yuan, Ching; Weng, Chih-Huang

2004-10-01

The objectives of this research are to investigate the remediation efficiency and electrokinetic behavior of ethylbenzene-contaminated clay by a surfactant-aided electrokinetic (SAEK) process under a potential gradient of 2 Vcm(-1). Experimental results indicated that the type of processing fluids played a key role in determining the removal performance of ethylbenzene from clay in the SAEK process. A mixed surfactant system consisted of 0.5% SDS and 2.0% PANNOX 110 showed the best performance of ethylbenzene removed in the SAEK system. The removal efficiency of ethylbenzene was determined to be 63-98% in SAEK system while only 40% was achieved in an electrokinetic system with tap water as processing fluid. It was found that ethylbenzene was accumulated in the vicinity of anode in an electrokinetic system with tap water as processing fluid. However, the concentration front of ethylbenzene was shifted toward cathode in the SAEK system. The electroosmotic permeability and power consumption were 0.17 x 10(-6)-3.01 x 10(-6) cm(2)V(-1)s(-1) and 52-123 kW h m(-3), respectively. The cost, including the expense of energy and surfactants, was estimated to be 5.15-12.65 USD m(-3) for SAEK systems, which was 2.0-4.9 times greater than that in the system of electrokinetic alone (2.6 USD m(-3)). Nevertheless, by taking the remediation efficiency of ethylbenzene and the energy expenditure into account for the overall process performance evaluation, the system SAEK was still a cost-effective alternative treatment method.

Determination of rock properties by low-frequency AC electrokinetics

NASA Astrophysics Data System (ADS)

Pengra, David B.; Xi Li, Sidney; Wong, Po-Zen

1999-12-01

In brine-saturated rock the existence of a mobile space charge at the fluid/solid interface leads to the electrokinetic phenomena of electroosmotic pressure and streaming potential. The coupling coefficients of these electrokinetic effects, when combined with the conductivity of the brine-saturated rock, determine the brine permeability of rock exactly. A sensitive low-frequency AC technique has been used to measure electrokinetic response of a collection of eight rock and four glass bead samples saturated with NaCl brine as a function of salt concentration (fluid conductivity of 0.5 to 6.38 S/m); the response of four of the original 12 samples has also been measured as a function of temperature from 0° to 50°C. All data verify the predicted permeability relationship. Additionally, the frequency response of the electroosmotic pressure signal alone can also be used to determine the permeability, given knowledge of experimental parameters. The concentration and temperature dependence of electroosmosis and streaming potential is found to mostly conform to the predictions of a simple model based on the Helmholtz-Smoluchowski equation, the Stern model of the electrochemical double layer, and an elementary theory of ionic conduction.

MICELLAR ELECTROKINETIC CHROMATOGRAPHY-MASS SPECTROMETRY (R823292)

EPA Science Inventory

The combination of micellar electrokinetic chromatography (MEKC) with mass spectrometry (MS) is very attractive for the direct identification of analyte molecules, for the possibility of selectivity enhancement, and for the structure confirmation and analysis in a MS-MS mode. The...

Electrokinetic stringency control in self-assembled monolayer-based biosensors for multiplex urinary tract infection diagnosis.

PubMed

Liu, Tingting; Sin, Mandy L Y; Pyne, Jeff D; Gau, Vincent; Liao, Joseph C; Wong, Pak Kin

2014-01-01

Rapid detection of bacterial pathogens is critical toward judicious management of infectious diseases. Herein, we demonstrate an in situ electrokinetic stringency control approach for a self-assembled monolayer-based electrochemical biosensor toward urinary tract infection diagnosis. The in situ electrokinetic stringency control technique generates Joule heating induced temperature rise and electrothermal fluid motion directly on the sensor to improve its performance for detecting bacterial 16S rRNA, a phylogenetic biomarker. The dependence of the hybridization efficiency reveals that in situ electrokinetic stringency control is capable of discriminating single-base mismatches. With electrokinetic stringency control, the background noise due to the matrix effects of clinical urine samples can be reduced by 60%. The applicability of the system is demonstrated by multiplex detection of three uropathogenic clinical isolates with similar 16S rRNA sequences. The results demonstrate that electrokinetic stringency control can significantly improve the signal-to-noise ratio of the biosensor for multiplex urinary tract infection diagnosis. Urinary tract infections remain a significant cause of mortality and morbidity as secondary conditions often related to chronic diseases or to immunosuppression. Rapid and sensitive identification of the causative organisms is critical in the appropriate management of this condition. These investigators demonstrate an in situ electrokinetic stringency control approach for a self-assembled monolayer-based electrochemical biosensor toward urinary tract infection diagnosis, establishing that such an approach significantly improves the biosensor's signal-to-noise ratio. © 2013.

Electrokinetic transport of aerobic microorganisms under low-strength electric fields.

PubMed

Maillacheruvu, Krishnanand Y; Chinchoud, Preethi R

2011-01-01

To investigate the feasibility of utilizing low strength electric fields to transport commonly available mixed cultures such as those from an activated sludge process, bench scale batch reactor studies were conducted in sand and sandy loam soils. A readily biodegradable substrate, dextrose, was used to test the activity of the transported microorganisms. Electric field strengths of 7V, 10.5V, and 14V were used. Results from this investigation showed that an electric field strength of 0.46 Volts per cm was sufficient to transport activated sludge microorganisms across a sandy loam soil across a distance of about 8 cm in 72 h. More importantly, the electrokinetically transported microbial culture remained active and viable after the transport process and was biodegrade 44% of the dextrose in the soil medium. Electrokinetic treatment without microorganisms resulted in removal of 37% and the absence of any treatment yielded a removal of about 15%.

Electrokinetic Particle Aggregation and Flow Instabilities in Non-Dilute Colloidal Suspensions

NASA Astrophysics Data System (ADS)

Navaneetham, Guru; Posner, Jonathan

2007-11-01

An experimental investigation of electrokinetic particle aggregation and flow instabilities of non-dilute colloidal suspensions in microfabricated channels is presented. The addition of charged colloidal particles can alter the solution's conductivity, permittivity as well as the average particle electrophoretic mobility. In this work, a colloid volume fraction gradient is achieved at the intersection of a Y-shaped PDMS microchannel. The solution conductivity and the particle mobility as a function of the particle (500 nm polystyrene) volume fraction are presented. The critical conditions required for particle aggregation and flow instability are given along with a scaling analysis which shows that the flow becomes unstable at a critical electric Rayleigh number for a wide range of applied electric fields and colloid volume fractions. Electrokinetic particle aggregation and instabilities of non-dilute colloidal suspensions may be important for applications such as the electrophoretic deposition of particles to form micropatterned colloidal assemblies, electrorheological devices, and on-chip, electrokinetic manipulation of colloids.

Selective Label-free Electrokinetic Cell Tracker (SELECT): a novel liquid platform for cell characterization

NASA Astrophysics Data System (ADS)

Taruvai Kalyana Kumar, Rajeshwari; de Mello Gindri, Izabelle; Kinnamon, David; Kanchustambham, Pradyotha; Rodrigues, Danieli; Prasad, Shalini; BiomaterialsOsseointegration; Novel Engineering Lab Collaboration

2015-03-01

Characterization and analysis of rare cells provide critical cues for early diagnosis of diseases. Electrokinetic cell separation has been previously established to have greater efficiency when compared to traditional flow cytometry methods. It has been shown by many researchers that buffer solutions in which cells are suspended in, have enormous effects on producing required dielectrophoretic (DEP) forces to characterize cells. Most commonly used suspension buffers used are deionized water and cell media. However, these solutions exhibit high level of intrinsic noise, which greatly masks the electrokinetic signals from cells under study. Ionic liquids (ILs) show promise towards the creation of conductive fluids with required electrical properties. The goal of this project is to design and test ILs for enhancing DEP forces on cells while creating an environment for preserving their integrity. We analyzed two methylimidazolium based ILs as suspension medium for cell separation. These dicationic ILs possess slight electrical and structural differences with high thermal stability. The two ILs were tested for cytotoxicity using HeLa and bone cells. The effects of electrical neutrality, free charge screening due to ILs towards enhanced electrokinetic signals from cells were studied with improved system resolution and no harmful effects.

Nonequilibrium electrokinetic effects in beds of ion-permselective particles.

PubMed

Leinweber, Felix C; Tallarek, Ulrich

2004-12-21

Electrokinetic transport of fluorescent tracer molecules in a bed of porous glass beads was investigated by confocal laser scanning microscopy. Refractive index matching between beads and the saturating fluid enabled a quantitative analysis of intraparticle and extraparticle fluid-side concentration profiles. Kinetic data were acquired for the uptake and release of electroneutral and counterionic tracer under devised conditions with respect to constant pressure-driven flow through the device and the effect of superimposed electrical fields. Transport of neutral tracer is controlled by intraparticle mass transfer resistance which can be strongly reduced by electroosmotic flow, while steady-state distributions and bead-averaged concentrations are unaffected by the externally applied fields. Electrolytes of low ionic strength caused the transport through the charged (mesoporous) beads to become highly ion-permselective, and concentration polarization is induced in the bulk solution due to the superimposed fields. The depleted concentration polarization zone comprises extraparticle fluid-side mass transfer resistance. Ionic concentrations in this diffusion boundary layer decrease at increasing field strength, and the flux densities approach an upper limit. Meanwhile, intraparticle transport of counterions by electromigration and electroosmosis continues to increase and finally exceeds the transport from bulk solution into the beads. A nonequilibrium electrical double layer is induced which consists of mobile and immobile space charge regions in the extraparticle bulk solution and inside a bead, respectively. These electrical field-induced space charges form the basis for nonequilibrium electrokinetic phenomena. Caused by the underlying transport discrimination (intraparticle electrokinetic vs extraparticle boundary-layer mass transfer), the dynamic adsorption capacity for counterions can be drastically reduced. Further, the extraparticle mobile space charge region

Development of microtitre plates for electrokinetic assays

NASA Astrophysics Data System (ADS)

Burt, J. P. H.; Goater, A. D.; Menachery, A.; Pethig, R.; Rizvi, N. H.

2007-02-01

Electrokinetic processes have wide ranging applications in microsystems technology. Their optimum performance at micro and nano dimensions allows their use both as characterization and diagnostic tools and as a means of general particle manipulation. Within analytical studies, measurement of the electrokinesis of biological cells has the sensitivity and selectivity to distinguish subtle differences between cell types and cells undergoing changes and is gaining acceptance as a diagnostic tool in high throughput screening for drug discovery applications. In this work the development and manufacture of an electrokinetic-based microtitre plate is described. The plate is intended to be compatible with automated sample loading and handling systems. Manufacturing of the microtitre plate, which employs indium tin oxide microelectrodes, has been entirely undertaken using excimer and ultra-fast pulsed laser micromachining due to its flexibility in materials processing and accuracy in microstructuring. Laser micromachining has the ability to rapidly realize iterations in device prototype design while also having the capability to be scaled up for large scale manufacture. Device verification is achieved by the measurement of the electrorotation and dielectrophoretic properties of yeast cells while the flexibility of the developed microtitre plate is demonstrated by the selective separation of live yeast from polystyrene microbeads.

Electrokinetic phenomena and dielectrophoresis in charged colloidal suspensions

NASA Astrophysics Data System (ADS)

Huang, J. P.; Karttunen, Mikko; Yu, K. W.; Dong, L.

2003-03-01

AC electrokinetic phenomena, i.e., electrorotation, dielectrophoresis and traveling wave dielectrophoresis, have gained an increasing amount of attention. This is due to their wide range of applications from cancer research to identifying and separating parasites, cell populations and viruses, and even to design of nanomotors. Despite the number of applications, there is need for a theory that treats the different aspects of electrokinetic phenomena on an equal footing starting from the general underlying physical principles. Here, we present a theoretical study of dielectrophoretic (DEP) crossover spectrum of two polarizable particles under the action of a nonuniform AC electric field. For two approaching particles, the mutual polarization interaction yields a change in their respective dipole moments, and hence, in the DEP crossover spectrum. We use the multiple image method to study the induced polarization effects and using spectral representation theory, an analytic expression for the DEP force is derived. Our results shows that the mutual polarization effects can change the crossover frequency at which the DEP force changes sign. The results are in agreement with recent experimental observations. Importantly, this approach goes beyond the standard theory and helps to clarify the important question of the underlying polarization mechanisms. The extension to dense systems and relation to electrorotation is discussed.

Modeling Aquatic Toxicity through Chromatographic Systems.

PubMed

Fernández-Pumarega, Alejandro; Amézqueta, Susana; Farré, Sandra; Muñoz-Pascual, Laura; Abraham, Michael H; Fuguet, Elisabet; Rosés, Martí

2017-08-01

Environmental risk assessment requires information about the toxicity of the growing number of chemical products coming from different origins that can contaminate water and become toxicants to aquatic species or other living beings via the trophic chain. Direct toxicity measurements using sensitive aquatic species can be carried out but they may become expensive and ethically questionable. Literature refers to the use of chromatographic measurements that correlate to the toxic effect of a compound over a specific aquatic species as an alternative to get toxicity information. In this work, we have studied the similarity in the response of the toxicity to different species and we have selected eight representative aquatic species (including tadpoles, fish, water fleas, protozoan, and bacteria) with known nonspecific toxicity to chemical substances. Next, we have selected four chromatographic systems offering good perspectives for surrogation of the eight selected aquatic systems, and thus prediction of toxicity from the chromatographic measurement. Then toxicity has been correlated to the chromatographic retention factor. Satisfactory correlation results have been obtained to emulate toxicity in five of the selected aquatic species through some of the chromatographic systems. Other aquatic species with similar characteristics to these five representative ones could also be emulated by using the same chromatographic systems. The final aim of this study is to model chemical products toxicity to aquatic species by means of chromatographic systems to reduce in vivo testing.

Effect of alternating bioremediation and electrokinetics on the remediation of n-hexadecane-contaminated soil

PubMed Central

Wang, Sa; Guo, Shuhai; Li, Fengmei; Yang, Xuelian; Teng, Fei; Wang, Jianing

2016-01-01

This study demonstrated the highly efficient degradation of n-hexadecane in soil, realized by alternating bioremediation and electrokinetic technologies. Using an alternating technology instead of simultaneous application prevented competition between the processes that would lower their efficiency. For the consumption of the soil dissolved organic matter (DOM) necessary for bioremediation by electrokinetics, bioremediation was performed first. Because of the utilization and loss of the DOM and water-soluble ions by the microbial and electrokinetic processes, respectively, both of them were supplemented to provide a basic carbon resource, maintain a high electrical conductivity and produce a uniform distribution of ions. The moisture and bacteria were also supplemented. The optimal DOM supplement (20.5 mg·kg−1 glucose; 80–90% of the total natural DOM content in the soil) was calculated to avoid competitive effects (between the DOM and n-hexadecane) and to prevent nutritional deficiency. The replenishment of the water-soluble ions maintained their content equal to their initial concentrations. The degradation rate of n-hexadecane was only 167.0 mg·kg−1·d−1 (1.9%, w/w) for the first 9 days in the treatments with bioremediation or electrokinetics alone, but this rate was realized throughout the whole process when the two technologies were alternated, with a degradation of 78.5% ± 2.0% for the n-hexadecane after 45 days of treatment. PMID:27032838

Effect of alternating bioremediation and electrokinetics on the remediation of n-hexadecane-contaminated soil

NASA Astrophysics Data System (ADS)

Wang, Sa; Guo, Shuhai; Li, Fengmei; Yang, Xuelian; Teng, Fei; Wang, Jianing

2016-04-01

This study demonstrated the highly efficient degradation of n-hexadecane in soil, realized by alternating bioremediation and electrokinetic technologies. Using an alternating technology instead of simultaneous application prevented competition between the processes that would lower their efficiency. For the consumption of the soil dissolved organic matter (DOM) necessary for bioremediation by electrokinetics, bioremediation was performed first. Because of the utilization and loss of the DOM and water-soluble ions by the microbial and electrokinetic processes, respectively, both of them were supplemented to provide a basic carbon resource, maintain a high electrical conductivity and produce a uniform distribution of ions. The moisture and bacteria were also supplemented. The optimal DOM supplement (20.5 mg·kg-1 glucose; 80-90% of the total natural DOM content in the soil) was calculated to avoid competitive effects (between the DOM and n-hexadecane) and to prevent nutritional deficiency. The replenishment of the water-soluble ions maintained their content equal to their initial concentrations. The degradation rate of n-hexadecane was only 167.0 mg·kg-1·d-1 (1.9%, w/w) for the first 9 days in the treatments with bioremediation or electrokinetics alone, but this rate was realized throughout the whole process when the two technologies were alternated, with a degradation of 78.5% ± 2.0% for the n-hexadecane after 45 days of treatment.

Reversible electrokinetic adsorption barriers for the removal of organochlorine herbicide from spiked soils.

PubMed

Rodrigo, S; Saez, C; Cañizares, P; Rodrigo, M A

2018-06-02

This work aims to describe the removal of clopyralid from clay soils using electrokinetically assisted soil flushing (EKSF) coupled with a permeable reactive barrier (PRB), consisting of beds of Granulated Activated Carbon (GAC). To do this, two strategies have been evaluated on bench-scale electroremediation facilities (175 dm 3 ): electrokinetic adsorption barrier (EKAB) and reversible electrokinetic adsorption barrier (REKAB). Likewise, to clarify the contribution of the different mechanisms to remediation process results are compared to those obtained in a reference test (without applying an electric field) and to results obtained in the EKSF of soils polluted with compounds with different polarity and vapour pressure. Results show that during EKAB and REKAB tests, clopyralid is removed from the soil by adsorption in PRB, electrokinetic transport and, very less decisively, by evaporation. The application of polarity reversion attains a higher retention of clopyralid in the activated carbon-PRB and a better regulation of pH because of the neutralization of H + and OH - generated in the electrolyte wells. After 30 days of operation, the removal of clopyralid by EKAB is 45% while it reaches 57% in the case of REKAB. Copyright © 2018. Published by Elsevier B.V.

The optimisation of electrokinetic remediation for heavy metals and radioactivity contamination on Holyrood-Lunas soil (acrisol species) in Sri Gading Industrial Area, Batu Pahat, Johor, Malaysia.

PubMed

Mohamed Johar, S; Embong, Z

2015-11-01

The optimisation of electrokinetic remediation of an alluvial soil, locally named as Holyrood-Lunas from Sri Gading Industrial Area, Batu Pahat, Johor, Malaysia, had been conducted in this research. This particular soil was chosen due to its relatively high level of background radiation in a range between 139.2 and 539.4 nGy h(-1). As the background radiation is correlated to the amount of parent nuclides, (238)U and (232)Th, hence, a remediation technique, such as electrokinetic, is very useful in reducing these particular concentrations of heavy metal and radionuclides in soils. Several series of electrokinetics experiments were performed in laboratory scale in order to study the influence of certain electrokinetic parameters in soil. The concentration before (pre-electrokinetic) and after the experiment (post-electrokinetic) was determined via X-ray fluorescence (XRF) analysis technique. The best electrokinetic parameter that contributed to the highest achievable concentration removal of heavy metals and radionuclides on each experimental series was incorporated into a final electrokinetic experiment. Here, High Pure Germanium (HPGe) was used for radioactivity elemental analysis. The XRF results suggested that the most optimised electrokinetic parameters for Cr, Ni, Zn, As, Pb, Th and U were 3.0 h, 90 volts, 22.0 cm, plate-shaped electrode by 8 × 8 cm and in 1-D configuration order whereas the selected optimised electrokinetic parameters gave very low reduction of (238)U and (232)Th at 0.23 ± 2.64 and 2.74 ± 23.78 ppm, respectively. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Characterization of electrokinetic gating valve in microfluidic channels.

PubMed

Zhang, Guiseng; Du, Wei; Liu, Bi-Feng; Hisamoto, Hideaki; Terabe, Shigeru

2007-02-12

Electrokinetic gating, functioning as a micro-valve, has been widely employed in microfluidic chips for sample injection and flow switch. Investigating its valving performance is fundamentally vital for microfluidics and microfluidics-based chemical analysis. In this paper, electrokinetic gating valve in microchannels was evaluated using optical imaging technique. Microflow profiles at channels junction were examined, revealing that molecular diffusion played a significant role in the valving disable; which could cause analyte leakage in sample injection. Due to diffusion, the analyte crossed the interface of the analyte flow and gating flow, and then formed a cometic tail-like diffusion area at channels junction. From theoretical calculation and some experimental evidences, the size of the area was related to the diffusion coefficient and the velocity of analytes. Additionally, molecular diffusion was also believed to be another reason of sampling bias in gated injection.

Catalytically induced electrokinetics for motors and micropumps.

PubMed

Paxton, Walter F; Baker, Paul T; Kline, Timothy R; Wang, Yang; Mallouk, Thomas E; Sen, Ayusman

2006-11-22

We have explored the role of electrokinetics in the spontaneous motion of platinum-gold nanorods suspended in hydrogen peroxide (H2O2) solutions that may arise from the bimetallic electrochemical decomposition of H2O2. The electrochemical decomposition pathway was confirmed by measuring the steady-state short-circuit current between platinum and gold interdigitated microelectrodes (IMEs) in the presence of H2O2. The resulting ion flux from platinum to gold implies an electric field in the surrounding solution that can be estimated from Ohm's Law. This catalytically generated electric field could in principle bring about electrokinetic effects that scale with the Helmholtz-Smoluchowski equation. Accordingly, we observed a linear relationship between bimetallic rod speed and the resistivity of the bulk solution. Previous observations relating a decrease in speed to an increase in ethanol concentration can be explained in terms of a decrease in current density caused by the presence of ethanol. Furthermore, we found that the catalytically generated electric field in the solution near a Pt/Au IME in the presence of H2O2 is capable of inducing electroosmotic fluid flow that can be switched on and off externally. We demonstrate that the velocity of the fluid flow in the plane of the IME is a function of the electric field, whether catalytically generated or applied from an external current source. Our findings indicate that the motion of PtAu nanorods in H2O2 is primarily due to a catalytically induced electrokinetic phenomenon and that other mechanisms, such as those related to interfacial tension gradients, play at best a minor role.

Molecular Theory for Electrokinetic Transport in pH-Regulated Nanochannels.

PubMed

Kong, Xian; Jiang, Jian; Lu, Diannan; Liu, Zheng; Wu, Jianzhong

2014-09-04

Ion transport through nanochannels depends on various external driving forces as well as the structural and hydrodynamic inhomogeneity of the confined fluid inside of the pore. Conventional models of electrokinetic transport neglect the discrete nature of ionic species and electrostatic correlations important at the boundary and often lead to inconsistent predictions of the surface potential and the surface charge density. Here, we demonstrate that the electrokinetic phenomena can be successfully described by the classical density functional theory in conjunction with the Navier-Stokes equation for the fluid flow. The new theoretical procedure predicts ion conductivity in various pH-regulated nanochannels under different driving forces, in excellent agreement with experimental data.

Characterization of C-PDMS electrodes for electrokinetic applications in microfluidic systems

NASA Astrophysics Data System (ADS)

Deman, A.-L.; Brun, M.; Quatresous, M.; Chateaux, J.-F.; Frenea-Robin, M.; Haddour, N.; Semet, V.; Ferrigno, R.

2011-09-01

This paper reports on the integration of thick carbon-polydimethylsiloxane (C-PDMS) electrodes in microfluidic systems for electrokinetic operations. The C-PDMS material, obtained by mixing carbon nanopowder and PDMS, preserves PDMS processing properties such as O2 plasma activation and soft-lithography patternability in thick or 3D electrodes. Conductivity in the order of 10 S m-1 was reached for a carbon concentration of 25 wt%. To evaluate the adhesion between PDMS and C-PDMS, we prepared bi-material strips and carried out a manual pull test. The cohesion and robustness of C-PDMS were also evaluated by applying a large range of electric field conditions from dc to ac (300 kHz). No damage to the electrodes or release of carbon was noticed. The use of such a material for electrokinetic manipulation was validated on polystyrene particles and cells. Here, we demonstrate that C-PDMS seems to be a valuable technological solution for electrokinetic in microfluidic and particularly for biological applications such as cell electrofusion, lysis and trapping, which are favored by uniform lateral electric fields across the microchannel section.

Reversible electrokinetic adsorption barriers for the removal of atrazine and oxyfluorfen from spiked soils.

PubMed

Vieira Dos Santos, E; Sáez, C; Cañizares, P; Martínez-Huitle, C A; Rodrigo, M A

2017-01-15

This study demonstrates the application of reversible electrokinetic adsorption barrier (REKAB) technology to soils spiked with low-solubility pollutants. A permeable reactive barrier (PRB) of granular activated carbon (GAC) was placed between the anode and cathode of an electrokinetic (EK) soil remediation bench-scale setup with the aim of enhancing the removal of two low-solubility herbicides (atrazine and oxyfluorfen) using a surfactant solution (sodium dodecyl sulfate) as the flushing fluid. This innovative study focused on evaluating the interaction between the EK system and the GAC-PRB, attempting to obtain insights into the primary mechanisms involved. The obtained results highlighted the successful treatment of atrazine and oxyfluorfen in contaminated soils. The results obtained from the tests after 15days of treatment were compared with those obtained using the more conventional electrokinetic soil flushing (EKSF) technology, and very important differences were observed. Although both technologies are efficient for removing the herbicides from soils, REKAB outperforms EKSF. After the 15-day treatment tests, only approximately 10% of atrazine and oxyfluorfen remained in the soil, and adsorption onto the GAC bed was an important removal mechanism (15-17% of herbicide retained). The evaporation loses in REKAB were lower than those obtained in EKSF (45-50% compared to 60-65%). Copyright © 2016 Elsevier B.V. All rights reserved.

Dual liquid and gas chromatograph system

DOEpatents

Gay, D.D.

A chromatographic system is described that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a nontransparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extreme low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

Dual liquid and gas chromatograph system

DOEpatents

Gay, Don D.

1985-01-01

A chromatographic system that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a non-transparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extremely low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

Toxic Elements in Soil and Groundwater: Short-Time Study on Electrokinetic Removal of Arsenic in the Presence of other Ions

PubMed Central

Leszczynska, Danuta; Ahmad, Hafiz

2006-01-01

The electrokinetic technique is an emerging technology presently tested in situ to remove dissolved heavy metals from contaminated groundwater. There is a growing interest for using this system to cleanse clayey soil contaminated by toxic metallic ions. Currently, there are very few available non-destructive treatment methods that could be successfully applied in situ on low permeable type of soil matrix. The main objective of presented study was to validate and possibly enhance the overall efficiency of decontamination by the electrokinetic technique of the low permeable soil polluted by the arsenic in combination with chromium and copper ions. The chosen mixture of ions was imitating leak of pesticide well known as chromate copper arsenate (CCA). The chosen technique is showing a big promise to be used in the future as a portable, easy to install and run on sites with spills or leaks hard to reach otherwise; such as in the dense populated and urbanized areas. Laboratory electrokinetic experiments were designed to understand and possibly manipulate main mechanisms involved during forced migration of ions. All tests were conducted on artificially contaminated kaolinite (low permeable clay soil). Electrokinetic migration was inducted by the low voltage dc current applied through soil column. Series of experiments were designed to assess the efficiency of arsenic-chromium-copper remediation by applying (1) only dc current; and (2) by altering the soil environment. Obtained results showed that arsenic could be successfully removed from the soil in one day (25 hours) span. It was significant time reduction, very important during emergency response. Mass recovered at the end of each test depended on initial condition of soil and type of flushing solution. The best results were obtained, when soil was flushed with either NaOH or NaOCl (total removal efficiency 74.4% and 78.1%, respectively). Direct analysis of remained arsenic in soil after these tests confirmed

Determination of patulin in commercial apple juice by micellar electrokinetic chromatography.

PubMed

Murillo, M; González-Peñas, E; Amézqueta, S

2008-01-01

A novel and validated micellar electrokinetic capillary chromatography (MEKC) method using ultraviolet detection (UV) has been applied to the quantitative analysis of patulin (PAT) in commercial apple juice. Patulin was extracted from samples with an ethylacetate solution. The micellar electrokinetic capillary chromatography (MECK) parameters studied for method optimization were buffer composition, voltage, temperature, and a separation between PAT and 5-hydroxymethylfurfural (HMF) (main interference in apple juice PAT analysis) peaks until reaching baseline. The method passes a series of validation tests including selectivity, linearity, limit of detection and quantification (0.7 and 2.5 microgL(-1), respectively), precision (within and between-day variability) and recovery (80.2% RSD=4%), accuracy, and robustness. This method was successfully applied to the measurement of 20 apple juice samples obtained from different supermarkets. One hundred percent of the samples were contaminated with a level greater than the limit of detection, with mean and median values of 41.3 and 35.7 microgL(-1), respectively.

Coupled electrokinetics-adsorption technique for simultaneous removal of heavy metals and organics from saline-sodic soil.

PubMed

Lukman, Salihu; Essa, Mohammed Hussain; Mu'azu, Nuhu Dalhat; Bukhari, Alaadin

2013-01-01

In situ remediation technologies for contaminated soils are faced with significant technical challenges when the contaminated soil has low permeability. Popular traditional technologies are rendered ineffective due to the difficulty encountered in accessing the contaminants as well as when employed in settings where the soil contains mixed contaminants such as petroleum hydrocarbons, heavy metals, and polar organics. In this study, an integrated in situ remediation technique that couples electrokinetics with adsorption, using locally produced granular activated carbon from date palm pits in the treatment zones that are installed directly to bracket the contaminated soils at bench-scale, is investigated. Natural saline-sodic soil, spiked with contaminant mixture (kerosene, phenol, Cr, Cd, Cu, Zn, Pb, and Hg), was used in this study to investigate the efficiency of contaminant removal. For the 21-day period of continuous electrokinetics-adsorption experimental run, efficiency for the removal of Zn, Pb, Cu, Cd, Cr, Hg, phenol, and kerosene was found to reach 26.8, 55.8, 41.0, 34.4, 75.9, 92.49, 100.0, and 49.8%, respectively. The results obtained suggest that integrating adsorption into electrokinetic technology is a promising solution for removal of contaminant mixture from saline-sodic soils.

Electrokinetic remediation of manganese and ammonia nitrogen from electrolytic manganese residue.

PubMed

Shu, Jiancheng; Liu, Renlong; Liu, Zuohua; Du, Jun; Tao, Changyuan

2015-10-01

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore, which mainly contains manganese and ammonia nitrogen and seriously damages the ecological environment. This work demonstrated the use of electrokinetic (EK) remediation to remove ammonia nitrogen and manganese from EMR. The transport behavior of manganese and ammonia nitrogen from EMR during electrokinetics, Mn fractionation before and after EK treatment, the relationship between Mn fractionation and transport behavior, as well as the effects of electrolyte and pretreatment solutions on removal efficiency and energy consumption were investigated. The results indicated that the use of H2SO4 and Na2SO4 as electrolytes and pretreatment of EMR with citric acid and KCl can reduce energy consumption, and the removal efficiencies of manganese and ammonia nitrogen were 27.5 and 94.1 %, respectively. In these systems, electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen transport. Moreover, ammonia nitrogen in EMR reached the regulated level, and the concentration of manganese in EMR could be reduced from 455 to 37 mg/L. In general, the electrokinetic remediation of EMR is a promising technology in the future.

Convective Electrokinetic Instability With Conductivity Gradients

NASA Astrophysics Data System (ADS)

Chen, Chuan-Hua; Lin, Hao; Lele, Sanjiva; Santiago, Juan

2003-11-01

Electrokinetic flow instability has been experimentally identified and quantified in a glass T-junction microchannel system with a cross section of 11 um x 155 um. In this system, buffers of different conductivities were electrokinetically driven into a common mixing channel by a DC electric field. A convective instability was observed with a threshold electric field of 0.45 kV/cm for a 10:1 conductivity ratio. A physical model has been developed which consists of a modified Ohmic model formulation for electrolyte solutions and the Navier-Stokes equations with an electric body force term. The model and experiments show that bulk charge accumulation in regions of conductivity gradients is the key mechanism of such instabilities. A linear stability analysis was performed in a convective framework, and Briggs-Bers criteria were applied to determine the nature of instability. The analysis shows the instability is governed by two key parameters: the ratio of molecular diffusion to electroviscous time scale which governs the onset of instability, and the ratio of electroviscous to electroosmotic velocity which governs whether the instability is convective or absolute. The model predicted critical electric field, growth rate, wavelength, and phase speed which were comparable to experimental data.

Electrokinetically Emplaced Amendments for Enhanced Bioremediation of Chlorinated Solvents in Clay: a Pilot Field Test

NASA Astrophysics Data System (ADS)

O'Carroll, D. M.; Inglis, A.; Head, N.; Chowdhury, A. I.; Garcia, A. N.; Reynolds, D. A.; Hogberg, D.; Edwards, E.; Lomheim, L.; Austrins, L. M.; Hayman, J.; Auger, M.; Sidebottom, A.; Eimers, J.; Gerhard, J.

2017-12-01

Bioremediation is an increasingly popular treatment technology for contaminated sites due to the proven success of biostimulation and bioaugmentation. However, bioremediation, along with other in-situ remediation technologies, faces limitations due to challenges with amendment delivery in low permeability media. Studies have suggested that electrokinetics (EK) can enhance the delivery of amendments in low permeability soils, such as clay. A pilot field trial was conducted to evaluate the potential for electrokinetics to support anaerobic dechlorination in clay by improving the transport of lactate and microorganisms. The study was performed on a former chlorinated solvent production facility in Ontario, Canada. Five transect cells were set up within the contaminated clay test area. Different amendments were injected in three of these cells to test various remediation strategies under the influence of EK. The other two cells were used as controls, one with EK applied and the other with no EK. This study focuses on the cell that applied electrokinetics for lactate emplacement followed by bioremediation (EK-Bio). This cell had an initial single injection of KB-1 bioaugmentation culture (SiREM, Canada) followed by injection of sodium lactate as a biostimulant while direct current was applied for 45 days between two electrodes 3 m apart. EK can enhance lactate migration by electromigration, while microorganisms have the potential to be influenced by electroosmosis of the bulk fluid or by electrophoresis of the charged bacteria themselves. All monitoring well locations in the EK-Bio cell exhibited evidence of successful lactate delivery corresponding to an increase in dissolved organic carbon. Reduction in chlorinated volatile organic compound (cVOC) concentrations, in particular 1,2-dichloroethane (1,2-DCA), were evident in monitoring locations coinciding with significant lactate breakthrough. Further investigation into the influence of EK-Bio on the abundance and

Interactions of structurally modified surfactants with reservoir minerals: Calorimetric, spectroscopic and electrokinetic study

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

Somasundaran, P.; Sivakumar, A.; Xu, Q.

1991-03-01

The objective of this project is to elucidate mechanisms of adsorption of structurally modified surfactants on reservoir minerals and to develop a full understanding of the effect of the surfactant structure on the nature of the adsorbed layers at the molecular level. An additional aim is to study the adsorption of surfactant mixtures on simple well-characterized minerals and on complex minerals representing real conditions. The practical goal of these studies is the identification of the optimum surfactant structures and their combinations for micellar flooding. In this work, the experiments on adsorption were focussed on the position of sulfonate and methylmore » groups on the aromatic ring of alkyl xylene sulfonates. A multi-pronged approach consisting of calorimetry, electrokinetics, wettability and spectroscopy is planned to elucidate the adsorption mechanism of surfactants and their mixtures on minerals such as alumina and kaolinite. 32 refs., 15 figs., 7 tabs.« less

Remediation of Pb/Cr co-contaminated soil using electrokinetic process and approaching electrode technique.

PubMed

Ng, Yee-Sern; Sen Gupta, Bhaskar; Hashim, Mohd Ali

2016-01-01

Electrokinetic process has emerged as an important tool for remediating heavy metal-contaminated soil. The process can concentrate heavy metals into smaller soil volume even in the absence of hydraulic flow. This makes it an attractive soil pre-treatment method before other remediation techniques are applied such that the chemical consumption in the latter stage can be reduced. The present study evaluates the feasibility of electrokinetic process in concentrating lead (Pb) and chromium (Cr) in a co-contaminated soil using different types of wetting agents, namely 0.01 M NaNO3, 0.1 M citric acid and 0.1 M EDTA. The data obtained showed that NaNO3 and citric acid resulted in poor Pb electromigration in this study. As for Cr migration, these agents were also found to give lower electromigration rate especially at low pH region as a result of Cr(VI) adsorption and possible reduction into Cr(III). In contrast, EDTA emerged as the best wetting agent in this study as it formed water-soluble anionic complexes with both Pb and Cr. This provided effective one-way electromigration towards the anode for both ions, and they were accumulated into smaller soil volume with an enrichment ratio of 1.55-1.82. A further study on the application of approaching cathode in EDTA test showed that soil alkalisation was achieved, but this did not provide significant enhancement on electromigration for Pb and Cr. Nevertheless, the power consumption for electrokinetic process was decreased by 22.5%.

Remediation of nitrate-contaminated groundwater by PRB-Electrokinetic integrated process.

PubMed

Ghaeminia, Mahdyar; Mokhtarani, Nader

2018-05-30

Activated carbon is used as a reactive media in Permeable Reactive Barrier (PRB) for the removal of inorganic contaminants such as nitrate from groundwater. Since removal rate by this media decreases by time and due to the high costs of excavation and replacement of new media, the usage of activated carbon as an adsorbent in PRB is limited. The present study aimed to solve this defect by integrating electrokinetic process and PRB, using in-situ regeneration of activated carbon. This research was carried out on a laboratory scale using synthetically contaminated water and modified activated carbon as a reactive media in PRB. The effects of pH, nitrate concentration, carbon to sand ratio, and also electric gradient on the performance of the process were evaluated, and optimal conditions were determined, to increase the system longevity. According to the results, by applying an electric gradient of 1.25 V cm -1 to the PRB alone process in optimum operating condition (135 mg L -1 initial nitrate concentration, flow rate of 2.3 L min -1 , pH = 6.8, and carbon to sand ratios of 1:1) the adsorbent capacity increased by 90%. Under these conditions, the integrated process could keep nitrate concentration in the effluent below the standard limit for about 111 h, while the PRB alone process could do the same job for about 59 h. Also, SEM analysis showed that by applying electrokinetic process, activated carbon was regenerated. Integration of electrokinetic process and PRB was also caused nitrate to transfer from activated carbon media into the soil layer above the system. This nitrate-rich soil has the potential for reuse in agricultural activities. Copyright © 2018 Elsevier Ltd. All rights reserved.

Coupled Electrokinetics-Adsorption Technique for Simultaneous Removal of Heavy Metals and Organics from Saline-Sodic Soil

PubMed Central

Lukman, Salihu; Essa, Mohammed Hussain; Mu'azu, Nuhu Dalhat; Bukhari, Alaadin

2013-01-01

In situ remediation technologies for contaminated soils are faced with significant technical challenges when the contaminated soil has low permeability. Popular traditional technologies are rendered ineffective due to the difficulty encountered in accessing the contaminants as well as when employed in settings where the soil contains mixed contaminants such as petroleum hydrocarbons, heavy metals, and polar organics. In this study, an integrated in situ remediation technique that couples electrokinetics with adsorption, using locally produced granular activated carbon from date palm pits in the treatment zones that are installed directly to bracket the contaminated soils at bench-scale, is investigated. Natural saline-sodic soil, spiked with contaminant mixture (kerosene, phenol, Cr, Cd, Cu, Zn, Pb, and Hg), was used in this study to investigate the efficiency of contaminant removal. For the 21-day period of continuous electrokinetics-adsorption experimental run, efficiency for the removal of Zn, Pb, Cu, Cd, Cr, Hg, phenol, and kerosene was found to reach 26.8, 55.8, 41.0, 34.4, 75.9, 92.49, 100.0, and 49.8%, respectively. The results obtained suggest that integrating adsorption into electrokinetic technology is a promising solution for removal of contaminant mixture from saline-sodic soils. PMID:24235885

In situ consolidation of offshore petroleum well structural casings by electrokinetic methods

NASA Astrophysics Data System (ADS)

Wrixon, Robert Christopher

Offshore drilling operations encounter cement wash-out problems while setting the initial structural casing (0--200 ft depth) due to the soft, unconsolidated nature of the sea-bed. Structural casings set by alternative methods have failed in up to 50% of cases due to insufficient frictional bearing capacity. This dissertation presents a method of increasing the bearing capacity of a jet-drilled or slick-drilled casing in-situ by applying a potential difference such that the casing is anodic compared to a remote cathode. It has been shown experimentally that clayey formations will swell and stick to a simulated anodic casing by the combined electrokinetic processes of electroosmosis and electrophoresis. Any cavities around the "casing" are eliminated and the formation is flush against the metal surface, increasing bearing capacity. The formation around the "casing" dries out due to electroosmotic migration of water away from the anode, increasing the shear strength of the surrounding soil. Corrosion products at the anode can further increase the soil shear strength by a process known as electrochemical hardening. This investigation has shown that the bearing capacity of anodic casings can potentially be increased by a factor of up to 1,000% in soft clays and silty clays. The existence of an optimal level of electrokinetic consolidation, beyond which the soil shear strength begins to degrade, has been demonstrated. The difficulties of applying electrokinetic methods to saline soil environments have been addressed and the process has been shown to be successful, as long as the requisite electric field strength is maintained. The efficiency of the electrokinetic consolidation technique has been shown to be affected by the soil water content, soil mineralogy, power supplied, time of treatment and the choice of anode material. Experiments in marine sediment show that increases in bearing capacities of about 300% can be achieved at optimal treatment conditions. With

On micro-electrokinetic scalar turbulence in microfluidics at a low Reynolds number.

PubMed

Wang, Guiren; Yang, Fang; Zhao, Wei; Chen, Chien-Pin

2016-03-21

We recently demonstrated the direct observation of micro-electrokinetic turbulence in a microchannel at a low Reynolds number (Re) when a pressure-driven flow was forced electrokinetically. Here, we characterize the corresponding scalar turbulence and surprisingly find that the corresponding turbulent mixing has some typical and important features of scalar turbulence, such as the Obukhov-Corrsin (O-C) -5/3 spectrum of concentration fluctuation, which can commonly be realized only at high Re in macroflows. This discovery could provide a new perspective of scalar turbulence and an avenue for control of transport phenomena in lab-on-a-chip platforms. This will deepen our fundamental understanding of transport phenomena in microfluidics.

Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids

DOEpatents

Ramirez, Abelardo L.; Cooper, John F.; Daily, William D.

1996-01-01

This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination.

Using electrokinetic phenomena and electrical resistance tomography to characterize the movement of subsurface fluids

DOEpatents

Ramirez, A.L.; Cooper, J.F.; Daily, W.D.

1996-02-27

This invention relates generally to the remote detections of subsurface liquid contaminants using in combination a geophysical technique known as ERT and an EKS. Electrokinetic transport is used to enhance the ability of electrical resistance tomography (ERT) to detect position and movement of subsurface contaminant liquids, particles or ions. ERT images alone are difficult to interpret because of natural inhomogeneities in soil composition and electrical properties. By subtracting two or more ERT images obtained before and after field induced movement, a high contrast image of a plume of distinct electrokinetic properties can be seen. The invention is applicable to important subsurface characterization problems including, as examples, (1) detection of liquid-saturated plumes of contaminants such as those associated with leaks from underground storage tanks containing hazardous concentrated electrolytes, (2) detection and characterization of soils contaminated with organic pollutants such as droplets of gasoline; and (3) monitoring the progress of electrokinetic containment or clean up of underground contamination. 1 fig.

Electrokinetic effects on motion of submicron particles in microchannel

NASA Astrophysics Data System (ADS)

Sato, Yohei; Hishida, Koichi

2006-11-01

Two-fluid mixing utilizing electrokinetically driven flow in a micro-channel is investigated by micron-resolution particle image velocimetry and an image processing technique. Submicron particles are transported and mixed with deionized water by electrophoresis. The particle electrophoretic velocity that is proportional to an applied electric field is measured in a closed cell, which is used to calculate the electroosmotic flow velocity. At a constant electric field, addition of pressure-driven flow to electrokinetically driven flow in a T-shaped micro-channel enhances two-fluid mixing because the momentum flux is increased. On the other hand, on application of an alternative sinusoidal electric field, the velocity difference between pressure-driven and electroosmotic flows has a significant effect on increasing the length of interface formed between two fluids. It is concluded from the present experiments that the transport and mixing process in the micro-channel will be enhanced by accurate flow-rate control of both pressure-driven and electroosmotic flows.

DEMONSTRATION BULLETIN: IN SITU ELECTROKINETIC EXTRACTION SYSTEM - SANDIA NATIONAL LABORATORIES

EPA Science Inventory

Sandia National Laboratories (SNL) has developed an in situ soil remediation system that uses electrokinetic principles to remediate hexavalent chromium-contaminated unsaturated or partially saturated soils. The technology involves the in situ application of direct current to the...

Micellar Electrokinetic Chromatography of Aminoglycosides.

PubMed

Holzgrabe, Ulrike; Schmitt, Stefanie; Wienen, Frank

2016-01-01

The components of the aminoglycosides, e.g., gentamicin, sisomicin, netilmicin, kanamycin, amikacin, and tobramycin, and related impurities of these antibiotics can be separated by means of micellar electrokinetic chromatography (MEKC). Derivatization with o-phthaldialdehyde and thioglycolic acid is found to be appropriate for these antibiotics. The background electrolyte was composed of sodium tetraborate (100 mM), sodium deoxycholate (20 mM), and β-cyclodextrin (15 mM) having a pH value of 10.0. This method is valid for evaluation of gentamicin, kanamycin, and tobramycin. It has to be adopted for amikacin, paromomycin, neomycin, and netilmicin.

Chemometric Deconvolution of Continuous Electrokinetic Injection Micellar Electrokinetic Chromatography Data for the Quantitation of Trinitrotoluene in Mixtures of Other Nitroaromatic Compounds

DTIC Science & Technology

2014-02-24

Suite 600 Washington, DC 20036 NRL/MR/ 6110 --14-9521 Approved for public release; distribution is unlimited. 1Science & Engineering Apprenticeship...Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/ 6110 --14-9521 Chemometric Deconvolution of Continuous Electrokinetic Injection Micellar... Engineering Apprenticeship Program American Society for Engineering Education Washington, DC Kevin Johnson Navy Technology Center for Safety and

Impact of pore size variability and network coupling on electrokinetic transport in porous media

NASA Astrophysics Data System (ADS)

Alizadeh, Shima; Bazant, Martin Z.; Mani, Ali

2016-11-01

We have developed and validated an efficient and robust computational model to study the coupled fluid and ion transport through electrokinetic porous media, which are exposed to external gradients of pressure, electric potential, and concentration. In our approach a porous media is modeled as a network of many pores through which the transport is described by the coupled Poisson-Nernst-Planck-Stokes equations. When the pore sizes are random, the interactions between various modes of transport may provoke complexities such as concentration polarization shocks and internal flow circulations. These phenomena impact mixing and transport in various systems including deionization and filtration systems, supercapacitors, and lab-on-a-chip devices. In this work, we present simulations of massive networks of pores and we demonstrate the impact of pore size variation, and pore-pore coupling on the overall electrokinetic transport in porous media.

Probing size-dependent electrokinetics of hematite aggregates

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

Kedra-Królik, Karolina; Rosso, Kevin M.; Zarzycki, Piotr

Aqueous particle suspensions of many kinds are stabilized by the electrostatic potential developed at their surfaces from reaction with water and ions. An important and less well understood aspect of this stabilization is the dependence of the electrostatic surface potential on particle size. Surface electrostatics are typically probed by measuring particle electrophoretic mobilities and quantified in the electrokinetic potential (f), using commercially available Zeta Potential Analyzers (ZPA). Even though ZPAs provide frequency-spectra (histograms) of electrophoretic mobility and hydrodynamic diameter, typically only the maximal-intensity values are reported, despite the information in the remainder of the spectra. Here we propose a mappingmore » procedure that inter-correlates these histograms to extract additional insight, in this case to probe particle size-dependent electrokinetics. Our method is illustrated for a suspension of prototypical iron (III) oxide (hematite, a-Fe2O3). We found that the electrophoretic mobility and f-potential are a linear function of the aggregate size. By analyzing the distribution of surface site types as a function of aggregate size we show that site coordination increases with increasing aggregate diameter. This observation explains why the acidity of the iron oxide particles decreases with increasing particle size.« less

The gas-chromatographic and gas-chromatographic-mass-spectrometric identification of halogen-containing organic compounds

NASA Astrophysics Data System (ADS)

Gidaspov, B. V.; Zenkevich, I. G.; Rodin, A. A.

1989-09-01

The problem of identifying halogen-containing organic compounds in their gas-chromatographic and gas-chromatographic-mass-spectrometric (GC-MS) determination in different materials has been examined. Particular attention has been paid not to the complete characterisation of methods for carrying out this analysis but to the most important problem of increasing the selectivity at the stages of sampling, separation, and interpretation of the gas-chromatographic and GC-MS information. The bibliography contains 292 references.

Electrokinetic Enhanced Permanganate Delivery for Low Permeability Soil Remediation

NASA Astrophysics Data System (ADS)

Chowdhury, A. I.; Gerhard, J.; Reynolds, D. A.; Sleep, B. E.; O'Carroll, D. M.

2016-12-01

Contaminant mass sequestered in low permeability zones (LPZ) in the subsurface has become a significant concern due to back diffusion of contaminants, leading to contaminant rebound following treatment of the high permeability strata. In-situ remediation technologies such as in-situ chemical oxidation (ISCO) are promising, however, successful delivery of oxidants into silts and clays remains a challenge. Electrokinetics (EK) has been proposed as a technique that can overcome this challenge by delivering oxidants into low permeability soils. This study demonstrates the ability of EK to facilitate permanganate delivery into silt for treatment of trichloroethene (TCE). A two-dimensional sandbox was packed with alternate vertical layers of coarse sand and silt contaminated with high concentrations of aqueous phase TCE. Nine experiments were conducted to compare EK-enhanced in-situ chemical oxidation (EK-ISCO) to ISCO alone or EK alone. Frequent groundwater sampling at multiple locations combined with image analysis provided detailed mapping of TCE, permanganate, and manganese dioxide mass distributions. EK-ISCO successfully delivered the permanganate throughout the silt cross-section while ISCO without EK resulted in permanganate delivery only to the edges of the silt layer. EK-ISCO resulted in a 4.4 order-of-magnitude (OoM) reduction in TCE concentrations in the coarse sand compared to a 3.5 OoM reduction for ISCO alone. This study suggests that electrokinetics coupled with ISCO can achieve enhanced remediation of lower permeability strata, where remediation technologies for successful contaminant mass removal would otherwise be limited.

Ultrafast electrokinetics.

PubMed

Rouhi Youssefi, Mehrnaz; Diez, Francisco Javier

2016-03-01

The influence of a high electric field applied on both fluid flow and particle velocities is quantified at large Peclet numbers. The experiments involved simultaneous particle image velocimetry and flow rate measurements. These are conducted in polydimethylsiloxane channels with spherical nonconducting polystyrene particles and DI water as the background flow. The high electric field tests produced up to three orders of magnitude higher electrokinetic velocities than any previous reports. The maximum electroosmotic velocity and electrophoretic velocity measured were 3.55 and 2.3 m/s. Electrophoretic velocities are measured over the range of 100 V/cm < E < 250 000 V/cm. The results are separated according to the different nonlinear theoretical models, including low and high Peclet numbers, and weak and strong concentration polarization. They show good agreement with the models. Such fast velocities could be used for flow separation, mixing, transport, control, and manipulation of suspended particles as well as microthrust generation among other applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrokinetic motion of a spherical micro particle at an oil-water interface in microchannel.

PubMed

Wang, Chengfa; Li, Mengqi; Song, Yongxin; Pan, Xinxiang; Li, Dongqing

2018-03-01

The electrokinetic motion of a negatively charged spherical particle at an oil-water interface in a microchannel is numerically investigated and analyzed in this paper. A three-dimensional (3D) transient numerical model is developed to simulate the particle electrokinetic motion. The channel wall, the surface of the particle and the oil-water interface are all considered negatively charged. The effects of the direct current (DC) electric field, the zeta potentials of the particle-water interface and the oil-water interface, and the dynamic viscosity ratio of oil to water on the velocity of the particle are studied in this paper. In addition, the influences of the particle size are also discussed. The simulation results show that the micro-particle with a small value of negative zeta potential moves in the same direction of the external electric field. However, if the zeta potential value of the particle-water interface is large enough, the moving direction of the particle is opposite to that of the electric field. The velocity of the particle at the interface increases with the increase in the electric field strength and the particle size, but decreases with the increase in the dynamic viscosity ratio of oil to water, and the absolute value of the negative zeta potentials of both the particle-water interface and the oil-water interface. This work is the first numerical study of the electrokinetic motion of a charged particle at an oil-water interface in a microchannel. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Removal of organic pollutants and heavy metals in soils by electrokinetic remediation.

PubMed

Ricart, M T; Pazos, M; Gouveia, S; Cameselle, C; Sanroman, M A

2008-07-01

In this work, the feasibility of electrokinetic remediation for the restoration of polluted soil with organic and inorganic compounds had been development and evaluated using a model soil sample. The model soil was prepared with kaolinite clay artificially polluted in the laboratory with chromium and an azo dye: Reactive Black 5 (RB5). The electromigration of Cr in a spiked kaolinite sample was studied in alkaline conditions. Despite of the high pH registered in the kaolinite sample (around pH 9.5), Cr migrated towards the cathode and it was accumulated in the cathode chamber forming a white precipitate. The removal was not complete, and 23% of the initial Cr was retained into the kaolinite sample close to the cathode side. The azo dye RB5 could be effectively removed from kaolinite by electrokinetics and the complete cleanup of the kaolinite could be achieved in alkaline environment. In this condition, RB5 formed an anion that migrated towards the anode where it was accumulated and quickly degraded upon the electrode surface. The electrokinetic treatment of a kaolinite sample polluted with both Cr and RB5 yielded very good results. The removal of Cr was improved compared to the experiment where Cr was the only pollutant, and RB5 reached a removal as high as 95%. RB5 was removed by electromigration towards the anode, where the dye was degraded upon the surface of the electrode by electrochemical oxidation. Cr was transported towards the cathode by electromigration and electroosmosis. It is supposed that the interaction among RB5 and Cr into the kaolinite sample prevented premature precipitation and allow Cr to migrate and concentrate in the cathode chamber.

Removal of Chalk River unidentified deposit (CRUD) radioactive waste by enhanced electrokinetic process

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

Kim, Won-Seok; Nam, Seongsik; Chang, Seeun

Decontamination techniques proposed and used to remove Chalk River unidentified deposit (CRUD) in radioactive waste management. In cases of huge volumes of metal or radionuclides contaminated by CRUD, removal of CRUD by mechanical or chemical decontamination is difficult. An advanced electrokinetic process combined with chemical decontamination was applied to remove CRUD and experimentally evaluated. We used oxalic acid for CRUD removal, and cobalt (Co) released from the CRUD was transferred to the cathode in an electrokinetic reactor. Our results indicate that the combined system is efficient for CRUD removal with enhanced, efficiency by use of the cation exchange membrane andmore » zeolite.« less

Removal of Chalk River unidentified deposit (CRUD) radioactive waste by enhanced electrokinetic process

DOE PAGES

Kim, Won-Seok; Nam, Seongsik; Chang, Seeun; ...

2017-08-13

Decontamination techniques proposed and used to remove Chalk River unidentified deposit (CRUD) in radioactive waste management. In cases of huge volumes of metal or radionuclides contaminated by CRUD, removal of CRUD by mechanical or chemical decontamination is difficult. An advanced electrokinetic process combined with chemical decontamination was applied to remove CRUD and experimentally evaluated. We used oxalic acid for CRUD removal, and cobalt (Co) released from the CRUD was transferred to the cathode in an electrokinetic reactor. Our results indicate that the combined system is efficient for CRUD removal with enhanced, efficiency by use of the cation exchange membrane andmore » zeolite.« less

Electrokinetic Transduction of Acoustic Waves In Ocean Sediments

DTIC Science & Technology

2002-09-30

acoustic —motion in ocean sediments. The Biot theory of poroelastic media captures much of the sediment physics left out by other models [2]. It fits...in subsurface acoustical imaging, Mine Counter- Measures, and Anti-Submarine Warfare. To obtain essential experimental data to support the modeling ...Electrokinetic Transduction of Acoustic Waves In Ocean Sediments Gareth I. Block Applied Research Laboratories, U.T. Austin P.O. Box 8029

Electrokinetic In Situ Treatment of Metal-Contaminated Soil

NASA Technical Reports Server (NTRS)

Quinn, Jacqueline; Clausen, Christian A., III; Geiger, Cherie; Reinhart, Debra

2004-01-01

An electrokinetic technique has been developed as a means of in situ remediation of soils, sludges, and sediments that are contaminated with heavy metals. Examples of common metal contaminants that can be removed by this technique include cadmium, chromium, zinc, lead, mercury, and radionuclides. Some organic contaminants can also be removed by this technique. In the electrokinetic technique, a low-intensity direct current is applied between electrodes that have been implanted in the ground on each side of a contaminated soil mass. The electric current causes electro-osmosis and migration of ions, thereby moving aqueous-phase subsurface contaminants from one electrode to the other. The half reaction at the anode yields H+, thereby generating an acid front that travels from the anode toward the cathode. As this acid front passes through a given location, the local increase in acidity increases the solubility of cations that were previously adsorbed on soil particles. Ions are transported towards one electrode or the other which one depending on their respective electric charges. Upon arrival at the electrodes, the ionic contaminants can be allowed to become deposited on the electrodes or can be extracted to a recovery system. Surfactants and other reagents can be introduced at the electrodes to enhance rates of removal of contaminants. Placements of electrodes and concentrations and rates of pumping of reagents can be adjusted to maximize efficiency. The basic concept of electrokinetic treatment of soil is not new. What is new here are some of the details of application and the utilization of this technique as an alternative to other techniques (e.g., flushing or bioremediation) that are not suitable for treating soils of low hydraulic conductivity. Another novel aspect is the use of this technique as a less expensive alternative to excavation: The cost advantage over excavation is especially large in settings in which contaminated soil lies near and/or under

Automated electric valve for electrokinetic separation in a networked microfluidic chip.

PubMed

Cui, Huanchun; Huang, Zheng; Dutta, Prashanta; Ivory, Cornelius F

2007-02-15

This paper describes an automated electric valve system designed to reduce dispersion and sample loss into a side channel when an electrokinetically mobilized concentration zone passes a T-junction in a networked microfluidic chip. One way to reduce dispersion is to control current streamlines since charged species are driven along them in the absence of electroosmotic flow. Computer simulations demonstrate that dispersion and sample loss can be reduced by applying a constant additional electric field in the side channel to straighten current streamlines in linear electrokinetic flow (zone electrophoresis). This additional electric field was provided by a pair of platinum microelectrodes integrated into the chip in the vicinity of the T-junction. Both simulations and experiments of this electric valve with constant valve voltages were shown to provide unsatisfactory valve performance during nonlinear electrophoresis (isotachophoresis). On the basis of these results, however, an automated electric valve system was developed with improved valve performance. Experiments conducted with this system showed decreased dispersion and increased reproducibility as protein zones isotachophoretically passed the T-junction. Simulations of the automated electric valve offer further support that the desired shape of current streamlines was maintained at the T-junction during isotachophoresis. Valve performance was evaluated at different valve currents based on statistical variance due to dispersion. With the automated control system, two integrated microelectrodes provide an effective way to manipulate current streamlines, thus acting as an electric valve for charged species in electrokinetic separations.

Application of electrokinetic soil flushing to four herbicides: A comparison.

PubMed

dos Santos, E Vieira; Souza, F; Saez, C; Cañizares, P; Lanza, M R V; Martinez-Huitle, C A; Rodrigo, M A

2016-06-01

In this work, four bench-scale plants containing soil spiked with four herbicides (2,4-Dichlorophenoxyacetic acid (2,4-D), oxyfluorfen, chlorsulfuron and atrazine) undergo treatment consisting of an electrokinetic soil flushing (EKSF). Results clearly demonstrate that efficiency of EKSF depends on the chemical characteristic of the pesticide used. The amount of pesticide collected in the anode well is more significant than that collected in the cathode wells, indicating that the electromigration is much more important than drainage by electro-osmotic flux for this application. After 15 d of treatment, the 2,4-D is the pesticide most efficiently removed (95% of removal), while chlorsulfuron is the pesticide more resilient to the treatment. Additionally, volatilization was found to be a process of the major significance in the application of electrokinetic techniques to soil polluted with herbicides and because of that it should always be taken into account in the future design of full-scale processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sequential electrokinetic treatment and oxalic acid extraction for the removal of Cu, Cr and As from wood.

PubMed

Isosaari, Pirjo; Marjavaara, Pieti; Lehmus, Eila

2010-10-15

Removal of Cu, Cr and As from utility poles treated with chromated copper arsenate (CCA) was investigated using different one- to three-step combinations of oxalic acid extraction and electrokinetic treatment. The experiments were carried out at room temperature, using 0.8% oxalic acid and 30 V (200 V/m) of direct current (DC) or alternating current in combination (DC/AC). Six-hour extraction removed only 15%, 11% and 28% and 7-day electrokinetic treatment 57%, 0% and 17% of Cu, Cr and As from wood chips, respectively. The best combination for all the metals was a three-step process consisting of pre-extraction, electrokinetics and post-extraction steps, yielding removals of 67% for Cu, 64% for Cr and 81% for As. Oxalic acid extraction prior to electrokinetic treatment was deleterious to further removal of Cu, but it was necessary for Cr and As removal. Chemical equilibrium modelling was used to explain the differences in the behaviour of Cu, Cr and As. Due to the dissimilar nature of these metals, it appeared that even more process sequences and/or stricter control of the process conditions would be needed to obtain the >99% removals required for safe recycling of the purified wood material. 2010 Elsevier B.V. All rights reserved.

Concentric-flow electrokinetic injector enables serial crystallography of ribosome and photosystem II

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

Sierra, Raymond G.; Gati, Cornelius; Laksmono, Hartawan

We describe a concentric-flow electrokinetic injector for efficiently delivering microcrystals for serial femtosecond X-ray crystallography analysis that enables studies of challenging biological systems in their unadulterated mother liquor. We used the injector to analyze microcrystals of Geobacillus stearothermophilus thermolysin (2.2-Å structure), Thermosynechococcus elongatus photosystem II (<3-Å diffraction) and Thermus thermophilus small ribosomal subunit bound to the antibiotic paromomycin at ambient temperature (3.4-Å structure).

Concentric-flow electrokinetic injector enables serial crystallography of ribosome and photosystem II.

PubMed

Sierra, Raymond G; Gati, Cornelius; Laksmono, Hartawan; Dao, E Han; Gul, Sheraz; Fuller, Franklin; Kern, Jan; Chatterjee, Ruchira; Ibrahim, Mohamed; Brewster, Aaron S; Young, Iris D; Michels-Clark, Tara; Aquila, Andrew; Liang, Mengning; Hunter, Mark S; Koglin, Jason E; Boutet, Sébastien; Junco, Elia A; Hayes, Brandon; Bogan, Michael J; Hampton, Christina Y; Puglisi, Elisabetta V; Sauter, Nicholas K; Stan, Claudiu A; Zouni, Athina; Yano, Junko; Yachandra, Vittal K; Soltis, S Michael; Puglisi, Joseph D; DeMirci, Hasan

2016-01-01

We describe a concentric-flow electrokinetic injector for efficiently delivering microcrystals for serial femtosecond X-ray crystallography analysis that enables studies of challenging biological systems in their unadulterated mother liquor. We used the injector to analyze microcrystals of Geobacillus stearothermophilus thermolysin (2.2-Å structure), Thermosynechococcus elongatus photosystem II (<3-Å diffraction) and Thermus thermophilus small ribosomal subunit bound to the antibiotic paromomycin at ambient temperature (3.4-Å structure).

Electro-kinetic remediation coupled with phytoremediation to remove lead, arsenic and cesium from contaminated paddy soil

PubMed Central

Mao, Xinyu; Han, Fengxiang X.; Shao, Xiaohou; Guo, Kai; McComb, Jacqueline; Arslan, Zikri; Zhang, Zhanyu

2017-01-01

The objectives of this study were to investigate distribution and solubility of Pb, Cs and As in soils under electrokinetic field and examine the processes of coupled electrokinetic phytoremediation of polluted soils. The elevated bioavailability and bioaccumulation of Pb, As and Cs in paddy soil under an electrokinetic field (EKF) were studied. The results show that the EKF treatment is effective on lowering soil pH to around 1.5 near the anode which is beneficial for the dissolution of metal(loid)s, thus increasing their overall solubility. The acidification in the anode soil efficiently increased the water soluble (SOL) and exchangeable (EXC) Pb, As and Cs, implying enhanced solubility and elevated overall potential bioavailability in the anode region while lower solubility in the cathode areas. Bioaccumulations of Pb, As and Cs were largely determined by the nature of elements, loading levels and EKF treatment. The native Pb in soil usually is not bioavailable. However, EKF treatment tends to transfer Pb to the SOL and EXC fractions improving the phytoextraction efficiency. Similarly, EKF transferred more EXC As and Cs to the SOL fraction significantly increasing their bioaccumulation in plant roots and shoots. Pb and As were accumulated more in plant roots than in shoots while Cs was accumulated more in shoots due to its similarity of chemical properties to potassium. Indian mustard, spinach and cabbage are good accumulators for Cs. Translocation of Pb, As and Cs from plant roots to shoots were enhanced by EKF. However, this study indicated the overall low phytoextraction efficiency of these plants. PMID:26650421

Mobilization of phenol and dichlorophenol in unsaturated soils by non-uniform electrokinetics.

PubMed

Luo, Qishi; Zhang, Xihui; Wang, Hui; Qian, Yi

2005-06-01

The poor mobility of organic pollutants in contaminated sites frequently results in slow remediation processes. Organics, especially hydrophobic compounds, are generally retained strongly in soil matrix as a result of sorption, sequestration, or even formation into non-aqueous-phase liquids and their mobility is thus greatly reduced. The objective of this study was to evaluate the feasibility of using non-uniform electrokinetic transport processes to enhance the mobility of organic pollutants in unsaturated soils with no injection reagents. Phenol and 2,4-dichlorophenol (2,4-DCP), and kaolin and a natural sandy loam soil were selected as model organics and soils, respectively. The results showed that non-uniform electrokinetics can accelerate the desorption and movement of phenol and 2,4-DCP in unsaturated soils. Electromigration and electroosmotic flow were the main driving forces, and their role in the mobilization of phenol and 2,4-DCP varied with soil pH. The movement of 2,4-DCP in the sandy loam towards the anode (about 1.0 cmd(-1)V(-1)) was 1.0-1.5 cmd(-1)V(-1) slower than that in the kaolin soil, but about 0.5 cmd(-1)V(-1) greater than that of phenol in the sandy loam. When the sandy loam was adjusted to pH 9.3, the movement of phenol and 2,4-DCP towards the anode was about twice and five times faster than that at pH 7.7, respectively. The results also demonstrated that the movement of phenol and 2,4-DCP in soils can be easily controlled by regulating the operational mode of electric field. It is believed that non-uniform electrokinetics has the potential for practical application to in situ remediation of organics-contaminated sites.

Time-dependent electrokinetic flows of non-Newtonian fluids in microchannel-array for energy conversion

NASA Astrophysics Data System (ADS)

Chun, Myung-Suk; Chun, Byoungjin; Lee, Ji-Young; Complex Fluids Team

2016-11-01

We investigate the externally time-dependent pulsatile electrokinetic viscous flows by extending the previous simulations concerning the electrokinetic microfluidics for different geometries. The external body force originated from between the nonlinear Poisson-Boltzmann field and the flow-induced electric field is employed in the Cauchy momentum equation, and then the Nernst-Planck equation in connection with the net current conservation is coupled. Our explicit model allows one to quantify the effects of the oscillating frequency and conductance of the Stern layer, considering the shear thinning effect and the strong electric double layer interaction. This presentation reports the new results regarding the implication of optimum frequency pressure pulsations toward realizing mechanical to electrical energy transfer with high conversion efficiencies. These combined factors for different channel dimension are examined in depth to obtain possible enhancements of streaming current, with taking advantage of pulsating pressure field. From experimental verifications by using electrokinetic power chip, it is concluded that our theoretical framework can serve as a useful basis for micro/nanofluidics design and potential applications to the enhanced energy conversion. NRF of Korea (No.2015R1A2A1A15052979) and KIST (No.2E26490).

Feasibility of electrokinetic oxygen supply for soil bioremediation purposes.

PubMed

Mena Ramírez, E; Villaseñor Camacho, J; Rodrigo Rodrigo, M A; Cañizares Cañizares, P

2014-12-01

This paper studies the possibility of providing oxygen to a soil by an electrokinetic technique, so that the method could be used in future aerobic polluted soil bioremediation treatments. The oxygen was generated from the anodic reaction of water electrolysis and transported to the soil in a laboratory-scale electrokinetic cell. Two variables were tested: the soil texture and the voltage gradient. The technique was tested in two artificial soils (clay and sand) and later in a real silty soil, and three voltage gradients were used: 0.0 (control), 0.5, and 1.0 V cm(-1). It was observed that these two variables strongly influenced the results. Oxygen transport into the soil was only available in the silty and sandy soils by oxygen diffusion, obtaining high dissolved oxygen concentrations, between 4 and 9 mg L(-1), useful for possible aerobic biodegradation processes, while transport was not possible in fine-grained soils such as clay. Electro-osmotic flow did not contribute to the transport of oxygen, and an increase in voltage gradients produced higher oxygen transfer rates. However, only a minimum fraction of the electrolytically generated oxygen was efficiently used, and the maximum oxygen transport rate observed, approximately 1.4 mgO2 L(-1)d(-1), was rather low, so this technique could be only tested in slow in-situ biostimulation processes for organics removal from polluted soils. Copyright © 2014 Elsevier Ltd. All rights reserved.

Improving electrokinetic microdevice stability by controlling electrolysis bubbles.

PubMed

Lee, Hwi Yong; Barber, Cedrick; Minerick, Adrienne R

2014-07-01

The voltage-operating window for many electrokinetic microdevices is limited by electrolysis gas bubbles that destabilize microfluidic system causing noise and irreproducible responses above ∼3 V DC and less than ∼1 kHz AC at 3 Vpp. Surfactant additives, SDS and Triton X-100, and an integrated semipermeable SnakeSkin® membrane were employed to control and assess electrolysis bubbles from platinum electrodes in a 180 by 70 μm, 10 mm long microchannel. Stabilized current responses at 100 V DC were observed with surfactant additives or SnakeSkin® barriers. Electrolysis bubble behaviors, visualized via video microscopy at the electrode surface and in the microchannels, were found to be influenced by surfactant function and SnakeSkin® barriers. Both SDS and Triton X-100 surfactants promoted smaller bubble diameters and faster bubble detachment from electrode surfaces via increasing gas solubility. In contrast, SnakeSkin® membranes enhanced natural convection and blocked bubbles from entering the microchannels and thus reduced current disturbances in the electric field. This data illustrated that electrode surface behaviors had substantially greater impacts on current stability than microbubbles within microchannels. Thus, physically blocking bubbles from microchannels is less effective than electrode functionalization approaches to stabilize electrokinetic microfluidic systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of three-dimensional integrated microchannel-electrode system to understand the particles' movement with electrokinetics

PubMed Central

Obara, H.; Sapkota, A.; Takei, M.

2016-01-01

An optical transparent 3-D Integrated Microchannel-Electrode System (3-DIMES) has been developed to understand the particles' movement with electrokinetics in the microchannel. In this system, 40 multilayered electrodes are embedded at the 2 opposite sides along the 5 square cross-sections of the microchannel by using Micro Electro-Mechanical Systems technology in order to achieve the optical transparency at the other 2 opposite sides. The concept of the 3-DIMES is that the particles are driven by electrokinetic forces which are dielectrophoretic force, thermal buoyancy, electrothermal force, and electroosmotic force in a three-dimensional scope by selecting the excitation multilayered electrodes. As a first step to understand the particles' movement driven by electrokinetic forces in high conductive fluid (phosphate buffer saline (PBS)) with the 3-DIMES, the velocities of particles' movement with one pair of the electrodes are measured three dimensionally by Particle Image Velocimetry technique in PBS; meanwhile, low conductive fluid (deionized water) is used as a reference. Then, the particles' movement driven by the electrokinetic forces is discussed theoretically to estimate dominant forces exerting on the particles. Finally, from the theoretical estimation, the particles' movement mainly results from the dominant forces which are thermal buoyancy and electrothermal force, while the velocity vortex formed at the 2 edges of the electrodes is because of the electroosmotic force. The conclusions suggest that the 3-DIMES with PBS as high conductive fluid helps to understand the three-dimensional advantageous flow structures for cell manipulation in biomedical applications. PMID:27042247

Concentric-flow electrokinetic injector enables serial crystallography of ribosome and photosystem II

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

Sierra, Raymond G.; Gati, Cornelius; Laksmono, Hartawan

In this paper, we describe a concentric-flow electrokinetic injector for efficiently delivering microcrystals for serial femtosecond X-ray crystallography analysis that enables studies of challenging biological systems in their unadulterated mother liquor. Finally, we used the injector to analyze microcrystals of Geobacillus stearothermophilus thermolysin (2.2-Å structure), Thermosynechococcus elongatus photosystem II (<3-Å diffraction) and Thermus thermophilus small ribosomal subunit bound to the antibiotic paromomycin at ambient temperature (3.4-Å structure).

Concentric-flow electrokinetic injector enables serial crystallography of ribosome and photosystem II

DOE PAGES

Sierra, Raymond G.; Gati, Cornelius; Laksmono, Hartawan; ...

2015-11-30

In this paper, we describe a concentric-flow electrokinetic injector for efficiently delivering microcrystals for serial femtosecond X-ray crystallography analysis that enables studies of challenging biological systems in their unadulterated mother liquor. Finally, we used the injector to analyze microcrystals of Geobacillus stearothermophilus thermolysin (2.2-Å structure), Thermosynechococcus elongatus photosystem II (<3-Å diffraction) and Thermus thermophilus small ribosomal subunit bound to the antibiotic paromomycin at ambient temperature (3.4-Å structure).

On-chip Micro- and Nanofluidic Electrokinetic Injection and Separation for PEGylation Analysis

NASA Astrophysics Data System (ADS)

Shelton, Elijah; Baum, Mary; Morse, Dan; Pennathur, Sumita; Pennathur Nanofluidics Laboratory Collaboration; Morse Laboratory Collaboration

2012-11-01

We present an experimental study of micro- and nanofluidic electrokinetic injection and separation in borosilcate channels as a method for characterizing size and zeta potential of biomolecules-specifically polyethlylene glycol (PEG), keyhole limpet hemocyanine (KLH), and pegylated KLH. While pegylation (the conjugation of proteins with PEG) is an established technique for enhancing a protein's therapeutic properties, reliable characterization of these conjugations by traditional analysis techniques (i.e. gel-electrophoresis, zetasizer) remains a challenge. Using a three-step electrokinetic sequence (load, gate, and inject), FITC labeled species and a fluorescein tracer dye are injected into a channel where they separate according to differences in electrophoretic mobility. We find the average absolute mobility of pegylated subunit KLH in 1 micron channels to be 56% that of unpegylated subunit KLH. In a 250 nm channel, we measure a 33% shift in the average absolute mobility of PEG dendrimers as compared to measurements in a 1 micron channel. These results begin to demonstrate how a micro- and nanofluidic-based approach might address the demand for effective and accessible nanoparticle characterization platforms. Supported by the Institute for Collaborative Biotechnologies.

The Physical Behavior of Stabilised Soft Clay by Electrokinetic Stabilisation Technology

NASA Astrophysics Data System (ADS)

Azhar, A. T. S.; Nordin, N. S.; Azmi, M. A. M.; Embong, Z.; Sunar, N.; Hazreek, Z. A. M.; Aziman, M.

2018-04-01

Electrokinetic Stabilisation (EKS) technology is the combination processes of electroosmosis and chemical grouting. This technique is most effective in silty and clayey soils where the hydraulic conductivity is very low. Stabilising agents will assist the EKS treatment by inducing it into soil under direct current. The movement of stabilising agents into soil is governed by the principle of electrokinetics. The aim of this study is to evaluate the physical behavior of soft soil using the EKS technology as an effective method to strengthen soft clay soils with calcium chloride (CaCl2) as the stabilising agent. Stainless steel plates were used as the electrodes, while 1.0 mol/l of CaCl2 was used as the electrolyte that fed at the anode compartment. Soft marine clay at Universiti Tun Hussein Onn Malaysia was used as the soil sample. The EKS treatment was developed at Research Centre for Soft Soil (RECESS), UTHM with a constant voltage gradient (50 V/m) in 21 days. The result shows that the shear strength of treated soil was increased across the soil sample. The treated soil near the cathode showed the highest value of shear strength (24.5 – 33 kPa) compared with the anode and in the middle of the soil sample.

Microfabricated packed gas chromatographic column

DOEpatents

Kottenstette, Richard; Matzke, Carolyn M.; Frye-Mason, Gregory C.

2003-12-16

A new class of miniaturized gas chromatographic columns has been invented. These chromatographic columns are formed using conventional micromachining techniques, and allow packed columns having lengths on the order of a meter to be fabricated with a footprint on the order of a square centimeter.

Comparison of bioleaching and electrokinetic remediation processes for removal of heavy metals from wastewater treatment sludge.

PubMed

Xu, Ying; Zhang, Chaosheng; Zhao, Meihua; Rong, Hongwei; Zhang, Kefang; Chen, Qiuli

2017-02-01

Heavy metals prevent the growing amount of sewage sludge from being disposed as fertilizeron land. The electrokinetic remediation and bioleaching technology are the promising methods to remove heavy metals. In recent years, some innovation has been made to achieve better efficiency, including the innovation of processes and agents. This paper reviews the development of the electrokinetic remediation and bioleaching technology and analyses their advantages and limitation, pointing out the need of the future research for the heavy metals-contaminated sewage sludge. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fundamental studies of chalcogenide nanocrystals, carbonaceous nanoparticles, and chromatographic materials

NASA Astrophysics Data System (ADS)

Baker, Jared Scott

2011-12-01

The development of novel nanomaterials and the understanding of their fundamental physical and chemical properties represent an exciting area of research. These materials are continuously being sought for ever-increasing applications; finding their way into uses that influence mankind on a daily basis. Combining elements from traditional nanoparticle characterization with electrophoretic-based techniques, this dissertation presents the analysis of carbon nanoparticles (CNPs) generated from a novel source (candle soot) as well as a unique perspective on the reactivity and degradation process of magic-sized cadmium chalcogenide nanocrystals. One potential application of CNPs is their use as an alternative fluorophore in a separation-based sensor system. Laser-induced-fluorescence (LIF) is a commonly used manner of detection in this type of platform, but is limited in many cases by problems associated with the fluorophore. Carbon-based nanoparticles have the potential to improve upon traditional fluorophores in applications that make use of LIF as the detection scheme. CNPs were extracted from the carbonaceous material produced by the incomplete combustion of a candle. The soot was submitted to an oxidizing treatment and extraction/filtration procedures rendering watersoluble luminescent species. Electron microscopy was used to identify globular, amorphous structures in the nanometer size-range. An aqueous suspension of CNPs demonstrated excellent stability in terms of its electronic properties, showing little change in absorption and emission spectra upon storage under ambient conditions over a two-year period. Capitalizing on the strengths of capillary electrophoresis (CE) as a characterization technique, we have analyzed the negatively-charged CNPs in terms of charge and size by studying the influence of variable CE conditions on the resulting separation. Separations at different pH revealed a highly complex mixture of CNPs, containing species with large

Electrokinetic motion of a rectangular nanoparticle in a nanochannel

NASA Astrophysics Data System (ADS)

Movahed, Saeid; Li, Dongqing

2012-08-01

This article presents a theoretical study of electrokinetic motion of a negatively charged cubic nanoparticle in a three-dimensional nanochannel with a circular cross-section. Effects of the electrophoretic and the hydrodynamic forces on the nanoparticle motion are examined. Because of the large applied electric field over the nanochannel, the impact of the Brownian force is negligible in comparison with the electrophoretic and the hydrodynamic forces. The conventional theories of electrokinetics such as the Poisson-Boltzmann equation and the Helmholtz-Smoluchowski slip velocity approach are no longer applicable in the small nanochannels. In this study, and at each time step, first, a set of highly coupled partial differential equations including the Poisson-Nernst-Plank equation, the Navier-Stokes equations, and the continuity equation was solved to find the electric potential, ionic concentration field, and the flow field around the nanoparticle. Then, the electrophoretic and hydrodynamic forces acting on the negatively charged nanoparticle were determined. Following that, the Newton second law was utilized to find the velocity of the nanoparticle. Using this model, effects of surface electric charge of the nanochannel, bulk ionic concentration, the size of the nanoparticle, and the radius of the nanochannel on the nanoparticle motion were investigated. Increasing the bulk ionic concentration or the surface charge of the nanochannel will increase the electroosmotic flow, and hence affect the particle's motion. It was also shown that, unlike microchannels with thin EDL, the change in nanochannel size will change the EDL field and the ionic concentration field in the nanochannel, affecting the particle's motion. If the nanochannel size is fixed, a larger particle will move faster than a smaller particle under the same conditions.

Physicochemical effects on uncontaminated kaolinite due to electrokinetic treatment using inert electrodes.

PubMed

Liaki, Christina; Rogers, Christopher D F; Boardman, David I

2008-07-01

To determine the consequences of applying electrokinetics to clay soils, in terms of mechanisms acting and resulting effects on the clay, tests were conducted in which an electrical gradient was applied across controlled specimens of English China Clay (ECC) using 'inert' electrodes and a 'Reverse Osmosis' water feed to the electrodes (i.e., to mimic electrokinetic stabilisation without the stabiliser added or electrokinetic remediation without the contaminant being present). The specimens in which electromigration was induced over time periods of 3, 7, 14 and 28 days were subsequently tested for Atterberg Limits, undrained shear strength using a hand shear vane, water content, pH, conductivity and zeta potential. Water flowed through the system from anode to cathode and directly affected the undrained shear strength of the clay. Acid and alkali fronts were created around the anode and cathode, respectively, causing changes in the pH, conductivity and zeta potential of the soil. Variations in zeta potential were linked to flocculation and dispersion of the soil particles, thus raising or depressing the Liquid Limit and Plastic Limit, and influencing the undrained shear strength. Initial weakening around the anode and cathode was replaced by a regain of strength at the anode once acidic conditions had been created, while highly alkaline conditions at the cathode induced a marked improvement in strength. A novel means of indicating strength improvement by chemical means, i.e., free from water content effects, is presented to assist in interpretation of the results.

Electrokinetic treatment of an agricultural soil contaminated with heavy metals.

PubMed

Figueroa, Arylein; Cameselle, Claudio; Gouveia, Susana; Hansen, Henrik K

2016-07-28

The high organic matter content in agricultural soils tends to complex and retain contaminants such as heavy metals. Electrokinetic remediation was tested in an agricultural soil contaminated with Co(+2), Zn(+2), Cd(+2), Cu(+2), Cr(VI), Pb(+2) and Hg(+2). The unenhanced electrokinetic treatment was not able to remove heavy metals from the soil due to the formation of precipitates in the alkaline environment in the soil section close to the cathode. Moreover, the interaction between metals and organic matter probably limited metal transportation under the effect of the electric field. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used in the catholyte as complexing agents in order to enhance the extractability and removal of heavy metals from soil. These complexing agents formed negatively charged complexes that migrated towards the anode. The acid front electrogenerated at the anode favored the dissolution of heavy metals that were transported towards the cathode. The combined effect of the soil pH and the complexing agents resulted in the accumulation of heavy metals in the center of the soil specimen.

Electrokinetic-enhanced bioaugmentation for remediation of chlorinated solvents contaminated clay

PubMed Central

Mao, Xuhui; Wang, James; Ciblak, Ali; Cox, Evan E.; Riis, Charlotte; Terkelsen, Mads; Gent, David B.; Alshawabkeh, Akram N.

2012-01-01

Successful bioremediation of contaminated soils is controlled by the ability to deliver bioremediation additives, such as bacteria and/or nutrients, to the contaminated zone. Because hydraulic advection is not practical for delivery in clays, electrokinetic (EK) injection is an alternative for efficient and uniform delivery of bioremediation additive into low-permeability soil and heterogeneous deposits. EK–enhanced bioaugmentation for remediation of clays contaminated with chlorinated solvents is evaluated. Dehalococcoides (Dhc) bacterial strain and lactate ions are uniformly injected in contaminated clay and complete dechlorination of chlorinated ethene is observed in laboratory experiments. The injected bacteria can survive, grow, and promote effective dechlorination under EK conditions and after EK application. The distribution of Dhc within the clay suggests that electrokinetic transport of Dhc is primarily driven by electroosmosis. In addition to biodegradation due to bioaugmentation of Dhc, an EK-driven transport of chlorinated ethenes is observed in the clay, which accelerates cleanup of chlorinated ethenes from the anode side. Compared with conventional advection-based delivery, EK injection is significantly more effective forestablis hingmicrobial reductive dechlorination capacity in low-permeability soils. PMID:22365139

Towards an understanding of induced-charge electrokinetics at large applied voltages in concentrated solutions.

PubMed

Bazant, Martin Z; Kilic, Mustafa Sabri; Storey, Brian D; Ajdari, Armand

2009-11-30

The venerable theory of electrokinetic phenomena rests on the hypothesis of a dilute solution of point-like ions in quasi-equilibrium with a weakly charged surface, whose potential relative to the bulk is of order the thermal voltage (kT/e approximately 25 mV at room temperature). In nonlinear electrokinetic phenomena, such as AC or induced-charge electro-osmosis (ACEO, ICEO) and induced-charge electrophoresis (ICEP), several V approximately 100 kT/e are applied to polarizable surfaces in microscopic geometries, and the resulting electric fields and induced surface charges are large enough to violate the assumptions of the classical theory. In this article, we review the experimental and theoretical literatures, highlight discrepancies between theory and experiment, introduce possible modifications of the theory, and analyze their consequences. We argue that, in response to a large applied voltage, the "compact layer" and "shear plane" effectively advance into the liquid, due to the crowding of counterions. Using simple continuum models, we predict two general trends at large voltages: (i) ionic crowding against a blocking surface expands the diffuse double layer and thus decreases its differential capacitance, and (ii) a charge-induced viscosity increase near the surface reduces the electro-osmotic mobility; each trend is enhanced by dielectric saturation. The first effect is able to predict high-frequency flow reversal in ACEO pumps, while the second may explain the decay of ICEO flow with increasing salt concentration. Through several colloidal examples, such as ICEP of an uncharged metal sphere in an asymmetric electrolyte, we show that nonlinear electrokinetic phenomena are generally ion-specific. Similar theoretical issues arise in nanofluidics (due to confinement) and ionic liquids (due to the lack of solvent), so the paper concludes with a general framework of modified electrokinetic equations for finite-sized ions.

Electro-kinetic remediation coupled with phytoremediation to remove lead, arsenic and cesium from contaminated paddy soil.

PubMed

Mao, Xinyu; Han, Fengxiang X; Shao, Xiaohou; Guo, Kai; McComb, Jacqueline; Arslan, Zikri; Zhang, Zhanyu

2016-03-01

The objectives of this study were to investigate distribution and solubility of Pb, Cs and As in soils under electrokinetic field and examine the processes of coupled electrokinetic phytoremediation of polluted soils. The elevated bioavailability and bioaccumulation of Pb, As and Cs in paddy soil under an electro-kinetic field (EKF) were studied. The results show that the EKF treatment is effective on lowering soil pH to around 1.5 near the anode which is beneficial for the dissolution of metal(loid)s, thus increasing their overall solubility. The acidification in the anode soil efficiently increased the water soluble (SOL) and exchangeable (EXC) Pb, As and Cs, implying enhanced solubility and elevated overall potential bioavailability in the anode region while lower solubility in the cathode areas. Bioaccumulations of Pb, As and Cs were largely determined by the nature of elements, loading levels and EKF treatment. The native Pb in soil usually is not bioavailable. However, EKF treatment tends to transfer Pb to the SOL and EXC fractions improving the phytoextraction efficiency. Similarly, EKF transferred more EXC As and Cs to the SOL fraction significantly increasing their bioaccumulation in plant roots and shoots. Pb and As were accumulated more in plant roots than in shoots while Cs was accumulated more in shoots due to its similarity of chemical properties to potassium. Indian mustard, spinach and cabbage are good accumulators for Cs. Translocation of Pb, As and Cs from plant roots to shoots were enhanced by EKF. However, this study indicated the overall low phytoextraction efficiency of these plants. Copyright © 2015 Elsevier Inc. All rights reserved.

SANDIA NATIONAL LABORATORIES IN SITU ELECTROKINETIC EXTRACTION TECHNOLOGY; INNOVATIVE TECHNOLOGY EVALUATION REPORT

EPA Science Inventory

As a part of the Superfund Innovative Technology Evaluation (SITE) Program, the U.S. Environmental Protection Agency evaluated the In-Situ Electrokinetic Extraction (ISEE) system at Sandia National Laboratories, Albuquerque, New Mexico.

The SITE demonstration results show ...

Validation of a rapid micellar electrokinetic capillary chromatographic method for the simultaneous determination of isoniazid and pyridoxine hydrochloride in pharmaceutical formulation.

PubMed

Nemutlu, E; Celebier, M; Uyar, B; Altinöz, S

2007-07-01

An efficient and reliable micellar electrokinetic capillary chromatography (MEKC) method has been developed for the simultaneous determination of isoniazid (ISO) and pyridoxine hydrochloride (PYR) in pharmaceutical formulations. A chemometric two level full factorial design approach was used to search for the optimum conditions of separation. Three parameters were selected for this study: the buffer pH, the buffer concentration and sodium dodecyl sulphate (SDS) concentrations. Resolution, peak symmetry and analysis time were established as response. The two analytes were separated within 6 min with the optimized conditions: 50 mM borate buffer, 25 mM SDS pH 7.8, 35 degrees C, at 50 mbar 4s injection and 30 kV by using a fused silica capillary (72 cm effective length, 50 microm i.d.). The detection wavelength was set to 205 nm. Meloxicam was used as internal standard. The method was validated with respect to stability, linearity range, limit of quantitation and detection, precision, accuracy, specificity and robustness. The detection limits of the method were 1.0 microg mL(-1) for ISO and 0.40 microg mL(-1) for PYR and the method was linear at least in the range of 3.0-100 microg mL(-1) for ISO and 1.0-100 microg mL(-1) for PYR with excellent correlation coefficients (0.9995 for ISO and 0.9998 for PYR). Relative standard deviations (R.S.D.s) of the described method ranged between 0.54 and 2.27% for intra-day precision and between 0.65 and 2.69% for inter-day precision. The developed method was applied to the tablet form of ISO and PYR-containing the pharmaceutical preparations and the data were compared with obtained from the standard addition method. No statistically significant difference was found.

Surface Charge Development on Transition Metal Sulfides: An Electrokinetic Study

NASA Astrophysics Data System (ADS)

Bebie, Joakim; Schoonen, Martin A. A.; Fuhrmann, Mark; Strongin, Daniel R.

1998-02-01

The isoelectric points, pH i.e.p., of ZnS, PbS, CuFeS 2, FeS, FeS 2, NiS 2, CoS 2, and MnS 2 in NaCl supported electrolyte solutions are estimated to be between pH 3.3 and 0.6, with most of the isoelectric points below pH 2. The first electrokinetic measurements on NiS 2, CoS 2, and MnS 2 are reported here. Below pH i.e.p. the metal-sulfide surfaces are positively charged, above pH i.e.p. the surfaces are negatively charged. The addition of Me 2+ ions shifts the pH i.e.p. and changes the pH dependence considerably. The isoelectric points of the measured transition metal sulfides in the absence of metal ions or dissolved sulfide (H 2S or HS -) are in agreement with those found in earlier studies. The pH range of observed isoelectric points for metal sulfides (0.6-3.3) is compared to the considerably wider pH i.e.p. range (2-12) found for oxides. The correlation between pH i.e.p. and the electronegativities of the metal sulfides suggests that all metal sulfides will have an isoelectric point between pH 0.6 and 3.3. Compared to metal oxides, sulfides exhibit an isoelectric point that is largely independent of the nature of the metal cation in the solid.

Liquid chromatographic extraction medium

DOEpatents

Horwitz, E. Philip; Dietz, Mark L.

1994-01-01

A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

Simultaneous determination of multiclass preservatives including isothiazolinones and benzophenone-type UV filters in household and personal care products by micellar electrokinetic chromatography.

PubMed

Lopez-Gazpio, Josu; Garcia-Arrona, Rosa; Millán, Esmeralda

2015-04-01

In this work, a simple and reliable micellar electrokinetic chromatography method for the separation and quantification of 14 preservatives, including isothiazolinones, and two benzophenone-type UV filters in household, cosmetic and personal care products was developed. The selected priority compounds are widely used as ingredients in many personal care products, and are included in the European Regulation concerning cosmetic products. The electrophoretic separation parameters were optimized by means of a modified chromatographic response function in combination with an experimental design, namely a central composite design. After optimization of experimental conditions, the BGE selected for the separation of the targets consisted of 60 mM SDS, 18 mM sodium tetraborate, pH 9.4 and 10% v/v methanol. The MEKC method was checked in terms of linearity, LODs and quantification, repeatability, intermediate precision, and accuracy, providing appropriate values (i.e. R(2) ≥ 0.992, repeatability RSD values ˂9%, and accuracy 90-115%). Applicability of the validated method was successfully assessed by quantifying preservatives and UV filters in commercial consumer products. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Principles of qualitative analysis in the chromatographic context.

PubMed

Valcárcel, M; Cárdenas, S; Simonet, B M; Carrillo-Carrión, C

2007-07-27

This article presents the state of the art of qualitative analysis in the framework of the chromatographic analysis. After establishing the differences between two main classes of qualitative analysis (analyte identification and sample classification/qualification) the particularities of instrumental qualitative analysis are commented on. Qualitative chromatographic analysis for sample classification/qualification through the so-called chromatographic fingerprint (for complex samples) or the volatiles profile (through the direct coupling headspace-mass spectrometry using the chromatograph as interface) is discussed. Next, more technical exposition of the qualitative chromatographic information is presented supported by a variety of representative examples.

Liquid chromatographic extraction medium

DOEpatents

Horwitz, E.P.; Dietz, M.L.

1994-09-13

A method and apparatus are disclosed for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water. 1 fig.

Heterogeneous surface charge enhanced micromixing for electrokinetic flows.

PubMed

Biddiss, Elaine; Erickson, David; Li, Dongqing

2004-06-01

Enhancing the species mixing in microfluidic applications is key to reducing analysis time and increasing device portability. The mixing in electroosmotic flow is usually diffusion-dominated. Recent numerical studies have indicated that the introduction of electrically charged surface heterogeneities may augment mixing efficiencies by creating localized regions of flow circulation. In this study, we experimentally visualized the effects of surface charge patterning and developed an optimized electrokinetic micromixer applicable to the low Reynolds number regime. Using the optimized micromixer, mixing efficiencies were improved between 22 and 68% for the applied potentials ranging from 70 to 555 V/cm when compared with the negatively charged homogeneous case. For producing a 95% mixture, this equates to a potential decrease in the required mixing channel length of up to 88% for flows with Péclet numbers between 190 and 1500.

Dual cloud point extraction coupled with hydrodynamic-electrokinetic two-step injection followed by micellar electrokinetic chromatography for simultaneous determination of trace phenolic estrogens in water samples.

PubMed

Wen, Yingying; Li, Jinhua; Liu, Junshen; Lu, Wenhui; Ma, Jiping; Chen, Lingxin

2013-07-01

A dual cloud point extraction (dCPE) off-line enrichment procedure coupled with a hydrodynamic-electrokinetic two-step injection online enrichment technique was successfully developed for simultaneous preconcentration of trace phenolic estrogens (hexestrol, dienestrol, and diethylstilbestrol) in water samples followed by micellar electrokinetic chromatography (MEKC) analysis. Several parameters affecting the extraction and online injection conditions were optimized. Under optimal dCPE-two-step injection-MEKC conditions, detection limits of 7.9-8.9 ng/mL and good linearity in the range from 0.05 to 5 μg/mL with correlation coefficients R(2) ≥ 0.9990 were achieved. Satisfactory recoveries ranging from 83 to 108% were obtained with lake and tap water spiked at 0.1 and 0.5 μg/mL, respectively, with relative standard deviations (n = 6) of 1.3-3.1%. This method was demonstrated to be convenient, rapid, cost-effective, and environmentally benign, and could be used as an alternative to existing methods for analyzing trace residues of phenolic estrogens in water samples.

Electrokinetic Control of Viscous Fingering

NASA Astrophysics Data System (ADS)

Mirzadeh, Mohammad; Bazant, Martin Z.

2017-10-01

We present a theory of the interfacial stability of two immiscible electrolytes under the coupled action of pressure gradients and electric fields in a Hele-Shaw cell or porous medium. Mathematically, our theory describes a phenomenon of "vector Laplacian growth," in which the interface moves in response to the gradient of a vector-valued potential function through a generalized mobility tensor. Physically, we extend the classical Saffman-Taylor problem to electrolytes by incorporating electrokinetic (EK) phenomena. A surprising prediction is that viscous fingering can be controlled by varying the injection ratio of electric current to flow rate. Beyond a critical injection ratio, stability depends only upon the relative direction of flow and current, regardless of the viscosity ratio. Possible applications include porous materials processing, electrically enhanced oil recovery, and EK remediation of contaminated soils.

Electrokinetic properties of polymer colloids

NASA Technical Reports Server (NTRS)

Micale, F. J.; Fuenmayor, D. Y.

1986-01-01

The surface of polymer colloids, especially polystyrene latexes, were modified for the purpose of controlling the electrokinetic properties of the resulting colloids. Achievement required a knowledge of electrical double layer charging mechanism, as a function of the electrolyte conditions, at the polymer/water interface. The experimental approach is to control the recipe formulation in the emulsion polymerization process so as to systematically vary the strong acid group concentration on the surface of the polymer particles. The electrophoretic mobility of these model particles will then be measured as a function of surface group concentration and as a function of electrolyte concentration and type. An effort was also made to evaluate the electrophoretic mobility of polystyrene latexes made in space and to compare the results with latexes made on the ground.

CHROMATOGRAPHIC AND MASS SPECTRAL STUDIES OF PERFLUOROOCTANESULFONATE AND THREE PERFLUOROOCTANESULFONAMIDES

EPA Science Inventory

The chromatographic and mass spectral characteristics of perfluorooctanesulfonate (PFOS) and three nitrogen-substituted perfluorooctanesulfonamides have been obtained. A methyl/phenol mixed phase fused silica capillary column was used for GC analysis, while a C18 reversed phase ...

Rapid Particle Patterning in Surface Deposited Micro-Droplets of Low Ionic Content via Low-Voltage Electrochemistry and Electrokinetics

PubMed Central

Sidelman, Noam; Cohen, Moshik; Kolbe, Anke; Zalevsky, Zeev; Herrman, Andreas; Richter, Shachar

2015-01-01

Electrokinetic phenomena are a powerful tool used in various scientific and technological applications for the manipulation of aqueous solutions and the chemical entities within them. However, the use of DC-induced electrokinetics in miniaturized devices is highly limited. This is mainly due to unavoidable electrochemical reactions at the electrodes, which hinder successful manipulation. Here we present experimental evidence that on-chip DC manipulation of particles between closely positioned electrodes inside micro-droplets can be successfully achieved, and at low voltages. We show that such manipulation, which is considered practically impossible, can be used to rapidly concentrate and pattern particles in 2D shapes in inter-electrode locations. We show that this is made possible in low ion content dispersions, which enable low-voltage electrokinetics and an anomalous bubble-free water electrolysis. This phenomenon can serve as a powerful tool in both microflow devices and digital microfluidics for rapid pre-concentration and particle patterning. PMID:26293477

Micro-valve using induced-charge electrokinetic motion of Janus particle.

PubMed

Daghighi, Yasaman; Li, Dongqing

2011-09-07

A new micro-valve using the electrokinetic motion of a Janus particle is introduced in this paper. A Janus particle with a conducting hemisphere and a non-conducting hemisphere is placed in a junction of several microchannels. Under an applied electric field, the induced-charge electrokinetic flow around the conducting side of the Janus particle forms vortices. The vortices push the particle moving forwards to block the entrance of a microchannel. By switching the direction of the applied electric field, the motion of the Janus particle can be changed to block different microchannels. This paper develops a theoretical model and conducts numerical simulations of the three-dimensional transient motion of the Janus particle. The results show that this Janus particle-based micro-valve is feasible for switching and controlling the flow rate in a microfluidic chip. This method is simple in comparison with other types of micro-valve methods. It is easy for fabrication, for operation control, and has a fast response time. To better understand the micro-valve functions, comparisons with a non-conducting particle and a fully conducting particle were made. Results proved that only a Janus particle can fulfill the requirements of such a micro-valve.

40 CFR 1065.267 - Gas chromatograph.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Gas chromatograph. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements § 1065.267 Gas chromatograph...

40 CFR 1065.267 - Gas chromatograph.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Gas chromatograph. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements § 1065.267 Gas chromatograph...

Evolution of microbial communities during electrokinetic treatment of antibiotic-polluted soil.

PubMed

Li, Hongna; Li, Binxu; Zhang, Zhiguo; Zhu, Changxiong; Tian, Yunlong; Ye, Jing

2018-02-01

The evolution of microbial communities during the electrokinetic treatment of antibiotic-polluted soil (EKA) was investigated with chlortetracycline (CTC), oxytetracycline (OTC) and tetracycline (TC) as template antibiotics. The total population of soil microorganisms was less affected during the electrokinetic process, while living anti-CTC, anti-OTC, anti-TC and anti-MIX bacteria were inactivated by 10.48%, 31.37%, 34.76%, and 22.08%, respectively, during the 7-day treatment compared with antibiotic-polluted soil without an electric field (NOE). Accordingly, samples with NOE treatment showed a higher Shannon index than those with EKA treatment, indicating a reduction of the microbial community diversity after electrokinetic processes. The major taxonomic phyla found in the samples of EKA and NOE treatment were Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria. And the distribution of Actinobacteria, Cyanobacteria, and Chloroflexi was greatly decreased compared with blank soil. In the phylum Proteobacteria, the abundance of Alphaproteobacteria was greatly reduced in the soils supplemented with antibiotics (from 13.40% in blank soil to 6.43-10.16% after treatment); while Betaproteobacteria and Deltaproteobacteria showed a different trend with their abundance increased compared to blank soil, and Gammaproteobacteria remained unchanged for all treatments (2.36-2.78%). The varied trends for different classes indicated that the major bacterial groups changed with the treatments due to their different adaptability to the antibiotics as well as to the electric field. SulI being an exception, the reduction ratio of the observed antibiotic resistance genes (ARGs) including tetC, tetG, tetW, tetM, intI1, and sulII in the 0-2cm soil sampled with EKA versus NOE treatment reached 55.17%, 3.59%, 99.26%, 89.51%, 30.40%, and 27.92%, respectively. Finally, correlation analysis was conducted between antibiotic-resistant bacteria, ARGs and taxonomic bacterial classes. It

Electrokinetic transport properties of deoxynucleotide monophosphates (dNMPs) through thermoplastic nanochannels.

PubMed

O'Neil, Colleen; Amarasekara, Charuni A; Weerakoon-Ratnayake, Kumuditha M; Gross, Bethany; Jia, Zheng; Singh, Varshni; Park, Sunggook; Soper, Steven A

2018-10-16

The electrokinetic behavior of molecules in nanochannels (<100 nm in length) have generated interest due to the unique transport properties observed that are not seen in microscale channels. These nanoscale dependent transport properties include transverse electromigration arising from partial electrical double layer overlap, enhanced solute/wall interactions due to the small channel diameter, and field-dependent intermittent motion produced by surface roughness. In this study, the electrokinetic transport properties of deoxynucleotide monophosphates (dNMPs) were investigated, including the effects of electric field strength, surface effects, and composition of the carrier electrolyte (ionic concentration and pH). The dNMPs were labeled with a fluorescent reporter (ATTO 532) to allow tracking of the electrokinetic transport of the dNMPs through a thermoplastic nanochannel fabricated via nanoimprinting (110 nm × 110 nm, width × depth, and 100 μm in length). We discovered that the transport properties in plastic nanochannels of the dye-labeled dNMPs produced differences in their apparent mobilities that were not seen using microscale columns. We built histograms for each dNMP from their apparent mobilities under different operating conditions and fit the histograms to Gaussian functions from which the separation resolution could be deduced as a metric to gage the ability to identify the molecule based on their apparent mobility. We found that the resolution ranged from 0.73 to 2.13 at pH = 8.3. Changing the carrier electrolyte pH > 10 significantly improved separation resolution (0.80-4.84) and reduced the standard deviation in the Gaussian fit to the apparent mobilities. At low buffer concentrations, decreases in separation resolution and increased standard deviations in Gaussian fits to the apparent mobilities of dNMPs were observed due to the increased thickness of the electric double layer leading to a partial parabolic flow profile

Geotechnical behaviour of low-permeability soils in surfactant-enhanced electrokinetic remediation.

PubMed

López-Vizcaíno, Rubén; Navarro, Vicente; Alonso, Juan; Yustres, Ángel; Cañizares, Pablo; Rodrigo, Manuel A; Sáez, Cristina

2016-01-01

Electrokinetic processes provide the basis of a range of very interesting techniques for the remediation of polluted soils. These techniques consist of the application of a current field in the soil that develops different transport mechanisms capable of mobilizing several types of pollutants. However, the use of these techniques could generate nondesirable effects related to the geomechanical behavior of the soil, reducing the effectiveness of the processes. In the case of the remediation of polluted soils with plasticity index higher than 35, an excessive shrinkage can be observed in remediation test. For this reason, the continued evaporation that takes place in the sample top can lead to the development of cracks, distorting the electrokinetic transport regime, and consequently, the development of the operation. On the other hand, when analyzing silty soils, in the surroundings of injection surfactant wells, high seepages can be generated that give rise to the development of piping processes. In this article methods are described to allow a reduction, or to even eliminate, both problems.

Portable gas chromatograph-mass spectrometer

DOEpatents

Andresen, B.D.; Eckels, J.D.; Kimmons, J.F.; Myers, D.W.

1996-06-11

A gas chromatograph-mass spectrometer (GC-MS) is described for use as a field portable organic chemical analysis instrument. The GC-MS is designed to be contained in a standard size suitcase, weighs less than 70 pounds, and requires less than 600 watts of electrical power at peak power (all systems on). The GC-MS includes: a conduction heated, forced air cooled small bore capillary gas chromatograph, a small injector assembly, a self-contained ion/sorption pump vacuum system, a hydrogen supply, a dual computer system used to control the hardware and acquire spectrum data, and operational software used to control the pumping system and the gas chromatograph. This instrument incorporates a modified commercial quadrupole mass spectrometer to achieve the instrument sensitivity and mass resolution characteristic of laboratory bench top units. 4 figs.

Portable gas chromatograph-mass spectrometer

DOEpatents

Andresen, Brian D.; Eckels, Joel D.; Kimmons, James F.; Myers, David W.

1996-01-01

A gas chromatograph-mass spectrometer (GC-MS) for use as a field portable organic chemical analysis instrument. The GC-MS is designed to be contained in a standard size suitcase, weighs less than 70 pounds, and requires less than 600 watts of electrical power at peak power (all systems on). The GC-MS includes: a conduction heated, forced air cooled small bore capillary gas chromatograph, a small injector assembly, a self-contained ion/sorption pump vacuum system, a hydrogen supply, a dual computer system used to control the hardware and acquire spectrum data, and operational software used to control the pumping system and the gas chromatograph. This instrument incorporates a modified commercial quadrupole mass spectrometer to achieve the instrument sensitivity and mass resolution characteristic of laboratory bench top units.

Electrokinetic remediation of inorganic and organic pollutants in textile effluent contaminated agricultural soil.

PubMed

Annamalai, Sivasankar; Santhanam, Manikandan; Sundaram, Maruthamuthu; Curras, Marta Pazos

2014-12-01

The discharge from the dyeing industries constitutes unfixed dyes, inorganic salts, heavy metal complexes etc., which spoil the surrounding areas of industrial sites. The present article reports the use of direct current electrokinetic technique for the treatment of textile contaminated soil. Impressed direct current voltage of 20 V facilitates the dye/metal ions movement in the naturally available dye contaminated soil towards the opposite electrode by electromigration. IrO2–RuO2–TiO2/Ti was used as anode and Ti used as cathode. UV–Visible spectrum reveals that higher dye intensity was nearer to the anode. Ni, Cr and Pb migration towards the cathode and migration of Cu, SO42− and Cl− towards anode were noticed. Chemical oxygen demand in soil significantly decreased upon employing electrokinetic. This technology may be exploited for faster and eco-friendly removal of dye in soil environment.

ENANTIOSEPARATION OF MALATHION, CRUFORMATE, AND FENSULFOTHION ORGANOSPHOSPHORUS PESTICIDES BY MIXED-MODE ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

EPA Science Inventory

Mixed-mode electrokinetic capillary chromatography (mixed-ECC) has been used for the enantioseparation of organophosphorus pesticides. In mixed-ECC, a combination of three pseudostationary phases including surfactants, neutral, and charged cyclodextrins, are used to resolve very ...

Chromatographic instrumentation in space: past, present and future developments for exobiological studies

NASA Astrophysics Data System (ADS)

Raulin, F.; Sternberg, R.; Coscia, D.; Vidal-Madjar, C.; Millot, M.-C.; Sébille, B.; Israel, G.

1999-01-01

Several planetary exploration missions have already used chromatographic techniques to search for organic compounds, including complex organics, in extraterrestrial environments. So far, only gas chromatography (GC) has been used. In two cases (Viking and Cassini-Huygens), a Py-GC-MS instrument, coupling GC with a pyrolyzer and a mass spectrometer, has been flown. Powerful miniaturized Py-GC-MS instrumentation, with high resolution multi-GC columns and time-of-flight or Ion Trap mass spectrometers are under development, in the frame of the preparation of the Rosetta mission. There is now a strong need for new chromatographic instrumentation in space, in particular to perform detailed molecular analyses of complex non-volatile organics, including macromolecular compounds. Liquid Chromatography (LC), in particular High Performance Liquid Chromatography (HPLC) Supercritical Fluid Chromatography (SFC) or Chemical-Derivatization Gas Chromatography (CDGC) could provide a very efficient mean of analyzing a wide variety of exobiologically important compounds. LC or CDGC have never been used in space yet, but feasibility studies on their application in planetary mission are needed.

Effects of triethyl phosphate and nitrate on electrokinetically enhanced biodegradation of diesel in low permeability soils.

PubMed

Lee, G T; Ro, H M; Lee, S M

2007-08-01

Bench-scale experiments for electrokinetically enhanced bioremediation of diesel in low permeability soils were conducted. An electrokinetic reactor (ER) was filled with kaolin that was artificially contaminated with diesel at a level of 2500 mg kg(-1). A constant voltage gradient of 1.0 V cm(-1) was applied. In phosphorus transport experiments, KH2PO4 was not distributed homogeneously along the ER, and most of the transported phosphorus was converted to water-insoluble aluminum phosphate after 12 days of electrokinetic (EK) operation. However, the advancing P front of triethyl phosphate (TEP) progressed with time and resulted in uniform P distribution. The treatments employed in the electrokinetically enhanced bioremediation of diesel were control (no addition of nitrogen and phosphorus), NP (KNO3+ KH2PO4), NT (KNO3+ TEP), UP (urea+ KH2PO4), and UT (urea+TEP). Analysis of effluent collected during the first 12 days of EK operation showed that diesel was not removed from the kaolin. After nutrient delivery, using the EK operation, the ER was transferred into an incubator for the biodegradation process. After 60 days of biodegradation, the concentrations of diesel in the kaolin for the NP, NT, UP, UT, and control treatments were 1356, 1002, 1658, 1612, and 2003 mg kg(-1), respectively. The ratio of biodegraded diesel concentration to initial concentration (2465 mg kg(-1)) in NP, NT, UP, UT, and control were 45.0%, 59.4%, 32.7%, 34.6%, and 18.7%, respectively. This result showed that TEP, treated along with NO3-, was most effective for the biodegradation of diesel. TEP was delivered more efficiently to the target zones and with less phosphorus loss than KH2PO4. However, this facilitated phosphorus delivery was effective in biodegrading diesel under anaerobic conditions only when electron acceptors, such as NO3-, were present.

Synergistic effects of bioremediation and electrokinetics in the remediation of petroleum-contaminated soil.

PubMed

Guo, Shuhai; Fan, Ruijuan; Li, Tingting; Hartog, Niels; Li, Fengmei; Yang, Xuelian

2014-08-01

The present study evaluated the coupling interactions between bioremediation (BIO) and electrokinetics (EK) in the remediation of total petroleum hydrocarbons (TPH) by using bio-electrokinetics (BIO-EK) with a rotatory 2-D electric field. The results demonstrated an obvious positive correlation between the degradation extents of TPH and electric intensity both in the EK and BIO-EK tests. The use of BIO-EK showed a significant improvement in degradation of TPH as compared to BIO or EK alone. The actual degradation curve in BIO-EK tests fitted well with the simulated curve obtained by combining the degradation curves in BIO- and EK-only tests during the first 60 d, indicating a superimposed effect of biological degradation and electrochemical stimulation. The synergistic effect was particularly expressed during the later phase of the experiment, concurrent with changes in the microbial community structure. The community composition changed mainly according to the duration of the electric field, leading to a reduction in diversity. No significant spatial shifts in microbial community composition and bacterial numbers were detected among different sampling positions. Soil pH was uniform during the experimental process, soil temperature showed no variations between the soil chambers with and without an electric field. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ligand-enhanced electrokinetic remediation of metal-contaminated marine sediments with high acid buffering capacity.

PubMed

Masi, Matteo; Iannelli, Renato; Losito, Gabriella

2016-06-01

The suitability of electrokinetic remediation for removing heavy metals from dredged marine sediments with high acid buffering capacity was investigated. Laboratory-scale electrokinetic remediation experiments were carried out by applying two different voltage gradients to the sediment (0.5 and 0.8 V/cm) while circulating water or two different chelating agents at the electrode compartments. Tap water, 0.1 M citric acid and 0.1 M ethylenediaminetetraacetic acid (EDTA) solutions were used respectively. The investigated metals were Zn, Pb, V, Ni and Cu. In the unenhanced experiment, the acid front could not propagate due to the high acid buffering capacity of the sediments; the production of OH(-) ions at the cathode resulted in a high-pH environment causing the precipitation of CaCO3 and metal hydroxides. The use of citric acid prevented the formation of precipitates, but solubilisation and mobilisation of metal species were not sufficiently achieved. Metal removal was relevant when EDTA was used as the conditioning agent, and the electric potential was raised up to 0.8 V/cm. EDTA led to the formation of negatively charged complexes with metals which migrated towards the anode compartment by electromigration. This result shows that metal removal from sediments with high acid buffering capacity may be achieved by enhancing the electrokinetic process by EDTA addition when the acidification of the medium is not economically and/or environmentally sustainable.

Studies on improved integrated membrane-based chromatographic process for bioseparation

NASA Astrophysics Data System (ADS)

Xu, Yanke

To improve protein separation and purification directly from a fermentation broth, a novel membrane filtration-cum-chromatography device configuration having a relatively impermeable coated zone near the hollow fiber module outlet has been developed. The integrated membrane filtration-cum-chromatography unit packed with chromatographic beads on the shell side of the hollow fiber unit enjoys the advantages of both membrane filtration and chromatography; it allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process. Interfacial polymerization was carried out to coat the bottom section of the hollow fiber membrane while leaving the rest of the hollow fiber membrane unaffected. Myoglobin (Mb), bovine serum albumin (BSA) and a-lactalbumin (a-LA) were used as model proteins in binary mixtures. Separation behaviors of binary protein mixtures were studied in devices using either an ultrafiltration (UF) membrane or a microfiltration (MF) membrane. Experimental results show that the breakthrough time and the protein loading capacities were dramatically improved after coating in both UF and MF modules. For a synthetic yeast fermentation broth feed, the Mb and a-LA elution profiles for the four consecutive cyclic runs were almost superimposable. Due to the lower transmembrane flux in this device plus the periodical washing-elution during the chromatographic separation, fouling was not a problem as it is in conventional microfiltration. A mathematical model describing the hydrodynamic and protein loading behaviors of the integrated device using UF membrane with a coated zone was developed. The simulation results for the breakthrough agree well with the experimental breakthrough curves. The optimal length of the coated zone was obtained from the simulation. A theoretical analysis of the protein mass transfer was performed using a diffusion-convection model

Fluorescence-correlation spectroscopy study of molecular transport within reversed-phase chromatographic particles compared to planar model surfaces.

PubMed

Cooper, Justin; Harris, Joel M

2014-12-02

Reversed-phase liquid chromatography (RPLC) is a widely used technique for molecular separations. Stationary-phase materials for RPLC generally consist of porous silica-gel particles functionalized with n-alkane ligands. Understanding motions of molecules within the interior of these particles is important for developing efficient chromatographic materials and separations. To characterize these dynamics, time-resolved spectroscopic methods (photobleach recovery, fluorescence correlation, single-molecule imaging) have been adapted to measure molecular diffusion rates, typically at n-alkane-modified planar silica surfaces, which serve as models of chromatographic interfaces. A question arising from these studies is how dynamics of molecules on a planar surface relate to motions of molecules within the interior of a porous chromatographic particle. In this paper, imaging-fluorescence-correlation spectroscopy is used to measure diffusion rates of a fluorescent probe molecule 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) within authentic RPLC porous silica particles and compared with its diffusion at a planar C18-modified surface. The results show that surface diffusion on the planar C18 substrate is much faster than the diffusion rate of the probe molecule through a chromatographic particle. Surface diffusion within porous particles, however, is governed by molecular trajectories along the tortuous contours of the interior surface of the particles. By accounting for the greater surface area that a molecule must explore to diffuse macroscopic distances through the particle, the molecular-scale diffusion rates on the two surfaces can be compared, and they are virtually identical. These results provide support for the relevance of surface-diffusion measurements made on planar model surfaces to the dynamic behavior of molecules on the internal surfaces of porous chromatographic particles.

Field Testing of Rapid Electrokinetic Nanoparticle Treatment for Corrosion Control of Steel in Concrete

NASA Technical Reports Server (NTRS)

Cardenas, Henry E.; Alexander, Joshua B.; Kupwade-Patil,Kunal; Calle, Luz Marina

2009-01-01

This work field tested the use of electrokinetics for delivery of concrete sealing nanoparticles concurrent with the extraction of chlorides. Several cylinders of concrete were batched and placed in immersion at the Kennedy Space Center Beach Corrosion Test Site. The specimens were batched with steel reinforcement and a 4.5 wt.% (weight percent) content of sodium chloride. Upon arrival at Kennedy Space Center, the specimens were placed in the saltwater immersion pool at the Beach Corrosion Test Site. Following 30 days of saltwater exposure, the specimens were subjected to rapid chloride extraction concurrent with electrokinetic nanoparticle treatment. The treatments were operated at up to eight times the typical current density in order to complete the treatment in 7 days. The findings indicated that the short-term corrosion resistance of the concrete specimens was significantly enhanced as was the strength of the concrete.

Chromatographic hydrogen isotope separation

DOEpatents

Aldridge, Frederick T.

1981-01-01

Intermetallic compounds with the CaCu.sub.5 type of crystal structure, particularly LaNiCo.sub.4 and CaNi.sub.5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

Chromatographic hydrogen isotope separation

DOEpatents

Aldridge, F.T.

Intermetallic compounds with the CaCu/sub 5/ type of crystal structure, particularly LaNiCo/sub 4/ and CaNi/sub 5/, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen cn produce large quantities of heavy water at an effective cost for use in heavy water reactors.

Electrokinetic-Enhanced Remediation of Phenanthrene-Contaminated Soil Combined with Sphingomonas sp. GY2B and Biosurfactant.

PubMed

Lin, Weijia; Guo, Chuling; Zhang, Hui; Liang, Xujun; Wei, Yanfu; Lu, Guining; Dang, Zhi

2016-04-01

Electrokinetic-microbial remediation (EMR) has emerged as a promising option for the removal of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils. The aim of this study was to enhance degradation of phenanthrene (Phe)-contaminated soils using EMR combined with biosurfactants. The electrokinetic (EK) remediation, combined with Phe-degrading Sphingomonas sp. GY2B, and biosurfactant obtained by fermentation of Pseudomonas sp. MZ01, degraded Phe in the soil with an efficiency of up to 65.1 % at the anode, 49.9 % at the cathode after 5 days of the treatment. The presence of biosurfactants, electricity, and a neutral electrolyte stimulated the growth of the degrading bacteria as shown by a rapid increase in microbial biomass with time. The electrical conductivity and pH changed little during the course of the treatment, which benefitted the growth of microorganisms and the remediation of Phe-contaminated soil. The EMR system with the addition of biosurfactant had the highest Phe removal, demonstrating the biosurfactant may enhance the bioavailability of Phe and the interaction with the microorganism. This study suggests that the EMR combined with biosurfactants can be used to enhance in situ bioremediation of PAH-contaminated soils.

Comparison of electrokinetic soil remediation methods using one fixed anode and approaching anodes.

PubMed

Shen, Zhemin; Chen, Xuejun; Jia, Jinping; Qu, Liya; Wang, Wenhua

2007-11-01

During the cation exchange membrane (CEM) enhanced electrokinetic (EK) soil remediation, the nearer to the anode, the higher are the H+ concentrations and the redox potentials. As both low pH and high redox potential are helpful to speed-up Cd electro-migration, soils near the anode can be quickly remedied. Usually EK process is operated with one fixed anode (FA). A novel CEM enhanced EK method with approaching anodes (AAs) is proposed to accelerate electro-migration effect. Several mesh Ti/Ru anodes were inserted as AAs in the treated soil. They were switched in turn from the anode towards the cathode. Thus high H+ ions concentrations and high redox potentials quickly migrate to the cathode. Consequently, soil remediation is accelerated and nearly 44% of energy and 40% of time can be saved. The mechanism of Cd electro-migration behavior in soils during CEM enhanced EK is described as the elution in an electrokinetically driven chromatogram.

Selecting enhancing solutions for electrokinetic remediation of dredged sediments polluted with fuel.

PubMed

Rozas, F; Castellote, M

2015-03-15

In this paper a procedure for selecting the enhancing solutions in electrokinetic remediation experiments is proposed. For this purpose, dredged marine sediment was contaminated with fuel, and a total of 22 different experimental conditions were tested, analysing the influence of different enhancing solutions by using three commercial non-ionic surfactants, one bio-surfactant, one chelating agent, and one weak acid. Characterisation, microelectrophoretic and electrokinetic remediation trials were carried out. The results are explained on the basis of the interactions between the fuel, the enhancing electrolytes and the matrix. For one specific system, the electrophoretic zeta potential, (ζ), of the contaminated matrix in the solution was found to be related to the electroosmotic averaged ζ in the experiment and not to the efficiency in the extraction. This later was correlated to a parameter accounting for both contributions, the contaminant and the enhancing solution, calculated on the basis of differences in the electrophoretic ζ in different conditions which has allowed to propose a methodology for selection of enhancing solutions. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Small-Scale Low-Cost Gas Chromatograph

ERIC Educational Resources Information Center

Gros, Natasa; Vrtacnik, Margareta

2005-01-01

The design and application of a small-scale portable gas chromatograph for learning of the basic concepts of chromatography is described. The apparatus consists of two basic separable units, which includes a chromatographic unit and an electronic unit.

Microemulsion Electrokinetic Chromatography.

PubMed

Buchberger, Wolfgang

2016-01-01

Microemulsion electrokinetic chromatography (MEEKC) is a special mode of capillary electrophoresis employing a microemulsion as carrier electrolyte. Analytes may partition between the aqueous phase of the microemulsion and its oil droplets which act as a pseudostationary phase. The technique is well suited for the separation of neutral species, in which case charged oil droplets (obtained by addition of an anionic or cationic surfactant) are present. A single set of separation parameters may be sufficient for separation of a wide range of analytes belonging to quite different chemical classes. Fine-tuning of resolution and analysis time may be achieved by addition of organic solvents, by changes in the nature of the surfactants (and cosurfactants) used to stabilize the microemulsion, or by various additives that may undergo some additional interactions with the analytes. Besides the separation of neutral analytes (which may be the most important application area of MEEKC), it can also be employed for cationic and/or anionic species. In this chapter, MEEKC conditions are summarized that have proven their reliability for routine analysis. Furthermore, the mechanisms encountered in MEEKC allow an efficient on-capillary preconcentration of analytes, so that the problem of poor concentration sensitivity of ultraviolet absorbance detection is circumvented.

ELECTROKINETIC DENSIFICATION OF COAL FINES IN WASTE PONDS

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

E. James Davis

1999-12-18

The objective of this research was to demonstrate that electrokinetics can be used to remove colloidal coal and mineral particles from coal-washing ponds and lakes without the addition of chemical additives such as salts and polymeric flocculants. The specific objectives were: Design and develop a scaleable electrophoresis apparatus to clarify suspensions of colloidal coal and clay particles; Demonstrate the separation process using polluted waste water from the coal-washing facilities at the coal-fired power plants in Centralia, WA; Develop a mathematical model of the process to predict the rate of clarification and the suspension electrical properties needed for scale up.

Faradaic AC Electrokinetic Flow and Particle Traps

NASA Astrophysics Data System (ADS)

Ben, Yuxing; Chang, Hsueh-Chia

2004-11-01

Faradaic reaction at higher voltages can produce co-ion polarization at AC electrodes instead of counter-ion polarization due to capacitive charging from the bulk. The Faradaic co-ion polarization also does not screen the external field and hence can produce large net electro-kinetic flows at frequencies lower than the inverse RC time of the double layer. Due to the opposite polarization of capacitve and Faradaic charging, we can reverse the direction of AC flows on electrodes by changing the voltage and frequency. Particles and bacteria are trapped and then dispersed at stagnation lines, at locations predicted by our theory, by using these two flows sequentially. This technique offers a good way to concentrate and detect bacteria.

Chromatographic Studies of Protein-Based Chiral Separations

PubMed Central

Bi, Cong; Zheng, Xiwei; Azaria, Shiden; Beeram, Sandya; Li, Zhao; Hage, David S.

2016-01-01

The development of separation methods for the analysis and resolution of chiral drugs and solutes has been an area of ongoing interest in pharmaceutical research. The use of proteins as chiral binding agents in high-performance liquid chromatography (HPLC) has been an approach that has received particular attention in such work. This report provides an overview of proteins that have been used as binding agents to create chiral stationary phases (CSPs) and in the use of chromatographic methods to study these materials and protein-based chiral separations. The supports and methods that have been employed to prepare protein-based CSPs will also be discussed and compared. Specific types of CSPs that are considered include those that employ serum transport proteins (e.g., human serum albumin, bovine serum albumin, and alpha1-acid glycoprotein), enzymes (e.g., penicillin G acylase, cellobiohydrolases, and α-chymotrypsin) or other types of proteins (e.g., ovomucoid, antibodies, and avidin or streptavidin). The properties and applications for each type of protein and CSP will also be discussed in terms of their use in chromatography and chiral separations. PMID:28344977

Using Aspen to Teach Chromatographic Bioprocessing: A Case Study in Weak Partitioning Chromatography for Biotechnology Applications

ERIC Educational Resources Information Center

Evans, Steven T.; Huang, Xinqun; Cramer, Steven M.

2010-01-01

The commercial simulator Aspen Chromatography was employed to study and optimize an important new industrial separation process, weak partitioning chromatography. This case study on antibody purification was implemented in a chromatographic separations course. Parametric simulations were performed to investigate the effect of operating parameters…

Electrokinetic transport in unsteady flow through peristaltic microchannel

NASA Astrophysics Data System (ADS)

Tripathi, Dharmendra; Mulchandani, Janak; Jhalani, Shubham

2016-04-01

We analyze the electrokinetic transport of aqueous electrolyte fluids with Newtonian model in presence of peristalsis through microchannel. Debye-Hückel linearization is employed to simplify the problem. Low Reynolds number and large wavelength approximations are taken into account subjected to microfluidics applications. Electrical double layer (EDL) is considered very thin and electroosmotic slip velocity (i.e. Helmholtz-Smoluchowski velocity) at the wall is subjected to study the effect of applied electrical field. The solutions for axial velocity and pressure difference along the channel length are obtained analytically and the effects of adding and opposing the flow by applied electric field have been discussed. It is revealed that the axial velocity and pressure gradient enhances with adding electric field and an opposite behavior is found in the flow direction on opposing the electric field. These results may also help towards designing organ-on-a-chip like devices for better drug design.

The Influence of Magnetic Field on Electrokinetic Potential of Colloidal Particles

NASA Astrophysics Data System (ADS)

Koshoridze, S. I.; Levin, Yu. K.

2018-06-01

The influence of a magnetic field on the electrokinetic potential of colloidal particles in a water flow oversaturated with deposited salts is reported. For the first time, the ionic hydration and dielectric permittivity of water in the double electrical layer are taken into consideration. It is demonstrated that the magnetic field influence is increased with the decreasing dielectric permittivity of water but is decreased due to ionic hydration.

Effects of surface roughness and electrokinetic heterogeneity on electroosmotic flow in microchannel

NASA Astrophysics Data System (ADS)

Masilamani, Kannan; Ganguly, Suvankar; Feichtinger, Christian; Bartuschat, Dominik; Rüde, Ulrich

2015-06-01

In this paper, a hybrid lattice-Boltzmann and finite-difference (LB-FD) model is applied to simulate the effects of three-dimensional surface roughness and electrokinetic heterogeneity on electroosmotic flow (EOF) in a microchannel. The lattice-Boltzmann (LB) method has been employed to obtain the flow field and a finite-difference (FD) method is used to solve the Poisson-Boltzmann (PB) equation for the electrostatic potential distribution. Numerical simulation of flow through a square cross-section microchannel with designed roughness is conducted and the results are critically analysed. The effects of surface heterogeneity on the electroosmotic transport are investigated for different roughness height, width, roughness interval spacing, and roughness surface potential. Numerical simulations reveal that the presence of surface roughness changes the nature of electroosmotic transport through the microchannel. It is found that the electroosmotic velocity decreases with the increase in roughness height and the velocity profile becomes asymmetric. For the same height of the roughness elements, the EOF velocity rises with the increase in roughness width. For the heterogeneously charged rough channel, the velocity profile shows a distinct deviation from the conventional plug-like flow pattern. The simulation results also indicate locally induced flow vortices which can be utilized to enhance the flow and mixing within the microchannel. The present study has important implications towards electrokinetic flow control in the microchannel, and can provide an efficient way to design a microfluidic system of practical interest.

Multivariate curve resolution based chromatographic peak alignment combined with parallel factor analysis to exploit second-order advantage in complex chromatographic measurements.

PubMed

Parastar, Hadi; Akvan, Nadia

2014-03-13

In the present contribution, a new combination of multivariate curve resolution-correlation optimized warping (MCR-COW) with trilinear parallel factor analysis (PARAFAC) is developed to exploit second-order advantage in complex chromatographic measurements. In MCR-COW, the complexity of the chromatographic data is reduced by arranging the data in a column-wise augmented matrix, analyzing using MCR bilinear model and aligning the resolved elution profiles using COW in a component-wise manner. The aligned chromatographic data is then decomposed using trilinear model of PARAFAC in order to exploit pure chromatographic and spectroscopic information. The performance of this strategy is evaluated using simulated and real high-performance liquid chromatography-diode array detection (HPLC-DAD) datasets. The obtained results showed that the MCR-COW can efficiently correct elution time shifts of target compounds that are completely overlapped by coeluted interferences in complex chromatographic data. In addition, the PARAFAC analysis of aligned chromatographic data has the advantage of unique decomposition of overlapped chromatographic peaks to identify and quantify the target compounds in the presence of interferences. Finally, to confirm the reliability of the proposed strategy, the performance of the MCR-COW-PARAFAC is compared with the frequently used methods of PARAFAC, COW-PARAFAC, multivariate curve resolution-alternating least squares (MCR-ALS), and MCR-COW-MCR. In general, in most of the cases the MCR-COW-PARAFAC showed an improvement in terms of lack of fit (LOF), relative error (RE) and spectral correlation coefficients in comparison to the PARAFAC, COW-PARAFAC, MCR-ALS and MCR-COW-MCR results. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrokinetic-enhanced phytoremediation of soils: status and opportunities.

PubMed

Cameselle, Claudio; Chirakkara, Reshma A; Reddy, Krishna R

2013-10-01

Phytoremediation is a sustainable process in which green plants are used for the removal or elimination of contaminants in soils. Both organic and inorganic contaminants can be removed or degraded by growing plants by several mechanisms, namely phytoaccumulation, phytostabilization, phytodegradation, rhizofiltration and rhizodegradation. Phytoremediation has several advantages: it can be applied in situ over large areas, the cost is low, and the soil does not undergo significant damages. However, the restoration of a contaminated site by phytoremediation requires a long treatment time since the remediation depends on the growth and the biological cycles of the plant. It is only applicable for shallow depths within the reach of the roots, and the remediation efficiency largely depends on the physico-chemical properties of the soil and the bioavailability of the contaminants. The combination of phytoremediation and electrokinetics has been proposed in an attempt to avoid, in part, the limitations of phytoremediation. Basically, the coupled phytoremediation-electrokinetic technology consists of the application of a low intensity electric field to the contaminated soil in the vicinity of growing plants. The electric field may enhance the removal of the contaminants by increasing the bioavailability of the contaminants. Variables that affect the coupled technology are: the use of AC or DC current, voltage level and mode of voltage application (continuous or periodic), soil pH evolution, and the addition of facilitating agents to enhance the mobility and bioavailability of the contaminants. Several technical and practical challenges still remain that must be overcome through future research for successful application of this coupled technology at actual field sites. Copyright © 2013 Elsevier Ltd. All rights reserved.

Electrochemical studies on the performance of SS316L electrode in electrokinetics

NASA Astrophysics Data System (ADS)

Choi, Jeong-Hee; Maruthamuthu, Sundaram; Lee, Hyun-Goo; Ha, Tae-Hyun; Bae, Jeong-Hyo

2009-10-01

Organic and trace metal pollutants are removed by employing various electrodes in an electrokinetic (EK) process. Stainless steel was used either as an anode or a cathode by various investigators in electroremediation systems. In the present study, the role of SS316L as an anode and cathode in EK system was studied by the measurements of pH, conductivity of electrolyte, and potential of the anode and cathode at different current densities. The weight loss of the anode and cathode and the leaching of chromium, iron, and nickel at different current densities were measured and discussed with an electroosmosis process. The electrochemical behavior of SS316L electrode in neutral, acidic and alkaline pH in soil environment was studied by an electrochemical technique viz. polarization study. Surface analysis of SS316L after EK was done by XPS and SEM. The higher conductivity was noticed at anolyte when compared to catholyte. The weight loss of the anode was in the following order 0.615 > 0.307 > 0.123 mA/cm2 and the cathode corrosion rate was vice versa. Peroxide production was also noticed at the anolyte, which may encourage the degradation of the total organic content (TOC) in the soil. The OCP (open circuit potential) of SS316L was about +75 mV vs SCE in the soil extract; while adding acetic acid, the potential shifted to the positive side, to about +380 mV vs SCE. The breakdown potential and the range of passivation potential were higher in acetic acid added system when compared to other systems. Pitting was observed on both the anode and cathode within 48 h during the EK process. The present study concludes that SS is not a proper electrode material for the EK process.

A nonlinear model for gas chromatograph systems

NASA Technical Reports Server (NTRS)

Feinberg, M. P.

1975-01-01

Fundamental engineering design techniques and concepts were studied for the optimization of a gas chromatograph-mass spectrometer chemical analysis system suitable for use on an unmanned, Martian roving vehicle. Previously developed mathematical models of the gas chromatograph are found to be inadequate for predicting peak heights and spreading for some experimental conditions and chemical systems. A modification to the existing equilibrium adsorption model is required; the Langmuir isotherm replaces the linear isotherm. The numerical technique of Crank-Nicolson was studied for use with the linear isotherm to determine the utility of the method. Modifications are made to the method eliminate unnecessary calculations which result in an overall reduction of the computation time of about 42 percent. The Langmuir isotherm is considered which takes into account the composition-dependent effects on the thermodynamic parameter, mRo.

[UPLC characteristic chromatographic profile of Poria].

PubMed

Zhang, Qi; Wang, Zhenzhong; Xiao, Wei; Zhang, Liangqi; Bi, Kaishun; Jia, Ying

2012-04-01

To establish a UPLC characteristic chromatographic profile analysis method to quickly assess Poria quality and provide basis fro controlling Poria quality. The UPLC characteristic chromatographic profiles of fifteen batches of Poria were determined by ACQUITY UPLC, with HSS T3 Column (2.1 mm x 100 mm, 1.8 microm) eluted with the mobile phases of water containing 0.05% phosphoric acid and acetonitrile in gradient mode. The detection wavelength was set at 243 nm. The common mode of the UPLC characteristic chromatographic profile was set up. There were 20 common peaks, seven of which were identified, and the similar degrees of the fifteen samples to the common mode were between 0.787 and 0.974. The method was so time-saving that it can be used for the quality control of Poria.

Probabilistic peak detection for first-order chromatographic data.

PubMed

Lopatka, M; Vivó-Truyols, G; Sjerps, M J

2014-03-19

We present a novel algorithm for probabilistic peak detection in first-order chromatographic data. Unlike conventional methods that deliver a binary answer pertaining to the expected presence or absence of a chromatographic peak, our method calculates the probability of a point being affected by such a peak. The algorithm makes use of chromatographic information (i.e. the expected width of a single peak and the standard deviation of baseline noise). As prior information of the existence of a peak in a chromatographic run, we make use of the statistical overlap theory. We formulate an exhaustive set of mutually exclusive hypotheses concerning presence or absence of different peak configurations. These models are evaluated by fitting a segment of chromatographic data by least-squares. The evaluation of these competing hypotheses can be performed as a Bayesian inferential task. We outline the potential advantages of adopting this approach for peak detection and provide several examples of both improved performance and increased flexibility afforded by our approach. Copyright © 2014 Elsevier B.V. All rights reserved.

Factors influencing the removal of antibiotic-resistant bacteria and antibiotic resistance genes by the electrokinetic treatment.

PubMed

Li, Hongna; Li, Binxu; Zhang, Zhiguo; Tian, Yunlong; Ye, Jing; Lv, Xiwu; Zhu, Changxiong

2018-09-30

The performance of the electrokinetic remediation process on the removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) was evaluated with different influencing factors. With chlortetracycline (CTC), oxytetracycline (OTC), and tetracycline (TC) as template chemicals, the removal of both ARB and ARGs was enhanced with the increase of voltage gradient (0.4-1.2 V cm -1 ) and prolonged reaction time (3-14 d). The greatest removal (26.01-31.48% for ARB, 37.93-83.10% for ARGs) was obtained applying a voltage of 1.2 V cm -1 , leading to the highest electrical consumption. The effect of polarity reversal intervals on the inactivation ratio of ARB followed the order of 0 h (66.06-80.00%) > 12 h (17.07-24.75%) > 24 h (10.44-13.93%). Lower pH, higher current density, and more evenly-distributed voltage drop was observed with a polarity reversal interval of 12 h compared with that of 24 h, leading to more efficient electrochemical reactions in soil. Compared with sul genes, tet genes were more vulnerable to be attacked in an electric field. It was mainly attributed to the lower abundance of tet genes (except tetM) and the varied effects of electrokinetic remediation process on different ARGs. Moreover, a relatively less removal ratio of tetC and tetG was obtained mainly due to the mechanism of the efflux pump upregulation. Both tet and sul genes were positively correlated with TC-resistant bacteria. The efflux pump genes like tetG and the cellular protection genes like tetM showed different correlations with ARB. This study enhances the current understanding on the removal strategies of ARB and ARGs, and it provides important parameters for their destruction by the electrokinetic treatment. Copyright © 2018 Elsevier Inc. All rights reserved.

Chiral separation of vinpocetine using cyclodextrin-modified micellar electrokinetic chromatography.

PubMed

Wan Ibrahim, Wan Aini; Abd Wahib, Siti Munirah; Hermawan, Dadan; Sanagi, Mohd Marsin; Aboul-Enein, Hassan Y

2012-03-01

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) technique has been developed for enantioseparation of vinpocetine using an inexpensive 2-hydroxypropyl-β-CD (HP-β-CD) as the chiral selector (CS). The best chiral separation was achieved using 40 mM HP-β-CD as the CS in 50 mM phosphate buffer (pH 7.0) consisting of 40 mM sodium dodecyl sulfate (SDS) at a separation temperature and separation voltage of 25°C and 25 kV, respectively. To the author's best knowledge, this is the first CD-MEKC study able to successfully separate the four stereoisomer of vinpocetine in separation time of 9.5 min and resolution of 1.04-3.87. Copyright © 2012 Wiley Periodicals, Inc.

The use of gas chromatographic-mass spectrometric-computer systems in pharmacokinetic studies.

PubMed

Horning, M G; Nowlin, J; Stafford, M; Lertratanangkoon, K; Sommer, K R; Hill, R M; Stillwell, R N

1975-10-29

Pharmacokinetic studies involving plasma, urine, breast milk, saliva and liver homogenates have been carried out by selective ion detection with a gas chromatographic-mass spectrometric-computer system operated in the chemical ionization mode. Stable isotope labeled drugs were used as internal standards for quantification. The half-lives, the concentration at zero time, the slope (regression coefficient), the maximum velocity of the reaction and the apparent Michaelis constant of the reaction were determined by regression analysis, and also by graphic means.

Method and apparatus for electrokinetic transport

NASA Technical Reports Server (NTRS)

James, Patrick Ismail (Inventor); Stejic, George (Inventor)

2012-01-01

Controlled electrokinetic transport of constituents of liquid media can be achieved by connecting at least two volumes containing liquid media with at least one dielectric medium with opposing dielectric surfaces in direct contact with said liquid media, and establishing at least one conduit across said dielectric medium, with a conduit inner surface surrounding a conduit volume and at least a first opening and a second opening opposite to the first opening. The conduit is arranged to connect two volumes containing liquid media and includes a set of at least three electrodes positioned in proximity of the inner conduit surface. A power supply is arranged to deliver energy to the electrodes such that time-varying potentials inside the conduit volume are established, where the superposition of said potentials represents at least one controllable traveling potential well that can travel between the opposing conduit openings.

Numerical analysis for electrokinetic soil processing enhanced by chemical conditioning of the electrode reservoirs.

PubMed

Park, Jin-Soo; Kim, Soon-Oh; Kim, Kyoung-Woong; Kim, Byung Ro; Moon, Seung-Hyeon

2003-04-04

A numerical analysis was undertaken for enhanced electrokinetic soil processing. To perform chemical conditioning of the electrode reservoirs, the electrokinetic soil process employed a membrane as a barrier between the electrode reservoirs and the contaminated soil. An alkaline solution was purged in the anode reservoir that was bounded by the membrane. A mathematical model was used for demonstration of pH change and phenol removal from a kaolinite soil bed, the prediction of pH variations in both electrode reservoirs, and the determination of an optimized injection time of the anode-purging solution. The time-dependent dispersion coefficient was employed in consideration of the averaging effect of the velocity profile on a one-dimensional transport. The estimation of pH and phenol profiles in the soil bed reasonably agreed with the experimental data. The simulation revealed that the removal efficiency of phenol from the kaolinite soil could be improved by maintaining pH of the anode solution.

An assessment of the effectiveness and impact of electrokinetic remediation for pyrene-contaminated soil.

PubMed

Xu, Sujuan; Guo, Shuhai; Wu, Bo; Li, Fengmei; Li, Tingting

2014-11-01

The effectiveness of electrokinetic remediation for pyrene-contaminated soil was investigated by an anode-cathode separated system using a salt bridge. The applied constant voltage was 24 V and the electrode gap was 24 cm. Two types of soil (sandy soil and loam soil) were selected because of their different conductive capabilities. The initial concentrations of pyrene in these soil samples were 261.3mg/kg sandy soil and 259.8 mg/kg loam soil. After treatment of the sandy soil and loam soil for seven days, 56.8% and 20.1% of the pyrene had been removed respectively. Under the same power supply voltage, the removal of the pollutant from the sandy soil was greater than that from the loam soil, due to the higher current and lower pH. Further analysis revealed that the effectiveness of electrokinetic remediation was affected by the energy expenditure, and was associated with changes in soil properties. Copyright © 2014. Published by Elsevier B.V.

Electrokinetic remediation of contaminated soil with waste-lubricant oils and zinc.

PubMed

Park, Sung-Woo; Lee, Jae-Young; Yang, Jung-Seok; Kim, Kyoung-Jo; Baek, Kitae

2009-09-30

The feasibility of electrokinetic technology on the remediation of mixed-waste-contaminated railroad soil, contaminated by lubricant oil and zinc, was investigated. To enhance the removal efficiency, catholyte purging with 0.1M HNO(3) and a supply of non-ionic surfactant, secondary alcohol ethoxylate, was applied to the anode to remove Zn and to solubilize the lubricant oil. The catholyte purging maintained the soil pH as acidic and enhanced desorption of zinc from the soil, where the zeta potential of the acidic soil became positive. Thereafter, the direction of electro-osmotic flow was changed from the cathode to anode and the flow rate was reduced. The lesser in magnitude reverse electro-osmotic flow inhibited the migration of zinc and the lubricant oil was removed by the electro-osmotic flow. The removal of zinc and lubricant oil was enhanced with an increase in voltage gradient; however, a higher voltage gradient resulted in higher energy expenditure. After electrokinetic operation over 17 days, the removal efficiency of zinc was 22.1-24.3%, and that of lubricant oil was 45.1-55.0%. Although the removal of lubricant oil was quite high, the residual concentration did not meet Korean regulation levels.

Sludge reduction in a small wastewater treatment plant by electro-kinetic disintegration.

PubMed

Chiavola, Agostina; Ridolfi, Alessandra; D'Amato, Emilio; Bongirolami, Simona; Cima, Ennio; Sirini, Piero; Gavasci, Renato

2015-01-01

Sludge reduction in a wastewater treatment plant (WWTP) has recently become a key issue for the managing companies, due to the increasing constraints on the disposal alternatives. Therefore, all the solutions proposed with the aim of minimizing sludge production are receiving increasing attention and are tested either at laboratory or full-scale to evaluate their real effectiveness. In the present paper, electro-kinetic disintegration has been applied at full-scale in the recycle loop of the sludge drawn from the secondary settlement tank of a small WWTP for domestic sewage. After the disintegration stage, the treated sludge was returned to the biological reactor. Three different percentages (50, 75 and 100%) of the return sludge flow rate were subjected to disintegration and the effects on the sludge production and the WWTP operation efficiency evaluated. The long-term observations showed that the electro-kinetic disintegration was able to drastically reduce the amount of biological sludge produced by the plant, without affecting its treatment efficiency. The highest reduction was achieved when 100% return sludge flow rate was subjected to the disintegration process. The reduced sludge production gave rise to a considerable net cost saving for the company which manages the plant.

Micromixer utilizing electrokinetic instability-induced shedding effect.

PubMed

Tai, Chang-Hsien; Yang, Ruey-Jen; Huang, Min-Zhong; Liu, Chia-Wei; Tsai, Chien-Hsiung; Fu, Lung-Ming

2006-12-01

This paper presents a T-shaped micromixer featuring 45 degrees parallelogram barriers (PBs) within the mixing channel. The presented device obtains a rapid mixing of two sample fluids with conductivity ratio of 10:1 (sample concentration:running buffer concentration) by means of the electrokinetic instability-induced shedding effects which are produced when a direct current (DC) electric field of an appropriate intensity is applied. The presented device uses a single high-voltage power source to simultaneously drive and mix the sample fluids. The effectiveness of the mixer is characterized experimentally as a function of the applied electrical field intensity and the extent to which the PBs obstruct the mixing channel. The experimental results indicate that the mixing performance reaches 91% at a cross-section located 2.3 mm downstream of the T-junction when the barriers obstruct 4/5 of the channel width and an electrical field of 300 V/cm is applied. The micromixing method presented in this study provides a simple low-cost solution to mixing problems in lab-on-a-chip systems.

Optimization of the separation of lysergic acid diethylamide in urine by a sweeping technique using micellar electrokinetic chromatography.

PubMed

Fang, Ching; Liu, Ju-Tsung; Lin, Cheng-Huang

2002-07-25

The separation and on-line concentrations of lysergic acid diethylamide (LSD), iso-lysergic acid diethylamide (iso-LSD) and lysergic acid N,N-methylpropylamide (LAMPA) in human urine were investigated by capillary electrophoresis-fluorescence spectroscopy using sodium dodecyl sulfate (SDS) as an anionic surfactant. A number of parameters such as buffer pH, SDS concentration, Brij-30 concentration and the content of organic solvent used in separation, were optimized. The techniques of sweeping-micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were used for determining on-line concentrations. The advantages and disadvantages of this procedure with respect to sensitivity, precision and simplicity are discussed and compared. Copyright 2002 Elsevier Science BV.

Deconvolution of gas chromatographic data

NASA Technical Reports Server (NTRS)

Howard, S.; Rayborn, G. H.

1980-01-01

The use of deconvolution methods on gas chromatographic data to obtain an accurate determination of the relative amounts of each material present by mathematically separating the merged peaks is discussed. Data were obtained on a gas chromatograph with a flame ionization detector. Chromatograms of five xylenes with differing degrees of separation were generated by varying the column temperature at selected rates. The merged peaks were then successfully separated by deconvolution. The concept of function continuation in the frequency domain was introduced in striving to reach the theoretical limit of accuracy, but proved to be only partially successful.

Electrokinetic-Fenton technology for the remediation of hydrocarbons historically polluted sites.

PubMed

Sandu, Ciprian; Popescu, Marius; Rosales, Emilio; Bocos, Elvira; Pazos, Marta; Lazar, Gabriel; Sanromán, M Angeles

2016-08-01

The feasibility of the electrokinetic-Fenton technology coupled with surfactants in the treatment of real historically hydrocarbons polluted soils has been studied. The characterisation of these soils from Spain and Romania was performed and identified as diesel and diesel-motor oil spillages, respectively. Moreover, the ageing of the spillages produced by the soil contamination was estimated showing the historical pollution of the sites (around 11 and 20 years for Romanian and Spanish soils, respectively). An ex-situ electrochemical treatment was performed to evaluate the adequacy of surfactants for the degradation of the hydrocarbons present in the soils. It was found an enhancement in the solubilisation and removal of TPHs with percentages increasing from 25.7 to 81.8% by the presence of Tween 80 for Spanish soil and from 15.1% to 71.6% for Triton X100 in Romanian soil. Therefore, the viability of coupling enhanced electrokinetic and Fenton remediation was evaluated through a simulated in-situ treatment at laboratory scale. The results demonstrated that the addition of the selected surfactants improved the solubilisation of the hydrocarbons and influenced the electroosmotic flow with a slight decrease. The efficiency of the treatment increased for both considered soil samples and a significant degradation level of the hydrocarbons compounds was observed. Buffering of pH coupled with the addition of a complexing agent showed to be important in the treatment process, facilitating the conditions for the degradation reactions that take place into the soil matrix. The results demonstrated the effectiveness of the selected techniques for remediation of the investigated soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

A simple novel device for air sampling by electrokinetic capture.

PubMed

Gordon, Julian; Gandhi, Prasanthi; Shekhawat, Gajendra; Frazier, Angel; Hampton-Marcell, Jarrad; Gilbert, Jack A

2015-12-27

A variety of different sampling devices are currently available to acquire air samples for the study of the microbiome of the air. All have a degree of technical complexity that limits deployment. Here, we evaluate the use of a novel device, which has no technical complexity and is easily deployable. An air-cleaning device powered by electrokinetic propulsion has been adapted to provide a universal method for collecting samples of the aerobiome. Plasma-induced charge in aerosol particles causes propulsion to and capture on a counter-electrode. The flow of ions creates net bulk airflow, with no moving parts. A device and electrode assembly have been re-designed from air-cleaning technology to provide an average air flow of 120 lpm. This compares favorably with current air sampling devices based on physical air pumping. Capture efficiency was determined by comparison with a 0.4 μm polycarbonate reference filter, using fluorescent latex particles in a controlled environment chamber. Performance was compared with the same reference filter method in field studies in three different environments. For 23 common fungal species by quantitative polymerase chain reaction (qPCR), there was 100 % sensitivity and apparent specificity of 87 %, with the reference filter taken as "gold standard." Further, bacterial analysis of 16S RNA by amplicon sequencing showed equivalent community structure captured by the electrokinetic device and the reference filter. Unlike other current air sampling methods, capture of particles is determined by charge and so is not controlled by particle mass. We analyzed particle sizes captured from air, without regard to specific analyte by atomic force microscopy: particles at least as low as 100 nM could be captured from ambient air. This work introduces a very simple plug-and-play device that can sample air at a high-volume flow rate with no moving parts and collect particles down to the sub-micron range. The performance of the device is

Zn (II) Removal from River Water Samples of Sembrong, Johor State, Malaysia by Electrokinetic Remediation

NASA Astrophysics Data System (ADS)

Zaidi, E.; Husna, MNF; Shakila, A.; Azhar, ATS; Arif, AM; Norshuhaila, MS

2017-08-01

Heavy metals pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. Even many physical, chemical and biological treatment processes have been proposed to remove heavy metals from river water, the use of these treatment processes are not efficient and relatively costly. This study focused on the potential application of electrokinetic (EK) remediation in Sembrong River water to remove zinc (Zn2+). The physicochemical and biological parameters and water quality index (WQI) of Sembrong River water was characterized. The electrokinetic remediation experiments were performed by controlling pH, and electric density on voltage were observed and investigated. The results indicated that all physicochemical and biological parameters of Sembrong River complied with the standard discharged limit set by the Department of Environment (DOE). However, suspended solids (SS) and pH can be categorized as Class III according to INWQS. The best performance of 88% efficiency of zinc can be achieved EK experiment run at a fixed voltage of 30 V at pH 5.14 after 60 min of the process operate. This technology may be proposed for faster and eco-friendly removal of heavy metals in the environment.

Simple automatic strategy for background drift correction in chromatographic data analysis.

PubMed

Fu, Hai-Yan; Li, He-Dong; Yu, Yong-Jie; Wang, Bing; Lu, Peng; Cui, Hua-Peng; Liu, Ping-Ping; She, Yuan-Bin

2016-06-03

Chromatographic background drift correction, which influences peak detection and time shift alignment results, is a critical stage in chromatographic data analysis. In this study, an automatic background drift correction methodology was developed. Local minimum values in a chromatogram were initially detected and organized as a new baseline vector. Iterative optimization was then employed to recognize outliers, which belong to the chromatographic peaks, in this vector, and update the outliers in the baseline until convergence. The optimized baseline vector was finally expanded into the original chromatogram, and linear interpolation was employed to estimate background drift in the chromatogram. The principle underlying the proposed method was confirmed using a complex gas chromatographic dataset. Finally, the proposed approach was applied to eliminate background drift in liquid chromatography quadrupole time-of-flight samples used in the metabolic study of Escherichia coli samples. The proposed method was comparable with three classical techniques: morphological weighted penalized least squares, moving window minimum value strategy and background drift correction by orthogonal subspace projection. The proposed method allows almost automatic implementation of background drift correction, which is convenient for practical use. Copyright © 2016 Elsevier B.V. All rights reserved.

A statistical approach of zinc remediation using acidophilic bacterium via an integrated approach of bioleaching enhanced electrokinetic remediation (BEER) technology.

PubMed

Selvi, Adikesavan; Aruliah, Rajasekar

2018-09-01

The aim of the present study was to isolate an indigenous acidophilic bacterium from tannery effluent contaminated sludge (TECS) sample and evaluate its potentiality towards the removal of zinc using an integrated approach of bioleaching enhanced electrokinetic remediation (BEER) technology in zinc spiked soil at an initial concentration of 1000 mg/kg. The isolated acidophilic bacterium was characterized by biochemical and 16S rRNA molecular identification and was named as Serratia marcescens SMAR1 bearing an accession no. MG742410 in NCBI database. The effect of pH and inoculum dosage of SMAR 1 strain showed an optimal growth at pH 5.0 and 4% (v/v) respectively. Based on these experimental data, a statistical analysis was done using Design Expert computer software, v11 to study the interaction between the process parameters with respect to zinc reduction as an output response. Electrokinetic experiments were conducted in a customised EK cell under optimised process conditions, employing titanium electrodes. Experiments for zinc removal were demonstrated for bioleaching, electrokinetic (EK) and BEER technology. On comparing, the integrated process was found to evidence as an excellent metal remediation option with a maximum zinc removal of 93.08% in 72 h than plain bioleaching (72.86%) and EK (56.67%) in 96 h. This is the first report of zinc removal in a short period of time using Serratia marcescens. It is therefore concluded that the BEER approach can be regarded as an effective technology in cleaning up the metal contaminated environment with an easy recovery and reuse option within short period of time. Copyright © 2018 Elsevier Ltd. All rights reserved.

Multivariate analysis of variance of designed chromatographic data. A case study involving fermentation of rooibos tea.

PubMed

Marini, Federico; de Beer, Dalene; Walters, Nico A; de Villiers, André; Joubert, Elizabeth; Walczak, Beata

2017-03-17

An ultimate goal of investigations of rooibos plant material subjected to different stages of fermentation is to identify the chemical changes taking place in the phenolic composition, using an untargeted approach and chromatographic fingerprints. Realization of this goal requires, among others, identification of the main components of the plant material involved in chemical reactions during the fermentation process. Quantitative chromatographic data for the compounds for extracts of green, semi-fermented and fermented rooibos form the basis of preliminary study following a targeted approach. The aim is to estimate whether treatment has a significant effect based on all quantified compounds and to identify the compounds, which contribute significantly to it. Analysis of variance is performed using modern multivariate methods such as ANOVA-Simultaneous Component Analysis, ANOVA - Target Projection and regularized MANOVA. This study is the first one in which all three approaches are compared and evaluated. For the data studied, all tree methods reveal the same significance of the fermentation effect on the extract compositions, but they lead to its different interpretation. Copyright © 2017 Elsevier B.V. All rights reserved.

Method to fabricate silicon chromatographic column comprising fluid ports

DOEpatents

Manginell, Ronald P.; Frye-Mason, Gregory C.; Heller, Edwin J.; Adkins, Douglas R.

2004-03-02

A new method for fabricating a silicon chromatographic column comprising through-substrate fluid ports has been developed. This new method enables the fabrication of multi-layer interconnected stacks of silicon chromatographic columns.

Monitoring of electrokinetic removal of heavy metals in tailing-soils using sequential extraction analysis.

PubMed

Kim, S O; Kim, K W

2001-08-17

This research focused on the monitoring of the electrokinetic removal of heavy metals from tailing-soils, and emphasizes the dependency of removal efficiencies upon their physico-chemical states, as demonstrated by the different extraction methods adopted, which included aqua regia and sequential extraction. The tailing-soils examined contained high concentrations of target metal contaminants (Cd=179mgkg(-1), Cu=207mgkg(-1), Pb=5175mgkg(-1), and Zn=7600mgkg(-1)). The removal efficiencies of the different metals were significantly influenced by their speciations, mobilities and affinities (adsorption capacities) in the soil matrix. The removal efficiencies of mobile and weakly bound fractions, such as the exchangeable fraction were more than 90% by electrokinetic treatment, but strongly bound fractions, such as the organically bound species and residual fraction were not significantly removed (less than 30% removal efficiencies). In accordance with the general sequence of mobilities of heavy metals in soils, the removal efficiencies of more mobile heavy metals (Cd, Cu, and Zn) were higher than that of less mobile heavy metal (Pb).

Environmental assessment on electrokinetic remediation of multimetal-contaminated site: a case study.

PubMed

Kim, Do-Hyung; Yoo, Jong-Chan; Hwang, Bo-Ram; Yang, Jung-Seok; Baek, Kitae

2014-05-01

In this study, an environmental assessment on an electrokinetic (EK) system for the remediation of a multimetal-contaminated real site was conducted using a green and sustainable remediation (GSR) tool. The entire EK process was classified into major four phases consisting of remedial investigations (RIs), remedial action construction (RAC), remedial action operation (RAO), and long-term monitoring (LTM) for environmental assessment. The environmental footprints, including greenhouse gas (GHG) emissions, total energy used, air emissions of criteria pollutants, such as NOx, SOx, and PM10, and water consumption, were calculated, and the relative contribution in each phase was analyzed in the environmental assessment. In the RAC phase, the relative contribution of the GHG emissions, total energy used, and PM10 emissions were 77.3, 67.6, and 70.4%, respectively, which were higher than those of the other phases because the material consumption and equipment used for system construction were high. In the RAO phase, the relative contributions of water consumption and NOx and SOx emissions were 94.7, 85.2, and 91.0%, respectively, which were higher than those of the other phases, because the water and electricity consumption required for system operation was high. In the RIs and LTM phases, the environmental footprints were negligible because the material and energy consumption was less. In conclusion, the consumable materials and electrical energy consumption might be very important for GSR in the EK remediation process, because the production of consumable materials and electrical energy consumption highly affects the GHG emissions, total energy used, and air emissions such as NOx and SOx.

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.

Capillary-valve-based fabrication of ion-selective membrane junction for electrokinetic sample preconcentration in PDMS chip.

PubMed

Liu, Vincent; Song, Yong-Ak; Han, Jongyoon

2010-06-07

In this paper, we report a novel method for fabricating ion-selective membranes in poly(dimethylsiloxane) (PDMS)/glass-based microfluidic preconcentrators. Based on the concept of capillary valves, this fabrication method involves filling a lithographically patterned junction between two microchannels with an ion-selective material such as Nafion resin; subsequent curing results in a high aspect-ratio membrane for use in electrokinetic sample preconcentration. To demonstrate the concentration performance of this high-aspect-ratio, ion-selective membrane, we integrated the preconcentrator with a surface-based immunoassay for R-Phycoerythrin (RPE). Using a 1x PBS buffer system, the preconcentrator-enhanced immunoassay showed an approximately 100x improvement in sensitivity within 30 min. This is the first time that an electrokinetic microfluidic preconcentrator based on ion concentration polarization (ICP) has been used in high ionic strength buffer solutions to enhance the sensitivity of a surface-based immunoassay.

Non-equilibrium electrokinetic micromixer with 3D nanochannel networks.

PubMed

Choi, Eunpyo; Kwon, Kilsung; Lee, Seung Jun; Kim, Daejoong; Park, Jungyul

2015-04-21

We report an active micromixer which utilizes vortex generation due to non-equilibrium electrokinetics near the interface between a microchannnel and a nanochannel networks membrane (NCNM), constructed from geometrically controlled in situ self-assembled nanoparticles. A large interfacing area where it is possible to generate vortices can be realized, because nano-interstices between the assembled nanoparticles are intrinsically collective three-dimensional nanochannel networks, which may be compared to typical silicon-based 2D nanochannels. The proposed mixer shows a 2-fold shorter mixing time (~0.78 ms) and a 34-fold shorter mixing length (~7.86 μm) compared to conventional 2D nanochannels.

TRACE ANALYSIS OF FLUORESCEIN-DERIVATIZED PHENOXY ACID HERBICIDES BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY WITH LASER-INDUCTED FLUORESCENCE DETECTION

EPA Science Inventory

Micellar electrokinetic chromatography (MEKC) with laser-induced fluorescence (LIF) detection was used for the trace analysis of phenoxy acid herbicides. Capillary electrophoresis (CE) with LIF detection, which has not previously been used for pesticide analysis, overcomes the po...

High-performance liquid chromatographic method for potency determination of amoxicillin in commercial preparations and for stability studies.

PubMed Central

Hsu, M C; Hsu, P W

1992-01-01

A reversed-phase column liquid chromatographic method was developed for the assay of amoxicillin and its preparations. The linear calibration range was 0.2 to 2.0 mg/ml (r = 0.9998), and recoveries were generally greater than 99%. The high-performance liquid chromatographic assay results were compared with those obtained from a microbiological assay of bulk drug substance and capsule, injection, and granule formulations containing amoxicillin and degraded amoxicillin. At the 99% confidence level, no significant intermethod differences were noted for the paired results. Commercial formulations were also analyzed, and the results obtained by the proposed method closely agreed with those found by the microbiological method. The results indicated that the proposed method is a suitable substitute for the microbiological method for assays and stability studies of amoxicillin preparations. PMID:1416827

Studies on Chromatographic Fingerprint and Fingerprinting Profile-Efficacy Relationship of Polygoni Perfoliati Herba

PubMed Central

Tian, Li; Chen, Hua-Guo; Zhao, Chao; Gong, Xiao-Jian

2013-01-01

Polygoni Perfoliati Herba is widely used in China with antibacterium, anti-inflammatory, expectorant, antitumor, and antivirus activities. To reveal the mechanisms of the activities of Polygoni Perfoliati Herba, the relationship between the fingerprinting profile and its bioactivities was investigated. In the present study, high-performance liquid chromatographic (HPLC) fingerprinting method was developed. The established method was applied to analyze 51 batches of Polygoni Perfoliati Herba samples collected from different locations or in different harvesting times in China. Chemometrics, including similarity analysis, hierarchical clustering analysis, and principal component analysis, were used to express their similarities. It was found that similarity values of the samples were in the range of 0.432–0.998. The results of analgesic tests indicated that Polygoni Perfoliati Herba could significantly inhibit pain induced by hot plate and acetic acid in mice. The results of anti-inflammatory tests showed that Polygoni Perfoliati Herba had good anti-inflammatory effects (P < 0.01) in two models including dimethyl benzene-induced ear edema and acetic acid-induced peritoneal permeability in mice. Combining the results from chromatographic fingerprints with those from bioactivities, we found that seven peaks from Polygoni Perfoliati Herba were mainly responsible for analgesic and anti-inflammatory activities. PMID:24023580

On the use of electrokinetic phenomena of the second kind for probing electrode kinetic properties of modified electron-conducting surfaces.

PubMed

Duval, Jérôme F L; Sorrenti, Estelle; Waldvogel, Yves; Görner, Tatiana; De Donato, Philippe

2007-04-14

The electrokinetic features of electron-conducting substrates, as measured in a conventional thin-layer electrokinetic cell, strongly depend on the extent of bipolar faradaic depolarisation of the interface formed with the adjacent electrolytic solution. Streaming potential versus applied pressure data obtained for metallic substrates must generally be interpreted on the basis of a modified Helmholtz-Smoluchowski equation corrected by an electronic conduction term-non linear with respect to the lateral potential and applied pressure gradient-that stems from the bipolar electrodic behavior of the metallic surface. In the current study, streaming potential measurements have been performed in KNO(3) solutions on porous plugs made of electron-conducting grains of pyrite (FeS(2)) covered by humic acids. For zero coverage, the extensive bipolar electronic conduction taking place in the plug-depolarized by concomitant and spatially distributed oxidation and reduction reactions of Fe(2+) and Fe(3+) species-leads to the complete extinction of the streaming potential over the entire range of applied pressure examined. For low to intermediate coverage, the local electron-transfer kinetics on the covered regions of the plug becomes more sluggish. The overall bipolar electronic conduction is then diminished which leads to an increase in the streaming potential with a non-linear dependence on the pressure. For significant coverage, a linear response is observed which basically reflects the interfacial double layer properties of the humics surface layer. A tractable, semi-analytical model is presented that reproduces the electrokinetic peculiarities of the complex and composite system FeS(2)/humics investigated. The study demonstrates that the streaming potential technique is a fast and valuable tool for establishing how well the electron transfer kinetics at a partially or completely depolarised bare electron-conducting substrate/electrolyte solution interface is either promoted

Chromatographic study of formation conditions of rhombododecahedral diamond crystals

NASA Astrophysics Data System (ADS)

Zhimulev, E. I.; Sonin, V. M.; Chepurov, A. I.; Tomilenko, A. A.

2009-06-01

The results of chromatographic study of the formation of rhombododecahedral diamonds synthesized in the Fe-Ni-(Ti)-C system at 5.5-6.0 GPa and 1350-1450°C are presented, including crystals with rounded surfaces of the rhombododecahedron with parallel striation, which are morphological analogues of natural diamonds abundant at various kimberlite, lamproite, and placer deposits. Chromatography was performed at 150°C with mechanical breakup of diamonds. The stable release of methane when diamonds of habit {110} are crushed is established. It is concluded that the appearance of the habit rhombododecahedron may be related not only to the effect of temperature and pressure on crystal growth but also to reductive conditions of crystallization. At the same time, the appearance of significant amounts of hydrocarbons in the system probably results in stopping of the growth of faces {110} and {100} and, instead, formation of specific surfaces that are composed of microscopic accessories faced by planes {111}.

Separation and determination of peptide metabolite of Bacillus licheniformis in a microbial fuel cell by high-speed capillary micellar electrokinetic chromatography.

PubMed

Wang, Wei; Bai, Ruiguang; Cai, Xiaoyu; Lin, Ping; Ma, Lihong

2017-11-01

A method using high-speed capillary micellar electrokinetic chromatography and a microbial fuel cell was applied to determine the metabolite of the peptides released by Bacillus licheniformis. Two peptides, l-carnosine and l-alanyl-l-glutamine were used as the substrate to feed Bacillus licheniformis in a microbial fuel cell. The metabolism process of the bacterium was monitored by analyzing the voltage outputs of the microbial fuel cell. A home-made spontaneous injection device was applied to perform high-speed capillary micellar electrokinetic chromatography. Under the optimized conditions, tryptophan, glycine, valine, tyrosine and the two peptides could be rapidly separated within 2.5 min with micellar electrokinetic chromatography mode. Then the method was applied to analyze the solutions sampled from the microbial fuel cell. After 92 h running, valine, as the metabolite, was successfully detected with concentration 3.90 × 10 -5 M. The results demonstrated that Bacillus licheniformis could convert l-carnosine and l-alanyl-l-glutamine into valine. The method employed in this work was proved to have great potential in analysis of metabolites, such as amino acids, for microorganisms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling electrokinetic flows by consistent implicit incompressible smoothed particle hydrodynamics

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

Pan, Wenxiao; Kim, Kyungjoo; Perego, Mauro

2017-04-01

We present an efficient implicit incompressible smoothed particle hydrodynamics (I2SPH) discretization of Navier-Stokes, Poisson-Boltzmann, and advection-diffusion equations subject to Dirichlet or Robin boundary conditions. It is applied to model various two and three dimensional electrokinetic flows in simple or complex geometries. The I2SPH's accuracy and convergence are examined via comparison with analytical solutions, grid-based numerical solutions, or empirical models. The new method provides a framework to explore broader applications of SPH in microfluidics and complex fluids with charged objects, such as colloids and biomolecules, in arbitrary complex geometries.

Modeling electrokinetic flows by consistent implicit incompressible smoothed particle hydrodynamics

DOE PAGES

Pan, Wenxiao; Kim, Kyungjoo; Perego, Mauro; ...

2017-01-03

In this paper, we present a consistent implicit incompressible smoothed particle hydrodynamics (I 2SPH) discretization of Navier–Stokes, Poisson–Boltzmann, and advection–diffusion equations subject to Dirichlet or Robin boundary conditions. It is applied to model various two and three dimensional electrokinetic flows in simple or complex geometries. The accuracy and convergence of the consistent I 2SPH are examined via comparison with analytical solutions, grid-based numerical solutions, or empirical models. Lastly, the new method provides a framework to explore broader applications of SPH in microfluidics and complex fluids with charged objects, such as colloids and biomolecules, in arbitrary complex geometries.

Anti-Brownian ELectrokinetic (ABEL) Trapping of Single High Density Lipoprotein (HDL) Particles

NASA Astrophysics Data System (ADS)

Bockenhauer, Samuel; Furstenberg, Alexandre; Wang, Quan; Devree, Brian; Jie Yao, Xiao; Bokoch, Michael; Kobilka, Brian; Sunahara, Roger; Moerner, W. E.

2010-03-01

The ABEL trap is a novel device for trapping single biomolecules in solution for extended observation. The trap estimates the position of a fluorescently-labeled object as small as ˜10 nm in solution and then applies a feedback electrokinetic drift every 20 us to trap the object by canceling its Brownian motion. We use the ABEL trap to study HDL particles at the single-copy level. HDL particles, essential in regulation of ``good'' cholesterol in humans, comprise a small (˜10 nm) lipid bilayer disc bounded by a belt of apolipoproteins. By engineering HDL particles with single fluorescent donor/acceptor probes and varying lipid compositions, we are working to study lipid diffusion on small length scales. We also use HDL particles as hosts for single transmembrane receptors, which should enable study of receptor conformational dynamics on long timescales.

Electrokinetically driven active micro-mixers utilizing zeta potential variation induced by field effect

NASA Astrophysics Data System (ADS)

Lee, Chia-Yen; Lee, Gwo-Bin; Fu, Lung-Ming; Lee, Kuo-Hoong; Yang, Ruey-Jen

2004-10-01

This paper presents a new electrokinetically driven active micro-mixer which uses localized capacitance effects to induce zeta potential variations along the surface of silica-based microchannels. The mixer is fabricated by etching bulk flow and shielding electrode channels into glass substrates and then depositing Au/Cr thin films within the latter to form capacitor electrodes, which establish localized zeta potential variations near the electrical double layer (EDL) region of the electroosmotic flow (EOF) within the microchannels. The potential variations induce flow velocity changes within a homogeneous fluid and a rapid mixing effect if an alternating electric field is provided. The current experimental data confirm that the fluid velocity can be actively controlled by using the capacitance effect of the buried shielding electrodes to vary the zeta potential along the channel walls. While compared with commonly used planar electrodes across the microchannels, the buried shielding electrodes prevent current leakage caused by bad bonding and allow direct optical observation during operation. It also shows that the buried shielding electrodes can significantly induce the field effect, resulting in higher variations of zeta potential. Computational fluid dynamic simulations are also used to study the fluid characteristics of the developed active mixers. The numerical and experimental results demonstrate that the developed microfluidic device permits a high degree of control over the fluid flow and an efficient mixing effect. Moreover, the developed device could be used as a pumping device as well. The development of the active electrokinetically driven micro-mixer could be crucial for micro-total-analysis-systems.

Electrokinetic Analysis of Cell Translocation in Low-Cost Microfluidic Cytometry for Tumor Cell Detection and Enumeration.

PubMed

Guo, Jinhong; Pui, Tze Sian; Ban, Yong-Ling; Rahman, Abdur Rub Abdur; Kang, Yuejun

2013-12-01

Conventional Coulter counters have been introduced as an important tool in biological cell assays since several decades ago. Recently, the emerging portable Coulter counter has demonstrated its merits in point of care diagnostics, such as on chip detection and enumeration of circulating tumor cells (CTC). The working principle is based on the cell translocation time and amplitude of electrical current change that the cell induces. In this paper, we provide an analysis of a Coulter counter that evaluates the hydrodynamic and electrokinetic properties of polystyrene microparticles in a microfluidic channel. The hydrodynamic force and electrokinetic force are concurrently analyzed to determine the translocation time and the electrical current pulses induced by the particles. Finally, we characterize the chip performance for CTC detection. The experimental results validate the numerical analysis of the microfluidic chip. The presented model can provide critical insight and guidance for developing micro-Coulter counter for point of care prognosis.

The Use of Electrical Resistivity Method to Mapping The Migration of Heavy Metals by Electrokinetic

NASA Astrophysics Data System (ADS)

Azhar, A. T. S.; Ayuni, S. A.; Ezree, A. M.; Nizam, Z. M.; Aziman, M.; Hazreek, Z. A. M.; Norshuhaila, M. S.; Zaidi, E.

2017-08-01

The presence of heavy metals contamination in soil environment highly needs innovative remediation. Basically, this contamination was resulted from ex-mining sites, motor workshop, petrol station, landfill and industrial sites. Therefore, soil treatment is very important due to metal ions are characterized as non-biodegradable material that may be harmful to ecological system, food chain, human health and groundwater sources. There are various techniques that have been proposed to eliminate the heavy metal contamination from the soil such as bioremediation, phytoremediation, electrokinetic remediation, solidification and stabilization. The selection of treatment needs to fulfill some criteria such as cost-effective, easy to apply, green approach and high remediation efficiency. Electrokinetic remediation technique (EKR) offers those solutions in certain area where other methods are impractical. While, electrical resistivity method offers an alternative geophysical technique for soil subsurface profiling to mapping the heavy metals migration by the influece of electrical gradient. Consequently, this paper presents an overview of the use of EKR to treat contaminated soil by using ERM method to verify their effectiveness to remove heavy metals.

A simple novel device for air sampling by electrokinetic capture

DOE PAGES

Gordon, Julian; Gandhi, Prasanthi; Shekhawat, Gajendra; ...

2015-12-27

A variety of different sampling devices are currently available to acquire air samples for the study of the microbiome of the air. All have a degree of technical complexity that limits deployment. Here, we evaluate the use of a novel device, which has no technical complexity and is easily deployable. An air-cleaning device powered by electrokinetic propulsion has been adapted to provide a universal method for collecting samples of the aerobiome. Plasma-induced charge in aerosol particles causes propulsion to and capture on a counter-electrode. The flow of ions creates net bulk airflow, with no moving parts. A device and electrodemore » assembly have been re-designed from air-cleaning technology to provide an average air flow of 120 lpm. This compares favorably with current air sampling devices based on physical air pumping. Capture efficiency was determined by comparison with a 0.4 μm polycarbonate reference filter, using fluorescent latex particles in a controlled environment chamber. Performance was compared with the same reference filter method in field studies in three different environments. For 23 common fungal species by quantitative polymerase chain reaction (qPCR), there was 100 % sensitivity and apparent specificity of 87%, with the reference filter taken as “gold standard.” Further, bacterial analysis of 16S RNA by amplicon sequencing showed equivalent community structure captured by the electrokinetic device and the reference filter. Unlike other current air sampling methods, capture of particles is determined by charge and so is not controlled by particle mass. We analyzed particle sizes captured from air, without regard to specific analyte by atomic force microscopy: particles at least as low as 100 nM could be captured from ambient air. This work introduces a very simple plug-and-play device that can sample air at a high-volume flow rate with no moving parts and collect particles down to the sub-micron range. In conclusion, the performance of

A simple novel device for air sampling by electrokinetic capture

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

Gordon, Julian; Gandhi, Prasanthi; Shekhawat, Gajendra

A variety of different sampling devices are currently available to acquire air samples for the study of the microbiome of the air. All have a degree of technical complexity that limits deployment. Here, we evaluate the use of a novel device, which has no technical complexity and is easily deployable. An air-cleaning device powered by electrokinetic propulsion has been adapted to provide a universal method for collecting samples of the aerobiome. Plasma-induced charge in aerosol particles causes propulsion to and capture on a counter-electrode. The flow of ions creates net bulk airflow, with no moving parts. A device and electrodemore » assembly have been re-designed from air-cleaning technology to provide an average air flow of 120 lpm. This compares favorably with current air sampling devices based on physical air pumping. Capture efficiency was determined by comparison with a 0.4 μm polycarbonate reference filter, using fluorescent latex particles in a controlled environment chamber. Performance was compared with the same reference filter method in field studies in three different environments. For 23 common fungal species by quantitative polymerase chain reaction (qPCR), there was 100 % sensitivity and apparent specificity of 87%, with the reference filter taken as “gold standard.” Further, bacterial analysis of 16S RNA by amplicon sequencing showed equivalent community structure captured by the electrokinetic device and the reference filter. Unlike other current air sampling methods, capture of particles is determined by charge and so is not controlled by particle mass. We analyzed particle sizes captured from air, without regard to specific analyte by atomic force microscopy: particles at least as low as 100 nM could be captured from ambient air. This work introduces a very simple plug-and-play device that can sample air at a high-volume flow rate with no moving parts and collect particles down to the sub-micron range. In conclusion, the performance of

Gas-Chromatographic Determination Of Water In Freon PCA

NASA Technical Reports Server (NTRS)

Melton, Donald M.

1994-01-01

Gas-chromatographic apparatus measures small concentrations of water in specimens of Freon PCA. Testing by use of apparatus faster and provides greater protection against accidental contamination of specimens by water in testing environment. Automated for unattended operation. Also used to measure water contents of materials, other than Freon PCA. Innovation extended to development of purgeable sampling accessory for gas chromatographs.

Gas chromatograph sample-transfer valve

NASA Technical Reports Server (NTRS)

Wang, W. S.; Wright, H. W., Jr.

1971-01-01

Slide-type gate valve incorporates sampling volume and transfer passageway for guiding a metered quantity of gas from pressurized test cell to gas chromatograph. Gate is moved by pneumatic bellows-type actuator.

Superhydrophobic nanofluidic channels for enhanced electrokinetic conversion

NASA Astrophysics Data System (ADS)

Checco, Antonio; Al Hossain, Aktaruzzaman; Rahmani, Amir; Black, Charles; Doerk, Gregory; Colosqui, Carlos

2017-11-01

We present current efforts in the development of novel slit nanofluidic channels with superhydrophobic nanostructured surfaces designed to enhance hydrodynamic conductivity and improve selective transport and electrokinetic energy conversion efficiencies (mechanical-electrical energy conversion). The nanochannels are fabricated on silicon wafers using UV lithography, and their internal surface is patterned with conical nanostructures (feature size and spacing 30 nm) defined by block copolymer self-assembly and plasma etching. These nanostructures are rendered superhydrophobic by passivation with a hydrophobic silane monolayer. We experimentally characterize hydrodynamic conductivity, effective zeta potentials, and eletrokinetic flows for the patterned nanochannels, comparing against control channels with bare surfaces. Experimental observations are rationalized using both continuum-based modeling and molecular dynamics simulations. Scientific and technical knowledge produced by this work is particularly relevant for sustainable energy conversion and storage, separation processes and water treatment using nanoporous materials. The ONR Contract # N000141613178 and NSF-CBET award# 1605809.

Electrokinetic mixing at high zeta potentials: ionic size effects on cross stream diffusion.

PubMed

Ahmadian Yazdi, Alireza; Sadeghi, Arman; Saidi, Mohammad Hassan

2015-03-15

The electrokinetic phenomena at high zeta potentials may show several unique features which are not normally observed. One of these features is the ionic size (steric) effect associated with the solutions of high ionic concentration. In the present work, attention is given to the influences of finite ionic size on the cross stream diffusion process in an electrokinetically actuated Y-shaped micromixer. The method consists of a finite difference based numerical approach for non-uniform grid which is applied to the dimensionless form of the governing equations, including the modified Poisson-Boltzmann equation. The results reveal that, neglecting the ionic size at high zeta potentials gives rise to the overestimation of the mixing length, because the steric effects retard liquid flow, thereby enhancing the mixing efficiency. The importance of steric effects is found to be more intense for channels of smaller width to height ratio. It is also observed that, in sharp contrast to the conditions that the ions are treated as point charges, increasing the zeta potential improves the cross stream diffusion when incorporating the ionic size. Moreover, increasing the EDL thickness decreases the mixing length, whereas the opposite is true for the channel aspect ratio. Copyright © 2014 Elsevier Inc. All rights reserved.

Method for the chromatographic separation of cations from aqueous samples

DOEpatents

Horwitz, E.P.; Chiarizia, R.; Dietz, M.L.

1997-07-29

An extraction chromatographic material is described for extracting metal cations from a liquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methanediphosphonic acid on an inert particulate support. 7 figs.

Method for the chromatographic separation of cations from aqueous samples

DOEpatents

Horwitz, E.P.; Chiarizia, R.; Dietz, M.L.

1998-12-22

An extraction chromatographic material is described for extracting metal cations from a liquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methane-diphosphonic acid on an inert particulate support. 7 figs.

High-performance liquid-chromatographic separation of subcomponents of antimycin-A

USGS Publications Warehouse

Abidi, S.L.

1988-01-01

Using a reversed-phase high-performance liquid chromatographic (HPLC) technique, a mixture of antimycins A was separated into eight hitherto unreported subcomponents, Ala, Alb, A2a, A2b, A3a, A3b, A4a, and A4b. Although a base-line resolution of the known four major antimycins Al, A2, A3, and A4 was readily achieved with mobile phases containing acetate buffers, the separation of the new antibiotic subcomponents was highly sensitive to variation in mobile phase conditions. The type and composition of organic modifiers, the nature of buffer salts, and the concentration of added electrolytes had profound effects on capacity factors, separation factors, and peak resolution values. Of the numerous chromatographic systems examined, a mobile phase consisting of methanol-water (70:30) and 0.005 M tetrabutylammonium phosphate at pH 3.0 yielded the most satisfactory results for the separation of the subcomponents. Reversed-phase gradient HPLC separation of the dansylated or methylated antibiotic compounds produced superior chromatographic characteristics and the presence of added electrolytes was not a critical factor for achieving separation. Differences in the chromatographic outcome between homologous and structural isomers were interpretated based on a differential solvophobic interaction rationale. Preparative reversed-phase HPLC under optimal conditions enabled isolation of pure samples of the methylated antimycin subcomponents for use in structural studies.

cDPD: A new dissipative particle dynamics method for modeling electrokinetic phenomena at the mesoscale

NASA Astrophysics Data System (ADS)

Deng, Mingge; Li, Zhen; Borodin, Oleg; Karniadakis, George Em

2016-10-01

We develop a "charged" dissipative particle dynamics (cDPD) model for simulating mesoscopic electrokinetic phenomena governed by the stochastic Poisson-Nernst-Planck and the Navier-Stokes equations. Specifically, the transport equations of ionic species are incorporated into the DPD framework by introducing extra degrees of freedom and corresponding evolution equations associated with each DPD particle. Diffusion of ionic species driven by the ionic concentration gradient, electrostatic potential gradient, and thermal fluctuations is captured accurately via pairwise fluxes between DPD particles. The electrostatic potential is obtained by solving the Poisson equation on the moving DPD particles iteratively at each time step. For charged surfaces in bounded systems, an effective boundary treatment methodology is developed for imposing both the correct hydrodynamic and electrokinetics boundary conditions in cDPD simulations. To validate the proposed cDPD model and the corresponding boundary conditions, we first study the electrostatic structure in the vicinity of a charged solid surface, i.e., we perform cDPD simulations of the electrostatic double layer and show that our results are in good agreement with the well-known mean-field theoretical solutions. We also simulate the electrostatic structure and capacity densities between charged parallel plates in salt solutions with different salt concentrations. Moreover, we employ the proposed methodology to study the electro-osmotic and electro-osmotic/pressure-driven flows in a micro-channel. In the latter case, we simulate the dilute poly-electrolyte solution drifting by electro-osmotic flow in a micro-channel, hence demonstrating the flexibility and capability of this method in studying complex fluids with electrostatic interactions at the micro- and nano-scales.

Integrated electrokinetics-adsorption remediation of saline-sodic soils: effects of voltage gradient and contaminant concentration on soil electrical conductivity.

PubMed

Essa, Mohammed Hussain; Mu'azu, Nuhu Dalhat; Lukman, Salihu; Bukhari, Alaadin

2013-01-01

In this study, an integrated in situ remediation technique which couples electrokinetics with adsorption, using locally produced granular activated carbon from date palm pits in the treatment zones that are installed directly to bracket the contaminated soils at bench-scale, is investigated. Natural saline-sodic clay soil, spiked with contaminant mixture (kerosene, phenol, Cr, Cd, Cu, Zn, Pb, and Hg), was used in this study to investigate the effects of voltage gradient, initial contaminant concentration, and polarity reversal rate on the soil electrical conductivity. Box-Behnken Design (BBD) was used for the experimental design and response surface methodology (RSM) was employed to model, optimize, and interpret the results obtained using Design-Expert version 8 platform. The total number of experiments conducted was 15 with voltage gradient, polarity reversal rate, and initial contaminant concentration as variables. The main target response discussed in this paper is the soil electrical conductivity due to its importance in electrokinetic remediation process. Responses obtained were fitted to quadratic models whose R (2) ranges from 84.66% to 99.19% with insignificant lack of fit in each case. Among the investigated factors, voltage gradient and initial contaminant concentration were found to be the most significant influential factors.

A comprehensive strategy in the development of a cyclodextrin-modified microemulsion electrokinetic chromatographic method for the assay of diclofenac and its impurities: Mixture-process variable experiments and quality by design.

PubMed

Orlandini, S; Pasquini, B; Caprini, C; Del Bubba, M; Squarcialupi, L; Colotta, V; Furlanetto, S

2016-09-30

A comprehensive strategy involving the use of mixture-process variable (MPV) approach and Quality by Design principles has been applied in the development of a capillary electrophoresis method for the simultaneous determination of the anti-inflammatory drug diclofenac and its five related substances. The selected operative mode consisted in microemulsion electrokinetic chromatography with the addition of methyl-β-cyclodextrin. The critical process parameters included both the mixture components (MCs) of the microemulsion and the process variables (PVs). The MPV approach allowed the simultaneous investigation of the effects of MCs and PVs on the critical resolution between diclofenac and its 2-deschloro-2-bromo analogue and on analysis time. MPV experiments were used both in the screening phase and in the Response Surface Methodology, making it possible to draw MCs and PVs contour plots and to find important interactions between MCs and PVs. Robustness testing was carried out by MPV experiments and validation was performed following International Conference on Harmonisation guidelines. The method was applied to a real sample of diclofenac gastro-resistant tablets. Copyright © 2016 Elsevier B.V. All rights reserved.

The Protein/Peptide Direct Virus Inactivation During Chromatographic Process: Developing Approaches.

PubMed

Volkov, Georgii L; Havryliuk, Sergiy P; Krasnobryzha, Ievgenia M; Havryliuk, Olena S

2017-01-01

Virus clearance is required for pharmaceutical preparations derived from animal or human sources such as blood products, vaccines, recombinant proteins produced in mammalian cell lines, etc. High cost and substantial protein losses during virus inactivation are significant problems for protein/peptide manufacturing. The goal of this project was to develop a method to perform virus inactivation in a course of protein chromatographic purification. Another goal was to show that the chromatographic adsorbent can serve as reliable "sieva" for mechanical washing away of infecting viruses. Using chromatographic, photometric, IFA, and RT-PCR approaches, it was discovered that high temperature-depending dynamic capacity of adsorbent allowed to perform a virus inactivation directly in a chromatographic column by solvent/detergent treatment. The peptide/protein biological activity was completely preserved. Using this new approach enveloped and nonenveloped viruses were effectively removed protein preparation. In addition, it was shown that RT-PCR method demonstrates more precise and reproducible results and robust properties for assessment of virus reduction than virus titer followed by infectivity studies. Presented method allowed to obtain the factor of virus concentration decrease (FVD) values that were higher than those provided by known technologies and was sufficient for a full inactivation of viruses. The method is recommended to use in pharmaceutical industry.

An electric stimulation system for electrokinetic particle manipulation in microfluidic devices.

PubMed

Lopez-de la Fuente, M S; Moncada-Hernandez, H; Perez-Gonzalez, V H; Lapizco-Encinas, B H; Martinez-Chapa, S O

2013-03-01

Microfluidic devices have grown significantly in the number of applications. Microfabrication techniques have evolved considerably; however, electric stimulation systems for microdevices have not advanced at the same pace. Electric stimulation of micro-fluidic devices is an important element in particle manipulation research. A flexible stimulation instrument is desired to perform configurable, repeatable, automated, and reliable experiments by allowing users to select the stimulation parameters. The instrument presented here is a configurable and programmable stimulation system for electrokinetic-driven microfluidic devices; it consists of a processor, a memory system, and a user interface to deliver several types of waveforms and stimulation patterns. It has been designed to be a flexible, highly configurable, low power instrument capable of delivering sine, triangle, and sawtooth waveforms with one single frequency or two superimposed frequencies ranging from 0.01 Hz to 40 kHz, and an output voltage of up to 30 Vpp. A specific stimulation pattern can be delivered over a single time period or as a sequence of different signals for different time periods. This stimulation system can be applied as a research tool where manipulation of particles suspended in liquid media is involved, such as biology, medicine, environment, embryology, and genetics. This system has the potential to lead to new schemes for laboratory procedures by allowing application specific and user defined electric stimulation. The development of this device is a step towards portable and programmable instrumentation for electric stimulation on electrokinetic-based microfluidic devices, which are meant to be integrated with lab-on-a-chip devices.

Electrokinetics of diffuse soft interfaces. 1. Limit of low Donnan potentials.

PubMed

Duval, Jérôme F L; van Leeuwen, Herman P

2004-11-09

The current theoretical approaches to electrokinetics of gels or polyelectrolyte layers are based on the assumption that the position of the very interface between the aqueous medium and the gel phase is well defined. Within this assumption, spatial profiles for the volume fraction of polymer segments (phi), the density of fixed charges in the porous layer (rho fix), and the coefficient modeling the friction to hydrodynamic flow (k) follow a step-function. In reality, the "fuzzy" nature of the charged soft layer is intrinsically incompatible with the concept of a sharp interface and therefore necessarily calls for more detailed spatial representations for phi, rho fix, and k. In this paper, the notion of diffuse interface is introduced. For the sake of illustration, linear spatial distributions for phi and rho fix are considered in the interfacial zone between the bulk of the porous charged layer and the bulk electrolyte solution. The corresponding distribution for k is inferred from the Brinkman equation, which for low phi reduces to Stokes' equation. Linear electrostatics, hydrodynamics, and electroosmosis issues are analytically solved within the context of streaming current and streaming potential of charged surface layers in a thin-layer cell. The hydrodynamic analysis clearly demonstrates the physical incorrectness of the concept of a discrete slip plane for diffuse interfaces. For moderate to low electrolyte concentrations and nanoscale spatial transition of phi from zero (bulk electrolyte) to phi o (bulk gel), the electrokinetic properties of the soft layer as predicted by the theory considerably deviate from those calculated on the basis of the discontinuous approximation by Ohshima.

An electric stimulation system for electrokinetic particle manipulation in microfluidic devices

NASA Astrophysics Data System (ADS)

Lopez-de la Fuente, M. S.; Moncada-Hernandez, H.; Perez-Gonzalez, V. H.; Lapizco-Encinas, B. H.; Martinez-Chapa, S. O.

2013-03-01

Microfluidic devices have grown significantly in the number of applications. Microfabrication techniques have evolved considerably; however, electric stimulation systems for microdevices have not advanced at the same pace. Electric stimulation of micro-fluidic devices is an important element in particle manipulation research. A flexible stimulation instrument is desired to perform configurable, repeatable, automated, and reliable experiments by allowing users to select the stimulation parameters. The instrument presented here is a configurable and programmable stimulation system for electrokinetic-driven microfluidic devices; it consists of a processor, a memory system, and a user interface to deliver several types of waveforms and stimulation patterns. It has been designed to be a flexible, highly configurable, low power instrument capable of delivering sine, triangle, and sawtooth waveforms with one single frequency or two superimposed frequencies ranging from 0.01 Hz to 40 kHz, and an output voltage of up to 30 Vpp. A specific stimulation pattern can be delivered over a single time period or as a sequence of different signals for different time periods. This stimulation system can be applied as a research tool where manipulation of particles suspended in liquid media is involved, such as biology, medicine, environment, embryology, and genetics. This system has the potential to lead to new schemes for laboratory procedures by allowing application specific and user defined electric stimulation. The development of this device is a step towards portable and programmable instrumentation for electric stimulation on electrokinetic-based microfluidic devices, which are meant to be integrated with lab-on-a-chip devices.

Electrokinetic Aggregation of Colloidal Particles on Electrodes

NASA Astrophysics Data System (ADS)

Anderson, John L.; Solomentsev, Yuri E.; Guelcher, Scott A.

1999-11-01

Colloidal particles deposited on an electrode have been observed to attract each other and form clusters in the presence of an applied electric field. This aggregation is important to the formation of dense monolayer films during electrophoretic depositon processes. Under dc fields two particles attract each other over a length scale comparable to the particle size, and the velocity of approach between two particles is proportional to the applied electric field and the particles' zeta potential. We have developed a theory for particle aggregation based on electroosmotic flow about each deposited particle. Experimental results for the relative motion of two particles are in good quantitative agreement with the theory. Our recent experiments with ac fields also show attraction between particles that is roughly proportional to the rms electric field but inversely proportional to the frequency. We discuss here a model based on electrokinetic processes that can account for some of the observations in ac fields.

Chromatographic and computational assessment of lipophilicity using sum of ranking differences and generalized pair-correlation.

PubMed

Andrić, Filip; Héberger, Károly

2015-02-06

Lipophilicity (logP) represents one of the most studied and most frequently used fundamental physicochemical properties. At present there are several possibilities for its quantitative expression and many of them stems from chromatographic experiments. Numerous attempts have been made to compare different computational methods, chromatographic methods vs. computational approaches, as well as chromatographic methods and direct shake-flask procedure without definite results or these findings are not accepted generally. In the present work numerous chromatographically derived lipophilicity measures in combination with diverse computational methods were ranked and clustered using the novel variable discrimination and ranking approaches based on the sum of ranking differences and the generalized pair correlation method. Available literature logP data measured on HILIC, and classical reversed-phase combining different classes of compounds have been compared with most frequently used multivariate data analysis techniques (principal component and hierarchical cluster analysis) as well as with the conclusions in the original sources. Chromatographic lipophilicity measures obtained under typical reversed-phase conditions outperform the majority of computationally estimated logPs. Oppositely, in the case of HILIC none of the many proposed chromatographic indices overcomes any of the computationally assessed logPs. Only two of them (logkmin and kmin) may be selected as recommended chromatographic lipophilicity measures. Both ranking approaches, sum of ranking differences and generalized pair correlation method, although based on different backgrounds, provides highly similar variable ordering and grouping leading to the same conclusions. Copyright © 2015. Published by Elsevier B.V.

Chromatographic methods for determination of S-substituted cysteine derivatives--a comparative study.

PubMed

Kubec, Roman; Dadáková, Eva

2009-10-09

A novel HPLC method for determination of a wide variety of S-substituted cysteine derivatives in Allium species has been developed and validated. This method allows simultaneous separation and quantification of S-alk(en)ylcysteine S-oxides, gamma-glutamyl-S-alk(en)ylcysteines and gamma-glutamyl-S-alk(en)ylcysteine S-oxides in a single run. The procedure is based on extraction of these amino acids and dipeptides by methanol, their derivatization by dansyl chloride and subsequent separation by reversed phase HPLC. The main advantages of the new method are simplicity, excellent stability of derivatives, high sensitivity, specificity and the ability to simultaneously analyze the whole range of S-substituted cysteine derivatives. This method was critically compared with other chromatographic procedures used for quantification of S-substituted cysteine derivatives, namely with two other HPLC methods (derivatization by o-phthaldialdehyde/tert-butylthiol and fluorenylmethyl chloroformate), and with determination by gas chromatography or capillary electrophoresis. Major advantages and drawbacks of these analytical procedures are discussed. Employing these various chromatographic methods, the content and relative proportions of individual S-substituted cysteine derivatives were determined in four most frequently consumed alliaceous vegetables (garlic, onion, shallot, and leek).

21 CFR 862.2230 - Chromatographic separation material for clinical use.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Chromatographic separation material for clinical... HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Laboratory Instruments § 862.2230 Chromatographic separation material for clinical use. (a) Identification. A...

Qualitative analysis of mycotoxins using micellar electrokinetic capillary chromatography

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

Holland, R.D.; Sepaniak, M.J.

1993-05-01

Naturally occurring mycotoxins are separated using micellar electrokinetic capillary chromatography. Trends in the retention of these toxins, resulting from changes in mobile-phase composition and pH, are reported and presented as a means of alleviating coelution problems. Two sets of mobile-phase conditions are determined that provide unique separation selectivity. The facile manner by which mobile-phase conditions can be altered, without changes in instrumental configuration, allowed the acquisition of two distinctive, fully resolved chromatograms of 10 mycotoxins in a period of approximately 45 min. By adjusting retention times, using indigenous or added components in mycotoxin samples as normalization standards, it is possiblemore » to obtain coefficients of variation in retention time that average less than 1%. The qualitative capabilities of this methodology are evaluated by separating randomly generated mycotoxin-interferent mixtures. In this study, the utilization of normalized retention times applied to separations obtained with two sets of mobile-phase conditions permitted the identification of all the mycotoxins in five unknown samples without any misidentifications. 24 refs., 3 figs., 2 tabs.« less

Optimisation of resolution in micellar electrokinetic chromatography by multivariate evaluation of electrolytes.

PubMed

Mikaeli, S; Thorsén, G; Karlberg, B

2001-01-12

A novel approach to multivariate evaluation of separation electrolytes for micellar electrokinetic chromatography is presented. An initial screening of the experimental parameters is performed using a Plackett-Burman design. Significant parameters are further evaluated using full factorial designs. The total resolution of the separation is calculated and used as response. The proposed scheme has been applied to the optimisation of the separation of phenols and the chiral separation of (+)-1-(9-anthryl)-2-propyl chloroformate-derivatized amino acids. A total of eight experimental parameters were evaluated and optimal conditions found in less than 48 experiments.

Ion chromatographic determination of sulfur in fuels

NASA Technical Reports Server (NTRS)

Mizisin, C. S.; Kuivinen, D. E.; Otterson, D. A.

1978-01-01

The sulfur content of fuels was determined using an ion chromatograph to measure the sulfate produced by a modified Parr bomb oxidation. Standard Reference Materials from the National Bureau of Standards, of approximately 0.2 + or - 0.004% sulfur, were analyzed resulting in a standard deviation no greater than 0.008. The ion chromatographic method can be applied to conventional fuels as well as shale-oil derived fuels. Other acid forming elements, such as fluorine, chlorine and nitrogen could be determined at the same time, provided that these elements have reached a suitable ionic state during the oxidation of the fuel.

Numerical simulation of a non-equilibrium electrokinetic micro/nano fluidic mixer

NASA Astrophysics Data System (ADS)

Hadidi, H.; Kamali, R.

2016-03-01

In this study we numerically simulate a novel micromixer that utilizes vortex generation from the non-equilibrium electrokinetics near the micro/nanochannels interface. After mixing in combined pressure-driven and electroosmotic flows was compared with mixing in a pure pressure-driven flow, the superior mixing performance of the former was evident: for a specific case study, 90% mixing of two fluid streams for a short mixing length was achieved. The results of our numerical study were very similar to those of previously reported experiments. In this paper we explain the phenomenon occurring adjacent to the nano-junctions by plotting the electrical field components, the velocity contours and the concentration distribution in the micromixer. The vortices at the micro/nanochannel interface were obviously indicators of non-equilibrium behaviour in these regions. At the end, the mixing performance was evaluated by the investigation of different applied voltages, Reynolds numbers and surface charge densities using the mixing index parameter, and the results showed that more efficient mixing occurred when the applied voltage and surface charge density magnitude were increased and the Reynolds number was decreased.

Surfactant-free microemulsion electrokinetic chromatography (SF-MEEKC) with UV and MS detection - a novel approach for the separation and ESI-MS detection of neutral compounds.

PubMed

Mohorič, Urška; Beutner, Andrea; Krickl, Sebastian; Touraud, Didier; Kunz, Werner; Matysik, Frank-Michael

2016-12-01

Microemulsion electrokinetic chromatography (MEEKC) is a powerful tool to separate neutral species based on differences in their hydrophobic and hydrophilic properties. However, as a major drawback the conventionally used SDS based microemulsions are not compatible with electrospray ionization mass spectrometry (ESI-MS). In this work, a surfactant-free microemulsion (SFME) consisting of water, ethanol, and 1-octanol is used for surfactant-free microemulsion electrokinetic chromatography (SF-MEEKC). Ammonium acetate was added to the SFME enabling electrophoretic separations. The stability of SFMEs containing ammonium acetate was investigated using small-angle X-ray scattering and dynamic light scattering. A method for the separation of a model system of hydrophobic and hydrophilic neutral vitamins, namely the vitamins B 2 and D 3 , and the cationic vitamin B 1 was developed using UV/VIS detection. The influence of the ammonium acetate concentration on the separation performance was studied in detail. The method was characterized concerning reproducibility of migration times and peak areas and concerning the linearity of the calibration data. Furthermore, SF-MEEKC was coupled to ESI-MS investigating the compatibility between SFMEs and the ESI process. The signal intensities of ESI-MS measurements of the model analytes were comparable for SFMEs and aqueous systems. Finally, the vitamin D 3 content of a drug treating vitamin D 3 deficiency was determined by SF-MEEKC coupled to ESI-MS using 25-hydroxycholecalciferol as an internal standard. Graphical abstract The concept of surfactant-free microemulsion electrokinetic chromatography coupled to electrospray ionization mass spectrometry.

In situ field application of electrokinetic remediation for an As-, Cu-, and Pb-contaminated rice paddy site using parallel electrode configuration.

PubMed

Jeon, Eun-Ki; Jung, Ji-Min; Ryu, So-Ri; Baek, Kitae

2015-10-01

The applicability of an in situ electrokinetic process with a parallel electrode configuration was evaluated to treat an As-, Cu-, and Pb-contaminated paddy rice field in full scale (width, 17 m; length, 12.2 m; depth, 1.6 m). A constant voltage of 100 V was supplied and electrodes were spaced 2 m apart. Most As, Cu, and Pb were bound to Fe oxide and the major clay minerals in the test site were kaolinite and muscovite. The electrokinetic system removed 48.7, 48.9, and 54.5 % of As, Cu, and Pb, respectively, from the soil during 24 weeks. The removal of metals in the first layer (0-0.4 m) was higher than that in the other three layers because it was not influenced by groundwater fluctuation. Fractionation analysis showed that As and Pb bound to amorphous Fe and Al oxides decreased mainly, and energy consumption was 1.2 kWh/m(3). The standard deviation of metal concentration in the soil was much higher compared to the hexagonal electrode configuration because of a smaller electrical active area; however, the electrode configuration removed similar amounts of metals compared to the hexagonal system. From these results, it was concluded that the electrokinetic process could be effective at remediating As-, Cu-, and Pb-contaminated paddy rice field in situ.

Chromatographic Assessment of Hydrogen-Bond Donating Ability

DTIC Science & Technology

1993-04-22

hydrogen-bond donors used in cocrystallizations . Hydrogen-bond donor solutes are chromatographed on a poly(vinylpyridine-divinylbenzene) column under...provides an a priori measure of the hydrogen- bond acidity of a potential cocrystal component. 20 DISTRIBUTION /AVAILABILITY OF ABSTRACT 21 ABSTRACT...general heuristic principle that has guided our cocrystallization studies is "the best hydrogen-bond donor hydrogen bonds to the best hydrogen-bond acceptor

Dielectrophoretic trapping of nanoparticles with an electrokinetic nanoprobe.

PubMed

Wood, Nicholas R; Wolsiefer, Amanda I; Cohn, Robert W; Williams, Stuart J

2013-07-01

A high aspect ratio 3D electrokinetic nanoprobe is used to trap polystyrene particles (200 nm), gold nanoshells (120 nm), and gold nanoparticles (mean diameter 35 nm) at low voltages (<1 V(rms)). The nanoprobe is fabricated using room temperature self-assembly methods, without the need for nanoresolution lithography. The nanoprobe (150-500 nm in diameter, 2-150 μm in length) is mounted on the end of a glass micropipette, enabling user-specified positioning. The nanoprobe is one electrode within a point-and-plate configuration, with an indium-tin oxide cover slip serving as the planar electrode. The 3D structure of the nanoprobe enhances dielectrophoretic capture; further, electro-hydrodynamic flow enhances trapping, increasing the effective trapping region. Numerical simulations show low heating (1 K), even in biological media of moderate conductivity (1 S/m). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ginkgolides and bilobalide: their physical, chromatographic and spectroscopic properties.

PubMed

van Beek, Teris A

2005-09-01

Ginkgolides A, B, C, J, K, L and M and bilobalide are rare terpene trilactones that have been isolated from leaves and root bark of the Chinese tree Ginkgo biloba. The structures of the highly oxidized ginkgolides were independently elucidated in the 1960s by the groups of Nakanishi and Sakabe. Later these compounds were found to be potent and selective antagonists of platelet activating factor, which fact triggered much new research. During the past 40 years, much physical, chromatographic and spectroscopic data have been published on these compounds in various, sometimes inaccessible, sources. The published melting points, solubility in different solvents, ionization constants, chromatographic behaviour, specific optical rotations, UV, IR, MS and NMR data, and X-ray studies are summarized and, where necessary, discussed. The literature until April 2005 has been reviewed.

Rapid and label-free separation of Burkitt's lymphoma cells from red blood cells by optically-induced electrokinetics.

PubMed

Liang, Wenfeng; Zhao, Yuliang; Liu, Lianqing; Wang, Yuechao; Dong, Zaili; Li, Wen Jung; Lee, Gwo-Bin; Xiao, Xiubin; Zhang, Weijing

2014-01-01

Early stage detection of lymphoma cells is invaluable for providing reliable prognosis to patients. However, the purity of lymphoma cells in extracted samples from human patients' marrow is typically low. To address this issue, we report here our work on using optically-induced dielectrophoresis (ODEP) force to rapidly purify Raji cells' (a type of Burkitt's lymphoma cell) sample from red blood cells (RBCs) with a label-free process. This method utilizes dynamically moving virtual electrodes to induce negative ODEP force of varying magnitudes on the Raji cells and RBCs in an optically-induced electrokinetics (OEK) chip. Polarization models for the two types of cells that reflect their discriminate electrical properties were established. Then, the cells' differential velocities caused by a specific ODEP force field were obtained by a finite element simulation model, thereby established the theoretical basis that the two types of cells could be separated using an ODEP force field. To ensure that the ODEP force dominated the separation process, a comparison of the ODEP force with other significant electrokinetics forces was conducted using numerical results. Furthermore, the performance of the ODEP-based approach for separating Raji cells from RBCs was experimentally investigated. The results showed that these two types of cells, with different concentration ratios, could be separated rapidly using externally-applied electrical field at a driven frequency of 50 kHz at 20 Vpp. In addition, we have found that in order to facilitate ODEP-based cell separation, Raji cells' adhesion to the OEK chip's substrate should be minimized. This paper also presents our experimental results of finding the appropriate bovine serum albumin concentration in an isotonic solution to reduce cell adhesion, while maintaining suitable medium conductivity for electrokinetics-based cell separation. In short, we have demonstrated that OEK technology could be a promising tool for efficient and

Analyzing chromatographic data using multilevel modeling.

PubMed

Wiczling, Paweł

2018-06-01

It is relatively easy to collect chromatographic measurements for a large number of analytes, especially with gradient chromatographic methods coupled with mass spectrometry detection. Such data often have a hierarchical or clustered structure. For example, analytes with similar hydrophobicity and dissociation constant tend to be more alike in their retention than a randomly chosen set of analytes. Multilevel models recognize the existence of such data structures by assigning a model for each parameter, with its parameters also estimated from data. In this work, a multilevel model is proposed to describe retention time data obtained from a series of wide linear organic modifier gradients of different gradient duration and different mobile phase pH for a large set of acids and bases. The multilevel model consists of (1) the same deterministic equation describing the relationship between retention time and analyte-specific and instrument-specific parameters, (2) covariance relationships relating various physicochemical properties of the analyte to chromatographically specific parameters through quantitative structure-retention relationship based equations, and (3) stochastic components of intra-analyte and interanalyte variability. The model was implemented in Stan, which provides full Bayesian inference for continuous-variable models through Markov chain Monte Carlo methods. Graphical abstract Relationships between log k and MeOH content for acidic, basic, and neutral compounds with different log P. CI credible interval, PSA polar surface area.

Combination of bioremediation and electrokinetics for the in-situ treatment of diesel polluted soil: A comparison of strategies.

PubMed

Mena Ramírez, Esperanza; Villaseñor Camacho, José; Rodrigo, Manuel A; Cañizares, Pablo

2015-11-15

The aim of this work is to compare different strategies based on electrokinetic soil flushing and bioremediation for the remediation of diesel-polluted soil. Four options were tested at the laboratory scale: single bioremediation (Bio), performed as a control test; a direct combination of electrokinetic soil flushing and biological technologies (EKSF-Bio); EKSF-Bio with daily polarity reversal of the electric field (PR-EKSF-Bio); and a combination of electrokinetic soil flushing and a permeable reactive biological barrier (EKSF-BioPRB). Four batch experiments of 14 days duration were carried out for comparing technologies at room temperature with an electric field of 1.0 V cm(-1) (in EKSF). A diesel degrading microbial consortium was used. The experimental procedure and some specific details, such as the flushing fluids used, varied depending on the strategy. When using the EKSF-Bio option, a high buffer concentration was required to control the pH, causing soil heating, which negatively affected the biological growth and thus the diesel removal. The PR-EKSF-Bio and the EKSF-BioPRB options attained suitable operating conditions and improved the transport processes for biological growth. Polarity reversal was an efficient option for pH, moisture and temperature control. Homogeneous microbial growth was observed, and approximately 20% of the diesel was removed. The BioPRB option was not as efficient as PR-EKSF-Bio in controlling the operating conditions, but the central biobarrier protected the biological activity. Microbial growth was observed not only in the biobarrier but also in a large portion of the soil, and 29% of the diesel was removed in the short remediation test. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of lysergic acid diethylamide (LSD) in mouse blood by capillary electrophoresis/ fluorescence spectroscopy with sweeping techniques in micellar electrokinetic chromatography.

PubMed

Fang, Ching; Liu, Ju-Tsung; Chou, Shiu-Huey; Lin, Cheng-Huang

2003-03-01

The separation and on-line concentration of lysergic acid diethylamide (LSD) in mouse blood was achieved by means of capillary electrophoresis/fluorescence spectroscopy using sodium dodecyl sulfate (SDS) as the surfactant. Techniques involving on-line sample concentration, including sweeping micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were applied; the optimum on-line concentration and separation conditions were determined. In the analysis of an actual sample, LSD was found in a blood sample from a test mouse (0.1 mg LSD fed to a 20 g mouse; approximately 1/10 to the value of LD(50)). As a result, 120 and 30 ng/mL of LSD was detected at 20 and 60 min, respectively, after ingestion of the doses.

Correlations between chromatographic parameters and bioactivity predictors of potential herbicides.

PubMed

Janicka, Małgorzata

2014-08-01

Different liquid chromatography techniques, including reversed-phase liquid chromatography on Purosphere RP-18e, IAM.PC.DD2 and Cosmosil Cholester columns and micellar liqud chromatography with a Purosphere RP-8e column and using buffered sodium dodecyl sulfate-acetonitrile as the mobile phase, were applied to study the lipophilic properties of 15 newly synthesized phenoxyacetic and carbamic acid derivatives, which are potential herbicides. Chromatographic lipophilicity descriptors were used to extrapolate log k parameters (log kw and log km) and log k values. Partitioning lipophilicity descriptors, i.e., log P coefficients in an n-octanol-water system, were computed from the molecular structures of the tested compounds. Bioactivity descriptors, including partition coefficients in a water-plant cuticle system and water-human serum albumin and coefficients for human skin partition and permeation were calculated in silico by ACD/ADME software using the linear solvation energy relationship of Abraham. Principal component analysis was applied to describe similarities between various chromatographic and partitioning lipophilicities. Highly significant, predictive linear relationships were found between chromatographic parameters and bioactivity descriptors. © The Author [2013]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Measurement of Nitroaromatic Explosives by Micellar Electrokinetic Chromatography in Waters Collected Along a Tropical Estuary

DTIC Science & Technology

2014-02-07

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/ 6110 --14-9504 Measurement of Nitroaromatic Explosives by Micellar Electrokinetic...Carolina CaMeron lindsay Science & Engineering Apprenticeship Program Office of Naval Research Arlington, Virginia i REPORT DOCUMENTATION PAGE Form...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 2 . REPORT TYPE1. REPORT DATE (DD-MM-YYYY) 4. TITLE

Adsorption behavior of plasmid DNA onto perfusion chromatographic matrix.

PubMed

Limonta, Miladys; Zumalacárregui, Lourdes; Soler, Dayana

2012-05-01

Anion exchange chromatography is the most popular chromatographic method for plasmid separation. POROS RI 50 is a perfusion chromatographic support which is a reversed phase matrix and is an alternative to conventional ones due to its mass transfer properties. The adsorption and elution of the pIDKE2 plasmid onto reversed phase POROS R1 50 was studied. Langmuir isotherm model was adjusted in order to get the maximum adsorption capacity and the dissociation constant for POROS R1 50-plasmid DNA (pDNA) system. Breakthrough curves were obtained for volumetric flows between 0.69-3.33 mL/min, given dynamic capacity up to 2.3 times higher than those reported for ionic exchange matrix used during the purification process of plasmids with similar size to that of pIDKE2. The efficiency was less than 45% for the flow conditions and initial concentration studied, which means that the support will not be operated under saturation circumstances.

Atmospheric Transport Studies Using In-situ Airborne Gas Chromatograph Measurements: An Overview of the NOAA Climate Monitoring and Diagnostics Laboratory (CMDL) Contribution.

NASA Astrophysics Data System (ADS)

Moore, F.; Dutton, G.; Elkins, J.; Hall, B.; Hurst, D.; Nance, D.; Ray, E.; Romashkin, P.; Thompson, T.; Volk, C. M.

2005-12-01

Accurate models of atmospheric transport are crucial to our current understanding of ozone production/loss and its coupling with climate change. Over the last ``20 years'', improvements in the ability to predict ``The Antarctic Ozone Hole and Polar Ozone Loss'' have tracked improvements in transport models. Data taken from the NOAA/CMDL airborne in-situ GC's (ACATS, LACE, PANTHER, and UCATS) have and will continue to play key roles in quantifying many aspects of stratospheric transport. Our data have been used in many of the model assessments to date. We will display an overview of the transport issues studied over the years using our data. They include descent with mixing within and into the polar vortex, entrainment of mid-latitude air across the vortex edge, upwelling and entrainment in the tropical pipe, isentropic transport across the tropopause into the lowermost stratosphere, mean ages of air parcels in the stratosphere, and stratospheric path distributions. ACATS - Airborne Chromatograph for Atmospheric Trace Species LACE - Lightweight Airborne Chromatograph Experiment PANTHER - PAN and Other Trace Hydrohalocarbons ExpeRiment UCATS - Unmanned aerial systems Chromatograph for Atmospheric Trace Species

Impact of ionization equilibrium on electrokinetic flow of weak electrolytes in nanochannels

NASA Astrophysics Data System (ADS)

Ji, Ziwei; Huang, Zhuo; Chen, Bowei; He, Yuhui; Tsutsui, Makusu; Miao, Xiangshui

2018-07-01

Weak electrolyte transport in nanochannels or nanopores has been actively explored in recent experiments. In this paper, we establish a new electrokinetic model where the ionization balance effect of weak electrolytes is outlined, and performed numerical calculations for H3PO4 concentration-biased nanochannel systems. By considering the roles of local chemical equilibrium in phosphorous acid ionization, the simulation results show quantitative agreement with experimental observations. Based on the model, we predict that enhanced energy harvesting capacity could be accomplished by utilizing weak electrolytes compared to the conventional strong electrolyte approaches in a concentration gradient-based power-generating system.

Assessment of the chromatographic lipophilicity of eight cephalosporins on different stationary phases.

PubMed

Dąbrowska, Monika; Starek, Małgorzata; Komsta, Łukasz; Szafrański, Przemysław; Stasiewicz-Urban, Anna; Opoka, Włodzimierz

2017-04-01

The retention behaviors were investigated for a series of eight cephalosporins in thin-layer chromatography (TLC) using stationary phases of RP-2, RP-8, RP-18, NH 2 , DIOL, and CN chemically bonded silica gel. Additionally, various binary mobile phases (water/methanol and water/acetone) were used in different volume proportions. The retention behavior of the analyzed molecules was defined by R M0 constant. In addition, reversed phase high performance liquid chromatography (RP-HPLC) was performed in lipophilicity studies by using immobilized artificial membrane (IAM) stationary phase. Obtained chromatographic data (R M0 and logk' IAM ) were correlated with the lipophilicity, expressed as values of the log calculated (logP calc ) and experimental (logP exp(shake-flask) ) partition coefficient. Principal component analysis (PCA) was applied in order to obtain an overview of similarity or dissimilarity among the analyzed compounds. Hierarchical cluster analysis (HCA) was performed to compare the separation characteristics of the applied stationary phases. This study was undertaken to identify the best chromatographic system and chromatographic data processing method to enable the prediction of logP values. A comprehensive chromatographic investigation into the retention of the analyzed cephalosporins revealed a similar behavior on RP-18, RP-8 and CN stationary phases. The weak correlations obtained between experimental and certain computed lipophilicity indices revealed that R M0 and PC1/RM are relevant lipophilicity parameters and the RP-8, CN and RP-18 plates are appropriate stationary phases for lipophilicity investigation, whereas computational approaches still cannot fully replace experimentation. Copyright © 2017 Elsevier B.V. All rights reserved.

A Quantitative Gas Chromatographic Ethanol Determination.

ERIC Educational Resources Information Center

Leary, James J.

1983-01-01

Describes a gas chromatographic experiment for the quantitative determination of volume percent ethanol in water ethanol solutions. Background information, procedures, and typical results are included. Accuracy and precision of results are both on the order of two percent. (JN)

MicrofluIdic circuit designs for performing electrokinetic manipulations that reduce the number of voltage sources and fluid reservoirs

DOEpatents

Jacobson, Stephen C.; Ramsey, J. Michael

2000-01-01

A microfabricated device and method for proportioning and mixing electrokinetically manipulated biological or chemical materials is disclosed. The microfabricated device mixes a plurality of materials in volumetric proportions controlled by the electrical resistances of tributary reagent channels through which the materials are transported. The microchip includes two or more tributary reagent channels combining at one or more junctions to form one or more mixing channels. By varying the geometries of the channels (length, cross section, etc.), a plurality of reagent materials can be mixed at a junction such that the proportions of the reagent materials in the mixing channel depend on a ratio of the channel geometries and material properties. Such an approach facilitates voltage division on the microchip without relying on external wiring schemes and voltage division techniques external to the microchip. Microchannel designs that provide the necessary voltage division to accomplish electrokinetic valving operations using a single voltage source and a switch are also described. In addition, microchannel designs that accomplish fluidic operation utilizing a minimal number of fluidic reservoirs are disclosed.

Environmental Electrokinetics for a sustainable subsurface.

PubMed

Lima, A T; Hofmann, A; Reynolds, D; Ptacek, C J; Van Cappellen, P; Ottosen, L M; Pamukcu, S; Alshawabekh, A; O'Carroll, D M; Riis, C; Cox, E; Gent, D B; Landis, R; Wang, J; Chowdhury, A I A; Secord, E L; Sanchez-Hachair, A

2017-08-01

Soil and groundwater are key components in the sustainable management of the subsurface environment. Source contamination is one of its main threats and is commonly addressed using established remediation techniques such as in-situ chemical oxidation (ISCO), in-situ chemical reduction (ISCR; most notably using zero-valent iron [ZVI]), enhanced in-situ bioremediation (EISB), phytoremediation, soil-washing, pump-and-treat, soil vapour extraction (SVE), thermal treatment, and excavation and disposal. Decades of field applications have shown that these techniques can successfully treat or control contaminants in higher permeability subsurface materials such as sands, but achieve only limited success at sites where low permeability soils, such as silts and clays, prevail. Electrokinetics (EK), a soil remediation technique mostly recognized in in-situ treatment of low permeability soils, has, for the last decade, been combined with more conventional techniques and can significantly enhance the performance of several of these remediation technologies, including ISCO, ISCR, EISB and phytoremediation. Herein, we discuss the use of emerging EK techniques in tandem with conventional remediation techniques, to achieve improved remediation performance. Furthermore, we highlight new EK applications that may come to play a role in the sustainable treatment of the contaminated subsurface. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of the polarity reversal frequency in the electrokinetic-biological remediation of oxyfluorfen polluted soil.

PubMed

Barba, Silvia; Villaseñor, José; Rodrigo, Manuel A; Cañizares, Pablo

2017-06-01

This work studies the feasibility of the periodic polarity reversal strategy (PRS) in a combined electrokinetic-biological process for the remediation of clayey soil polluted with a herbicide. Five two-weeks duration electrobioremediation batch experiments were performed in a bench scale set-up using spiked clay soil polluted with oxyfluorfen (20 mg kg -1 ) under potentiostatic conditions applying an electric field between the electrodes of 1.0 V cm -1 (20.0 V) and using PRS with five frequencies (f) ranging from 0 to 6 d -1 . Additionally, two complementary reference tests were done: single bioremediation and single electrokinetic. The microbial consortium used was obtained from an oil refinery wastewater treatment plant and acclimated to oxyfluorfen degradation. Main soil conditions (temperature, pH, moisture and conductivity) were correctly controlled using PRS. On the contrary, the electroosmotic flow clearly decreased as f increased. The uniform soil microbial distribution at the end of the experiments indicated that the microbial activity remained in every parts of the soil after two weeks when applying PRS. Despite the adapted microbial culture was capable of degrade 100% of oxyfluorfen in water, the remediation efficiency in soil in a reference test, without the application of electric current, was negligible. However, under the low voltage gradients and polarity reversal, removal efficiencies between 5% and 15% were obtained, and it suggested that oxyfluorfen had difficulties to interact with the microbial culture or nutrients and that PRS promoted transport of species, which caused a positive influence on remediation. An optimal f value was observed between 2 and 3 d -1 . Copyright © 2017 Elsevier Ltd. All rights reserved.

Micellar electrokinetic chromatography with acid labile surfactant.

PubMed

Stanley, Bob; Lucy, Charles A

2012-02-24

We present a study of a degradable surfactant, sodium 4-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propane sulfonate that is also known as an acid-labile surfactant (ALS). The performance of ALS as a pseudostationary phase is assessed and compared with established pseudostationary phases such as sodium dodecyl sulphate (SDS), volatile surfactants and polymeric micelles. ALS achieves separation efficiency of 100,000-145,000 theoretical plates and relative standard deviation (RSD) of electrophoretic mobility (n=5) of less than 3%. Retention factors with ALS are strongly correlated with those with SDS. This is shown by the R2=0.79 for all eleven analytes and an R2=0.992 for specifically the non-hydrogen bonding (NHB) analytes. However, ALS displays different selectivity than SDS for hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) solutes (R2 of 0.74 and 0.88, respectively). ALS is degraded to less surface active compounds in acidic solution. These less surface-active compounds are more compatible with the electrospray ionization mass spectrometry (ESI-MS). ALS has a half-life of 48 min at pH 4. ALS has the potential to couple micellar electrokinetic chromatography (MEKC) with the ESI-MS. ALS can be used as a pseudostationary phase for a high efficiency separation and later acid hydrolyzed to enable an ESI-MS analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

Micro-column plasma emission liquid chromatograph

DOEpatents

Gay, Don D.

1984-01-01

In a direct current plasma emission spectrometer for use in combination with a micro-column liquid chromatograph, an improved plasma source unit. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

Electrokinetic Supercapacitor for Simultaneous Harvesting and Storage of Mechanical Energy.

PubMed

Yang, Peihua; Qu, Xiaopeng; Liu, Kang; Duan, Jiangjiang; Li, Jia; Chen, Qian; Xue, Guobin; Xie, Wenke; Xu, Zhimou; Zhou, Jun

2018-03-07

Energy harvesting and storage are two distinct processes that are generally achieved using two separated parts based on different physical and chemical principles. Here we report a self-charging electrokinetic supercapacitor that directly couples the energy harvesting and storage processes into one device. The device consists of two identical carbon nanotube/titanium electrodes, separated by a piece of anodic aluminum oxide nanochannels membrane. Pressure-driven electrolyte flow through the nanochannels generates streaming potential, which can be used to charge the capacitive electrodes, accomplishing simultaneous energy generation and storage. The device stores electric charge density of 0.4 mC cm -2 after fully charging under pressure of 2.5 bar. This work may offer a train of thought for the development of a new type of energy unit for self-powered systems.

INTERLABORATORY STUDY OF A THERMOSPRAY-LIQUID CHROMATOGRAPHIC/MASS SPECTROMETRIC METHOD FOR SELECTED N-METHYL CARBAMATES, N-METHYL CARBAMOYLOXIMES, AND SUBSTITUTED UREA PESTICIDES

EPA Science Inventory

A thermospray-liquid chromatographic/mass spectrometric (TS-LC/MS) method was evaluated in an interlaboratory study for determining 3 N-methyl carbamates (bendiocarb, carbaryl, and carbofuran), 3-N-methyl carbamoyloximes (aldicarb, methomyl, and oxamyl), 2 substituted urea pestic...

Gas Chromatographic Determination of Enrivonmentally Significant Pesticides.

ERIC Educational Resources Information Center

Rudzinski, Walter E.; Beu, Steve

1982-01-01

A chromatographic procedure for analyzing organophosphorus pesticides (such as PCB's, nitrosamines, and phthalate esters) in orange juice is described, including a summary of the method, instrumentation, methodology, results/discussion, and calculations. (JN)

Chromatographic and mass spectral methods of identification for the side-chain and ring regioisomers of methylenedioxymethamphetamine.

PubMed

Aalberg, L; DeRuiter, J; Noggle, F T; Sippola, E; Clark, C R

2000-08-01

The popular drug of abuse 3,4-methylenedioxymethamphetamine (MDMA) is one of a total of 10 regioisomeric 2,3- and 3,4-methylenedioxyphenethylamines of MW 193 that yields regioisomeric fragment ions with equivalent mass (m/z 58 and 135/136) in the electron-impact (EI) mass spectrum. Thus, these 10 methylenedioxyphenethylamines are uniquely isomeric; they have the same molecular weight and equivalent major fragments in their mass spectra. The specific identification of one of these compounds (i.e., Ecstasy or 3,4-MDMA) in a forensic drug sample depends upon the analyst's ability to eliminate the other regioisomers as possible interfering or coeluting substances. This study reports the synthesis, chemical properties, spectral characterization, and chromatographic analysis of these 10 unique regioisomers. The ten 2,3- and 3,4-regioisomers of MDMA are synthesized from commercially available precursor chemicals. In the EI mass spectra, the side-chain regioisomers show some variation in the relative intensity of the major ions, with the exception of only one or two minor ions that might be considered side-chain specific fragments. The position of substitution for the methylenedioxy ring is not easily determined by mass spectral techniques, and the ultimate identification of any one of these amines with the elimination of the other nine must depend heavily upon chromatographic methods. The chromatographic separation of these 10 uniquely regioisomeric amines are studied using reversed-phase liquid chromatographic methods with gradient elution and gas chromatographic techniques with temperature program optimization.

On-line gas chromatographic analysis of airborne particles

DOEpatents

Hering, Susanne V [Berkeley, CA; Goldstein, Allen H [Orinda, CA

2012-01-03

A method and apparatus for the in-situ, chemical analysis of an aerosol. The method may include the steps of: collecting an aerosol; thermally desorbing the aerosol into a carrier gas to provide desorbed aerosol material; transporting the desorbed aerosol material onto the head of a gas chromatography column; analyzing the aerosol material using a gas chromatograph, and quantizing the aerosol material as it evolves from the gas chromatography column. The apparatus includes a collection and thermal desorption cell, a gas chromatograph including a gas chromatography column, heated transport lines coupling the cell and the column; and a quantization detector for aerosol material evolving from the gas chromatography column.

Quantitative analysis of synthetic dyes in lipstick by micellar electrokinetic capillary chromatography.

PubMed

Desiderio, C; Marra, C; Fanali, S

1998-06-01

The separation of synthetic dyes, used as color additives in cosmetics, by micellar electrokinetic capillary chromatography (MEKC) is described in this study. The separation of seven dyes, namely eosine, erythrosine, cyanosine, rhodamine B, orange II, chromotrope FB and tartrazine has been achieved in about 3 min in an untreated fused silica capillary containing as background electrolyte a 25 mM tetraborate/phosphate buffer, pH 8.0, and 30 mM sodium dodecyl sulfate. The electrophoretic method exhibits precision and relatively high sensitivity. A detection limit (LOD, signal/noise = 3) in the range of 5-7.5 X 10(-7) M of standard compounds was recorded. Intra-day repeatability of all the studied dye determinations (8 runs) gave the following results (limit values), % standard deviation: 0.24-1.54% for migration time, 0.99-1.24% for corrected peak areas, 0.99-1.24% for corrected peak area ratio (analyte/internal standard) and 1.56-2.74% for peak areas. The optimized method was successfully applied to the analysis of a lipstick sample where eosine and cyanosine were present.

Electrokinetically driven continuous-flow enrichment of colloidal particles by Joule heating induced temperature gradient focusing in a convergent-divergent microfluidic structure.

PubMed

Zhao, Cunlu; Ge, Zhengwei; Song, Yongxin; Yang, Chun

2017-09-07

Enrichment of colloidal particles in continuous flow has not only numerous applications but also poses a great challenge in controlling physical forces that are required for achieving particle enrichment. Here, we for the first time experimentally demonstrate the electrokinetically-driven continuous-flow enrichment of colloidal particles with Joule heating induced temperature gradient focusing (TGF) in a microfluidic convergent-divergent structure. We consider four mechanisms of particle transport, i.e., advection due to electroosmosis, electrophoresis, dielectrophoresis and, and further clarify their roles in the particle enrichment. It is experimentally determined and numerically verified that the particle thermophoresis plays dominant roles in enrichment of all particle sizes considered in this study and the combined effect of electroosmosis-induced advection and electrophoresis is mainly to transport particles to the zone of enrichment. Specifically, the enrichment of particles is achieved with combined DC and AC voltages rather than a sole DC or AC voltage. A numerical model is formulated with consideration of the abovementioned four mechanisms, and the model can rationalize the experimental observations. Particularly, our analysis of numerical and experimental results indicates that thermophoresis which is usually an overlooked mechanism of material transport is crucial for the successful electrokinetic enrichment of particles with Joule heating induced TGF.

Comparison of two gas chromatograph models and analysis of binary data

NASA Technical Reports Server (NTRS)

Keba, P. S.; Woodrow, P. T.

1972-01-01

The overall objective of the gas chromatograph system studies is to generate fundamental design criteria and techniques to be used in the optimum design of the system. The particular tasks currently being undertaken are the comparison of two mathematical models of the chromatograph and the analysis of binary system data. The predictions of two mathematical models, an equilibrium absorption model and a non-equilibrium absorption model exhibit the same weaknesses in their inability to predict chromatogram spreading for certain systems. The analysis of binary data using the equilibrium absorption model confirms that, for the systems considered, superposition of predicted single component behaviors is a first order representation of actual binary data. Composition effects produce non-idealities which limit the rigorous validity of superposition.

Method for liquid chromatographic extraction of strontium from acid solutions

DOEpatents

Horwitz, E. Philip; Dietz, Mark L.

1992-01-01

A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

Use of solar cell in electrokinetic remediation of cadmium-contaminated soil.

PubMed

Yuan, Songhu; Zheng, Zhonghua; Chen, Jing; Lu, Xiaohua

2009-03-15

This preliminary study used a solar cell, instead of direct current (DC) power supply, to generate electric field for electrokinetic (EK) remediation of cadmium-contaminated soil. Three EK tests were conducted and compared; one was conducted on a cloudy and rainy day with solar cell, one was conducted on a sunny day with solar cell and another was conducted periodically with DC power supply. It was found that the output potential of solar cell depended on daytime and was influenced by weather conditions; the applied potential in soil was affected by the output potential and weather conditions, and the current achieved by solar cell was comparable with that achieved by DC power supply. Solar cell could be used to drive the electromigration of cadmium in contaminated soil, and removal efficiency achieved by solar cell was comparable with that achieved by DC power supply. Compared with traditional DC power supply, using solar cell as power supply for EK remediation can greatly reduce energy expenditure. This study provided an alternative to improve the EK soil remediation and expanded the use of solar cell in environmental remediation.

Note on the chromatographic analyses of marine polyunsaturated fatty acids

USGS Publications Warehouse

Schultz, D.M.; Quinn, J.G.

1977-01-01

Gas-liquid chromatography was used to study the effects of saponification/methylation and thin-layer chromatographic isolation on the analyses of polyunsaturated fatty acids. Using selected procedures, the qualitative and quantitative distribution of these acids in marine organisms can be determined with a high degree of accuracy. ?? 1977 Springer-Verlag.

Micelle to solvent stacking of organic cations in micellar electrokinetic chromatography with sodium dodecyl sulfate.

PubMed

Quirino, Joselito P; Aranas, Agnes T

2011-10-14

The on-line sample concentration technique, micelle to solvent stacking (MSS), was studied for small organic cations (quaternary ammonium herbicides, β-blocker drugs, and tricyclic antidepressant drugs) in reversed migration micellar electrokinetic chromatography. Electrokinetic chromatography was carried out in fused silica capillaries with a background solution of sodium dodecyl sulfate (SDS) in a low pH phosphate buffer. MSS was performed using anionic SDS micelles in the sample solution for analyte transport and methanol or acetonitrile as organic solvent in the background solution for analyte effective electrophoretic mobility reversal. The solvent also allowed for the separation of the analyte test mixtures. A model for focusing and separation was developed and the mobility reversal that involved micelle collapse was experimentally verified. The effect of analyte retention factor was observed by changing the % organic solvent in the background solution or the concentration of SDS in the sample matrix. With an injection length of 31.9 cm (77% of effective capillary length) for the 7 test drugs, the LODs (S/N=3) of 5-14 ng/mL were 101-346-fold better when compared to typical injection. The linearity (R(2), range=0.025-0.8 μg/mL), intraday and interday repeatability (%RSD, n=10) were ≥0.988, <6.0% and <8.5%, respectively. In addition, analysis of spiked urine samples after 10-fold dilution with the sample matrix yielded LODs=0.02-0.10 μg/mL. These LODs are comparable to published electrophoretic methods that required off-line sample concentration. However, the practicality of the technique for more complex samples will rely on dedicated sample preparation schemes. Copyright © 2011 Elsevier B.V. All rights reserved.

Transesterification of propylene glycol methyl ether in chromatographic reactors using anion exchange resin as a catalyst.

PubMed

Oh, Jungmin; Sreedhar, Balamurali; Donaldson, Megan E; Frank, Timothy C; Schultz, Alfred K; Bommarius, Andreas S; Kawajiri, Yoshiaki

2016-09-30

Reactive chromatography using an anion exchange resin is proposed for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) with ethyl acetate to produce propylene glycol methyl ether acetate (DOWANOL™ PMA). This reaction is studied in batch and chromatographic reactors catalyzed by an anion exchange resin. Several anion exchange resins are tested and compared based on the performance of resin as an adsorbent and a catalyst. A chromatographic column is packed with a selected catalyst, AMBERLITE™ IRA904, and both reaction and chromatographic elution are studied at different temperatures and feed concentrations. The resulting chromatograms are fitted to a mathematical model to obtain adsorption equilibrium and reaction kinetic parameters by the inverse method. Compared to esterification investigated in a previous study, transesterification has advantages such as a higher conversion at lower temperature and easy removal of the byproduct which may lead to higher productivity. Deactivation of anion exchange resins is observed and potential solutions are suggested. Copyright © 2016 Elsevier B.V. All rights reserved.

Microplate-Based Method for High-Throughput Screening (HTS) of Chromatographic Conditions Studies for Recombinant Protein Purification.

PubMed

Carvalho, Rimenys J; Cruz, Thayana A

2018-01-01

High-throughput screening (HTS) systems have emerged as important tools to provide fast and low cost evaluation of several conditions at once since it requires small quantities of material and sample volumes. These characteristics are extremely valuable for experiments with large number of variables enabling the application of design of experiments (DoE) strategies or simple experimental planning approaches. Once, the capacity of HTS systems to mimic chromatographic purification steps was established, several studies were performed successfully including scale down purification. Here, we propose a method for studying different purification conditions that can be used for any recombinant protein, including complex and glycosylated proteins, using low binding filter microplates.

Measuring the DC electrokinetic coupling coefficient of porous rock samples in the laboratory : a new apparatus

NASA Astrophysics Data System (ADS)

Walker, E.; Tardif, E.; Glover, P. W.; Ruel, J.; Hadjigeorgiou, J.

2009-12-01

Electro-kinetic properties of rocks allow the generation of an electric potential by the flow of an aqueous fluid through a porous media. The electrical potential is called the streaming potential, and the streaming potential coupling coefficient Cs is the ratio of the generated electric potential to the pressure difference that causes the fluid flow. The streaming potential coupling coefficient for rocks is described in the steady-state regime by the well known Helmholtz-Smoluchowski equation, and is supported by a relatively small body of experimental data. However, the electrokinetic coupling coefficient measurement is important for the further development of different area of expertise such as reservoir prospection and monitoring, volcano and earthquake monitoring and the underground sequestration of CO2. We have designed, constructed and tested a new experimental cell that is capable of measuring the DC streaming potential of consolidated and unconsolidated porous media. The new cell is made from stainless steel, perspex and other engineering polymers. Cylindrical samples of 25.4 mm can be placed in a deformable rubber sleeve and subjected to a radial confining pressure of compressed nitrogen up to 4.5 MPa. Actively degassed aqueous fluids can be flowed by an Agilent 1200 series binary pump (2 to 10 mL/min). A maximum input fluid pressure of 2.5 MPa can be applied, with a maximum exit pressure of 1 MPa to ensure sample saturation is stable and to reduce gas bubbles. The pressures each side of the sample are measured by high stability pressure transducers (Omega PX302-300GV), previously calibrated by a high precision differential pressure transducer Endress and Hauser Deltabar S PMD75. The streaming potentials are measured with Harvard Apparatus LF-1 and LF-2 Ag/AgCl non-polarising miniature electrodes. An axial pressure is applied (1 to 6.5 MPa) to counteract the radial pressure and provide additional axial load with a hydraulic piston. It is our intention to

Measuring the DC electrokinetic coupling coefficient of porous rock samples in the laboratory : A new apparatus

NASA Astrophysics Data System (ADS)

Walker, Emilie; Tardif, Eric; Glover, Paul; Ruel, Jean; Lalande, Guillaume; Hadjigeorgiou, John

2010-05-01

Electro-kinetic properties of rocks allow the generation of an electric potential by the flow of an aqueous fluid through a porous media. The electrical potential is called the streaming potential, and the streaming potential coupling coefficient is the ratio of the generated electric potential to the pressure difference that causes the fluid flow. The streaming potential coupling coefficient for rocks is described in the steady-state regime by the well known Helmholtz-Smoluchowski equation, and is supported by a relatively small body of experimental data. However, the electrokinetic coupling coefficient measurement is important for the further development of different area of expertise such as reservoir prospection and monitoring, volcano and earthquake monitoring and the underground sequestration of carbon dioxide. We have designed, constructed and tested a new experimental cell that is capable of measuring the DC streaming potential of consolidated and unconsolidated porous media. The new cell is made from stainless steel, perspex and other engineering polymers. Cylindrical samples of 25.4 mm can be placed in a deformable rubber sleeve and subjected to a radial confining pressure of compressed nitrogen up to 4.5 MPa. Actively degassed aqueous fluids can be flowed by an Agilent 1200 series binary pump (2 to 10 mL/min). A maximum input fluid pressure of 2.5 MPa can be applied, with a maximum exit pressure of 1 MPa to ensure sample saturation is stable and to reduce gas bubbles. The pressures each side of the sample are measured by high stability pressure transducers (Omega PX302-300GV), previously calibrated by a high precision differential pressure transducer Endress and Hauser Deltabar S PMD75. The streaming potentials are measured with Harvard Apparatus LF-1 and LF-2 Ag/AgCl non-polarising miniature electrodes. An axial pressure is applied (1 to 6.5 MPa) to counteract the radial pressure and provide additional axial load with a hydraulic piston. It is our

Hematite/silica nanoparticle bilayers on mica: AFM and electrokinetic characterization.

PubMed

Morga, Maria; Adamczyk, Zbigniew; Kosior, Dominik; Oćwieja, Magdalena

2018-06-06

Quantitative studies on self-assembled hematite/silica nanoparticle (NP) bilayers on mica were performed by applying scanning electron microscopy (SEM), atomic force microscopy (AFM), and streaming potential measurements. The coverage of the supporting hematite layers was adjusted by changing the bulk concentration of the suspension and the deposition time. The coverage was determined by direct enumeration of deposited particles from AFM images and SEM micrographs. Afterward, silica nanoparticle monolayers were assembled under diffusion-controlled transport. A unique functional relationship was derived connecting the silica coverage with the hematite precursor layer coverage. The formation of the hematite monolayer and the hematite/silica bilayer was also monitored in situ by streaming potential measurements. It was confirmed that the zeta potential of the bilayers was independent of the supporting layer coverage, exceeding 0.15. These measurements were theoretically interpreted in terms of the general electrokinetic model that allowed for deriving a formula for calculating nanoparticle coverage in the bilayers. Additionally, from desorption experiments, the interactions among hematite/silica particles in the bilayers were determined using DLVO theory. These results facilitate the development of a robust method of preparing nanoparticle bilayers with controlled properties, with potential applications in catalytic processes.

Separation of Protactinium Employing Sulfur-Based Extraction Chromatographic Resins.

PubMed

Mastren, Tara; Stein, Benjamin W; Parker, T Gannon; Radchenko, Valery; Copping, Roy; Owens, Allison; Wyant, Lance E; Brugh, Mark; Kozimor, Stosh A; Nortier, F Meiring; Birnbaum, Eva R; John, Kevin D; Fassbender, Michael E

2018-06-05

Protactinium-230 ( t 1/2 = 17.4 d) is the parent isotope of 230 U ( t 1/2 = 20.8 d), a radionuclide of interest for targeted alpha therapy (TAT). Column chromatographic methods have been developed to separate no-carrier-added 230 Pa from proton irradiated thorium targets and accompanying fission products. Results reported within demonstrate the use of novel sulfur bearing chromatographic extraction resins for the selective separation of protactinium. The recovery yield of 230 Pa was 93 ± 4% employing a R 3 P═S type commercially available resin and 88 ± 4% employing a DGTA (diglycothioamide) containing custom synthesized extraction chromatographic resin. The radiochemical purity of the recovered 230 Pa was measured via high purity germanium γ-ray spectroscopy to be >99.5% with the remaining radioactive contaminant being 95 Nb due to its similar chemistry to protactinium. Measured equilibrium distribution coefficients for protactinium, thorium, uranium, niobium, radium, and actinium on both the R 3 P═S type and the DGTA resin in hydrochloric acid media are reported, to the best of our knowledge, for the first time.

A Versatile, Automatic Chromatographic Column Packing Device

ERIC Educational Resources Information Center

Barry, Eugene F.; And Others

1977-01-01

Describes an inexpensive apparatus for packing liquid and gas chromatographic columns of high efficiency. Consists of stainless steel support struts, an Automat Getriebmotor, and an associated three-pulley system capable of 10, 30, and 300 rpm. (MLH)

Novel Technique to improve the pH of Acidic Barren Soil using Electrokinetic-bioremediation with the application of Vetiver Grass

NASA Astrophysics Data System (ADS)

Azhar, A. T. S.; Nabila, A. T. A.; Nurshuhaila, M. S.; Zaidi, E.; Azim, M. A. M.; Zahin, A. M. F.

2016-11-01

Residual acidic slopes which are not covered by vegetation greatly increases the risk of soil erosion. In addition, low soil pH can bring numerous problems such as Al and Fe toxicity, land degradation issues and some problems related to vegetation. In this research, a series of electrokinetic bioremediation (EK-Bio) treatments using Bacillus sphaericus, Bacillus subtilis and Pseudomonas putida with a combination of Vetiver grass were performed in the laboratory. Investigations were conducted for 14 days and included the observation of changes in the soil pH and the mobilization of microorganism cells through an electrical gradient of 50 V/m under low pH. Based on the results obtained, this study has successfully proven that the pH of soil increases after going through electrokinetic bioremediation (EK-Bio). The treatment using Bacillus sphaericus increases the pH from 2.95 up to 4.80, followed by Bacillus subtilis with a value of 4.66. Based on the overall performance, Bacillus sphaericus show the highest number of bacterial cells in acidic soil with a value of 6.6 × 102 cfu/g, followed by Bacillus subtilis with a value of 5.7 × 102 cfu/g. In conclusion, Bacillus sphaericus and Bacillus subtilis show high survivability and is suitable to be used in the remediation of acidic soil.

Microfluidic thread based electroanalytical system for green chromatographic separations.

PubMed

Agustini, Deonir; Fedalto, Lucas; Bergamini, Márcio F; Marcolino-Junior, Luiz Humberto

2018-02-13

The use of miniaturized chromatographic systems is an important strategy for reducing the consumption of supplies related to separations, allowing the development of more sustainable analytical methodologies. However, the high cost and complexity in the production of these systems combined with the operational difficulties and the need for the use of solvent and sample pretreatment are challenges to be overcome in order to make the chromatographic methods greener. Here, we report the construction and development of a low cost microfluidic system for green and solvent-free chromatographic separations with electrochemical detection integrated into cotton threads without the use of any mechanical pumping to transport the solutions. The manufacture of the proposed system was performed by simple assembly of the components, with the separation of the species based on an ion exchange mechanism and detection using gold electrodes manufactured directly on the cotton threads. A linear range of 0.025-5.0 mM was obtained for the effective separation of ascorbic acid (AA) and dopamine (DA) with detection limits of 2.89 μM (for AA) and 4.41 μM (for DA). Each analysis was performed at a low cost (less than 0.01 dollars), and with a small volume of waste generated (107.1 μL). So, the proposed system was successfully employed to determine the levels of AA and DA present in the tears of healthy volunteers without sample pretreatment, indicating the good analytical performance of the system and the possibility of performing greener chromatographic separations.

Forsterite surface composition in aqueous solutions: a combined potentiometric, electrokinetic, and spectroscopic approach

NASA Astrophysics Data System (ADS)

Pokrovsky, Oleg S.; Schott, Jacques

2000-10-01

Surfaces of natural and synthetic forsterite (Fo 91 and Fo 100) in aqueous solutions at 25°C were investigated using surface titrations in batch and limited residence time reactors, column filtration experiments, electrokinetic measurements (streaming potential and electrophoresis techniques), Diffuse Reflectance Infrared Spectroscopy (DRIFT), and X-ray Photoelectron Spectroscopy (XPS). At pH < 9, a Mg-depleted, Si-rich layer (<20 Å thick) is formed on the forsterite surface due to a Mg 2+ ↔ H + exchange reaction. Electrokinetic measurements yield a pH IEP value of 4.5 corresponding to the dominance of SiO 2 in the surface layer at pH < 9. In contrast, surface titrations of fresh powders give an apparent pH PZC of about 10 with the development of a large positive charge (up to 10 -4 mol/m 2 or 10 C/m 2) in the acid pH region. This may be explained by penetration of H + into the first unit cells of forsterite surface. The surface charge of acid-reacted forsterite is one or two orders of magnitude lower than that of unreacted forsterite with an apparent pH PZC at around 6.5 and a pH IEP value of 2.1 which is close to that for amorphous silica and reflects the formation of a silica-rich layer on the surface. XPS analyses indicate the penetration of hydrogen into the surface and the polymerization of silica tetrahedra in this leached layer. At pH > 10, a Si-deficient, Mg-rich surface layer is formed as shown by XPS analyses and the preferential Si release from the surface during column filtration experiments.

Similarity analyses of chromatographic herbal fingerprints: a review.

PubMed

Goodarzi, Mohammad; Russell, Paul J; Vander Heyden, Yvan

2013-12-04

Herbal medicines are becoming again more popular in the developed countries because being "natural" and people thus often assume that they are inherently safe. Herbs have also been used worldwide for many centuries in the traditional medicines. The concern of their safety and efficacy has grown since increasing western interest. Herbal materials and their extracts are very complex, often including hundreds of compounds. A thorough understanding of their chemical composition is essential for conducting a safety risk assessment. However, herbal material can show considerable variability. The chemical constituents and their amounts in a herb can be different, due to growing conditions, such as climate and soil, the drying process, the harvest season, etc. Among the analytical methods, chromatographic fingerprinting has been recommended as a potential and reliable methodology for the identification and quality control of herbal medicines. Identification is needed to avoid fraud and adulteration. Currently, analyzing chromatographic herbal fingerprint data sets has become one of the most applied tools in quality assessment of herbal materials. Mostly, the entire chromatographic profiles are used to identify or to evaluate the quality of the herbs investigated. Occasionally only a limited number of compounds are considered. One approach to the safety risk assessment is to determine whether the herbal material is substantially equivalent to that which is either readily consumed in the diet, has a history of application or has earlier been commercialized i.e. to what is considered as reference material. In order to help determining substantial equivalence using fingerprint approaches, a quantitative measurement of similarity is required. In this paper, different (dis)similarity approaches, such as (dis)similarity metrics or exploratory analysis approaches applied on herbal medicinal fingerprints, are discussed and illustrated with several case studies. Copyright © 2013

Evaluation of electrokinetic parameters for all DNA bases with sputter deposited nanocarbon film electrode.

PubMed

Kato, Dai; Sumimoto, Michinori; Ueda, Akio; Hirono, Shigeru; Niwa, Osamu

2012-12-18

The electrokinetic parameters of all the DNA bases were evaluated using a sputter-deposited nanocarbon film electrode. It is very difficult to evaluate the electrokinetic parameters of DNA bases with conventional electrodes, and particularly those of pyrimidine bases, owing to their high oxidation potentials. Nanocarbon film formed by employing an electron cyclotron resonance sputtering method consists of a nanocrystalline sp(2) and sp(3) mixed bond structure that exhibits a sufficient potential window, very low adsorption of DNA molecules, and sufficient electrochemical activity to oxidize all DNA bases. A precise evaluation of rate constants (k) between all the bases and the electrodes is achieved for the first time by obtaining rotating disc electrode measurements with our nanocarbon film electrode. We found that the k value of each DNA base was dominantly dependent on the surface oxygen-containing group of the nanocarbon film electrode, which was controlled by electrochemical pretreatment. In fact, the treated electrode exhibited optimum k values for all the mononucleotides, namely, 2.0 × 10(-2), 2.5 × 10(-1), 2.6 × 10(-3), and 5.6 × 10(-3) cm s(-1) for GMP, AMP, TMP, and CMP, respectively. The k value of AMP was sufficiently enhanced by up to 33 times with electrochemical pretreatment. We also found the k values for pyrimidine bases to be much lower than those of purine bases although there was no large difference between their diffusion coefficient constants. Moreover, the theoretical oxidation potential values for all the bases coincided with those obtained in electrochemical experiments using our nanocarbon film electrode.

Liquid chromatographic determination of histamine in fish, sauerkraut, and wine: interlaboratory study.

PubMed

Beljaars, P R; Van Dijk, R; Jonker, K M; Schout, L J

1998-01-01

An interlaboratory study of the liquid chromatographic (LC) determination of histamine in fish, sauerkraut, and wine was conducted. Diminuted and homogenized samples were suspended in water followed by clarification of extracts with perchloric acid, filtration, and dilution with water. After LC separation on a reversed-phase C18 column with phosphate buffer (pH 3.0)--acetonitrile (875 + 125, v/v) as mobile phase, histamine was measured fluorometrically (excitation, 340 nm; emission, 455 nm) in samples and standards after postcolumn derivatization with o-phthaldialdehyde (OPA). Fourteen samples (including 6 blind duplicates and 1 split level) containing histamine at about 10-400 mg/kg or mg/L were analyzed singly according to the proposed procedure by 11 laboratories. Results from one participant were excluded from statistical analysis. For all samples analyzed, repeatability relative standard deviations varied from 2.1 to 5.6%, and reproducibility relative standard deviations ranged from 2.2 to 7.1%. Averaged recoveries of histamine for this concentration range varied from 94 to 100%.

Injection by hydrostatic pressure in conjunction with electrokinetic force on a microfluidic chip.

PubMed

Gai, Hongwei; Yu, Linfen; Dai, Zhongpeng; Ma, Yinfa; Lin, Bingcheng

2004-06-01

A simple method was developed for injecting a sample on a cross-form microfluidic chip by means of hydrostatic pressure combined with electrokinetic forces. The hydrostatic pressure was generated simply by adjusting the liquid level in different reservoirs without any additional driven equipment such as a pump. Two dispensing strategies using a floating injection and a gated injection, coupled with hydrostatic pressure loading, were tested. The fluorescence observation verified the feasibility of hydrostatic pressure loading in the separation of a mixture of fluorescein sodium salt and fluorescein isothiocyanate. This method was proved to be effective in leading cells to a separation channel for single cell analysis.

Mixed C18 and C1 modification on an optical fiber for chromatographic sensing.

PubMed

Zhou, Leiji; Wang, Kemin; Zuo, Xinbing; Choi, Martin M F; Chen, Yunqing; Huang, Shasheng

2003-09-01

An optical fiber-chromatographic sensor, aiming at simultaneous and selective response to multiple components following a chromatographic separation, is described. We report an improved approach for immobilization of octadecyl (C(18)) and methyl (C(1)) moieties as stationary phase on an optical fiber suitable as a sensing phase for organic solutes. By this approach, the stability and lifetime of the sensing layer as well as the detectability and retention behavior of the chromatographic sensor could be improved. Infrared spectroscopy was employed to confirm the presence of C(18) and C(1) moieties on the modified surface of the optical fiber. The chromatographic sensor was applied, with good sensitivity and chemical selectivity, to the simultaneous separation and detection of bromobenzene and toluene, using water as the mobile phase.

Electrokinetic remediation of plutonium-contaminated nuclear site wastes: results from a pilot-scale on-site trial.

PubMed

Agnew, Kieran; Cundy, Andrew B; Hopkinson, Laurence; Croudace, Ian W; Warwick, Phillip E; Purdie, Philip

2011-02-28

This paper examines the field-scale application of a novel low-energy electrokinetic technique for the remediation of plutonium-contaminated nuclear site soils, using soil wastes from the Atomic Weapons Establishment (AWE) Aldermaston site, Berkshire, UK as a test medium. Soils and sediments with varying composition, contaminated with Pu through historical site operations, were electrokinetically treated at laboratory-scale with and without various soil pre-conditioning agents. Results from these bench-scale trials were used to inform a larger on-site remediation trial, using an adapted containment pack with battery power supply. 2.4 m(3) (ca. 4t onnes) of Pu-contaminated soil was treated for 60 days at a power consumption of 33 kWh/m(3), and then destructively sampled. Radiochemical data indicate mobilisation of Pu in the treated soil, and migration (probably as a negatively charged Pu-citrate complex) towards the anodic compartment of the treatment cell. Soil in the cathodic zone of the treatment unit was remediated to a level below free-release disposal thresholds (1.7 Bq/g, or <0.4 Bq/g above background activities). The data show the potential of this method as a low-cost, on-site tool for remediation of radioactively contaminated soils and wastes which can be operated remotely on working sites, with minimal disruption to site infrastructure or operations. Copyright © 2010 Elsevier B.V. All rights reserved.

Arsenic speciation in sulfidic waters: reconciling contradictory spectroscopic and chromatographic evidence.

PubMed

Planer-Friedrich, Britta; Suess, Elke; Scheinost, Andreas C; Wallschläger, Dirk

2010-12-15

In recent years, analytical methods have been developed that have demonstrated that soluble arsenic-sulfur species constitute a major fraction of dissolved arsenic in sulfidic waters. However, an intense debate is going on about the exact chemical nature of these compounds, since X-ray absorption spectroscopy (XAS) data generated at higher (mmol/L) concentrations suggest the presence of (oxy)thioarsenites in such waters, while ion chromatographic (IC) and mass spectroscopic data at lower (μmol/L to nmol/L) concentrations indicate the presence of (oxy)thioarsenates. In this contribution, we connect and explain these two apparently different types of results. We show by XAS that thioarsenites are the primary reaction products of arsenite and sulfide in geochemical model experiments in the complete absence of oxygen. However, thioarsenites are extremely unstable toward oxidation, and convert rapidly into thioarsenates when exposed to atmospheric oxygen, e.g., while waiting for analysis on the chromatographic autosampler. This problem can only be eliminated when the entire chromatographic process is conducted inside a glovebox. We also show that thioarsenites are unstable toward sample dilution, which is commonly employed prior to chromatographic analysis when ultrasensitive detectors like ICP-MS are used. This instability has two main reasons: if pH changes during dilution, then equilibria between individual arsenic-sulfur species rearrange rapidly due to their different stability regions within the pH range, and if pH is kept constant during dilution, then this changes the ratio between OH(-) and SH(-) in solution, which in turn shifts the underlying speciation equilibria. This problem is avoided by analyzing samples undiluted. Our studies show that thioarsenites appear as thioarsenates in IC analyses if oxygen is not excluded completely, and as arsenite if samples are diluted in alkaline anoxic medium. This also points out that thioarsenites are necessary

Electrokinetic nanoparticle treatment for corrosion remediation on simulated reinforced bridge deck

NASA Astrophysics Data System (ADS)

Kupwade-Patil, Kunal; Cardenas, Henry E.

2013-09-01

ASTM G109 specimens were used in this work as these simulate the configuration of the bridge deck and subjected to elevated chloride levels. Nanoparticles which were 24 nm in size were driven directly through the concrete matrix and to the reinforcement using an electric field. The intent was to use the nanoparticles as pore blocking agents that could prevent chlorides from re-entering and accessing the rebar. Electrochemical, microstructure, and pore structure characterization was conducted on the electrokinetic nanoparticle (EN) treated and control specimens. At the end of post saltwater exposure period EN-treated specimens exhibited lower corrosion current densities, chloride contents below the threshold limit for new construction and 22 % reduction in porosity as compared to the controls. EN treatment was successful in mitigating reinforcement corrosion in concrete.

Electrokinetic behavior of melamine-formaldehyde latex particles at moderate electrolyte concentration.

PubMed

Dahlsten, Per; Próchniak, Piotr; Kosmulski, Marek; Rosenholm, Jarl B

2009-11-15

The electrokinetic behavior of micrometer-sized melamine-formaldehyde latex particles in 10(-3)-10(-1)M monovalent electrolyte dispersions was investigated by electrophoresis and electroacoustics. Specific adsorption of the electrolytes was identified as a shift of the isoelectric point (pH(iep)) with an increased ionic strength. All salts had an equal dependence on the ionic strength. The pH(iep) was correlated with the anion sequence predicted by the hard-soft acid-base (HSAB) principle, Hofmeister series, and Born charging. The Born and the Hofmeister anion scale were successful in producing a systematic dependency of the isoelectric point (pH(iep)), particularly in high (10(-1)M) and low (10(-3)M) MF electrolyte dispersions. No clear trend could be found for the pH(iep) dependence on the anion HSAB scale.

Research on technology of online gas chromatograph for SF6 decomposition products

NASA Astrophysics Data System (ADS)

Li, L.; Fan, X. P.; Zhou, Y. Y.; Tang, N.; Zou, Z. L.; Liu, M. Z.; Huang, G. J.

2017-12-01

Sulfur hexafluoride (SF6) decomposition products were qualitatively and quantitatively analyzed by several gas chromatographs in the laboratory. Test conditions and methods were selected and optimized to minimize and eliminate the SF6’ influences on detection of other trace components. The effective separation and detection of selected characteristic gases were achieved. And by comparison among different types of gas chromatograph, it was found that GPTR-S101 can effectively separate and detect SF6 decomposition products and has best the best detection limit and sensitivity. On the basis of GPTR-S101, online gas chromatograph for SF6decomposition products (GPTR-S201) was developed. It lays the foundation for further online monitoring and diagnosis of SF6.

Microminiature gas chromatograph

DOEpatents

Yu, C.M.

1996-12-10

A microminiature gas chromatograph ({mu}GC) comprising a least one silicon wafer, a gas injector, a column, and a detector. The gas injector has a normally closed valve for introducing a mobile phase including a sample gas in a carrier gas. The valve is fully disposed in the silicon wafer(s). The column is a microcapillary in silicon crystal with a stationary phase and is mechanically connected to receive the mobile phase from the gas injector for the molecular separation of compounds in the sample gas. The detector is mechanically connected to the column for the analysis of the separated compounds of sample gas with electronic means, e.g., ion cell, field emitter and PIN diode. 7 figs.

Microminiature gas chromatograph

DOEpatents

Yu, Conrad M.

1996-01-01

A microminiature gas chromatograph (.mu.GC) comprising a least one silicon wafer, a gas injector, a column, and a detector. The gas injector has a normally closed valve for introducing a mobile phase including a sample gas in a carrier gas. The valve is fully disposed in the silicon wafer(s). The column is a microcapillary in silicon crystal with a stationary phase and is mechanically connected to receive the mobile phase from the gas injector for the molecular separation of compounds in the sample gas. The detector is mechanically connected to the column for the analysis of the separated compounds of sample gas with electronic means, e.g., ion cell, field emitter and PIN diode.

Field Testing of High Current Electrokinetic Nanoparticle Treatment for Corrosion Mitigation in Reinforced Concrete

NASA Technical Reports Server (NTRS)

Cardenas, Henry; Alexander, Joshua; Kupwade-Patil, Kunal; Calle, Luz marina

2010-01-01

Electrokinetic Nanoparticle (EN) treatment was used as a rapid repair measure to mitigate chloride induced corrosion of reinforced concrete in the field. EN treatment uses an electric field to transport positively charged nanoparticles to the reinforcement through the concrete capillary pores. Cylindrical reinforced concrete specimens were batched with 4.5 wt % salt content (based on cement mass). Three distinct electrokinetic treatments were conducted using high current density (up to 5 A/m2) to form a chloride penetration barrier that was established in 5 days, as opposed to the traditional 6-8 weeks, generally required for electrochemical chloride extraction (ECE). These treatments included basic EN treatment, EN with additional calcium treatment, and basic ECE treatment. Field exposures were conducted at the NASA Beachside Corrosion Test Site, Kennedy Space Center, Florida, USA. The specimens were subjected to sea water immersion at the test site as a posttreatment exposure. Following a 30-day post-treatment exposure period, the specimens were subjected to indirect tensile testing to evaluate treatment impact. The EN treated specimens exhibited 60% and 30% increases in tensile strength as compared to the untreated controls and ECE treated specimens respectively. The surfaces of the reinforcement bars of the control specimens were 67% covered by corrosion products. In contrast, the EN treated specimens exhibited corrosion coverage of only 4%. Scanning electron microscopy (SEM) revealed a dense concrete microstructure adjacent to the bars of the treated specimens as compared to the control and ECE specimens. Energy dispersive spectroscopic (EDS) analysis of the polished EN treated specimens showed a reduction in chloride content by a factor of 20 adjacent to the bars. This study demonstrated that EN treatment was successful in forming a chloride penetration barrier rapidly. This work also showed that the chloride barrier was effective when samples were exposed to

A Gas Chromatograph/Mass Spectrometer System for UltraLow-Emission Combustor Exhaust Studies

NASA Technical Reports Server (NTRS)

Brabbs, Theodore A.; Wey, Chowen Chou

1996-01-01

A gas chromatograph (GC)/mass spectrometer (MS) system that allows the speciation of unburnt hydrocarbons in the combustor exhaust has been developed at the NASA Lewis Research Center. Combustion gas samples are withdrawn through a water-cooled sampling probe which, when not in use, is protected from contamination by a high-pressure nitrogen purge. The sample line and its connecting lines, filters, and valves are all ultraclean and are heated to avoid condensation. The system has resolution to the parts-per-billion (ppb) level.

Separation of Protactinium Employing Sulfur-Based Extraction Chromatographic Resins

DOE PAGES

Mastren, Tara; Stein, Benjamin W.; Parker, T. Gannon; ...

2018-05-14

Protactinium-230 (t 1/2 = 17.4 d) is the parent isotope of 230U (t 1/2 = 20.8 d), a radionuclide of interest for targeted alpha therapy (TAT). Column chromatographic methods have been developed to separate no-carrier-added 230Pa from proton irradiated thorium targets and accompanying fission products. Results reported within this paper demonstrate the use of novel sulfur bearing chromatographic extraction resins for the selective separation of protactinium. The recovery yield of 230Pa was 93 ± 4% employing a R 3P=S type commercially available resin and 88 ± 4% employing a DGTA (diglycothioamide) containing custom synthesized extraction chromatographic resin. The radiochemical puritymore » of the recovered 230Pa was measured via high purity germanium γ-ray spectroscopy to be >99.5% with the remaining radioactive contaminant being 95Nb due to its similar chemistry to protactinium. Finally, measured equilibrium distribution coefficients for protactinium, thorium, uranium, niobium, radium, and actinium on both the R 3P=S type and the DGTA resin in hydrochloric acid media are reported, to the best of our knowledge, for the first time.« less

Separation of Protactinium Employing Sulfur-Based Extraction Chromatographic Resins

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

Mastren, Tara; Stein, Benjamin W.; Parker, T. Gannon

Protactinium-230 (t 1/2 = 17.4 d) is the parent isotope of 230U (t 1/2 = 20.8 d), a radionuclide of interest for targeted alpha therapy (TAT). Column chromatographic methods have been developed to separate no-carrier-added 230Pa from proton irradiated thorium targets and accompanying fission products. Results reported within this paper demonstrate the use of novel sulfur bearing chromatographic extraction resins for the selective separation of protactinium. The recovery yield of 230Pa was 93 ± 4% employing a R 3P=S type commercially available resin and 88 ± 4% employing a DGTA (diglycothioamide) containing custom synthesized extraction chromatographic resin. The radiochemical puritymore » of the recovered 230Pa was measured via high purity germanium γ-ray spectroscopy to be >99.5% with the remaining radioactive contaminant being 95Nb due to its similar chemistry to protactinium. Finally, measured equilibrium distribution coefficients for protactinium, thorium, uranium, niobium, radium, and actinium on both the R 3P=S type and the DGTA resin in hydrochloric acid media are reported, to the best of our knowledge, for the first time.« less

Chromatographic background drift correction coupled with parallel factor analysis to resolve coelution problems in three-dimensional chromatographic data: quantification of eleven antibiotics in tap water samples by high-performance liquid chromatography coupled with a diode array detector.

PubMed

Yu, Yong-Jie; Wu, Hai-Long; Fu, Hai-Yan; Zhao, Juan; Li, Yuan-Na; Li, Shu-Fang; Kang, Chao; Yu, Ru-Qin

2013-08-09

Chromatographic background drift correction has been an important field of research in chromatographic analysis. In the present work, orthogonal spectral space projection for background drift correction of three-dimensional chromatographic data was described in detail and combined with parallel factor analysis (PARAFAC) to resolve overlapped chromatographic peaks and obtain the second-order advantage. This strategy was verified by simulated chromatographic data and afforded significant improvement in quantitative results. Finally, this strategy was successfully utilized to quantify eleven antibiotics in tap water samples. Compared with the traditional methodology of introducing excessive factors for the PARAFAC model to eliminate the effect of background drift, clear improvement in the quantitative performance of PARAFAC was observed after background drift correction by orthogonal spectral space projection. Copyright © 2013 Elsevier B.V. All rights reserved.

Scale-up of the electrokinetic fence technology for the removal of pesticides. Part II: Does size matter for removal of herbicides?

PubMed

López-Vizcaíno, R; Risco, C; Isidro, J; Rodrigo, S; Saez, C; Cañizares, P; Navarro, V; Rodrigo, M A

2017-01-01

This work reports results of the application of electrokinetic fence technology in a 32 m 3 -prototype which contains soil polluted with 2,4-D and oxyfluorfen, focusing on the evaluation of the mechanisms that describe the removal of these two herbicides and comparing results to those obtained in smaller plants: a pilot-scale mockup (175 L) and a lab-scale soil column (1 L). Results show that electric heating of soil (coupled with the increase in the volatility) is the key to explain the removal of pollutants in the largest scale facility while electrokinetic transport processes are the primary mechanisms that explain the removal of herbicides in the lab-scale plant. 2-D and 3-D maps of the temperature and pollutant concentrations are used in the discussion of results trying to give light about the mechanisms and about how the size of the setup can lead to different conclusions, despite the same processes are occurring in the soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

[A peak recognition algorithm designed for chromatographic peaks of transformer oil].

PubMed

Ou, Linjun; Cao, Jian

2014-09-01

In the field of the chromatographic peak identification of the transformer oil, the traditional first-order derivative requires slope threshold to achieve peak identification. In terms of its shortcomings of low automation and easy distortion, the first-order derivative method was improved by applying the moving average iterative method and the normalized analysis techniques to identify the peaks. Accurate identification of the chromatographic peaks was realized through using multiple iterations of the moving average of signal curves and square wave curves to determine the optimal value of the normalized peak identification parameters, combined with the absolute peak retention times and peak window. The experimental results show that this algorithm can accurately identify the peaks and is not sensitive to the noise, the chromatographic peak width or the peak shape changes. It has strong adaptability to meet the on-site requirements of online monitoring devices of dissolved gases in transformer oil.

Nano-fabricated size exclusion chromatograph

NASA Technical Reports Server (NTRS)

Svehla, D.; Feldman, S.; Feldman, J.; Grunthaner, F.; Shakkottai, P.; Castillo, L. del; White, V.

2002-01-01

This paper describes the development of a nano-fabricated size exclusion chromatograph (nSEC) based on the principle that molecules traveling through amicrocolumn containing nano-fabricated features will have characteristic elution times that directly correlate to molecular weight. Compared to conventional size exclusion chromatography, the nSEC offers greater control over the size exclusion process; mass fabrication; integration of the separation column with associated valves, pumps, and detectors; and dramatic reductions in instrument mass and power requirements.

Electrokinetic supercharging with a system-induced terminator and an optimized capillary versus electrode configuration for parts-per-trillion detection of rare-earth elements in CZE.

PubMed

Xu, Zhongqi; Kawahito, Kouji; Ye, Xiaoxue; Timerbaev, Andrei R; Hirokawa, Takeshi

2011-05-01

A further improvement of electrokinetic supercharging (EKS) methodology has been proposed, with the objective to enhance the sensitivity of the conventional CZE-UV method down to a single-digit part per trillion (ppt) level. The advanced EKS procedure is based on a novel phenomenon displaying the formation of a zone with an increased concentration of the hydrogen ion, capable to perform the function of a terminator, behind the sample zone upon electrokinetic injection. In combination with a visualizing co-ion of BGE, protonated 4-methylbenzylamine, acting as the leading ion, such system-induced terminator a effected the transient ITP state to efficiently concentrate cationic analytes prior to CZE. Furthermore, to amass more analyte ions within the effective electric field at the injection stage, a standard sample vial was replaced with an elongated vial that allowed the sample volume to be increased from 500 to 900 μL. Alongside, this replacement made the upright distance between the electrode and the capillary tips prolonged to 40.0 mm to achieve high-efficiency electrokinetic injection. The computer simulation was used for profiling analyte concentration, pH, and field strength in order to delineate formation of the terminator during sample injection. The proposed preconcentration strategy afforded an enrichment factor of 80,000 and thereby the LODs of rare-earth metal ions at the ppt level, e.g. 0.04 nM (6.7 ng/L) for erbium(III). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enantiomeric separation of non-protein amino acids by electrokinetic chromatography.

PubMed

Pérez-Míguez, Raquel; Marina, María Luisa; Castro-Puyana, María

2016-10-07

New analytical methodologies enabling the enantiomeric separation of a group of non-protein amino acids of interest in the pharmaceutical and food analysis fields were developed in this work using Electrokinetic Chromatography. The use of FMOC as derivatization reagent and the subsequent separation using acidic conditions (formate buffer at pH 2.0) and anionic cyclodextrins as chiral selectors allowed the chiral separation of eight from the ten non-protein amino acids studied. Pyroglutamic acid, norvaline, norleucine, 3,4-dihydroxyphenilalanine, 2-aminoadipic acid, and selenomethionine were enantiomericaly separated using sulfated-α-CD while sulfated-γ-CD enabled the enantiomeric separation of norvaline, 3,4-dihydroxyphenilalanine, 2-aminoadipic acid, selenomethionie, citrulline, and pipecolic acid. Moreover, the potential of the developed methodologies was demonstrated in the analysis of citrulline and its enantiomeric impurity in food supplements. For that purpose, experimental and instrumental variables were optimized and the analytical characteristics of the proposed method were evaluated. LODs of 2.1×10 -7 and 1.8×10 -7 M for d- and l-citrulline, respectively, were obtained. d-Cit was not detectable in any of the six food supplement samples analyzed showing that the effect of storage time on the racemization of citrulline was negligible. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrokinetic-Fenton remediation of organochlorine pesticides from historically polluted soil.

PubMed

Ni, Maofei; Tian, Shulei; Huang, Qifei; Yang, Yanmei

2018-04-01

Soil contamination by persistent organic pollutants (POPs) poses a great threat to historically polluted soil worldwide. In this study, soils were characterized, and organochlorine pesticides contained in the soils were identified and quantified. Individual electrokinetic (IE), EK-Fenton-coupled technologies (EF), and enhanced EK-Fenton treatment (E-1, E-2, and E-3) were applied to remediate soils contaminated with hexachloro-cyclohexane soprocide (HCH) and dichloro-diphenyl-trichloroethane (DDT). Variation of pH, electrical conductivity, and electroosmotic flow was evaluated during the EK-Fenton process. The IE treatment showed low removal efficiency for HCHs (30.5%) and DDTs (25.9%). In the EF treatment, the highest removal level (60.9%) was obtained for α-HCH, whereas P,P-DDT was the lowest (40.0%). Low solubility of pollutants impeded the HCH and DDT removal. After enhanced EK-Fenton treatment, final removal of pollutants decreased as follows: β-HCH (82.6%) > γ-HCH (81.6%) > α-HCH (81.2%) > δ-HCH (80.0%) > P,P-DDD (73.8%) > P,P-DDE (73.1%) > P,P-DDT (72.6%) > O,P-DDT (71.5%). The results demonstrate that EK-Fenton is a promising technology for POP removal in historically polluted soil.

Multiple electrokinetic actuators for feedback control of colloidal crystal size.

PubMed

Juárez, Jaime J; Mathai, Pramod P; Liddle, J Alexander; Bevan, Michael A

2012-10-21

We report a feedback control method to precisely target the number of colloidal particles in quasi-2D ensembles and their subsequent assembly into crystals in a quadrupole electrode. Our approach relies on tracking the number of particles within a quadrupole electrode, which is used in a real-time feedback control algorithm to dynamically actuate competing electrokinetic transport mechanisms. Particles are removed from the quadrupole using DC-field mediated electrophoretic-electroosmotic transport, while high-frequency AC-field mediated dielectrophoretic transport is used to concentrate and assemble colloidal crystals. Our results show successful control of the size of crystals containing 20 to 250 colloidal particles with less than 10% error. Assembled crystals are characterized by their radius of gyration, crystallinity, and number of edge particles, and demonstrate the expected size-dependent properties. Our findings demonstrate successful ensemble feedback control of the assembly of different sized colloidal crystals using multiple actuators, which has broad implications for control over nano- and micro- scale assembly processes involving colloidal components.

The contribution of the hydrogen bond acidity on the lipophilicity of drugs estimated from chromatographic measurements.

PubMed

Pallicer, Juan M; Pascual, Rosalia; Port, Adriana; Rosés, Martí; Ràfols, Clara; Bosch, Elisabeth

2013-02-14

The influence of the hydrogen bond acidity when the 1-octanol/water partition coefficient (log P(o/w)) of drugs is determined from chromatographic measurements was studied in this work. This influence was firstly evaluated by means of the comparison between the Abraham solvation parameter model when it is applied to express the 1-octanol/water partitioning and the chromatographic retention, expressed as the solute polarity p. Then, several hydrogen bond acidity descriptors were compared in order to determine properly the log P(o/w) of drugs. These descriptors were obtained from different software and comprise two-dimensional parameters such as the calculated Abraham hydrogen bond acidity A and three-dimensional descriptors like HDCA-2 from CODESSA program or WO1 and DRDODO descriptors calculated from Volsurf+software. The additional HOMO-LUMO polarizability descriptor should be added when the three-dimensional descriptors are used to complement the chromatographic retention. The models generated using these descriptors were compared studying the correlations between the determined log P(o/w) values and the reference ones. The comparison showed that there was no significant difference between the tested models and any of them was able to determine the log P(o/w) of drugs from a single chromatographic measurement and the correspondent molecular descriptors terms. However, the model that involved the calculated A descriptor was simpler and it is thus recommended for practical uses. Copyright © 2012 Elsevier B.V. All rights reserved.

Electrokinetic-flow-induced viscous drag on a tethered DNA inside a nanopore.

PubMed

Ghosal, Sandip

2007-12-01

Recent work has shown that the resistive force arising from viscous effects within the pore region could explain observed translocation times in certain experiments involving voltage-driven translocations of DNA through nanopores [Ghosal, Phys. Rev. E 71, 051904 (2006); Phys. Rev. Lett. 98, 238104 (2007)]. The electrokinetic flow inside the pore and the accompanying viscous effects also play a crucial role in the interpretation of experiments where the DNA is immobilized inside a nanopore [Keyser, Nat. Phys. 2, 473 (2006)]. In this paper the viscous force is explicitly calculated for a nanopore of cylindrical geometry. It is found that the reductions of the tether force due to viscous drag and due to charge reduction by Manning condensation are of similar size. The result is of importance in the interpretation of experimental data on tethered DNA.

Electrokinetic decontamination of concrete. Final report, August 3, 1993--September 15, 1996

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

NONE

1998-12-31

The ELECTROSORB{reg_sign} {open_quotes}C{close_quotes} process is an electrokinetic process for decontaminating concrete. ELECTROSORB{reg_sign} {open_quotes}C{close_quotes} uses a carpet-like extraction pad which is placed on the contaminated concrete surface. An electrolyte solution is circulated from a supporting module. This module keeps the electrolyte solution clean. The work is advancing through the engineering development stage with steady progress toward a full scale demonstration unit which will be ready for incorporation in the DOE Large Scale Demonstration Program by Summer 1997. A demonstration was carried out at the Mound Facility in Miamisburg, Ohio, in June 1996. Third party verification by EG&G verified the effectiveness ofmore » the process. Results of this work and the development work that proceeded are described herein.« less

Comparison of core-shell and totally porous ultra high performance liquid chromatographic stationary phases based on their selectivity towards alfuzosin compounds.

PubMed

Szulfer, Jarosław; Plenis, Alina; Bączek, Tomasz

2014-06-13

This paper focuses on the application of a column classification system based on the Katholieke Universiteit Leuven for the characterization of physicochemical properties of core-shell and ultra-high performance liquid chromatographic stationary phases, followed by the verification of the reliability of the obtained column classification in pharmaceutical practice. In the study, 7 stationary phases produced in core-shell technology and 18 ultra-high performance liquid chromatographic columns were chromatographically tested, and ranking lists were built on the FKUL-values calculated against two selected reference columns. In the column performance test, an analysis of alfuzosin in the presence of related substances was carried out using the brands of the stationary phases with the highest ranking positions. Next, a system suitability test as described by the European Pharmacopoeia monograph was performed. Moreover, a study was also performed to achieve a purposeful shortening of the analysis time of the compounds of interest using the selected stationary phases. Finally, it was checked whether methods using core-shell and ultra-high performance liquid chromatographic columns can be an interesting alternative to the high-performance liquid chromatographic method for the analysis of alfuzosin in pharmaceutical practice. Copyright © 2014 Elsevier B.V. All rights reserved.

ChromAlign: A two-step algorithmic procedure for time alignment of three-dimensional LC-MS chromatographic surfaces.

PubMed

Sadygov, Rovshan G; Maroto, Fernando Martin; Hühmer, Andreas F R

2006-12-15

We present an algorithmic approach to align three-dimensional chromatographic surfaces of LC-MS data of complex mixture samples. The approach consists of two steps. In the first step, we prealign chromatographic profiles: two-dimensional projections of chromatographic surfaces. This is accomplished by correlation analysis using fast Fourier transforms. In this step, a temporal offset that maximizes the overlap and dot product between two chromatographic profiles is determined. In the second step, the algorithm generates correlation matrix elements between full mass scans of the reference and sample chromatographic surfaces. The temporal offset from the first step indicates a range of the mass scans that are possibly correlated, then the correlation matrix is calculated only for these mass scans. The correlation matrix carries information on highly correlated scans, but it does not itself determine the scan or time alignment. Alignment is determined as a path in the correlation matrix that maximizes the sum of the correlation matrix elements. The computational complexity of the optimal path generation problem is reduced by the use of dynamic programming. The program produces time-aligned surfaces. The use of the temporal offset from the first step in the second step reduces the computation time for generating the correlation matrix and speeds up the process. The algorithm has been implemented in a program, ChromAlign, developed in C++ language for the .NET2 environment in WINDOWS XP. In this work, we demonstrate the applications of ChromAlign to alignment of LC-MS surfaces of several datasets: a mixture of known proteins, samples from digests of surface proteins of T-cells, and samples prepared from digests of cerebrospinal fluid. ChromAlign accurately aligns the LC-MS surfaces we studied. In these examples, we discuss various aspects of the alignment by ChromAlign, such as constant time axis shifts and warping of chromatographic surfaces.

Determination of pore size distributions of porous chromatographic adsorbents by inverse size-exclusion chromatography.

PubMed

Yao, Yan; Lenhoff, Abraham M

2004-05-28

The macroscopic properties of porous chromatographic adsorbents are directly influenced by the pore structure, with the pore size distribution (PSD) playing a major role beyond simply the mean pore size. Inverse size-exclusion chromatography (ISEC), a widely used chromatographic method for determining the PSD of porous media, provides more relevant information on liquid chromatographic materials in situ than traditional methods, such as gas sorption and mercury intrusion. The fundamentals and applications of ISEC in the characterization of the pore structure are reviewed. The description of the probe solutes and the pore space, as well as theoretical models for deriving the PSD from solute partitioning behavior, are discussed. Precautions to ensure integrity of the experiments are also outlined, including accounting for probe polydispersity and minimization of solute-adsorbent interactions. The results that emerge are necessarily model-dependent, but ISEC nonetheless represents a powerful and non-destructive source of quantitative pore structure information that can help to elucidate chromatographic performance observations covering both retention and rate aspects.

Determination of catechins in matcha green tea by micellar electrokinetic chromatography.

PubMed

Weiss, David J; Anderton, Christopher R

2003-09-05

Catechins in green tea are known to have many beneficial health properties. Recently, it has been suggested that matcha has greater potential health benefits than other green teas. Matcha is a special powdered green tea used in the Japanese tea ceremony. However, there has been no investigation to quantitate the catechin intake from matcha compared to common green teas. We have developed a rapid method of analysis of five catechins and caffeine in matcha using micellar electrokinetic chromatography. Results are presented for water and methanol extractions of matcha compared with water extraction of a popular green tea. Using a mg catechin/g of dry leaf comparison, results indicate that the concentration of epigallocatechin gallate (EGCG) available from drinking matcha is 137 times greater than the amount of EGCG available from China Green Tips green tea, and at least three times higher than the largest literature value for other green teas.

Chiral ionic liquids in chromatographic and electrophoretic separations.

PubMed

Kapnissi-Christodoulou, Constantina P; Stavrou, Ioannis J; Mavroudi, Maria C

2014-10-10

This report provides an overview of the application of chiral ionic liquids (CILs) in separation technology, and particularly in capillary electrophoresis and both gas and liquid chromatography. There is a large number of CILs that have been synthesized and designed as chiral agents. However, only a few have successfully been applied in separation technology. Even though this application of CILs is still in its early stages, the scientific interest is increasing dramatically. This article is focused on the use of CILs as chiral selectors, background electrolyte additives, chiral ligands and chiral stationary phases in electrophoretic and chromatographic techniques. Different examples of CILs, which contain either a chiral cation, a chiral anion or both, are presented in this review article, and their major advantages along with their potential applications in chiral electrophoretic and chromatographic recognition are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Micro-column plasma emission liquid chromatograph. [Patent application

DOEpatents

Gay, D.D.

1982-08-12

In a direct current plasma emission spectrometer for use in combination with a microcolumn liquid chromatograph, an improved plasma source unit is claimed. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

Multi-objective optimization of chromatographic rare earth element separation.

PubMed

Knutson, Hans-Kristian; Holmqvist, Anders; Nilsson, Bernt

2015-10-16

The importance of rare earth elements in modern technological industry grows, and as a result the interest for developing separation processes increases. This work is a part of developing chromatography as a rare earth element processing method. Process optimization is an important step in process development, and there are several competing objectives that need to be considered in a chromatographic separation process. Most studies are limited to evaluating the two competing objectives productivity and yield, and studies of scenarios with tri-objective optimizations are scarce. Tri-objective optimizations are much needed when evaluating the chromatographic separation of rare earth elements due to the importance of product pool concentration along with productivity and yield as process objectives. In this work, a multi-objective optimization strategy considering productivity, yield and pool concentration is proposed. This was carried out in the frame of a model based optimization study on a batch chromatography separation of the rare earth elements samarium, europium and gadolinium. The findings from the multi-objective optimization were used to provide with a general strategy for achieving desirable operation points, resulting in a productivity ranging between 0.61 and 0.75 kgEu/mcolumn(3), h(-1) and a pool concentration between 0.52 and 0.79 kgEu/m(3), while maintaining a purity above 99% and never falling below an 80% yield for the main target component europium. Copyright © 2015 Elsevier B.V. All rights reserved.

Correlation of the Capacity Factor in Vesicular Electrokinetic Chromatography with the Octanol:Water Partition Coefficient for Charged and Neutral Analytes

PubMed Central

Razak, J. L.; Cutak, B. J.; Larive, C. K.; Lunte, C. E.

2008-01-01

Purpose The aim of this study was to develop a method based upon electrokinetic chromatography (EKC) using oppositely charged surfactant vesicles as a buffer modifier to estimate hydrophobicity (log P) for a range of neutral and charged compounds. Methods Vesicles were formed from cetyltrimethylammonium bromide (CTAB) and sodium n-octyl sulfate (SOS). The size and polydispersity of the vesicles were characterized by electron microscopy, dynamic light scattering, and pulsed-field gradient NMR (PFG-NMR). PFG-NMR was also used to determine if ion-pairing between cationic analytes and free SOS monomer occurred. The CTAB/SOS vesicles were used as a buffer modifier in capillary electrophoresis (CE). The capacity factor (log k′) was calculated by determining the mobility of the analytes both in the presence and absence of vesicles. Log k′ was determined for 29 neutral and charged analytes. Results There was a linear relationship between the log of capacity factor (log k′) and octanol/water partition coefficient (log P) for both neutral and basic species at pH 6.0, 7.3, and 10.2. This indicated that interaction between the cation and vesicle was dominated by hydrophobic forces. At pH 4.3, the log k′ values for the least hydrophobic basic analytes were higher than expected, indicating that electrostatic attraction as well as hydrophobic forces contributed to the overall interaction between the cation and vesicle. Anionic compounds could not be evaluated using this system. Conclusion Vesicular electrokinetic chromatography (VEKC) using surfactant vesicles as buffer modifiers is a promising method for the estimation of hydrophobicity. PMID:11336344

Recovery of Drug Delivery Nanoparticles from Human Plasma using an Electrokinetic Platform Technology

PubMed Central

Ibsen, Stuart; Sonnenberg, Avery; Schutt, Carolyn; Mukthavaram, Rajesh; Yeh, Yasan; Ortac, Inanc; Manouchehri, Sareh; Kesari, Santosh; Esener, Sadik

2015-01-01

The effect of complex biological fluids on the surface and structure of nanoparticles is a rapidly expanding field of study. One of the challenges holding back this research is the difficulty of recovering therapeutic nanoparticles from biological samples due to their small size, low density, and stealth surface coatings. Here we present the first demonstration of the recovery and analysis of drug delivery nanoparticles from undiluted human plasma samples through the use of a new electrokinetic platform technology. The particles are recovered from plasma through a dielectrophoresis separation force that is created by innate differences in the dielectric properties between the unaltered nanoparticles and the surrounding plasma. We show this can be applied to a wide range of drug delivery nanoparticles of different morphologies and materials, including low density nano-liposomes. These recovered particles can then be analyzed using different methods including scanning electron microscopy to monitor surface and structural changes that result from plasma exposure. We believe that this new recovery technique is broadly applicable to the recovery of nanoparticles from high conductance fluids in a wide range of applications. PMID:26274918

Determination of lipid bilayer affinities and solvation characteristics by electrokinetic chromatography using polymer-bound lipid bilayer nanodiscs.

PubMed

Penny, William M; Palmer, Christopher P

2018-03-01

Styrene-maleic acid polymer-bound lipid bilayer nanodiscs have been investigated and characterized by electrokinetic chromatography. Linear solvation energy relationship analysis was employed to characterize the changes in solvation environment of nanodiscs of varied belt to lipid ratio, belt polymer chemistry and molecular weight, and lipid composition. Increases in the lipid to belt polymer ratio resulted in smaller, more cohesive nanodiscs with greater electrophoretic mobility. Nanodisc structures with belt polymers of different chemistry and molecular weight were compared and showed only minor changes in solvent characteristics and selectivity consistent with changes in structure of the lipid bilayer. Seven phospholipid and sphingomyelin nanodiscs of different lipid composition were characterized. Changes in lipid head group structure had a significant effect on bilayer-solute interactions. In most cases, changes in alkyl tail structure had no discernible effect on solvation environment aside from those explained by changes in the gel-liquid transition temperature. Comparison to vesicles of similar lipid composition show only minor differences in solvation environment, likely due to differences in lipid composition and bilayer curvature. Together these results provide evidence that the dominant solute-nanodisc interactions are with the lipid bilayer and that head group chemistry has a greater impact on bilayer-solute interactions than alkyl tail or belt polymer structure. Nanodisc electrokinetic chromatography is demonstrated to allow characterization of solute interactions with lipid bilayers of varied composition. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial distribution of mechanical forces and ionic flux in electro-kinetic instability near a permselective membrane

NASA Astrophysics Data System (ADS)

Magnico, Pierre

2018-01-01

This paper is devoted to the numerical investigation of electro-kinetic instability in a polarization layer next to a cation-exchange membrane. An analysis of some properties of the electro-kinetic instability is followed by a detailed description of the fluid flow structure and of the spatial distribution of the ionic flux. In this aim, the Stokes-Poisson-Nernst-Planck equation set is solved until the Debye length scale. The results show that the potential threshold of the marginal instability and the current density depend on the logarithm of the concentration at the membrane surface. The size of the stable vortices seems to be an increasing function of the potential drop. The fluid motion is induced by the electric force along the maximum concentration in the extended space charge (ESC) region and by the pressure force in the region around the inner edge of the ESC layer. Two spots of kinetic energy are located in the ESC region and between the vortices. The cationic motion, controlled by the electric field and the convection, presents counter-rotating vortices in the stagnation zone located in the fluid ejection region. The anion transport is also characterized by two independent layers which contain counter-rotating vortices. The first one is in contact with the stationary reservoir. In the second layer against the membrane, the convection, and the electric field control, the transversal motion, the Fickian diffusion, and the convection are dominant in the longitudinal direction. Finally, the longitudinal disequilibrium of potential and pressure along the membrane is analyzed.

Removal of aluminum from drinking water treatment sludge using vacuum electrokinetic technology.

PubMed

Xu, Hang; Ding, Mingmei; Shen, Kunlun; Cui, Jianfeng; Chen, Wei

2017-04-01

A vacuum electrokinetic apparatus was operated at a municipal water supply plant in Wuxi, China to study the removal of aluminum from the plant's drinking water treatment sludge, high in trivalent aluminum content. The effect of several experimental variables (initial pH, potential gradient, and zone in the sludge tank) and the trivalent aluminum removal mechanism were analyzed. The speciation of trivalent aluminum mainly depends on the initial pH of drinking water treatment sludge, and more fractions of trivalent aluminum were migrated at pH 4 than at higher or lower pH. The application of high voltage can enhance the removal efficiency of aluminum. A three-dimensional electric field analysis explained the difference in the removal efficiency at different zones in the sludge tank. In view of energy consumption, when the initial pH was 4 and a potential gradient of 2 V cm -1 was applied, achieving a final aluminum concentration of 30 g kg -1 after 120 h. The specific energy consumption was 11.7 kWh kg -1 of Al removed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Computational analysis of electrokinetically driven flow mixing in microchannels with patterned blocks

NASA Astrophysics Data System (ADS)

Chang, C.-C.; Yang, R.-J.

2004-04-01

Electroosmotic flow in microchannels is restricted to low Reynolds number regimes characterized by extremely weak inertia forces and laminar flow. Consequently, the mixing of different species occurs primarily through diffusion, and hence cannot readily be achieved within a short mixing channel. The current study presents a numerical investigation of electrokinetically driven flow mixing in microchannels with various numbers of incorporated patterned rectangular blocks. Furthermore, a novel approach is introduced which patterns heterogeneous surfaces on the upper faces of these rectangular blocks in order to enhance species mixing. The simulation results confirm that the introduction of rectangular blocks within the mixing channel slightly enhances species mixing by constricting the bulk flow, hence creating a stronger diffusion effect. However, it is noted that a large number of blocks and hence a long mixing channel are required if a complete mixing of the species is to be obtained. The results also indicate that patterning heterogeneous upper surfaces on the rectangular blocks is an effective means of enhancing the species mixing. It is shown that increasing the magnitude of the heterogeneous surface zeta potential enables a reduction in the mixing channel length and an improved degree of mixing efficiency.

Simultaneous determination of eleven preservatives in cosmetics by micellar electrokinetic chromatography.

PubMed

Wang, Ping; Ding, Xiaojing; Li, Yun; Yang, Yuanyuan

2012-01-01

A new method for the simultaneous quantitation of 11 preservatives-imidazolidinyl urea, benzyl alcohol, dehydroacetic acid, sorbic acid, phenoxyethanol, benzoic acid, salicylic acid, and four parabens (methyl, ethyl, propyl, and butyl)-in cosmetics by micellar electrokinetic capillary chromatography was established and validated. The separation was performed using an uncoated fused-silica capillary (50 pm id x 60.2 cm, effective length 50 cm) with a running buffer consisting of 15 mmol/L sodium tetraborate, 60 mmol/L boric acid, and 100 mmol/L sodium dodecyl sulfate. A 1:10 dilution of the running buffer was used as the sample buffer to extract the cosmetic samples. The key factors, such as the concentration and pH of the running and sample buffers, which influence quantitative analysis of the above 11 preservatives in cosmetic samples, were investigated in detail. The linear ranges of the calibration curves for imidazolidinyl urea and the other 10 preservatives were 50-1000 and 10-200 mg/L, respectively. The correlation coefficients of the standard curves were all higher than 0.999. The recoveries at the concentrations studied ranged from 93.0 to 102.7%. RSDs were all less than 5%. The new method with simple sample pretreatment met the needs for routine analysis of the 11 preservatives in cosmetics.

Gas chromatograph-mass spectrometer (GC/MS) system for quantitative analysis of reactive chemical compounds

DOEpatents

Grindstaff, Quirinus G.

1992-01-01

Described is a new gas chromatograph-mass spectrometer (GC/MS) system and method for quantitative analysis of reactive chemical compounds. All components of such a GC/MS system external to the oven of the gas chromatograph are programmably temperature controlled to operate at a volatilization temperature specific to the compound(s) sought to be separated and measured.

FTIR gas chromatographic analysis of perfumes

NASA Astrophysics Data System (ADS)

Diederich, H.; Stout, Phillip J.; Hill, Stephen L.; Krishnan, K.

1992-03-01

Perfumes, natural or synthetic, are complex mixtures consisting of numerous components. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques have been extensively utilized for the analysis of perfumes and essential oils. A limited number of perfume samples have also been analyzed by FT-IR gas chromatographic (GC-FTIR) techniques. Most of the latter studies have been performed using the conventional light pipe (LP) based GC-FTIR systems. In recent years, cold-trapping (in a matrix or neat) GC-FTIR systems have become available. The cold-trapping systems are capable of sub-nanogram sensitivities. In this paper, comparison data between the LP and the neat cold-trapping GC- FTIR systems is presented. The neat cold-trapping interface is known as Tracer. The results of GC-FTIR analysis of some commercial perfumes is also presented. For comparison of LP and Tracer GC-FTIR systems, a reference (synthetic) mixture containing 16 major and numerous minor constituents was used. The components of the mixture are the compounds commonly encountered in commercial perfumes. The GC-FTIR spectra of the reference mixture was obtained under identical chromatographic conditions from an LP and a Tracer system. A comparison of the two sets of data thus generated do indeed show the enhanced sensitivity level of the Tracer system. The comparison also shows that some of the major components detected by the Tracer system were absent from the LP data. Closer examination reveals that these compounds undergo thermal decomposition on contact with the hot gold surface that is part of the LP system. GC-FTIR data were obtained for three commercial perfume samples. The major components of these samples could easily be identified by spectra search against a digitized spectral library created using the Tracer data from the reference mixture.

Chromatographic multivariate quality control of pharmaceuticals giving strongly overlapped peaks based on the chromatogram profile.

PubMed

Escuder-Gilabert, L; Ruiz-Roch, D; Villanueva-Camañas, R M; Medina-Hernández, M J; Sagrado, S

2004-03-12

In the present paper, the simultaneous quantification of two analytes showing strongly overlapped chromatographic peaks (alpha = 1.02), under the assumption that both available equipment and training of the laboratory staff are basic, is studied. A pharmaceutical preparation (Mutabase) containing two drugs of similar physicochemical properties (amitriptyline and perphenazine) is selected as case of study. The assays are carried out under realistic working conditions (i.e. routine testing laboratories). Uncertainty considerations are introduced in the study. A partial least squares model is directly applied to the chromatographic data (with no previous signal transformation) to perform quality control of the pharmaceutical formulation. Under the adequate protocol, the relative error in prediction of analytes is within the tolerances found in the pharmacopeia (10%). For spiked samples simulating formulation mistakes, the errors found have the same magnitude and sign to those provoked.

Chromatographic determination of the diffusion coefficients of light hydrocarbons in polymers

NASA Astrophysics Data System (ADS)

Yakubenko, E. E.; Korolev, A. A.; Chapala, P. P.; Bermeshev, M. V.; Kanat'eva, A. Yu.; Kurganov, A. A.

2017-01-01

Gas-chromatographic determination of the diffusion coefficients that allows for the compressibility of the mobile phase has been suggested. The diffusion coefficients were determined for light hydrocarbons C1-C4 in four polymers with a high free volume, which are candidates for use as gas-separating membranes. The diffusion coefficients calculated from chromatographic data were shown to be one or two orders of magnitude smaller than the values obtained by the membrane method. This may be due to the presence of an additional flow through the membrane caused by the pressure gradient across the membrane in membrane methods.

Electrokinetic electrode system for extraction of soil contaminants from unsaturated soils

DOEpatents

Lindgren, Eric R.; Mattson, Earl D.

1995-01-01

There is presented an electrokinetic electrode assembly for use in extraction of soil contaminants from unsaturated soil in situ. The assembly includes a housing for retaining a liquid comprising an electrolyte solution, pure water, and soil water, the housing being in part of porous material capable of holding a vacuum. An electrode is mounted in the housing. The housing is provided with a vacuum orifice for effecting a vacuum within the housing selectively to control flow of soil water through the housing into the chamber and to control outflow of the liquid from the chamber. The assembly further includes conduit means for removing the liquid from the housing and returning the electrolyte solution to the housing, and a conduit for admitting pure water to the housing. There is further presented an electrode system and method for extraction of soil contaminants, the system and method utilizing at least two electrode assemblies as described above.

Electrokinetic electrode system for extraction of soil contaminants from unsaturated soils

DOEpatents

Lindgren, E.R.; Mattson, E.D.

1995-07-25

An electrokinetic electrode assembly is described for use in extraction of soil contaminants from unsaturated soil in situ. The assembly includes a housing for retaining a liquid comprising an electrolyte solution, pure water, and soil water, the housing being in part of porous material capable of holding a vacuum. An electrode is mounted in the housing. The housing is provided with a vacuum orifice for effecting a vacuum within the housing selectively to control flow of soil water through the housing into the chamber and to control outflow of the liquid from the chamber. The assembly further includes conduit means for removing the liquid from the housing and returning the electrolyte solution to the housing, and a conduit for admitting pure water to the housing. An electrode system and method are also revealed for extraction of soil contaminants. The system and method utilize at least two electrode assemblies as described above. 5 figs.

Creating Sub-50 nm Nanofluidic Junctions in PDMS Microchip via Self-Assembly Process of Colloidal Silica Beads for Electrokinetic Concentration of Biomolecules

PubMed Central

Syed, A.; Mangano, L.; Mao, P.; Han, J.

2014-01-01

In this work we describe a novel and simple self-assembly of colloidal silica beads to create nanofluidic junction between two microchannels. The nanoporous membrane was used to induce ion concentration polarization inside the microchannel and this electrokinetic preconcentration system allowed rapid concentration of DNA samples by ∼1700 times and protein samples by ∼100 times within 5 minutes. PMID:25254651

Reduction of heavy metal from soil in Bakri Landfill, Muar, Johor by using Electrokinetic method

NASA Astrophysics Data System (ADS)

Azhar, ATS; Muhammad, E.; Zaidi, E.; Ezree, AM; Aziman, M.; Hazreek, ZAM; Nizam, ZM; Norshuhaila, MS

2017-08-01

The present study focuses on the contamination levels and distribution of heavy metals in soil samples located at Bakri Landfill area, Muar, Johor, Malaysia. The aim of this study is to determine the type of heavy metal elements that contribute towards soil contamination and to reduce them based on the comparison of elemental analysis between pre and post Electrokinetic (EK) processes. The ppm level concentration of elements in this landfill soil is measured by using X-ray Fluorescence analysis. ICP-MS testing was carried out for liquid samples analysis. There were two set of EK experiments conducted. In first phase, voltage was maintained at 3 Vcm-1 and prolonged for 3 hours, while second phase was operated at 1 Vcm-1 for 48 hours. In this work, distilled water was used as an electrolyte for the process and two identical copper foil were used as electrodes due to high electrical conductivity. The application of EK remediation revealed that successful removal of Rb and Ba elements in the soil were observed by 2-3%, however other heavy metals have not changed.

Gas chromatographic concepts for the analysis of planetary atmospheres

NASA Technical Reports Server (NTRS)

Valentin, J. R.; Cullers, D. K.; Hall, K. W.; Krekorian, R. L.; Phillips, J. B.

1991-01-01

Over the last few years, new gas chromatographic (GC) concepts were developed for use on board spacecraft or any other restricted environments for determining the chemical composition of the atmosphere and surface material of various planetary bodies. Future NASA Missions include an entry probe that will be sent to Titan and various spacecraft that will land on Mars. In order to be able to properly respond to the mission science requirements and physical restrictions imposed on the instruments by these missions, GC analytical techniques are being developed. Some of these techniques include hardware and mathematical techniques that will improve GC sensitivity and increase the sampling rate of a GC descending through a planetary atmosphere. The technique of Multiplex Gas Chromatography (MGC) is an example of a technique that was studied in a simulated Titan atmosphere. In such an environment, the atmospheric pressure at instrument deployment is estimated to be a few torr. Thus, at such pressures, the small amount of sample that is acquired might not be enough to satisfy the detection requirements of the gas chromatograph. In MGC, many samples are pseudo-randomly introduced to the chromatograph without regard to elution of preceding components. The resulting data is then reduced using mathematical techniques such as cross-correlation of Fourier Transforms. Advantages realized from this technique include: improvement in detection limits of several orders of magnitude and increase in the number of analyses that can be conducted in a given period of time. Results proving the application of MGC at very low pressures emulating the same atmospheric pressures that a Titan Probe will encounter when the instruments are deployed are presented. The sample used contained hydrocarbons that are expected to be found in Titan's atmosphere. In addition, a new selective modulator was developed to monitor water under Martian atmospheric conditions. Since this modulator is selective only

Chromatographic immunoassays: strategies and recent developments in the analysis of drugs and biological agents

PubMed Central

Matsuda, Ryan; Rodriguez, Elliott; Suresh, Doddavenkatanna; Hage, David S

2015-01-01

A chromatographic immunoassay is a technique in which an antibody or antibody-related agent is used as part of a chromatographic system for the isolation or measurement of a specific target. Various binding agents, detection methods, supports and assay formats have been developed for this group of methods, and applications have been reported that range from drugs, hormones and herbicides to peptides, proteins and bacteria. This review discusses the general principles and applications of chromatographic immunoassays, with an emphasis being given to methods and formats that have been developed for the analysis of drugs and biological agents. The relative advantages or limitations of each format are discussed. Recent developments and research in this field, as well as possible future directions, are also considered. PMID:26571109

Liquid chromatographic determination of minocycline in brain-to-plasma distribution studies in the rat.

PubMed

Colovic, Milena; Caccia, Silvio

2003-07-05

An isocratic reversed-phase high-performance liquid chromatographic procedure was developed for the determination of minocycline in rat plasma and brain and applied to brain-to-blood (plasma) distribution studies. The procedure is based on isolation of the compound and the internal standard (either demeclocycline or tetracycline may be used) from plasma and brain constituents using the Oasis HLB cartridge, with satisfactory recovery and specificity, and separation on a Symmetry Shield RP8 (15 cm x 4.6 mm, 3.5 microm) column coupled with a UV detector set at 350 nm. The assay was linear over a wide range, with a lower limit of quantification of 50 ng ml(-1) or g(-1), using 0.2 ml of plasma and about 200 mg of brain tissue. Precision and accuracy were acceptable. In the rat minocycline crossed the blood-brain barrier slowly, achieving mean brain concentrations between 30 and 40% of the equivalent systemic exposure, regardless of the dose and route of administration.

Electroviscous effect and electrokinetic energy conversion in time periodic pressure-driven flow through a parallel-plate nanochannel with surface charge-dependent slip

NASA Astrophysics Data System (ADS)

Buren, Mandula; Jian, Yongjun; Zhao, Yingchun; Chang, Long

2018-05-01

In this paper we analytically investigate the electroviscous effect and electrokinetic energy conversion in the time periodic pressure-driven flow of an incompressible viscous Newtonian liquid through a parallel-plate nanochannel with surface charge-dependent slip. Analytical and semi-analytical solutions for electric potential, velocity and streaming electric field are obtained and are utilized to compute electrokinetic energy conversion efficiency. The results show that velocity amplitude and energy conversion efficiency are reduced when the effect of surface charge on slip length is considered. The surface charge effect increases with zeta potential and ionic concentration. In addition, the energy conversion efficiency is large when the ratio of channel half-height to the electric double layer thickness is small. The boundary slip results in a large increase in energy conversion. Higher values of the frequency of pressure pulsation lead to higher values of the energy conversion efficiency. We also obtain the energy conversion efficiency in constant pressure-driven flow and find that the energy conversion efficiency in periodical pressure-driven flow becomes larger than that in constant pressure-driven flow when the frequency is large enough.

Simultaneous determination of gaseous and particulate carbonyls in air by coupling micellar electrokinetic capillary chromatography with molecular imprinting solid-phase extraction.

PubMed

Sun, Hui; Lai, Jia-Ping; Fung, Ying Sing

2014-09-05

A novel method coupling molecular imprinting solid-phase extraction (MISPE) and micellar electrokinetic capillary chromatography (MEKC) was developed to enable the hourly determination of low level of ambient carbonyls, and study their partition between gaseous phase and particulate phase. With 2,4-dinitroaniline (DNAN) as dummy imprinting template, the unreacted 2,4-Dinitrophenylhydrazine (DNPH) in sampling solution could be removed effectively using MISPE, and an average recovery of 97±5.3% (n=5) for the carbonyl-DNPH derivatives was achieved. Owing to the high enrichment due to sample clean-up, and the improvement of MEKC separation efficiency, many low abundant carbonyls could be detected by hourly in the field study. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of Janus Particles and Alternating Current Electrokinetic Measurements with a Rapidly Fabricated Indium Tin Oxide Electrode Array.

PubMed

Chen, Yu-Liang; Jiang, Hong-Ren

2017-06-23

This article provides a simple method to prepare partially or fully coated metallic particles and to perform the rapid fabrication of electrode arrays, which can facilitate electrical experiments in microfluidic devices. Janus particles are asymmetric particles that contain two different surface properties on their two sides. To prepare Janus particles, a monolayer of silica particles is prepared by a drying process. Gold (Au) is deposited on one side of each particle using a sputtering device. The fully coated metallic particles are completed after the second coating process. To analyze the electrical surface properties of Janus particles, alternating current (AC) electrokinetic measurements, such as dielectrophoresis (DEP) and electrorotation (EROT)- which require specifically designed electrode arrays in the experimental device- are performed. However, traditional methods to fabricate electrode arrays, such as the photolithographic technique, require a series of complicated procedures. Here, we introduce a flexible method to fabricate a designed electrode array. An indium tin oxide (ITO) glass is patterned by a fiber laser marking machine (1,064 nm, 20 W, 90 to 120 ns pulse-width, and 20 to 80 kHz pulse repetition frequency) to create a four-phase electrode array. To generate the four-phase electric field, the electrodes are connected to a 2-channel function generator and to two invertors. The phase shift between the adjacent electrodes is set at either 90° (for EROT) or 180° (for DEP). Representative results of AC electrokinetic measurements with a four-phase ITO electrode array are presented.

Principal coordinate analysis assisted chromatographic analysis of bacterial cell wall collection: A robust classification approach.

PubMed

Kumar, Keshav; Cava, Felipe

2018-04-10

In the present work, Principal coordinate analysis (PCoA) is introduced to develop a robust model to classify the chromatographic data sets of peptidoglycan sample. PcoA captures the heterogeneity present in the data sets by using the dissimilarity matrix as input. Thus, in principle, it can even capture the subtle differences in the bacterial peptidoglycan composition and can provide a more robust and fast approach for classifying the bacterial collection and identifying the novel cell wall targets for further biological and clinical studies. The utility of the proposed approach is successfully demonstrated by analysing the two different kind of bacterial collections. The first set comprised of peptidoglycan sample belonging to different subclasses of Alphaproteobacteria. Whereas, the second set that is relatively more intricate for the chemometric analysis consist of different wild type Vibrio Cholerae and its mutants having subtle differences in their peptidoglycan composition. The present work clearly proposes a useful approach that can classify the chromatographic data sets of chromatographic peptidoglycan samples having subtle differences. Furthermore, present work clearly suggest that PCoA can be a method of choice in any data analysis workflow. Copyright © 2018 Elsevier Inc. All rights reserved.

Ion size effects on the electrokinetics of spherical particles in salt-free concentrated suspensions

NASA Astrophysics Data System (ADS)

Roa, Rafael; Carrique, Felix; Ruiz-Reina, Emilio

2012-02-01

In this work we study the influence of the counterion size on the electrophoretic mobility and on the dynamic mobility of a suspended spherical particle in a salt-free concentrated colloidal suspension. Salt-free suspensions contain charged particles and the added counterions that counterbalance their surface charge. A spherical cell model approach is used to take into account particle-particle electro-hydrodynamic interactions in concentrated suspensions. The finite size of the counterions is considered including an entropic contribution, related with the excluded volume of the ions, in the free energy of the suspension, giving rise to a modified counterion concentration profile. We are interested in studying the linear response of the system to an electric field, thus we solve the different electrokinetic equations by using a linear perturbation scheme. We find that the ionic size effect is quite important for moderate to high particles charges at a given particle volume fraction. In addition for such particle surface charges, both the electrophoretic mobility and the dynamic mobility suffer more important changes the larger the particle volume fraction for each ion size. The latter effects are more relevant the larger the ionic size.

Quality evaluation of extracted ion chromatograms and chromatographic peaks in liquid chromatography/mass spectrometry-based metabolomics data.

PubMed

Zhang, Wenchao; Zhao, Patrick X

2014-01-01

Extracted ion chromatogram (EIC) extraction and chromatographic peak detection are two important processing procedures in liquid chromatography/mass spectrometry (LC/MS)-based metabolomics data analysis. Most commonly, the LC/MS technique employs electrospray ionization as the ionization method. The EICs from LC/MS data are often noisy and contain high background signals. Furthermore, the chromatographic peak quality varies with respect to its location in the chromatogram and most peaks have zigzag shapes. Therefore, there is a critical need to develop effective metrics for quality evaluation of EICs and chromatographic peaks in LC/MS based metabolomics data analysis. We investigated a comprehensive set of potential quality evaluation metrics for extracted EICs and detected chromatographic peaks. Specifically, for EIC quality evaluation, we analyzed the mass chromatographic quality index (MCQ index) and propose a novel quality evaluation metric, the EIC-related global zigzag index, which is based on an EIC's first order derivatives. For chromatographic peak quality evaluation, we analyzed and compared six metrics: sharpness, Gaussian similarity, signal-to-noise ratio, peak significance level, triangle peak area similarity ratio and the local peak-related local zigzag index. Although the MCQ index is suited for selecting and aligning analyte components, it cannot fairly evaluate EICs with high background signals or those containing only a single peak. Our proposed EIC related global zigzag index is robust enough to evaluate EIC qualities in both scenarios. Of the six peak quality evaluation metrics, the sharpness, peak significance level, and zigzag index outperform the others due to the zigzag nature of LC/MS chromatographic peaks. Furthermore, using several peak quality metrics in combination is more efficient than individual metrics in peak quality evaluation.

Gas-liquid chromatographic method for determining ethylenethiourea in potatoes, spinach, applesauce, and milk: collaborative study.

PubMed

Onley, H H

1977-09-01

Eight laboratories collaboratively tested a gas-liquid chromatographic method for determining ethylenetiourea (ETU) in potatoes, spinach, applesauce, and milk. In the determinative step, ETU is converted to the S-butyl derivative (2-n-butylmercapto-2-imidazoline) which is detected by a flame photometric detector, sulfur mode. For unknown fortification levels of 0.06, 0.12, and 0.30 ppm, the collaborators reported an overall average recovery range of 85-97% in the various commodities. The method has been adopted as interim official first action.

Electro-kinetically driven peristaltic transport of viscoelastic physiological fluids through a finite length capillary: Mathematical modeling.

PubMed

Tripathi, Dharmendra; Yadav, Ashu; Bég, O Anwar

2017-01-01

Analytical solutions are developed for the electro-kinetic flow of a viscoelastic biological liquid in a finite length cylindrical capillary geometry under peristaltic waves. The Jefferys' non-Newtonian constitutive model is employed to characterize rheological properties of the fluid. The unsteady conservation equations for mass and momentum with electro-kinetic and Darcian porous medium drag force terms are reduced to a system of steady linearized conservation equations in an axisymmetric coordinate system. The long wavelength, creeping (low Reynolds number) and Debye-Hückel linearization approximations are utilized. The resulting boundary value problem is shown to be controlled by a number of parameters including the electro-osmotic parameter, Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity), and Jefferys' first parameter (ratio of relaxation and retardation time), wave amplitude. The influence of these parameters and also time on axial velocity, pressure difference, maximum volumetric flow rate and streamline distributions (for elucidating trapping phenomena) is visualized graphically and interpreted in detail. Pressure difference magnitudes are enhanced consistently with both increasing electro-osmotic parameter and Helmholtz-Smoluchowski velocity, whereas they are only elevated with increasing Jefferys' first parameter for positive volumetric flow rates. Maximum time averaged flow rate is enhanced with increasing electro-osmotic parameter, Helmholtz-Smoluchowski velocity and Jefferys' first parameter. Axial flow is accelerated in the core (plug) region of the conduit with greater values of electro-osmotic parameter and Helmholtz-Smoluchowski velocity whereas it is significantly decelerated with increasing Jefferys' first parameter. The simulations find applications in electro-osmotic (EO) transport processes in capillary physiology and also bio-inspired EO pump devices in chemical and aerospace engineering. Copyright © 2016 Elsevier Inc

Distinct Motion of GFP-Tagged Histone Expressing Cells Under AC Electrokinetics in Electrode-Multilayered Microfluidic Device.

PubMed

Yao, Jiafeng; Sugawara, Michiko; Obara, Hiromichi; Mizutani, Takeomi; Takei, Masahiro

2017-12-01

The distinct motion of GFP-tagged histone expressing cells (Histone-GFP type cells) has been investigated under ac electrokinetics in an electrode-multilayered microfluidic device as compared with Wild type cells and GFP type cells in terms of different intracellular components. The Histone-GFP type cells were modified by the transfection of green fluorescent protein-fused histone from the human lung fibroblast cell line. The velocity of the Histone-GFP type cells obtained by particle tracking velocimetry technique is faster than Wild type cells by 24.9% and GFP type cells by 57.1%. This phenomenon is caused by the more amount of proteins in the intracellular of single Histone-GFP type cell than that of the Wild type and GFP type cells. The more amount of proteins in the Histone-GFP type cells corresponds to a lower electric permittivity ϵ c of the cells, which generates a lower dielectrophoretic force exerting on the cells. The velocity of Histone-GFP type cells is well agreed with Eulerian-Lagrangian two-phase flow simulation by 4.2% mean error, which proves that the fluid motion driven by thermal buoyancy and electrothermal force dominates the direction of cells motion, while the distinct motion of Histone-GFP type cells is caused by dielectrophoretic force. The fluid motion does not generate a distinct drag motion for Histone-GFP type cells because the Histone-GFP type cells have the same size to the Wild type and GFP type cells. These results clarified the mechanism of cells motion in terms of intracellular components, which helps to improve the cell manipulation efficiency with electrokinetics.

Identification and phylogeny of Arabian snakes: Comparison of venom chromatographic profiles versus 16S rRNA gene sequences.

PubMed

Al Asmari, Abdulrahman; Manthiri, Rajamohammed Abbas; Khan, Haseeb Ahmad

2014-11-01

Identification of snake species is important for various reasons including the emergency treatment of snake bite victims. We present a simple method for identification of six snake species using the gel filtration chromatographic profiles of their venoms. The venoms of Echis coloratus, Echis pyramidum, Cerastes gasperettii, Bitis arietans, Naja arabica, and Walterinnesia aegyptia were milked, lyophilized, diluted and centrifuged to separate the mucus from the venom. The clear supernatants were filtered and chromatographed on fast protein liquid chromatography (FPLC). We obtained the 16S rRNA gene sequences of the above species and performed phylogenetic analysis using the neighbor-joining method. The chromatograms of venoms from different snake species showed peculiar patterns based on the number and location of peaks. The dendrograms generated from similarity matrix based on the presence/absence of particular chromatographic peaks clearly differentiated Elapids from Viperids. Molecular cladistics using 16S rRNA gene sequences resulted in jumping clades while separating the members of these two families. These findings suggest that chromatographic profiles of snake venoms may provide a simple and reproducible chemical fingerprinting method for quick identification of snake species. However, the validation of this methodology requires further studies on large number of specimens from within and across species.

[Identification of impurity peaks in the HPLC chromatogram by LC-MS and two-dimensional chromatographic correlation spectroscopy].

PubMed

Chen, Zhen-Zhen; Zhang, Dou-Sheng; Wang, Nan; Feng, Fang; Hu, Chang-Qin

2012-04-01

A novel qualitative analytical method by using two-dimensional chromatographic correlation spectroscopy techniques for recognizing impurity peaks of HPLC methods of quality control and LC-MS chromatographic system was established. The structures of major degradation products of ceftizoxime and cefdinir were identified by LC-MS and MassWorks application; the standard chromatographic and spectral data of the degradation impurities were obtained by high-performance liquid chromatography with diode array detection. The impurity peaks of two-dimensional chromatography were matched by comparison of spectra and calculating correlation coefficients. Peaks in chromatography can be identified accurately and rapidly in different chromatographic systems such as column and mobile phase changed. The method provides a new way and thought to identify the peaks in quality control of impurities without reference impurity substances.

QbD-oriented development and validation of a bioanalytical method for nevirapine with enhanced liquid-liquid extraction and chromatographic separation.

PubMed

Beg, Sarwar; Chaudhary, Vandna; Sharma, Gajanand; Garg, Babita; Panda, Sagar Suman; Singh, Bhupinder

2016-06-01

The present studies describe the systematic quality by design (QbD)-oriented development and validation of a simple, rapid, sensitive and cost-effective reversed-phase HPLC bioanalytical method for nevirapine in rat plasma. Chromatographic separation was carried out on a C18 column using isocratic 68:9:23% v/v elution of methanol, acetonitrile and water (pH 3, adjusted by orthophosphoric acid) at a flow rate of 1.0 mL/min using UV detection at 230 nm. A Box-Behnken design was applied for chromatographic method optimization taking mobile phase ratio, pH and flow rate as the critical method parameters (CMPs) from screening studies. Peak area, retention time, theoretical plates and peak tailing were measured as the critical analytical attributes (CAAs). Further, the bioanalytical liquid-liquid extraction process was optimized using an optimal design by selecting extraction time, centrifugation speed and temperature as the CMPs for percentage recovery of nevirapine as the CAA. The search for an optimum chromatographic solution was conducted through numerical desirability function. Validation studies performed as per the US Food and Drug Administration requirements revealed results within the acceptance limit. In a nutshell, the studies successfully demonstrate the utility of analytical QbD approach for the rational development of a bioanalytical method with enhanced chromatographic separation and recovery of nevirapine in rat plasma. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Phospholipid bilayer affinities and solvation characteristics by electrokinetic chromatography with a nanodisc pseudostationary phase.

PubMed

Penny, William M; Steele, Harmen B; Ross, J B Alexander; Palmer, Christopher P

2017-03-01

Phospholipid bilayer nanodiscs composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine and synthetic maleic acid-styrene copolymer belts have been introduced as a pseudostationary phase (PSP) in electrokinetic chromatography and demonstrated good performance. The nanodiscs provide a suitable migration range and high theoretical plate counts. Using this nanodisc pseudostationary phase, the affinity of the bilayer structure for probe solutes was determined and characterized. Good correlation is observed between retention factors and octanol water partition coefficients for particular categories of solutes, but the general correlation is weak primarily because the nanodiscs show stronger affinity than octanol for hydrogen bond donors. This suggests that a more appropriate application of this technology is to measure and characterize interactions between solutes and lipid bilayers directly. Linear solvation energy relationship analysis of the nanodisc-solute interactions in this study demonstrates that the nanodiscs provide a solvation environment with low cohesivity and weak hydrogen bond donating ability, and provide relatively strong hydrogen bond acceptor strength. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface study of stainless steel electrode deposition from soil electrokinetic (EK) treatment using X-ray photoelectron spectroscopy (XPS)

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

Embong, Zaidi, E-mail: zaidi@uthm.edu.my; Research Centre for Soft Soils; Johar, Saffuwan

2015-04-29

Electrokinetic (EK) remediation relies upon application of a low-intensity direct current through the soil between stainless steel electrodes that are divided into a cathode array and an anode array. This mobilizes charged species, causing ions and water to move toward the electrodes. Metal ions and positively charged organic compounds move toward the cathode. Anions such as chloride, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Here, this remediation techniques lead to a formation of a deposition at the both cathode and anode surface that mainly contributed byanion and cation from the remediated soil. In this research, Renggam-Jerangaumore » soil species (HaplicAcrisol + RhodicFerralsol) with a surveymeter reading of 38.0 ± 3.9 μR/hr has been investigation in order to study the mobility of the anion and cation under the influence electric field. Prior to the EK treatment, the elemental composition of the soil and the stainless steel electrode are measured using XRF analyses. Next, the soil sample is remediated at a constant electric potential of 30 V within an hour of treatment period. A surface study for the deposition layer of the cathode and anode using X-ray Photoelectron spectroscopy (XPS) revealed that a narrow photoelectron signal from oxygen O 1s, carbon, C 1s silica, Si 2p, aluminium, Al 2p and chromium, Cr 2p exhibited on the electrode surface and indicate that a different in photoelectron intensity for each element on both electrode surface. In this paper, the mechanism of Si{sup 2+} and Al{sup 2+} cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.« less

Characterization of Gas Chromatographic Liquid Phases Using McReynolds Constants. An Experiment for Instrumental Analysis Laboratory.

ERIC Educational Resources Information Center

Erskine, Steven R.; And Others

1986-01-01

Describes a laboratory experiment that is designed to aid in the understanding of the fundamental process involved in gas chromatographic separations. Introduces the Kovats retention index system for use by chemistry students to establish criteria for the optimal selection of gas chromatographic stationary phases. (TW)

Simultaneous analysis of tea catechins, caffeine, gallic acid, theanine and ascorbic acid by micellar electrokinetic capillary chromatography.

PubMed

Aucamp, J P; Hara, Y; Apostolides, Z

2000-04-21

A micellar electrokinetic capillary chromatography (MEKC) method for the simultaneous analysis of five tea catechins, theanine, caffeine, gallic acid and ascorbic acid has been developed. The catechins are (-)-epicatechin, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate. p-Nitrophenol serves as both reference and internal standard. All the components are separated within 13 min with a 57 cm uncoated fused-silica column. On-column detection was carried out at 200 nm. This method has been used to measure these compounds in fresh tea leaves and tea liquor. The limit of detection for all analytes ranged from 1 to 20 microg/ml.

Flight contaminant trace analyser. Phase 1: Chromatographic input system

NASA Technical Reports Server (NTRS)

Zlatkis, A.

1976-01-01

The purpose of this investigation was to develop two chromatographic columns which would enable a mass spectral identification of 40 specified compounds. The columns are for use in a toxic gas analyzer, which incorporates an automated gas chromatograph-mass spectrometer. Different types of stationary phases were investigated. The columns used were of the open tubular capillary type and were made of nickel. Limitations of initial and final temperature of operation led to final development of a column which could resolve most of the compounds required. The few unresolved components are capable of resolution and identification by the mass spectrometer. The columns (182m Ni x 0.8m 0.D x 0.5mm I.D) coated with Witconal La 23, yielded in excess of 200,000 theoretical plates and completed the analysis in less than 90 minutes using a carrier gas flow rate of 4 cc/min hydrogen.

Electrokinetic framework of dielectrophoretic deposition devices

NASA Astrophysics Data System (ADS)

Burg, Brian R.; Bianco, Vincenzo; Schneider, Julian; Poulikakos, Dimos

2010-06-01

Numerical modeling and experiments are performed investigating the properties of a dielectrophoresis-based deposition device, in order to establish the electrokinetic framework required to understand the effects of applied inhomogeneous electric fields while moving particles to desired locations. By capacitively coupling electrodes to a conductive substrate, the controlled large-scale parallel dielectrophoretic assembly of nanostructures in individually accessible devices at a high integration density is accomplished. Thermal gradients in the solution, which give rise to local permittivity and conductivity changes, and velocity fields are solved by coupling electric, thermal, and fluid-mechanical equations. The induced electrothermal flow (ETF) causes vortices above the electrode gap, attracting particles, such as single-walled carbon nanotubes (SWNTs), before they are trapped by the dielectrophoretic force and deposit across the electrodes. Long-range carbon nanotube transport is governed by hydrodynamic effects, while local trapping is dominated by dielectrophoretic forces in low concentration SWNT dispersions. Results show that by decreasing the ac frequency ac electroosmosis on the metallic electrodes occurs due to the emergence of an electric double layer, disturbing the initial flow pattern of the system. By superimposing a dc potential offset, a generated tangential electroosmotic fluid flow in the dielectric electrode gap also disrupts the ETF. Capacitive coupling is most efficient in the high frequency regime where it is the dominating impedance contribution. Understanding the occurrence and interaction of these different effects, including a self-limiting integration mechanism for individual nanostructures, allows an increased deposition yield at overall lower electric field strengths through a prudent choice of electric field parameters. The findings provide important avenues toward gentler particle handling, without direct current throughput, a relevant

Quality evaluation of extracted ion chromatograms and chromatographic peaks in liquid chromatography/mass spectrometry-based metabolomics data

PubMed Central

2014-01-01

Background Extracted ion chromatogram (EIC) extraction and chromatographic peak detection are two important processing procedures in liquid chromatography/mass spectrometry (LC/MS)-based metabolomics data analysis. Most commonly, the LC/MS technique employs electrospray ionization as the ionization method. The EICs from LC/MS data are often noisy and contain high background signals. Furthermore, the chromatographic peak quality varies with respect to its location in the chromatogram and most peaks have zigzag shapes. Therefore, there is a critical need to develop effective metrics for quality evaluation of EICs and chromatographic peaks in LC/MS based metabolomics data analysis. Results We investigated a comprehensive set of potential quality evaluation metrics for extracted EICs and detected chromatographic peaks. Specifically, for EIC quality evaluation, we analyzed the mass chromatographic quality index (MCQ index) and propose a novel quality evaluation metric, the EIC-related global zigzag index, which is based on an EIC's first order derivatives. For chromatographic peak quality evaluation, we analyzed and compared six metrics: sharpness, Gaussian similarity, signal-to-noise ratio, peak significance level, triangle peak area similarity ratio and the local peak-related local zigzag index. Conclusions Although the MCQ index is suited for selecting and aligning analyte components, it cannot fairly evaluate EICs with high background signals or those containing only a single peak. Our proposed EIC related global zigzag index is robust enough to evaluate EIC qualities in both scenarios. Of the six peak quality evaluation metrics, the sharpness, peak significance level, and zigzag index outperform the others due to the zigzag nature of LC/MS chromatographic peaks. Furthermore, using several peak quality metrics in combination is more efficient than individual metrics in peak quality evaluation. PMID:25350128

Recovery of Drug Delivery Nanoparticles from Human Plasma Using an Electrokinetic Platform Technology.

PubMed

Ibsen, Stuart; Sonnenberg, Avery; Schutt, Carolyn; Mukthavaram, Rajesh; Yeh, Yasan; Ortac, Inanc; Manouchehri, Sareh; Kesari, Santosh; Esener, Sadik; Heller, Michael J

2015-10-01

The effect of complex biological fluids on the surface and structure of nanoparticles is a rapidly expanding field of study. One of the challenges holding back this research is the difficulty of recovering therapeutic nanoparticles from biological samples due to their small size, low density, and stealth surface coatings. Here, the first demonstration of the recovery and analysis of drug delivery nanoparticles from undiluted human plasma samples through the use of a new electrokinetic platform technology is presented. The particles are recovered from plasma through a dielectrophoresis separation force that is created by innate differences in the dielectric properties between the unaltered nanoparticles and the surrounding plasma. It is shown that this can be applied to a wide range of drug delivery nanoparticles of different morphologies and materials, including low-density nanoliposomes. These recovered particles can then be analyzed using different methods including scanning electron microscopy to monitor surface and structural changes that result from plasma exposure. This new recovery technique can be broadly applied to the recovery of nanoparticles from high conductance fluids in a wide range of applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation of flavonol-2-O-glycosides from Calendula officinalis and Sambucus nigra by high-performance liquid and micellar electrokinetic capillary chromatography.

PubMed

Pietta, P; Bruno, A; Mauri, P; Rava, A

1992-02-28

Calendula officinalis and Sambucus nigra flowers were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC) and micellar electrokinetic capillary chromatography (MECC). RP-HPLC was performed on C8 Aquapore RP 300 columns with eluents containing 2-propanol and tetrahydrofuran. MECC was carried out on a 72-cm fused-silica capillary using sodium dodecyl sulphate and sodium borate (pH 8.3) as the running buffer. The results obtained by these techniques are compared.

QSAR models for prediction of chromatographic behavior of homologous Fab variants.

PubMed

Robinson, Julie R; Karkov, Hanne S; Woo, James A; Krogh, Berit O; Cramer, Steven M

2017-06-01

While quantitative structure activity relationship (QSAR) models have been employed successfully for the prediction of small model protein chromatographic behavior, there have been few reports to date on the use of this methodology for larger, more complex proteins. Recently our group generated focused libraries of antibody Fab fragment variants with different combinations of surface hydrophobicities and electrostatic potentials, and demonstrated that the unique selectivities of multimodal resins can be exploited to separate these Fab variants. In this work, results from linear salt gradient experiments with these Fabs were employed to develop QSAR models for six chromatographic systems, including multimodal (Capto MMC, Nuvia cPrime, and two novel ligand prototypes), hydrophobic interaction chromatography (HIC; Capto Phenyl), and cation exchange (CEX; CM Sepharose FF) resins. The models utilized newly developed "local descriptors" to quantify changes around point mutations in the Fab libraries as well as novel cluster descriptors recently introduced by our group. Subsequent rounds of feature selection and linearized machine learning algorithms were used to generate robust, well-validated models with high training set correlations (R 2  > 0.70) that were well suited for predicting elution salt concentrations in the various systems. The developed models then were used to predict the retention of a deamidated Fab and isotype variants, with varying success. The results represent the first successful utilization of QSAR for the prediction of chromatographic behavior of complex proteins such as Fab fragments in multimodal chromatographic systems. The framework presented here can be employed to facilitate process development for the purification of biological products from product-related impurities by in silico screening of resin alternatives. Biotechnol. Bioeng. 2017;114: 1231-1240. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

MULTISPECTRAL IDENTIFICATION OF POTENTIALLY HAZARDOUS BYPRODUCTS OF OZONATION AND CHLORINATION - PART I: STUDIES OF CHROMATOGRAPHIC AND SPECTROSCOPIC PROPERTIES OF MX

EPA Science Inventory

The gas chromatographic (GC) and Fourier transform infrared and mass spectroscopic (FT-IR and MS, respectively) properties of (Z)-2-chloro-3-(dichloromethyl)4-oxobutenoic acid (MX) (a highly mutagenic byproduct of drinking water chlorination) and several related compounds were st...

Pilot Field Test of Electrokinetically-Delivered and Thermally Activated Persulfate (EKTAP) for Remediation of Chlorinated Solvents in Clay

NASA Astrophysics Data System (ADS)

O'Carrol, D. M.; Head, N.; Chowdhury, A. I.; Inglis, A.; Garcia, A. N.; Reynolds, D. A.; Hayman, J.; Hogberg, D.; Austrins, L. M.; Sidebottom, A.; Auger, M.; Eimers, J.; Gerhard, J.

2017-12-01

Remediation of low-permeability soils that are contaminated with chlorinated solvents is challenging. In-situ chemical oxidation (ISCO) with persulfate is promising, however, the delivery of the oxidant by hydraulic gradient is limited in low-permeability soils. Electrokinetic (EK) enhanced transport of amendments has shown the potential to overcome these limitations. In particular, the combined technology of EK-delivered and thermally activated persulfate (EKTAP) has been recently demonstrated in the laboratory as promising in these challenging environments (Chowdhury A. I. (2016) Hydraulic and Electrokinetic Delivery of Remediants for In-situ Remediation. Electronic Thesis and Dissertation Repository, Paper 4135). This study presents the first pilot field test to evaluate EKTAP to enhance the distribution and effectiveness of persulfate in clayey soil. The pilot field test was conducted at a contaminated site formerly occupied by a chlorinated solvent production facility. In the EK transport phase, 925 L of 40 g/L persulfate was injected over 57 days, during which 9A of direct current (DC) was applied between two electrodes spaced 3 m apart. In the subsequent heating phase, 10A of alternate current (AC) was applied across the same electrodes for an additional 70 days. Extensive sampling of soil and groundwater in this EKTAP cell were compared to those from two parallel control cells, one with EK only and one with no electrodes. Results indicated that EK can significantly increase transport rates of persulfate in clayey soil. Persulfate activation primarily occurred in the period of DC application, indicating that the natural reduction capacity of the clay soil had a significant impact on persulfate decomposition. Temperature mapping indicated that AC current was able to increase soil temperatures, validating the EKTAP concept. Degradation of chlorinated compounds, in particular, 1-2, dichloroethane (1,2- DCA), was observed to be substantial in areas of persulfate

Influence of the three-dimensional heterogeneous roughness on electrokinetic transport in microchannels.

PubMed

Hu, Yandong; Werner, Carsten; Li, Dongqing

2004-12-15

Surface roughness has been considered as a passive means of enhancing species mixing in electroosmotic flow through microfluidic systems. It is highly desirable to understand the synergetic effect of three-dimensional (3D) roughness and surface heterogeneity on the electrokinetic flow through microchannels. In this study, we developed a three-dimensional finite-volume-based numerical model to simulate electroosmotic transport in a slit microchannel (formed between two parallel plates) with numerous heterogeneous prismatic roughness elements arranged symmetrically and asymmetrically on the microchannel walls. We consider that all 3D prismatic rough elements have the same surface charge or zeta potential, the substrate (the microchannel wall) surface has a different zeta potential. The results showed that the rough channel's geometry and the electroosmotic mobility ratio of the roughness elements' surface to that of the substrate, epsilon(mu), have a dramatic influence on the induced-pressure field, the electroosmotic flow patterns, and the electroosmotic flow rate in the heterogeneous rough microchannels. The associated sample-species transport presents a tidal-wave-like concentration field at the intersection between four neighboring rough elements under low epsilon(mu) values and has a concentration field similar to that of the smooth channels under high epsilon(mu) values.

Electrokinetic flows through a parallel-plate channel with slipping stripes on walls

NASA Astrophysics Data System (ADS)

Chu, Henry C. W.; Ng, Chiu-On

2011-11-01

Electrohydrodynamic flows through a periodically-micropatterned plane channel are considered. One unit of wall pattern consists of a slipping and non-slipping stripe, each with a distinct zeta potential. The problems are solved semi-analytically by eigenfunction expansion and point collocation. In the regime of linear response, the Onsager relation for the fluid and current fluxes are deduced as linear functions of the hydrodynamic and electric forcings. The phenomenological coefficients are explicitly expressed as functions of the channel height, the Debye parameter, the slipping area fraction of the wall, the intrinsic slip length, and the zeta potentials. We generalize the theoretical limits made in previous studies on electrokinetic flow over an inhomogeneously slipping surface. One should be cautious when applying these limits. First, when a surface is not 100% uniformly slipping but has a small fraction of area being covered by no-slip slots, the electroosmotic enhancement can be appreciably reduced. Second, when the electric double layer is only moderately thin, slipping-uncharged regions on a surface will have finite inhibition effect on the electroosmotic flow. Financial support by the RGC of the HKSAR, China: Project Nos. HKU715609E, HKU715510E; and the HKU under the Seed Funding Programme for Basic Research: Project Code 200911159024.

Development of and fabrication of high resolution gas chromatographic capillary columns

NASA Technical Reports Server (NTRS)

Zlatkis, A.

1982-01-01

Gas chromatographic columns which are used in the trace gas analyzer (TGA) for the space shuttle are coated with a polyoxyethylene lauryl ether. This stationary phase is of medium polarity and has a temperature limit of 160 C. A polymer for this application which has an improved thermal stability is investigated. The use of fused silica capillary columns with specially bonded phases as well as an introduction system (on column) was also studied.

Cast-to-shape electrokinetic trapping medium

DOEpatents

Shepodd, Timothy J.; Franklin, Elizabeth; Prickett, Zane T.; Artau, Alexander

2004-08-03

A three-dimensional microporous polymer network material, or monolith, cast-to-shape in a microchannel. The polymer monolith, produced by a phase separation process, is capable of trapping and retaining charged protein species from a mixture of charged and uncharged species under the influence of an applied electric field. The retained charged protein species are released from the porous polymer monolith by a pressure driven flow in the substantial absence of the electric field. The pressure driven flow is independent of direction and thus neither means to reverse fluid flow nor a multi-directional flow field is required, a single flow through the porous polymer monolith can be employed, in contrast to prior art systems. The monolithic polymer material produced by the invention can function as a chromatographic medium. Moreover, by virtue of its ability to retain charged protein species and quantitatively release the retained species the porous polymer monolith can serve as a means for concentrating charged protein species from, for example, a dilute solution.

Cast-to-shape electrokinetic trapping medium

DOEpatents

Shepodd, Timothy J [Livermore, CA; Franklin, Elizabeth [Rolla, MO; Prickett, Zane T [Golden, CO; Artau, Alexander [Pleasanton, CA

2006-05-30

A three-dimensional microporous polymer network material, or monolith, cast-to-shape in a microchannel. The polymer monolith, produced by a phase separation process, is capable of trapping and retaining charged protein species from a mixture of charged and uncharged species under the influence of an applied electric field. The retained charged protein species are released from the porous polymer monolith by a pressure driven flow in the substantial absence of the electric field. The pressure driven flow is independent of direction and thus neither means to reverse fluid flow nor a multi-directional flow field is required, a single flow through the porous polymer monolith can be employed, in contrast to prior art systems. The monolithic polymer material produced by the invention can function as a chromatographic medium. Moreover, by virtue of its ability to retain charged protein species and quantitatively release the retained species the porous polymer monolith can serve as a means for concentrating charged protein species from, for example, a dilute solution.

Linear regression analysis and its application to multivariate chromatographic calibration for the quantitative analysis of two-component mixtures.

PubMed

Dinç, Erdal; Ozdemir, Abdil

2005-01-01

Multivariate chromatographic calibration technique was developed for the quantitative analysis of binary mixtures enalapril maleate (EA) and hydrochlorothiazide (HCT) in tablets in the presence of losartan potassium (LST). The mathematical algorithm of multivariate chromatographic calibration technique is based on the use of the linear regression equations constructed using relationship between concentration and peak area at the five-wavelength set. The algorithm of this mathematical calibration model having a simple mathematical content was briefly described. This approach is a powerful mathematical tool for an optimum chromatographic multivariate calibration and elimination of fluctuations coming from instrumental and experimental conditions. This multivariate chromatographic calibration contains reduction of multivariate linear regression functions to univariate data set. The validation of model was carried out by analyzing various synthetic binary mixtures and using the standard addition technique. Developed calibration technique was applied to the analysis of the real pharmaceutical tablets containing EA and HCT. The obtained results were compared with those obtained by classical HPLC method. It was observed that the proposed multivariate chromatographic calibration gives better results than classical HPLC.

Confocal Raman characterization of different protein desorption behaviors from chromatographic particles.

PubMed

Xiao, Yuewu; Stone, Thomas; Moya, Wilson; Killian, Paul; Herget, Thomas

2014-01-21

Confocal Raman spectroscopy is a nondestructive analytical technique that combines the chemical information from vibrational spectroscopy with the spatial resolution of confocal microscopy. It was applied, for the first time, to measure protein desorption from chromatographic particles. Monoclonal antibody was loaded onto the Fractogel EMD SO3 (M) cation exchanger at either pH 5 or pH 4. Confocal Raman measurement suggests that only the protein loaded at pH 5 is able to release from chromatographic particles in the elution buffer. Detailed comparison of high-quality spectra indicates that, while proteins loaded at both pH values showed a predominant β-sheet conformation, protein loaded at pH 4 has a broader amide I band with more intensity in the >1680 cm(-1) region. This small but clear and reproducible amide I bandwidth increase is not observed for protein in the solution state at pH 4. No definitive assignment of the increased Raman intensity in the >1680 cm(-1) region could be made, but it might be related to structural changes involved in the association of protein molecules in the adsorbed state, which helps to explain the nearly 100% retention under elution conditions of the monoclonal antibody adsorbed at pH 4 in chromatographic particles.

Electrokinetically induced alterations in dynamic response of viscoelastic fluids in narrow confinements.

PubMed

Bandopadhyay, Aditya; Chakraborty, Suman

2012-05-01

We investigate a dynamical interplay between interfacial electrokinetics and a combined dissipative and elastic behavior of flow through narrow confinements, in analogy with spatiotemporal hydrodynamics of porous media. In particular, we investigate the effects of streaming potential on the pertinent dynamic responses, by choosing a Maxwell fluid model for representing the consequent electro-hydrodynamic characteristics. We transform the pertinent governing equation to the frequency domain, so that a dynamic generalization of Darcy's law in the presence of streaming potential effects can be effectively realized. We show that the frequencies corresponding to local maxima in the dynamic permeability also correspond to local maxima in the induced streaming potential. We also bring out the effects of Stern layer conductivity on the dynamic permeability. Our analytical estimates do reveal that serious overestimations in the commonly portrayed notion of massive amplifications of dynamic permeability at resonating frequencies may be possible, if interactions between spontaneous electrochemical interfacial phenomena and pulsating pressure-gradient-driven viscoelastic transport are trivially ignored.

The Influence of Soft Layer Electrokinetics on Electroporation of Gram-positive Bacteria

NASA Astrophysics Data System (ADS)

Dingari, Naga Neehar; Moran, Jeffrey L.; Garcia, Paulo A.; Buie, Cullen R.

2016-11-01

Bacterial electroporation involves subjecting cells to intense ( 10 kV/cm) electric pulses, to open pores on the cell membrane for intracellular delivery of exogenous molecules. Its high efficiency in genetic transformation makes it an attractive tool for synthetic biology. While mammalian cell electroporation has received extensive theoretical and experimental investigation, bacterial electroporation has received markedly less attention. In this work, we develop a theoretical model of electroporation for gram-positive bacteria, taking into account the effect of the bacterial cell envelope on the cell's response to an electroporation pulse. We model the influence of the cell wall charge on the electrokinetic transport (and hence the pore properties) around the bacterial cell envelope using the Poisson-Nernst-Planck equations. Further, we account for the influence of the cell wall's mechanical elasticity on the pore radius evolution during electroporation, which is typically neglected in mammalian cell electroporation. This yields valuable information about favorable conditions for pore formation and will enable designing optimal platforms for bacteria electroporation.

Multivariate curve resolution of incomplete fused multiset data from chromatographic and spectrophotometric analyses for drug photostability studies.

PubMed

De Luca, Michele; Ragno, Gaetano; Ioele, Giuseppina; Tauler, Romà

2014-07-21

An advanced and powerful chemometric approach is proposed for the analysis of incomplete multiset data obtained by fusion of hyphenated liquid chromatographic DAD/MS data with UV spectrophotometric data from acid-base titration and kinetic degradation experiments. Column- and row-wise augmented data blocks were combined and simultaneously processed by means of a new version of the multivariate curve resolution-alternating least squares (MCR-ALS) technique, including the simultaneous analysis of incomplete multiset data from different instrumental techniques. The proposed procedure was applied to the detailed study of the kinetic photodegradation process of the amiloride (AML) drug. All chemical species involved in the degradation and equilibrium reactions were resolved and the pH dependent kinetic pathway described. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced transport of materials into enamel nanopores via electrokinetic flow.

PubMed

Gan, H Y; Sousa, F B; Carlo, H L; Maciel, P P; Macena, M S; Han, J

2015-04-01

The ability to infiltrate various molecules and resins into dental enamel is highly desirable in dentistry, yet transporting materials into dental enamel is limited by the nanometric scale of their pores. Materials that cannot be infiltrated into enamel by diffusion/capillarity are often considered molecules with sizes above a critical threshold, which are often considered to be larger than the pores of enamel. We challenge this notion by reporting the use of electrokinetic flow to transport solutions with molecules with sizes above a critical threshold-namely, an aqueous solution with a high refractive index (Thoulet's solution) and a curable fluid resin infiltrant (without acid etching)-deep into the normal enamel layer. Volume infiltration by Thoulet's solution is increased by 5- to 6-fold, and resin infiltration depths as large as 600 to 2,000 µm were achieved, in contrast to ~10 µm resulting from diffusion/capillarity. Incubation with demineralization solution for 192 h resulted in significant demineralization at noninfiltrated histologic points but not at resin infiltrated. These results open new avenues for the transport of materials in dental enamel. © International & American Associations for Dental Research 2015.

ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT, EXPLOSIVES DETECTION TECHNOLOGY, SRI INSTRUMENTS, MODEL 8610C, GAS CHROMATOGRAPH/THERMIONIC IONIZATION DETECTION

EPA Science Inventory

The SRI Model 86 1 OC gas chromatograph (GC) is a transportable instrument that can provide on-site analysis of soils for explosives. Coupling this transportable gas chromatograph with a thermionic ionization detector (TID) allows for the determination of explosives in soil matri...

GAS CHROMATOGRAPHIC TECHNIQUES FOR THE MEASUREMENT OF ISOPRENE IN AIR

EPA Science Inventory

The chapter discusses gas chromatographic techniques for measuring isoprene in air. Such measurement basically consists of three parts: (1) collection of sufficient sample volume for representative and accurate quantitation, (2) separation (if necessary) of isoprene from interfer...

[Research on the application of grey system theory in the pattern recognition for chromatographic fingerprints of traditional Chinese medicine].

PubMed

Wei, Hang; Lin, Li; Zhang, Yuan; Wang, Lianjing; Chen, Qinqun

2013-02-01

A model based on grey system theory was proposed for pattern recognition in chromatographic fingerprints (CF) of traditional Chinese medicine (TCM). The grey relational grade among the data series of each testing CF and the ideal CF was obtained by entropy and norm respectively, then the principle of "maximal matching degree" was introduced to make judgments, so as to achieve the purpose of variety identification and quality evaluation. A satisfactory result in the high performance liquid chromatographic (HPLC) analysis of 56 batches of different varieties of Exocarpium Citrus Grandis was achieved with this model. The errors in the chromatographic fingerprint analysis caused by traditional similarity method or grey correlation method were overcome, as the samples of Citrus grandis 'Tomentosa' and Citrus grandis (L.) Osbeck were correctly distinguished in the experiment. Furthermore in the study on the variety identification of Citrus grandis 'Tomentosa', the recognition rates were up to 92.85%, although the types and the contents of the chemical compositions of the samples were very close. At the same time, the model had the merits of low computation complexity and easy operation by computer programming. The research indicated that the grey system theory has good applicability to pattern recognition in the chromatographic fingerprints of TCM.

Systematic Evaluation of Chromatographic Parameters for Isoquinoline Alkaloids on XB-C18 Core-Shell Column Using Different Mobile Phase Compositions

PubMed Central

Sowa, Ireneusz; Zielińska, Sylwia; Sawicki, Jan; Bogucka-Kocka, Anna; Staniak, Michał; Bartusiak-Szcześniak, Ewa; Podolska-Fajks, Maja; Kocjan, Ryszard

2018-01-01

Chelidonium majus L. is a rich source of isoquinoline alkaloids with confirmed anti-inflammatory, choleretic, spasmolytic, antitumor, and antimicrobial activities. However, their chromatographic analysis is difficult because they may exist both in charged and uncharged forms and may result in the irregular peak shape and the decrease in chromatographic system efficacy. In the present work, the separation of main C. majus alkaloids was optimized using a new-generation XB-C18 endcapped core-shell column dedicated for analysis of alkaline compounds. The influence of organic modifier concentration, addition of salts, and pH of eluents on chromatographic parameters such as retention, resolution, chromatographic plate numbers, and peak asymmetry was investigated. The results were applied to elaborate the optimal chromatographic system for simultaneous quantification of seven alkaloids from the root, herb, and fruit of C. majus. PMID:29675288

Optimizing Chromatographic Separation: An Experiment Using an HPLC Simulator

ERIC Educational Resources Information Center

Shalliker, R. A.; Kayillo, S.; Dennis, G. R.

2008-01-01

Optimization of a chromatographic separation within the time constraints of a laboratory session is practically impossible. However, by employing a HPLC simulator, experiments can be designed that allow students to develop an appreciation of the complexities involved in optimization procedures. In the present exercise, a HPLC simulator from "JCE…

Bioanalytical method transfer considerations of chromatographic-based assays.

PubMed

Williard, Clark V

2016-07-01

Bioanalysis is an important part of the modern drug development process. The business practice of outsourcing and transferring bioanalytical methods from laboratory to laboratory has increasingly become a crucial strategy for successful and efficient delivery of therapies to the market. This chapter discusses important considerations when transferring various types of chromatographic-based assays in today's pharmaceutical research and development environment.

Synthesis and Characterization of a Hydrogel with Controllable Electroosmosis: A Potential Brain Tissue Surrogate for Electrokinetic Transport

PubMed Central

Faraji, Amir H.; Cui, Jonathan J.; Guy, Yifat; Li, Ling; Weber, Stephen G.

2011-01-01

Electroosmosis is the bulk fluid flow initiated by application of an electric field to an electrolyte solution in contact with immobile objects with a non-zero ζ-potential such as the surface of a porous medium. Electroosmosis may be used to assist analytical separations. Several gel-based systems with varying electroosmotic mobilities have been made in this context. A method was recently developed to determine the ζ-potential of organotypic hippocampal slice cultures (OHSC) as a representative model for normal brain tissue. The ζ-potential of the tissue is significant. However, determining the role of the ζ-potential in solute transport in tissue in an electric field is difficult because the tissue's ζ-potential cannot be altered. We hypothesized that mass transport properties, namely the ζ-potential and tortuosity, could be modulated by controlling the composition of a set of hydrogels. Thus, poly(acrylamide-co-acrylic acid) gels were prepared with three compositions (by monomer weight percent): acrylamide/acrylic acid 100/0, 90/10, and 75/25. The ζ-potentials of these gels at pH 7.4 are distinctly different, and in fact vary approximately linearly with the weight percent of acrylic acid. We discovered that the 25% acrylic acid gel is a respectable model for brain tissue, as its ζ-potential is comparable to the OHSC. This series of gels permits the experimental determination of the importance of electrokinetic properties in a particular experiment or protocol. Additionally, tortuosities were measured electrokinetically and by evaluating diffusion coefficients. Hydrogels with well-defined ζ-potential and tortuosity may find utility in biomaterials, analytical separations, and as a surrogate model for OHSC and living biological tissues. PMID:21905710

Electrokinetic treatment of polluted soil at pilot level coupled to an advanced oxidation process of its wastewater

NASA Astrophysics Data System (ADS)

Ochoa, B.; Ramos, L.; Garibay, A.; Pérez-Corona, M.; Cuevas, M. C.; Cárdenas, J.; Teutli, M.; Bustos, E.

2016-02-01

Soil contaminated with hydrocarbons is a current problem of great importance. These contaminants may be toxic, can retain water and block gas exchange with the atmosphere, which produces a poor-quality soil unsuitable for ecological health. Electroremediation is among the treatments for the removal of such contaminants. In this research, a pilot-level electroremediation test was applied using a circular arrangement of electrodes with a Ti cathode at the middle of the cell surrounded by six IrO2-Ta2O5 | Ti anodes. The presence of an NaOH electrolyte helps to develop the electromigration and electro-osmosis of gasoline molecules (at 1126 mg kg-1) surrounded by Na+ ions. The hydrocarbons are directed towards the cathode and subsequently removed in an aqueous Na+ - hydrocarbon solution, and the -OH migrates to the anode. During electrokinetic treatment, the physicochemical characteristics of the soil close to either the cathode or anode and at the half-cell were evaluated during the three weeks of treatment. During that time, more than 80% of hydrocarbons were removed. Hydrocarbons removed by the electrokinetic treatment of gasoline-polluted soil were collected in a central wastewater compartment and subsequently treated with a Fenton-type advanced oxidation process. This achieved more than 70% mineralization of the hydrocarbons to CO2 and H2O within 1.5 h; its low toxicity status was verified using the Deltatox® kit test. With this approach, the residual water complied with the permissible limits of COD, pH, and electrical conductivity for being discharged into water bodies, according to Mexican norm NOM-001-SEMARNAT-1996.

Automated chromatographic laccase-mediator-system activity assay.

PubMed

Anders, Nico; Schelden, Maximilian; Roth, Simon; Spiess, Antje C

2017-08-01

To study the interaction of laccases, mediators, and substrates in laccase-mediator systems (LMS), an on-line measurement was developed using high performance anion exchange chromatography equipped with a CarboPac™ PA 100 column coupled to pulsed amperometric detection (HPAEC-PAD). The developed method was optimized for overall chromatographic run time (45 to 120 min) and automated sample drawing. As an example, the Trametes versicolor laccase induced oxidation of 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-dihydroxypropane (adlerol) using 1-hydroxybenzotriazole (HBT) as mediator was measured and analyzed on-line. Since the Au electrode of the PAD detects only hydroxyl group containing substances with a limit of detection being in the milligram/liter range, not all products are measureable. Therefore, this method was applied for the quantification of adlerol, and-based on adlerol conversion-for the quantification of the LMS activity at a specific T. versicolor laccase/HBT ratio. The automated chromatographic activity assay allowed for a defined reaction start of all laccase-mediator-system reactions mixtures, and the LMS reaction progress was automatically monitored for 48 h. The automatization enabled an integrated monitoring overnight and over-weekend and minimized all manual errors such as pipetting of solutions accordingly. The activity of the LMS based on adlerol consumption was determined to 0.47 U/mg protein for a laccase/mediator ratio of 1.75 U laccase/g HBT. In the future, the automated method will allow for a fast screening of combinations of laccases, mediators, and substrates which are efficient for lignin modification. In particular, it allows for a fast and easy quantification of the oxidizing activity of an LMS on a lignin-related substrate which is not covered by typical colorimetric laccase assays. ᅟ.

Chromatographic extraction with di(2-ethylhexyl)orthophosphoric acid for production and purification of promethium-147

DOEpatents

Boll, Rose A [Knoxville, TN; Mirzadeh, Saed [Knoxville, TN

2008-10-14

A method of producing and purifying promethium-147 including the steps of: irradiating a target material including neodymium-146 with neutrons to produce promethium-147 within the irradiated target material; dissolving the irradiated target material to form an acidic solution; loading the acidic solution onto a chromatographic separation apparatus containing HDEHP; and eluting the apparatus to chromatographically separate the promethium-147 from the neodymium-146.

Gas Chromatographic/Mass Spectrometric Differentiation of Atenolol, Metoprolol, Propranolol, and an Interfering Metabolite Product of Metoprolol

DTIC Science & Technology

2004-10-01

Gas Chromatographic/Mass Spectrometric Differentiation of Atenolol, Metoprolol , Propranolol, and an Interfering Metabolite Product of Metoprolol ...4. Title and Subtitle 5. Report Date October 2004 Gas Chromatographic/Mass Spectrometric Differentiation of Atenolol, Metoprolol , Propranolol...and an Interfering Metabolite Product of Metoprolol 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Angier MK

Moving charged particles in lattice Boltzmann-based electrokinetics

NASA Astrophysics Data System (ADS)

Kuron, Michael; Rempfer, Georg; Schornbaum, Florian; Bauer, Martin; Godenschwager, Christian; Holm, Christian; de Graaf, Joost

2016-12-01

The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled set of differential equations, along with boundary conditions, collectively referred to as the electrokinetic equations. Capuani et al. [J. Chem. Phys. 121, 973 (2004)] introduced a lattice-based method for solving this system of equations, which builds upon the lattice Boltzmann algorithm for the simulation of hydrodynamic flow and exploits computational locality. However, thus far, a description of how to incorporate moving boundary conditions into the Capuani scheme has been lacking. Moving boundary conditions are needed to simulate multiple arbitrarily moving colloids. In this paper, we detail how to introduce such a particle coupling scheme, based on an analogue to the moving boundary method for the pure lattice Boltzmann solver. The key ingredients in our method are mass and charge conservation for the solute species and a partial-volume smoothing of the solute fluxes to minimize discretization artifacts. We demonstrate our algorithm's effectiveness by simulating the electrophoresis of charged spheres in an external field; for a single sphere we compare to the equivalent electro-osmotic (co-moving) problem. Our method's efficiency and ease of implementation should prove beneficial to future simulations of the dynamics in a wide range of complex nanoscopic and colloidal systems that were previously inaccessible to lattice-based continuum algorithms.

Chemometrics-assisted chromatographic fingerprinting: An illicit methamphetamine case study.

PubMed

Shekari, Nafiseh; Vosough, Maryam; Tabar Heidar, Kourosh

2017-03-01

The volatile chemical constituents in complex mixtures can be analyzed using gas chromatography with mass spectrometry. This analysis allows the tentative identification of diverse impurities of an illicit methamphetamine sample. The acquired two-dimensional data of liquid-liquid extraction was resolved by multivariate curve resolution alternating curve resolution to elucidate the embedded peaks effectively. This is the first report on the application of a curve resolution approach for chromatogram fingerprinting to identify particularly the embedded impurities of a drug of abuse. Indeed, the strong and broad peak of methamphetamine makes identifying the underlying peaks problematic and even impossible. Mathematical separation instead of conventional chromatographic approaches was performed in a way that trace components embedded in methamphetamine peak were successfully resolved. Comprehensive analysis of the chromatogram, using multivariate curve resolution, resulted in elution profiles and mass spectra for each pure compound. Impurities such as benzaldehyde, benzyl alcohol, benzene, propenyl methyl ketone, benzyl methyl ketone, amphetamine, N-benzyl-2-methylaziridine, phenethylamine, N,N,α-trimethylamine, phenethylamine, N,α,α-trimethylmethamphetamine, N-acetylmethamphetamine, N-formylmethamphetamine, and other chemicals were identified. A route-specific impurity, N-benzyl-2-methylaziridine, indicating a synthesis route based on ephedrine/pseudoephedrine was identified. Moreover, this is the first report on the detection of impurities such as phenethylamine, N,α,α-trimethylamine (a structurally related impurity), and clonitazene (as an adulterant) in an illicit methamphetamine sample. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative structure-retention relationships for gas chromatographic retention indices of alkylbenzenes with molecular graph descriptors.

PubMed

Ivanciuc, O; Ivanciuc, T; Klein, D J; Seitz, W A; Balaban, A T

2001-02-01

Quantitative structure-retention relationships (QSRR) represent statistical models that quantify the connection between the molecular structure and the chromatographic retention indices of organic compounds, allowing the prediction of retention indices of novel, not yet synthesized compounds, solely from their structural descriptors. Using multiple linear regression, QSRR models for the gas chromatographic Kováts retention indices of 129 alkylbenzenes are generated using molecular graph descriptors. The correlational ability of structural descriptors computed from 10 molecular matrices is investigated, showing that the novel reciprocal matrices give numerical indices with improved correlational ability. A QSRR equation with 5 graph descriptors gives the best calibration and prediction results, demonstrating the usefulness of the molecular graph descriptors in modeling chromatographic retention parameters. The sequential orthogonalization of descriptors suggests simpler QSRR models by eliminating redundant structural information.

Electrokinetically driven microfluidic mixing with patchwise surface heterogeneity and AC applied electric field

NASA Astrophysics Data System (ADS)

Luo, Win-Jet; Yue, Cheng-Feng

2004-12-01

This paper investigates two-dimensional, time-dependent electroosmotic flows driven by an AC electric field via patchwise surface heterogeneities distributed along the microchannel walls. The time-dependent flow fields through the microchannel are simulated for various patchwise heterogeneous surface patterns using the backwards-Euler time stepping numerical method. Different heterogeneous surface patterns are found to create significantly different electrokinetic transport phenomena. It is shown that the presence of oppositely charged surface heterogeneities on the microchannel walls results in the formation of localized flow circulations within the bulk flow. These circulation regions grow and decay periodically in accordance with the applied periodic AC electric field intensity. The circulations provide an effective means of enhancing species mixing in the microchannel. A suitable design of the patchwise heterogeneous surface pattern permits the mixing channel length and the retention time required to attain a homogeneous solution to be reduced significantly.

Measurement of water absorption capacity in wheat flour by a headspace gas chromatographic technique.

PubMed

Xie, Wei-Qi; Yu, Kong-Xian; Gong, Yi-Xian

2018-04-17

The purpose of this work is to introduce a new method for quantitatively analyzing water absorption capacity in wheat flour by a headspace gas chromatographic technique. This headspace gas chromatographic technique was based on measuring the water vapor released from a series of wheat flour samples with different contents of water addition. According to the different trends between the vapor and wheat flour phase before and after the water absorption capacity in wheat flour, a turning point (corresponding to water absorption capacity in wheat flour) can be obtained by fitting the data of the water gas chromatography peak area from different wheat flour samples. The data showed that the phase equilibrium in the vial can be achieved in 25 min at desired temperature (35°C). The relative standard deviation of the reaction headspace gas chromatographic technique in water absorption capacity determination was within 3.48%, the relative differences has been determined by comparing the water absorption capacity obtained from this new analytical technique with the data from the reference technique (i.e., the filtration method), which are less than 8.92%. The new headspace gas chromatographic method is automated, accurate and be a reliable tool for quantifying water absorption capacity in wheat flour in both laboratory research and mill applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integration of gas chromatographs into the Federal Highway Administration/Environmental Protection Agency near road MSAT study in Las Vegas, NV

EPA Science Inventory

This paper documents the technical evaluation of a semi-continuous gas chromatograph (GC) for the measurement of benzene and 1,33butadiene in the near road environment. This paper will also consider the some of the non-technical implications associated with the operation of a GC ...

Gas chromatographic analysis of simmondsins and simmondsin ferulates in jojoba meal.

PubMed

Van Boven, M; Holser, R; Cokelaere, M; Flo, G; Decuypere, E

2000-09-01

A capillary gas chromatographic method was developed for the simultaneous determination of simmondsins and simmondsin ferulates in jojoba meal, in detoxified jojoba meal, in jojoba meal extracts, and in animal food mixtures.

Determinations of gas-liquid partition coefficients using capillary chromatographic columns. Alkanols in squalane.

PubMed

Tascon, Marcos; Romero, Lílian M; Acquaviva, Agustín; Keunchkarian, Sonia; Castells, Cecilia

2013-06-14

This study focused on an investigation into the experimental quantities inherent in the determination of partition coefficients from gas-liquid chromatographic measurements through the use of capillary columns. We prepared several squalane - (2,6,10,15,19,23-hexamethyltetracosane) - containing columns with very precisely known phase ratios and determined solute retention and hold-up times at 30, 40, 50 and 60°C. We calculated infinite dilution partition coefficients from the slopes of the linear regression of retention factors as a function of the reciprocal of the phase ratio by means of fundamental chromatographic equations. In order to minimize gas-solid and liquid-solid interface contributions to retention, the surface of the capillary inner wall was pretreated to guarantee a uniform coat of stationary phase. The validity of the proposed approach was first tested by estimating the partition coefficients of n-alkanes between n-pentane and n-nonane, for which compounds data from the literature were available. Then partition coefficients of sixteen aliphatic alcohols in squalane were determined at those four temperatures. We deliberately chose these highly challenging systems: alcohols in the reference paraffinic stationary phase. These solutes exhibited adsorption in the gas-liquid interface that contributed to retention. The corresponding adsorption constant values were estimated. We fully discuss here the uncertainties associated with each experimental measurement and how these fundamental determinations can be performed precisely by circumventing the main drawbacks. The proposed strategy is reliable and much simpler than the classical chromatographic method employing packed columns. Copyright © 2013 Elsevier B.V. All rights reserved.

Enhanced binding by dextran-grafting to Protein A affinity chromatographic media.

PubMed

Zhao, Lan; Zhu, Kai; Huang, Yongdong; Li, Qiang; Li, Xiunan; Zhang, Rongyue; Su, Zhiguo; Wang, Qibao; Ma, Guanghui

2017-04-01

Dextran-grafted Protein A affinity chromatographic medium was prepared by grafting dextran to agarose-based matrix, followed by epoxy-activation and Protein A coupling site-directed to sulfhydryl groups of cysteine molecules. An enhancement of both the binding performance and the stability was achieved for this dextran-grafted Protein A chromatographic medium. Its dynamic binding capacity was 61 mg immunoglobulin G/mL suction-dried gel, increased by 24% compared with that of the non-grafted medium. The binding capacity of dextran-grafted medium decreased about 7% after 40 cleaning-in-place cycles, much lower than that of the non-grafted medium as decreased about 15%. Confocal laser scanning microscopy results showed that immunoglobulin G was bound to both the outside and the inside of dextran-grafted medium faster than that of non-grafted one. Atomic force microscopy showed that this dextran-grafted Protein A medium had much rougher surface with a vertical coordinate range of ±80 nm, while that of non-grafted one was ±10 nm. Grafted dextran provided a more stereo surface morphology and immunoglobulin G molecules were more easily to be bound. This high-performance dextran-grafted Protein A affinity chromatographic medium has promising applications in large-scale antibody purification. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liquid chromatographic method for the simultaneous determination of cefalexin and trimethoprim in dog plasma and application to the pharmacokinetic studies of a coformulated preparation.

PubMed

Qi, Meiling; Wang, Peng; Sun, Ping; Liu, Xia

2006-03-07

A liquid chromatographic method is described for the simultaneous determination of cefalexin and trimethoprim in dog plasma. A simple protein precipitation procedure was adopted for the sample preparation with satisfactory extraction recoveries for both analytes. Chromatographic separation of the analytes was achieved on a C(18) column using a mixture of 2 mol/l formate buffer (pH 3.5), methanol and acetonitrile (22:7:7, v/v/v) containing a 0.002 mol/l sodium dodecyl sulfate as mobile phase and detection was performed at 240 nm. The linearity was obtained over the concentration ranges of 1.0-100.0 microg/ml for cefalexin and 0.5-50.0 microg/ml for trimethoprim. For each level of QC samples including the lower limit of quantification, both inter- and intra-day precisions (R.S.D.) were < or =14.0% for cefalexin and < or =11.4% for trimethoprim, and accuracy (RE) was -1.4% for cefalexin and -3.0% for trimethoprim. The present LC method was successfully applied to the pharmacokinetic studies of coformulated cefalexin dispersible tablets after oral administration to beagle dogs.

Chromatographic fingerprinting: An innovative approach for food 'identitation' and food authentication - A tutorial.

PubMed

Cuadros-Rodríguez, Luis; Ruiz-Samblás, Cristina; Valverde-Som, Lucia; Pérez-Castaño, Estefanía; González-Casado, Antonio

2016-02-25

Fingerprinting methods describe a variety of analytical methods that provide analytical signals related to the composition of foodstuffs in a non-selective way such as by collecting a spectrum or a chromatogram. Mathematical processing of the information in such fingerprints may allow the characterisation and/or authentication of foodstuffs. In this context, the particular meaning of 'fingerprinting', in conjunction with 'profiling', is different from the original meanings used in metabolomics. This fact has produced some confusion with the use of these terms in analytical papers. Researchers coming from the metabolomic field could use 'profiling' or 'fingerprinting' on a different way to researchers who are devoted to food science. The arrival of an eclectic discipline, named 'foodomics' has not been enough to allay this terminological problem, since the authors keep on using the terms with both meanings. Thus, a first goal of this tutorial is to clarify the difference between both terms. In addition, the chemical approaches for food authentication, i.e., chemical markers, component profiling and instrumental fingerprinting, have been described. A new term, designated as 'food identitation', has been introduced in order to complete the life cycle of the chemical-based food authentication process. Chromatographic fingerprinting has been explained in detail and some strategies which could be applied has been clarified and discussed. Particularly, the strategies for chromatographic signals acquisition and chromatographic data handling are unified in a single framework. Finally, an overview about the applications of chromatographic (GC and LC) fingerprints in food authentication using different chemometric techniques has been included. Copyright © 2016 Elsevier B.V. All rights reserved.

How Much Can We Learn from a Single Chromatographic Experiment? A Bayesian Perspective.

PubMed

Wiczling, Paweł; Kaliszan, Roman

2016-01-05

In this work, we proposed and investigated a Bayesian inference procedure to find the desired chromatographic conditions based on known analyte properties (lipophilicity, pKa, and polar surface area) using one preliminary experiment. A previously developed nonlinear mixed effect model was used to specify the prior information about a new analyte with known physicochemical properties. Further, the prior (no preliminary data) and posterior predictive distribution (prior + one experiment) were determined sequentially to search towards the desired separation. The following isocratic high-performance reversed-phase liquid chromatographic conditions were sought: (1) retention time of a single analyte within the range of 4-6 min and (2) baseline separation of two analytes with retention times within the range of 4-10 min. The empirical posterior Bayesian distribution of parameters was estimated using the "slice sampling" Markov Chain Monte Carlo (MCMC) algorithm implemented in Matlab. The simulations with artificial analytes and experimental data of ketoprofen and papaverine were used to test the proposed methodology. The simulation experiment showed that for a single and two randomly selected analytes, there is 97% and 74% probability of obtaining a successful chromatogram using none or one preliminary experiment. The desired separation for ketoprofen and papaverine was established based on a single experiment. It was confirmed that the search for a desired separation rarely requires a large number of chromatographic analyses at least for a simple optimization problem. The proposed Bayesian-based optimization scheme is a powerful method of finding a desired chromatographic separation based on a small number of preliminary experiments.

Analysis of different beta-lactams antibiotics in pharmaceutical preparations using micellar electrokinetic capillary chromatography.

PubMed

Pérez, M I Bailón; Rodríguez, L Cuadros; Cruces-Blanco, C

2007-01-17

The potential of micellar electrokinetic capillary chromatography (MEKC) for analyzing nine beta-lactams antibiotics (cloxacillin, dicloxacillin, oxacillin, penicillin G, penicillin V, ampicillin, nafcillin, piperacillin, amoxicillin) in different pharmaceutical preparations, have been demonstrated. An experimental design strategy has been applied to optimize the main variables: pH and buffer concentration, concentration of the micellar medium, separation voltage and capillary temperature. Borate buffer (26mM) at pH 8.5 containing 100mM sodium dodecyl sulphate (SDS) was used as the background electrolyte. The method was validated. Linearity, limit of detection and quantitation and precision were established for each compound. The analysis of some of the beta-lactams in Orbenin capsules, Britapen tables and in Veterin-Micipen injectable, all used in human and veterinary medicine, have demonstrated the applicability of these technique for quality control in the pharmaceutical industry.

High-pressure liquid chromatographic gradient mixer

DOEpatents

Daughton, C.G.; Sakaji, R.H.

1982-09-08

A gradient mixer effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum band-broadening.

Gas Chromatographic Separation of an Acetylene Vinyl Fluoride-Difluoroethane Mixture on Triethylene Glycol and Silicone Oil,

DTIC Science & Technology

The purpose of the research was to study gas-chromatographic separation of impurities of acetylene and difluoroethane in vinyl fluoride obtained by...and difluoroethane . All the components are separated, and the criteria of separation of acetylene-vinyl fluoride and vinyl fluoride- difluoroethane

Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

NASA Astrophysics Data System (ADS)

Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

2015-06-01

Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas

PubMed Central

Zaidi, Nayyer Abbas; Tahir, Muhammad Waseem; Vellekoop, Michael J.; Lang, Walter

2017-01-01

Ethylene gas is a naturally occurring gas that has an influence on the shelf life of fruit during their transportation in cargo ships. An unintentional exposure of ethylene gas during transportation results in a loss of fruit. A gas chromatographic system is presented here for the detection of ethylene gas. The gas chromatographic system was assembled using a preconcentrator, a printed 3D printed gas chromatographic column, a humidity sensor, solenoid valves, and an electrochemical ethylene gas sensor. Ambient air was used as a carrier gas in the gas chromatographic system. The flow rate was fixed to 10 sccm. It was generated through a mini-pump connected in series with a mass flow controller. The metal oxide gas sensor is discussed with its limitation in ambient air. The results show the chromatogram obtained from metal oxide gas sensor has low stability, drifts, and has uncertain peaks, while the chromatogram from the electrochemical sensor is stable and precise. Furthermore, ethylene gas measurements at higher ppb concentration and at lower ppb concentration were demonstrated with the electrochemical ethylene gas sensor. The system separates ethylene gas and humidity. The chromatograms obtained from the system are stable, and the results are 1.2% repeatable in five similar measurements. The statistical calculation of the gas chromatographic system shows that a concentration of 2.3 ppb of ethylene gas can be detected through this system. PMID:28991173

A Gas Chromatographic System for the Detection of Ethylene Gas Using Ambient Air as a Carrier Gas.

PubMed

Zaidi, Nayyer Abbas; Tahir, Muhammad Waseem; Vellekoop, Michael J; Lang, Walter

2017-10-07

Ethylene gas is a naturally occurring gas that has an influence on the shelf life of fruit during their transportation in cargo ships. An unintentional exposure of ethylene gas during transportation results in a loss of fruit. A gas chromatographic system is presented here for the detection of ethylene gas. The gas chromatographic system was assembled using a preconcentrator, a printed 3D printed gas chromatographic column, a humidity sensor, solenoid valves, and an electrochemical ethylene gas sensor. Ambient air was used as a carrier gas in the gas chromatographic system. The flow rate was fixed to 10 sccm. It was generated through a mini-pump connected in series with a mass flow controller. The metal oxide gas sensor is discussed with its limitation in ambient air. The results show the chromatogram obtained from metal oxide gas sensor has low stability, drifts, and has uncertain peaks, while the chromatogram from the electrochemical sensor is stable and precise. Furthermore, ethylene gas measurements at higher ppb concentration and at lower ppb concentration were demonstrated with the electrochemical ethylene gas sensor. The system separates ethylene gas and humidity. The chromatograms obtained from the system are stable, and the results are 1.2% repeatable in five similar measurements. The statistical calculation of the gas chromatographic system shows that a concentration of 2.3 ppb of ethylene gas can be detected through this system.

Oxygen carrier for gas chromatographic analysis of inert gases in propellants

NASA Technical Reports Server (NTRS)

Cannon, W. A.

1972-01-01

Gas chromatographic determination of small quantities of inert gases in reactive propellants is discussed. Operating conditions used for specific analyses of helium in diborane and nitrogen in oxygen difluoride are presented in tabular form.

Shell structure of natural rubber particles: evidence of chemical stratification by electrokinetics and cryo-TEM.

PubMed

Rochette, Christophe N; Crassous, Jérôme J; Drechsler, Markus; Gaboriaud, Fabien; Eloy, Marie; de Gaudemaris, Benoît; Duval, Jérôme F L

2013-11-26

The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (μ) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a ∼2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of μ on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged ∼3.5 nm thick layer (mean dissociation pK ∼ 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK ∼ 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid-protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.

Clinical applications of gas chromatograph/mass spectrometer/computer systems.

PubMed

Horning, M G; Nowlin, J; Butler, C M; Lertratanangkoon, K; Sommer, K; Hill, R M

1975-08-01

Gas chromatograph/mass spectrometer/computer systems can be used to quantify a wide variety of compounds of clinical interest. A quadrupole instrument operated in the chemical ionization (Cl) mode was used in these studies. Because of the sensitivity and specificity of selective ion detection, it is possible to make measurements routinely in the nanogram to picogram range, with 0.1-1.0 ml samples of plasma and 1-5 ml samples or urine. Internal standards, preferably stable-isotope-labeled compounds, were added to the biological samples before isolation was begun. We describe clinical applications of these procedures to problems in toxicology, pharmacokinetics, and perinatal pharmacology.

Dynamic technique for measuring adsorption in a gas chromatograph

NASA Technical Reports Server (NTRS)

Deuel, C. L.; Hultgren, N. W.; Mobert, M. L.

1973-01-01

Gas-chromatographic procedure, together with mathematical analysis of adsorption isotherm, allows relative surface areas and adsorptive powers for trace concentrations to be determined in a few minutes. Technique may be used to evaluate relative surface areas of different adsorbates, expressed as volume of adsorbent/gram of adsorbate, and to evaluate their relative adsorptive power.

Gas-liquid chromatographic determination of resmethrin in corn, cornmeal, flour, and wheat.

PubMed

Simonaitis, R A; Cail, R S

1975-09-01

A gas-liquid chromatographic (GLC) method was developed for the determination of residues of resmethrin ((5-benzyl-3-furyl)methyl cis-trans-(+/-)-2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylate) in corn, cornmeal, flour, and wheat. The commodity, fortified with resmethrin, was extracted by tumbling with pentane and transferred to acetonitrile, the fat was partitioned off, and the sample was chromatographed with 3% ethyl acetate in pentane on Florisil containing 0.5% water. The resmethrin residue was determined by GLC with a flame ionization detector. The results were compared with known standards that had undergone the same cleanup procedures. The method was sensitive to concentrations of resmethrin to 0.2 ppm, recoveries averaged 83%, and reproducibility was good.

Virus elimination during the recycling of chromatographic columns used during the manufacture of coagulation factors.

PubMed

Roberts, Peter L

2014-07-01

Various chromatographic procedures are used during the purification and manufacture of plasma products such as coagulation factors. These steps contribute to the overall safety of such products by removing potential virus contamination. Virus removal by two affinity chromatography procedures, i.e. monoclonal antibody chromatography and metal chelate chromatography (immobilised metal ion affinity chromatography), used during the manufacture of the high purity factor VIII (Replenate®) and factor IX (Replenine®-VF), respectively, has been investigated. In addition, as these columns are recycled after use, the effectiveness of the sanitisation procedures for preventing possible cross-contamination, has also been investigated. Both chromatographic steps proved effective for eliminating a range of model enveloped and non-enveloped viruses by 4 to >6 and 5 to >8 log for the monoclonal and metal chelate columns, respectively. The effectiveness of the relatively mild column sanitisation conditions used, i.e. ethanol for factor IX and acetic acid for factor VIII, was confirmed using non-spiked column runs. The chemicals used contributed to virus elimination by inactivation and/or by physical removal of the virus. In summary, these studies demonstrate that potential virus contamination between chromatographic runs can be prevented when an effective column recycling and sanitisation procedure is included. Copyright © 2014 The International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved.

Development of Self-Potential Tomography for Early Warning System of rainfall induced Landslides: Electro-kinetic Effects and Sandbox Experiments

NASA Astrophysics Data System (ADS)

Hattori, K.; Yamazaki, T.; Terajima, T.; Huang, Q.

2017-12-01

Electro-kinetic effects is one of the possible mechanism for ULF electromagnetic phenomena preceeding landlisdes and large earthquakes. To understand general tendencies of electromagnetic changes related to electro-kinetic effects, we struggle with the integrated research to clarify the coupling among hydrological, geotechnical, and electromagnetic changes. Our final goal is to understand the ULF elecromagnetic phenomena in order to develop a simple technology for earthquake monitoring/forecasting. So, in this paper, we first show the observed waveforms possibly related to the Boso slow slip events in 2003 and 2007 and indoor landslide experiments with artificial rainfall. Then, numerical computations on the self-potential variation by the simulated groundwater flow, and compare the results with those observed by laboratory experiments. In the result, the simulated self-potential variation is consistent with observed one. FInally, we developed self-potential tomography to estimate the ground water condition. And we also characterize the pressure from the self-potential data, and compare the result with observed pressure head that is measured by pore-pressure gauge and found that the inverted pressure head is consistent with observed one. In addition, we apply the self-potential data observed by the flume test. The estimated pressure head from observed self-potential data shows the consistency with observed pressure head. And estimated pressure head also show the characteristic distribution before the landslide occurred. These facts are highly suggestive in effectiveness of the self-potential tomography to monitor groundwater changes associated with landslide. The details will be given in our presentation.

Electrokinetic flow in a capillary with a charge-regulating surface polymer layer.

PubMed

Keh, Huan J; Ding, Jau M

2003-07-15

An analytical study of the steady electrokinetic flow in a long uniform capillary tube or slit is presented. The inside wall of the capillary is covered by a layer of adsorbed or covalently bound charge-regulating polymer in equilibrium with the ambient electrolyte solution. In this solvent-permeable and ion-penetrable surface polyelectrolyte layer, ionogenic functional groups and frictional segments are assumed to distribute at uniform densities. The electrical potential and space charge density distributions in the cross section of the capillary are obtained by solving the linearized Poisson-Boltzmann equation. The fluid velocity profile due to the application of an electric field and a pressure gradient through the capillary is obtained from the analytical solution of a modified Navier-Stokes/Brinkman equation. Explicit formulas for the electroosmotic velocity, the average fluid velocity and electric current density on the cross section, and the streaming potential in the capillary are also derived. The results demonstrate that the direction of the electroosmotic flow and the magnitudes of the fluid velocity and electric current density are dominated by the fixed charge density inside the surface polymer layer, which is determined by the regulation characteristics such as the dissociation equilibrium constants of the ionogenic functional groups in the surface layer and the concentration of the potential-determining ions in the bulk solution.

Enhanced electrokinetic properties and antimicrobial activities of biodegradable chitosan/organo-bentonite composites.

PubMed

Cabuk, Mehmet; Alan, Yusuf; Unal, H Ibrahim

2017-04-01

In this study, chitosan (CS), Na + -bentonite (Na + -BNT) and chitosan/organo-bentonite (CS/O-BNT) biodegradable composites having three different compositions were investigated. Electrokinetic measurements were examined in aqueous medium by taking the effects pH, electrolytes (NaCl and BaCl 2 ), surfactants (CTAB and SDS), and temperature into account. It was noticed that the initial ζ-potential of Na + -BNT shifted from negative (ζ=-35mV) to positive region (ζ=+13mV) with increasing polycationic CS content in the composite structure as aimed. Divalent 2:1 electrolyte (BaCl 2 ) caused to shift the ζ-potentials of all the dispersions to more positive regions. While the most negative effect on ζ-potential of the composites was reached with SDS, which reduced the value of ζ-potential to -39mV for CS(1)/O-BNT composite, the most positive effect was monitored with CTAB (ζ=+40mV) for CS(3)/O-BNT composite. Further, the composites were tested against various bacterial (Gram-positive and Gram-negative) and fungal microorganisms at various concentrations and results obtained were compared with the reference antibiotics and fungicide. According to inhibition zone values accomplished, antibacterial and antifungal activities of the CS/O-BNT composites are increased with increasing CS content as proportional with their positive ζ-potential values. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of urea induced protein conformational changes on ion exchange chromatographic behavior.

PubMed

Hou, Ying; Hansen, Thomas B; Staby, Arne; Cramer, Steven M

2010-11-19

Urea is widely employed to facilitate protein separations in ion exchange chromatography at various scales. In this work, five model proteins were used to examine the chromatographic effects of protein conformational changes induced by urea in ion exchange chromatography. Linear gradient experiments were carried out at various urea concentrations and the protein secondary and tertiary structures were evaluated by far UV CD and fluorescence measurements, respectively. The results indicated that chromatographic retention times were well correlated with structural changes and that they were more sensitive to tertiary structural change. Steric Mass Action (SMA) isotherm parameters were also examined and the results indicated that urea induced protein conformational changes could affect both the characteristic charge and equilibrium constants in these systems. Dynamic light scattering analysis of changes in protein size due to urea-induced unfolding indicated that the size of the protein was not correlated with SMA parameter changes. These results indicate that while urea-induced structural changes can have a marked effect on protein chromatographic behavior in IEX, this behavior can be quite complicated and protein specific. These differences in protein behavior may provide insight into how these partially unfolded proteins are interacting with the resin material. Copyright © 2010 Elsevier B.V. All rights reserved.

Storing of Extracts in Polypropylene Microcentrifuge Tubes Yields Contaminant Peak During Ultra-flow Liquid Chromatographic Analysis.

PubMed

Kshirsagar, Parthraj R; Hegde, Harsha; Pai, Sandeep R

2016-05-01

This study was designed to understand the effect of storage in polypropylene microcentrifuge tubes and glass vials during ultra-flow liquid chromatographic (UFLC) analysis. One ml of methanol was placed in polypropylene microcentrifuge tubes (PP material, Autoclavable) and glass vials (Borosilicate) separately for 1, 2, 4, 8, 10, 20, 40, and 80 days intervals stored at -4°C. Contaminant peak was detected in methanol stored in polypropylene microcentrifuge tubes using UFLC analysis. The contaminant peak detected was prominent, sharp detectable at 9.176 ± 0.138 min on a Waters 250-4.6 mm, 4 μ, Nova-Pak C18 column with mobile phase consisting of methanol:water (70:30). It was evident from the study that long-term storage of biological samples prepared using methanol in polypropylene microcentrifuge tubes produce contaminant peak. Further, this may mislead in future reporting an unnatural compound by researchers. Long-term storage of biological samples prepared using methanol in polypropylene microcentrifuge tubes produce contaminant peakContamination peak with higher area under the curve (609993) was obtained in ultra-flow liquid chromatographic run for methanol stored in PP microcentrifuge tubesContamination peak was detected at retention time 9.113 min with a lambda max of 220.38 nm and 300 mAU intensity on the given chromatographic conditionsGlass vials serve better option over PP microcentrifuge tubes for storing biological samples. Abbreviations used: UFLC: Ultra Flow Liquid Chromatography; LC: Liquid Chromatography; MS: Mass spectrometry; AUC: Area Under Curve.

Using nonlinear ac electrokinetics vortex flow to enhance catalytic activities of sol-gel encapsulated trypsin in microfluidic devices

PubMed Central

Wang, Shau-Chun; Chen, Hsiao-Ping; Lai, Yi-Wen; Chau, Lai-Kwan; Chuang, Yu-Chun; Chen, Yi-Jie

2007-01-01

A novel microstirring strategy is applied to accelerate the digestion rate of the substrate Nα-benzoyl-L-arginine-4-nitroanilide (L-BAPA) catalyzed by sol-gel encapsulated trypsin. We use an ac nonlinear electrokinetic vortex flow to stir the solution in a microfluidic reaction chamber to reduce the diffusion length between the immobilized enzyme and substrate in the solution. High-intensity nonlinear electroosmotic microvortices, with angular speeds in excess of 1 cm∕s, are generated around a small (∼1.2 mm) conductive ion exchange granule when ac electric fields (133 V∕cm) are applied across a miniature chamber smaller than 10 μl. Coupling between these microvortices and the on-and-off electrophoretic motion of the granule in low frequency (0.1 Hz) ac fields produces chaotic stream lines to stir substrate molecules sufficiently. We demonstrate that, within a 5-min digestion period, the catalytic reaction rate of immobilized trypsin increases almost 30-fold with adequate reproducibility (15%) due to sufficient stirring action through the introduction of the nonlinear electrokinetic vortices. In contrast, low-frequency ac electroosmotic flow without the granule, provides limited stirring action and increases the reaction rate approximately ninefold with barely acceptable reproducibility (30%). Dye molecules are used to characterize the increases in solute diffusivity in the reaction reservoir in which sol-gel particles are placed, with and without the presence of granule, and compared with the static case. The solute diffusivity enhancement data show respective increases of ∼30 and ∼8 times, with and without the presence of granule. These numbers are consistent with the ratios of the enhanced reaction rate. PMID:19693360

Using nonlinear ac electrokinetics vortex flow to enhance catalytic activities of sol-gel encapsulated trypsin in microfluidic devices.

PubMed

Wang, Shau-Chun; Chen, Hsiao-Ping; Lai, Yi-Wen; Chau, Lai-Kwan; Chuang, Yu-Chun; Chen, Yi-Jie

2007-09-04

A novel microstirring strategy is applied to accelerate the digestion rate of the substrate N(alpha)-benzoyl-L-arginine-4-nitroanilide (L-BAPA) catalyzed by sol-gel encapsulated trypsin. We use an ac nonlinear electrokinetic vortex flow to stir the solution in a microfluidic reaction chamber to reduce the diffusion length between the immobilized enzyme and substrate in the solution. High-intensity nonlinear electroosmotic microvortices, with angular speeds in excess of 1 cms, are generated around a small ( approximately 1.2 mm) conductive ion exchange granule when ac electric fields (133 Vcm) are applied across a miniature chamber smaller than 10 mul. Coupling between these microvortices and the on-and-off electrophoretic motion of the granule in low frequency (0.1 Hz) ac fields produces chaotic stream lines to stir substrate molecules sufficiently. We demonstrate that, within a 5-min digestion period, the catalytic reaction rate of immobilized trypsin increases almost 30-fold with adequate reproducibility (15%) due to sufficient stirring action through the introduction of the nonlinear electrokinetic vortices. In contrast, low-frequency ac electroosmotic flow without the granule, provides limited stirring action and increases the reaction rate approximately ninefold with barely acceptable reproducibility (30%). Dye molecules are used to characterize the increases in solute diffusivity in the reaction reservoir in which sol-gel particles are placed, with and without the presence of granule, and compared with the static case. The solute diffusivity enhancement data show respective increases of approximately 30 and approximately 8 times, with and without the presence of granule. These numbers are consistent with the ratios of the enhanced reaction rate.

Integration of Multiplexed Microfluidic Electrokinetic Concentrators with a Morpholino Microarray via Reversible Surface Bonding for Enhanced DNA Hybridization.

PubMed

Martins, Diogo; Wei, Xi; Levicky, Rastislav; Song, Yong-Ak

2016-04-05

We describe a microfluidic concentration device to accelerate the surface hybridization reaction between DNA and morpholinos (MOs) for enhanced detection. The microfluidic concentrator comprises a single polydimethylsiloxane (PDMS) microchannel onto which an ion-selective layer of conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) ( PSS) was directly printed and then reversibly surface bonded onto a morpholino microarray for hybridization. Using this electrokinetic trapping concentrator, we could achieve a maximum concentration factor of ∼800 for DNA and a limit of detection of 10 nM within 15 min. In terms of the detection speed, it enabled faster hybridization by around 10-fold when compared to conventional diffusion-based hybridization. A significant advantage of our approach is that the fabrication of the microfluidic concentrator is completely decoupled from the microarray; by eliminating the need to deposit an ion-selective layer on the microarray surface prior to device integration, interfacing between both modules, the PDMS chip for electrokinetic concentration and the substrate for DNA sensing are easier and applicable to any microarray platform. Furthermore, this fabrication strategy facilitates a multiplexing of concentrators. We have demonstrated the proof-of-concept for multiplexing by building a device with 5 parallel concentrators connected to a single inlet/outlet and applying it to parallel concentration and hybridization. Such device yielded similar concentration and hybridization efficiency compared to that of a single-channel device without adding any complexity to the fabrication and setup. These results demonstrate that our concentrator concept can be applied to the development of a highly multiplexed concentrator-enhanced microarray detection system for either genetic analysis or other diagnostic assays.

Electrokinetic gated injection-based microfluidic system for quantitative analysis of hydrogen peroxide in individual HepG2 cells.

PubMed

Zhang, Xinyuan; Li, Qingling; Chen, Zhenzhen; Li, Hongmin; Xu, Kehua; Zhang, Lisheng; Tang, Bo

2011-03-21

A microfluidic system to determine hydrogen peroxide (H(2)O(2)) in individual HepG2 cells based on the electrokinetic gated injection was developed for the first time. A home-synthesized fluorescent probe, bis(p-methylbenzenesulfonate)dichlorofluorescein (FS), was employed to label intracellular H(2)O(2) in the intact cells. On a simple cross microchip, multiple single-cell operations, including single cell injection, cytolysis, electrophoresis separation and detection of H(2)O(2), were automatically carried out within 60 s using the electrokinetic gated injection and laser-induced fluorescence detection (LIFD). The performance of the method was evaluated under the optimal conditions. The linear calibration curve was over a range of 4.39-610 amol (R(2)=0.9994). The detection limit was 0.55 amol or 9.0×10(-10) M (S/N=3). The relative standard deviations (RSDs, n=6) of migration time and peak area were 1.4% and 4.8%, respectively. With the use of this method, the average content of H(2)O(2) in single HepG2 cells was found to be 16.09±9.84 amol (n=15). Separation efficiencies in excess of 17,000 theoretical plates for the cells were achieved. These results demonstrated that the efficient integration and automation of these single-cell operations enabled the sensitive, reproducible, and quantitative examination of intracellular H(2)O(2) at single-cell level. Owing to the advantages of simple microchip structure, controllable single-cell manipulation and ease in building, this platform provides a universal way to automatically determine other intracellular constituents within single cells. This journal is © The Royal Society of Chemistry 2011

Chromatographic fingerprinting through chemometric techniques for herbal slimming pills: A way of adulterant identification.

PubMed

Shekari, Nafiseh; Vosough, Maryam; Tabar Heidar, Kourosh

2018-05-01

In the current study, gas chromatography-mass spectrometry (GC-MS) fingerprinting of herbal slimming pills assisted by chemometric methods has been presented. Deconvolution of two-way chromatographic signals of nine herbal slimming pills into pure chromatographic and spectral patterns was performed. The peak clusters were resolved using multivariate curve resolution-alternating least squares (MCR-ALS) by employing appropriate constraints. It was revealed that more useful chemical information about the composition of the slimming pills can be obtained by employing sophisticated GC-MS method coupled with proper chemometric tools yielding the extended number of identified constituents. The thorough fingerprinting of the complex mixtures proved the presence of some toxic or carcinogen components, such as toluene, furfural, furfuryl alcohol, styrene, itaconic anhydride, citraconic anhydride, trimethyl phosphate, phenol, pyrocatechol, p-propenylanisole and pyrogallol. In addition, some samples were shown to be adulterated with undeclared ingredients, including stimulants, anorexiant and laxatives such as phenolphthalein, amfepramone, caffeine and sibutramine. Copyright © 2018 Elsevier B.V. All rights reserved.

Chromatographic fingerprint analysis of yohimbe bark and related dietary supplements using UHPLC/UV/MS.

PubMed

Sun, Jianghao; Chen, Pei

2012-03-05

A practical ultra high-performance liquid chromatography (UHPLC) method was developed for fingerprint analysis of and determination of yohimbine in yohimbe barks and related dietary supplements. Good separation was achieved using a Waters Acquity BEH C(18) column with gradient elution using 0.1% (v/v) aqueous ammonium hydroxide and 0.1% ammonium hydroxide in methanol as the mobile phases. The study is the first reported chromatographic method that separates corynanthine from yohimbine in yohimbe bark extract. The chromatographic fingerprint analysis was applied to the analysis of 18 yohimbe commercial dietary supplement samples. Quantitation of yohimbine, the traditional method for analysis of yohimbe barks, were also performed to evaluate the results of the fingerprint analysis. Wide variability was observed in fingerprints and yohimbine content among yohimbe dietary supplement samples. For most of the dietary supplements, the yohimbine content was not consistent with the label claims. Copyright © 2011. Published by Elsevier B.V.

21 CFR 862.2230 - Chromatographic separation material for clinical use.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Chromatographic separation material for clinical use. 862.2230 Section 862.2230 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical...

21 CFR 862.2230 - Chromatographic separation material for clinical use.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Chromatographic separation material for clinical use. 862.2230 Section 862.2230 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical...

21 CFR 862.2230 - Chromatographic separation material for clinical use.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Chromatographic separation material for clinical use. 862.2230 Section 862.2230 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical...

21 CFR 862.2230 - Chromatographic separation material for clinical use.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Chromatographic separation material for clinical use. 862.2230 Section 862.2230 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical...

Role of Bismuth in the Electrokinetics of Silicon Photocathodes for Solar Rechargeable Vanadium Redox Flow Batteries.

PubMed

Flox, Cristina; Murcia-López, Sebastián; Carretero, Nina M; Ros, Carles; Morante, Juan R; Andreu, Teresa

2018-01-10

The ability of crystalline silicon to photoassist the V 3+ /V 2+ cathodic reaction under simulated solar irradiation, combined with the effect of bismuth have led to important electrochemical improvements. Besides the photovoltage supplied by the photovoltaics, additional decrease in the onset potentials, high reversibility of the V 3+ /V 2+ redox pair, and improvement in the electrokinetics were attained thanks to the addition of bismuth. In fact, Bi 0 deposition has shown to slightly decrease the photocurrent, but the significant enhancement in the charge transfer, reflected in the overall electrochemical performance clearly justifies its use as additive in a photoassisted system for maximizing the efficiency of solar charge to battery. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

ION-EXCLUSION CHROMATOGRAPHIC DETERMINATION OF CARBOXYLIC ACIDS USED TO SUPPORT THE MICROBIALLY MEDIATED REDUCTIVE DECHLORINATION OF TETRACHLOROETHENE

EPA Science Inventory

An analytical method was developed for the determination of lactic acid, formic acid, acetic acid, propionic acid, and butyric acid in environmental microcosm samples using ion-exclusion chromatography. The chromatographic behavior of various eluents was studied to determine the ...

A Novel High Performance Liquid Chromatographic Method for Simultaneous Determination of Ceftriaxone and Sulbactam in Sulbactomax

PubMed Central

Shrivastava, Sanjay Mohan; Singh, Rajkumar; Tariq, Abu; Siddiqui, Masoom Raza; Yadav, Jitendar; Negi, P. S.; Chaudhary, Manu

2009-01-01

An isocratic liquid chromatographic method with UV detection at 220 nm is described for simultaneous determination of ceftriaxone sodium and sulbactam sodium in Sulbactomax. Chromatographic separation of two drugs was achieved on a Hypersil ODS C-18 column using a mobile phase consisting of a binary mixture of acetonitrile and tetrabutyl ammonium hydroxide adjusted to pH7.0 with orthophosphoric acid in ratio 70:30. The developed Liquid Chromatographic method offers symmetric peak shape, good resolution and reasonable retention time for both drugs. Linearity, accuracy and precision were found to be acceptable over the concentration range of 125-750 ppm for ceftriaxone sodium and 62.5-375 ppm for sulbactam sodium. The LC method can be used for the quality control of formulated products containing ceftriaxone and sulbactam. PMID:23675112

High-speed peak matching algorithm for retention time alignment of gas chromatographic data for chemometric analysis

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

Johnson, Kevin J.; Wright, Bob W.; Jarman, Kristin H.

2003-05-09

A rapid retention time alignment algorithm was developed as a preprocessing utility to be used prior to chemometric analysis of large datasets of diesel fuel gas chromatographic profiles. Retention time variation from chromatogram-to-chromatogram has been a significant impediment against the use of chemometric techniques in the analysis of chromatographic data due to the inability of current multivariate techniques to correctly model information that shifts from variable to variable within a dataset. The algorithm developed is shown to increase the efficacy of pattern recognition methods applied to a set of diesel fuel chromatograms by retaining chemical selectivity while reducing chromatogram-to-chromatogram retentionmore » time variations and to do so on a time scale that makes analysis of large sets of chromatographic data practical.« less

Review of chemical and electrokinetic remediation of PCBs contaminated soils and sediments.

PubMed

Fan, Guangping; Wang, Yu; Fang, Guodong; Zhu, Xiangdong; Zhou, Dongmei

2016-09-14

Polychlorinated biphenyls (PCBs) are manmade organic compounds, and pollution due to PCBs has been a global environmental problem because of their persistence, long-range atmospheric transport and bioaccumulation. Many physical, chemical and biological technologies have been utilized to remediate PCBs contaminated soils and sediments, and there are some emerging new technologies and combined methods that may provide cost-effective alternatives to the existing remediation practice. This review provides a general overview on the recent developments in chemical treatment and electrokinetic remediation (EK) technologies related to PCBs remediation. In particular, four technologies including photocatalytic degradation of PCBs combined with soil washing, Fe-based reductive dechlorination, advanced oxidation process, and EK/integrated EK technology (e.g., EK coupled with chemical oxidation, nanotechnology and bioremediation) are reviewed in detail. We focus on the fundamental principles and governing factors of chemical technologies, and EK/integrated EK technologies. Comparative analysis of these technologies including their major advantages and disadvantages is summarized. The existing problems and future prospects of these technologies regarding PCBs remediation are further highlighted.

Evaluation of a multiarray system for pharmaceutical analysis by microemulsion electrokinetic chromatography.

PubMed

Lynen, Frederic; Saavedra, Luis; Saveedra, Luis; Nickerson, Beverly; Sandra, Pat

2011-05-15

A multiplexed capillary electrophoresis (CE) system equipped with 96 channels was evaluated for high-throughput screening in drug discovery by microemulsion electrokinetic chromatography (MEEKC). Method transfer from a single channel to a multichannel CE system is described. Loss of efficiency and reduced migration times could be elucidated to the poor efficacy in Joule heat dissipation by forced air cooling in the multiarray system compared to liquid cooling in the single channel instrument. On the other hand, only 48 channels could actually be used because of the maximum total current of 3 mA. Precision data remained below 8% and 9% for migration times and peak areas, respectively. Some UV-detector cross-talk interference between neighboring capillary channels was noted. Impurities at 0.5% compared to the main peak (100%) could be detected with the multiplexed system which is 10 times lower compared to the single capillary system. Higher efficiency and improved figures of merit (absolute sensitivity and no cross-talk interferences) were obtained by using an array of only 24 capillaries. Copyright © 2011 Elsevier B.V. All rights reserved.

Enantioseparation of dopa and related compounds by cyclodextrin-modified microemulsion electrokinetic chromatography.

PubMed

Borst, Claudia; Holzgrabe, Ulrike

2008-09-19

A chiral microemulsion electrokinetic chromatography method has been developed for the enantiomeric separation of 3,4-dihydroxyphenylalanine (dopa), its precursors phenylalanine and tyrosine, and the structurally related substance methyldopa. The separations were achieved using an oil-in-water microemulsion, which consisted of the oil-compound ethyl acetate, the surfactant sodium dodecylsulfate (SDS), the co-surfactant 1-butanol, the organic modifier propan-2-ol and 20mM phosphate buffer pH 2.5 or 2.0 as aqueous phase. For enantioseparation sulfated beta-cyclodextrin was added. The resolution of each racemate was optimized by varying the concentration of the buffer and all components of the microemulsion. Enantioseparation could be achieved for dl-dopa, dl-phenylalanine and dl-tyrosine within 13 min with a resolution of 4.3, 3.1 and 3.3, respectively, and for methyldopa in 17 min (Rs: 1.4). The established methods allowed the detection of dopa, phenylalanine, tyrosine and methyldopa with a limit at 0.5, 1.0, 0.2 and 2.0 microg/ml.

Electrokinetic Analysis of Energy Harvest from Natural Salt Gradients in Nanochannels.

PubMed

He, Yuhui; Huang, Zhuo; Chen, Bowei; Tsutsui, Makusu; Shui Miao, Xiang; Taniguchi, Masateru

2017-10-13

The Gibbs free energy released during the mixing of river and sea water has been illustrated as a promising source of clean and renewable energy. Reverse electrodialysis (RED) is one major strategy to gain electrical power from this natural salinity, and recently by utilizing nanochannels a novel mode of this approach has shown improved power density and energy converting efficiency. In this work, we carry out an electrokinetic analysis of the work extracted from RED in the nanochannels. First, we outline the exclusion potential effect induced by the inhomogeneous distribution of extra-counterions along the channel axis. This effect is unique in nanochannel RED and how to optimize it for energy harvesting is the central topic of this work. We then discuss two important indexes of performance, which are the output power density and the energy converting efficiency, and their dependence on the nanochannel parameters such as channel material and geometry. In order to yield maximized output electrical power, we propose a device design by stepwise usage of the saline bias, and the lengths of the nanochannels are optimized to achieve the best trade-off between the input thermal power and the energy converting efficiency.

Micellar electrokinetic chromatography and capillary electrochromatography of nitroaromatic explosives in seawater.

PubMed

Giordano, Braden C; Copper, Christine L; Collins, Greg E

2006-02-01

The ability to separate nitroaromatic and nitramine explosives in seawater sample matrices is demonstrated using both MEKC and CEC. While several capillary-based separations exist for explosives, none address direct sampling from seawater, a sample matrix of particular interest in the detection of undersea mines. Direct comparisons are made between MEKC and CEC in terms of sensitivity and separation efficiency for the analysis of 14 explosives and explosive degradation products in seawater and diluted seawater. The use of high-salt stacking with MEKC results, on average, in a three-fold increase in the number of theoretical plates, and nearly double resolution for samples prepared in 25% seawater. By taking advantage of long injection times in conjunction with stacking, detection limits down to sub mg/L levels are attainable; however, resolution is sacrificed. CEC of explosive mixtures using sol-gels prepared from methyltrimethoxysilane does not perform as well as MEKC in terms of resolving power, but does permit extended injection times for concentrating analyte onto the head of the separation column with little or no subsequent loss in resolution. Electrokinetic injections of 8 min at high voltage allow for detection limits of explosives below 100 microg/L.

Self-Consistent Approach to Global Charge Neutrality in Electrokinetics: A Surface Potential Trap Model

NASA Astrophysics Data System (ADS)

Wan, Li; Xu, Shixin; Liao, Maijia; Liu, Chun; Sheng, Ping

2014-01-01

In this work, we treat the Poisson-Nernst-Planck (PNP) equations as the basis for a consistent framework of the electrokinetic effects. The static limit of the PNP equations is shown to be the charge-conserving Poisson-Boltzmann (CCPB) equation, with guaranteed charge neutrality within the computational domain. We propose a surface potential trap model that attributes an energy cost to the interfacial charge dissociation. In conjunction with the CCPB, the surface potential trap can cause a surface-specific adsorbed charge layer σ. By defining a chemical potential μ that arises from the charge neutrality constraint, a reformulated CCPB can be reduced to the form of the Poisson-Boltzmann equation, whose prediction of the Debye screening layer profile is in excellent agreement with that of the Poisson-Boltzmann equation when the channel width is much larger than the Debye length. However, important differences emerge when the channel width is small, so the Debye screening layers from the opposite sides of the channel overlap with each other. In particular, the theory automatically yields a variation of σ that is generally known as the "charge regulation" behavior, attendant with predictions of force variation as a function of nanoscale separation between two charged surfaces that are in good agreement with the experiments, with no adjustable or additional parameters. We give a generalized definition of the ζ potential that reflects the strength of the electrokinetic effect; its variations with the concentration of surface-specific and surface-nonspecific salt ions are shown to be in good agreement with the experiments. To delineate the behavior of the electro-osmotic (EO) effect, the coupled PNP and Navier-Stokes equations are solved numerically under an applied electric field tangential to the fluid-solid interface. The EO effect is shown to exhibit an intrinsic time dependence that is noninertial in its origin. Under a step-function applied electric field, a

Biological permeable reactive barriers coupled with electrokinetic soil flushing for the treatment of diesel-polluted clay soil.

PubMed

Mena, Esperanza; Ruiz, Clara; Villaseñor, José; Rodrigo, Manuel A; Cañizares, Pablo

2015-01-01

Removal of diesel from spiked kaolin has been studied in the laboratory using coupled electrokinetic soil flushing (EKSF) and bioremediation through an innovative biological permeable reactive barriers (Bio-PRBs) positioned between electrode wells. The results show that this technology is efficient in the removal of pollutants and allows the soil to maintain the appropriate conditions for microorganism growth in terms of pH, temperature, and nutrients. At the same time, EKSF was demonstrated to be a very interesting technology for transporting pollutants, microorganisms and nutrients, although results indicate that careful management is necessary to avoid the depletion of nutrients, which are effectively transported by electro-migration. After two weeks of operation, 30% of pollutants are removed and energy consumption is under 70 kWh m(-3). Main fluxes (electroosmosis and evaporation) and changes in the most relevant parameters (nutrients, diesel, microorganisms, surfactants, moisture conductivity and pH) during treatment and in a complete post-study analysis are studied to give a comprehensive description of the most relevant processes occurring in the soil (pollutant transport and biodegradation). Copyright © 2014 Elsevier B.V. All rights reserved.

Some high-performance liquid-chromatographic studies of the metabolism of aflatoxins by rat liver microsomal preparations.

PubMed Central

Neal, G E; Colley, P J

1978-01-01

The metabolism of aflatoxin B1 in vitro was examined in rat liver microsomal preparations. 2. H.p.l.c. (high-performance liquid-chromatographic) systems were used. A silica column was used to separate non-polar metabolites. A system utilizing a reversed-phase column which separates both poar and non-polar metabolites was also developed. 3. The principal metabolites of aflatoxin B1 found were aflatoxin M1, aflatoxin Q1 and a compound which co-chromatographed with a degradation product of aflatoxin B1 2,3-dihydrodiol. 4. The time course of metabolism of aflatoxin B1 by microsomal preparations isolated from control and phenobarbitone-pretreated rats was examined. The rate and extent of metabolism was greater with microsomal preparations from the latter. The formation of aflatoxin Q1 was enhanced 4--5-fold by phenobarbitone pretreatment, whereas the production of aflatoxin M1 was only increased 1--2-fold. The formation of the degradation product of aflatoxin B1 2,3-dihydrodiol was increased 4--5-fold by the pretreatment with phenobarbitone. 5. The microsomal metabolism of aflatoxins M1, P1 and Q1 was examined. Aflatoxin M1 apparently underwent very limited microsomal metabolism to more polar compounds. Aflatoxin P1 was not metabolized. The situation with aflatoxin Q1 was complicated in that it was metabolized in the absence of NADPH to an unidentified metabolite. Aflatoxin B1 appeared as a metabolite of aflatoxin Q1 only when NADPH was present, and the formation of more polar metabolites was also then observed. PMID:728090

High pressure liquid chromatographic gradient mixer

DOEpatents

Daughton, Christian G.; Sakaji, Richard H.

1985-01-01

A gradient mixer which effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum "band-broadening".

Interface for liquid chromatograph-mass spectrometer

DOEpatents

Andresen, Brian D.; Fought, Eric R.

1989-01-01

A moving belt interface for real-time, high-performance liquid chromatograph (HPLC)/mass spectrometer (MS) analysis which strips away the HPLC solvent as it emerges from the end of the HPLC column and leaves a residue suitable for mass-spectral analysis. The interface includes a portable, stand-alone apparatus having a plural stage vacuum station, a continuous ribbon or belt, a drive train magnetically coupled to an external drive motor, a calibrated HPLC delivery system, a heated probe tip and means located adjacent the probe tip for direct ionization of the residue on the belt. The interface is also capable of being readily adapted to fit any mass spectrometer.

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.

40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements...

40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements...

40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements...

Core-Shell in Liquid Chromatography: Application for Determining Sulphonamides in Feed and Meat Using Conventional Chromatographic Systems

PubMed Central

Armentano, Antonio; Summa, Simona; Magro, Sonia Lo; D’Antini, Pasquale; Palermo, Carmen; Muscarella, Marilena

2016-01-01

A C18 column packed with core-shell particles was used for the chromatographic separation of sulphonamides in feed and meat by a conventional high performance liquid chromatography system coupled with a diode array detector. Two analytical methods, already used in our laboratory, have been modified without any changes in the extraction and clean-up steps and in the liquid chromatography instrumentation. Chromatographic conditions applied on a traditional 5-µm column have been optimized on a column packed with 2.6 µm core-shell particles. A binary mobile phase [acetate buffer solution at pH 4.50 and a mixture of methanol acetonitrile 50: 50 (v/v)] was employed in gradient mode at the flow rate of 1.2 mL with an injection volume of 6 µL. These chromatographic conditions allow the separation of 13 sulphonamides with an entire run of 13 minutes. Preliminary studies have been carried out comparing blanks and spiked samples of feed and meat. A good resolution and the absence of interferences were achieved in chromatograms for both matrices. Since no change was made to the sample preparation, the optimized method does not require a complete revalidation and can be used to make routine analysis faster. PMID:28217560

Toward a Micro Gas Chromatograph/Mass Spectrometer (GC/MS) System

NASA Technical Reports Server (NTRS)

Wiberg, D. V.; Eyre, F. B.; Orient, O.; Chutjian, A.; Garkarian, V.

2001-01-01

Miniature mass filters (e.g., quadrupoles, ion traps) have been the subject of several miniaturization efforts. A project is currently in progress at JPL to develop a miniaturized Gas Chromatograph/Mass Spectrometer (GC/MS) system, incorporating and/or developing miniature system components including turbomolecular pumps, scroll type roughing pump, quadrupole mass filter, gas chromatograph, precision power supply and other electronic components. The preponderance of the system elements will be fabricated using microelectromechanical systems (MEMS) techniques. The quadrupole mass filter will be fabricated using an X-ray lithography technique producing high precision, 5x5 arrays of quadrupoles with pole lengths of about 3 mm and a total volume of 27 cubic mm. The miniature scroll pump will also be fabricated using X-ray lithography producing arrays of scroll stages about 3 mm in diameter. The target detection range for the mass spectrometer is 1 to 300 atomic mass units (AMU) with are solution of 0.5 AMU. This resolution will allow isotopic characterization for geochronology, atmospheric studies and other science efforts dependant on the understanding of isotope ratios of chemical species. This paper will discuss the design approach, the current state-of-the art regarding the system components and the progress toward development of key elements. The full system is anticipated to be small enough in mass, volume and power consumption to allow in situ chemical analysis on highly miniaturized science craft for geochronology, atmospheric characterization and detection of life experiments applicable to outer planet roadmap missions.

Gas chromatographic column for the Viking 1975 molecular analysis experiment

NASA Technical Reports Server (NTRS)

Novotny, M.; Hayes, J. M.; Bruner, F.; Simmonds, P. G.

1975-01-01

A gas chromatographic column has been developed for use in the remote analysis of the Martian surface. The column, which utilizes a liquid-modified organic adsorbent (Tenax) as the stationary phase, provides efficient transmission and resolution of nanogram quantities of organic materials in the presence of millionfold excesses of water and carbon dioxide.

Predicting the chromatographic retention of polymers: poly(methyl methacrylate)s and polyacryate blends.

PubMed

Bashir, Mubasher A; Radke, Wolfgang

2007-09-07

The suitability of a retention model especially designed for polymers is investigated to describe and predict the chromatographic retention behavior of poly(methyl methacrylate)s as a function of mobile phase composition and gradient steepness. It is found that three simple yet rationally chosen chromatographic experiments suffice to extract the analyte specific model parameters necessary to calculate the retention volumes. This allows predicting accurate retention volumes based on a minimum number of initial experiments. Therefore, methods for polymer separations can be developed in relatively short time. The suitability of the virtual chromatography approach to predict the separation of polymer blend is demonstrated for the first time using a blend of different polyacrylates.

Determination of water-soluble vitamins in multivitamin dietary supplements and in artichokes by micellar electrokinetic chromatography.

PubMed

Serni, Enrico; Audino, Valeria; Del Carlo, Sara; Manera, Clementina; Saccomanni, Giuseppe; Macchia, Marco

2013-01-01

Several procedures of extraction with solvents for the simultaneous determination of vitamin C and some vitamins belonging to the B group (thiamine, riboflavine, nicotinic acid and nicotinamide) in multivitamin preparations and in artichokes (Cynara cardunculus subsp. scolymus [L.] Hegi) were developed. Different experimental conditions were used, in terms of heat treatment, composition and pH of the extraction mixture, with particular attention to high-temperature steps; purification of the extracts with solid phase extraction and stabilisation through lyophilisation were discussed. Analyses of the extracts were conducted by capillary electrophoresis in micellar electrokinetic chromatography modality. Borate buffer at pH 8.2 was used, and sodium dodecyl sulphate was added to the background electrolyte as surfactant. A range of linearity was determined and calibration curves were plotted for all the analytes.

Interface for liquid chromatograph-mass spectrometer

DOEpatents

Andresen, B.D.; Fought, E.R.

1989-09-19

A moving belt interface is described for real-time, high-performance liquid chromatograph (HPLC)/mass spectrometer (MS) analysis which strips away the HPLC solvent as it emerges from the end of the HPLC column and leaves a residue suitable for mass-spectral analysis. The interface includes a portable, stand-alone apparatus having a plural stage vacuum station, a continuous ribbon or belt, a drive train magnetically coupled to an external drive motor, a calibrated HPLC delivery system, a heated probe tip and means located adjacent the probe tip for direct ionization of the residue on the belt. The interface is also capable of being readily adapted to fit any mass spectrometer. 8 figs.

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

Analysis of microfluidic flow driven by electrokinetic and pressure forces

NASA Astrophysics Data System (ADS)

Chen, Chien-Hsin

2011-12-01

This work presents an analysis of microfluidic flow introduced by mixed electrokinetic force and pressure gradient. Analytical solutions are presented for the case of constant surface heat flux, taking the Joule heating effect into account. The present problem is governed by two scale ratios and the dimensionless source term. The two important ratios are the length scale ratio e (the ratio of Debye length to the tube radius R) and the velocity scale ratio Γ (the ratio of the pressuredriven velocity scale for Poiseuille flow to Helmholtz-Smoluchowski velocity for electroosmotic flow). For mixed electroosmotic and pressure-driven flow, the resulting velocity profile is the superimposed effect of both electroosmotic and Poiseuille flow phenomena. It is found that the velocity profile decreases as e increases and the normalized temperature profiles across the tube increases monotonously form the core to the wall. The maximum dimensionless temperature is observed at the wall and the wall temperature increases with increasing Joule heating. Also, the temperature is increased with increasing the value of ɛ . The fully developed Nusselt number takes the maximum value at the limiting case of ɛ --> 0 , and then decreases with increasing ɛ . Moreover, the Nusselt number decreases with Γ and then goes asymptotically to the limit of Poiseuille flow as Γ --> ∞ , where the flow is dominated by the pressure force.

AC electrokinetic manipulation of selenium nanoparticles for potential nanosensor applications

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

Mahmoodi, Seyed Reza; Bayati, Marzieh, E-mail: m-bayati@tums.ac.ir; Hosseinirad, Somayeh

2013-03-15

Highlights: ► Se nanoparticles were synthesized using a reverse-microemulsion process. ► AC osmotic fluid flow repulses the particles from electrode edges. ► Dielectrophoretic force attracts the particles to electrode edges. ► Dielectrophoresis electrode showed non-ohmic behavior. ► The device can potentially be used as a nanosensor. - Abstract: We report the AC electrokinetic behavior of selenium (Se) nanoparticles for electrical characterization and possible application as micro/nano devices. selenium Se nanoparticles were successfully synthesized using a reverse-microemulsion process and investigated structurally using X-ray diffraction and transmission electron microscope. Interdigitated castellated ITO and non-castellated platinum electrodes were employed for manipulation of suspendedmore » materials in the fluid. Using ITO electrodes at low frequency limits resulted in deposition of Se particles on electrode surface. When Se particles exposed to platinum electrodes in the 10 Hz–1 kHz range and V {sub p−p}> 8, AC osmotic fluid flow repulses the particles from electrode edges. However, in 10 kHz–10 MHz range and V {sub p−p}> 5, dielectrophoretic force attracts the particles to electrode edges. As the Se particle concentration increased, the trapped Se particles were aligned along the electric field line and bridged the electrode gap. The device was characterized and can potentially be useful in making micro/nano electronic devices.« less

Inner chromatogram projection (ICP) for resolution of GC-MS data with embedded chromatographic peaks.

PubMed

Wang, Zhi-Guo; Chen, Zeng-Ping; Gong, Fan; Wu, Hai-Long; Yu, Ru-Qin

2002-05-01

The chromatographic peak located inside another peak in the time direction is called an embedded or inner peak in contradistinction with the embedding peak, which is called an outer peak. The chemical components corresponding to inner and outer peaks are called inner and outer components, respectively. This special case of co-eluting chromatograms was investigated using chemometric approaches taking GC-MS as an example. A novel method, named inner chromatogram projection (ICP), for resolution of GC-MS data with embedded chromatographic peaks is derived. Orthogonal projection resolution is first utilized to obtain the chromatographic profile of the inner component. Projection of the two-way data matrix columnwise-normalized along the time direction to the normalized profile of the inner component found is subsequently performed to find the selective m/z points, if they exist, which represent the chromatogram of the outer component by itself. With the profiles obtained, the mass spectra can easily be found by means of a least-squares procedure. The results for both simulated data and real samples demonstrate that the proposed method is capable of achieving satisfactory resolution performance not affected by the shapes of chromatograms and the relative positions of the components involved.

Chromatographic analysis of tryptophan metabolites

PubMed Central

Sadok, Ilona; Gamian, Andrzej

2017-01-01

The kynurenine pathway generates multiple tryptophan metabolites called collectively kynurenines and leads to formation of the enzyme cofactor nicotinamide adenine dinucleotide. The first step in this pathway is tryptophan degradation, initiated by the rate‐limiting enzymes indoleamine 2,3‐dioxygenase, or tryptophan 2,3‐dioxygenase, depending on the tissue. The balanced kynurenine metabolism, which has been a subject of multiple studies in last decades, plays an important role in several physiological and pathological conditions such as infections, autoimmunity, neurological disorders, cancer, cataracts, as well as pregnancy. Understanding the regulation of tryptophan depletion provide novel diagnostic and treatment opportunities, however it requires reliable methods for quantification of kynurenines in biological samples with complex composition (body fluids, tissues, or cells). Trace concentrations, interference of sample components, and instability of some tryptophan metabolites need to be addressed using analytical methods. The novel separation approaches and optimized extraction protocols help to overcome difficulties in analyzing kynurenines within the complex tissue material. Recent developments in chromatography coupled with mass spectrometry provide new opportunity for quantification of tryptophan and its degradation products in various biological samples. In this review, we present current accomplishments in the chromatographic methodologies proposed for detection of tryptophan metabolites and provide a guide for choosing the optimal approach. PMID:28590049

Salinity effects during immiscible displacement in porous media: electrokinetic stabilization of viscous fingering

NASA Astrophysics Data System (ADS)

Mirzadeh, Mohammad; Bazant, Martin

2017-11-01

Interfacial instabilities are ubiquitous in Fluid Mechanics and have been one of the main the subjects of pattern formation. However, these instabilities could lead to inefficiencies which are undesired in many applications. For instance, viscous fingering results in residual trapping of oil during secondary recovery when a low-viscosity fluid, e.g. water, is used for injection. In their seminal work, Saffman and Taylor showed that the onset of this instability is controlled by the viscosity ratio of the two fluids. However, other physiochemical processes could enhance or suppress viscous fingering. Here we consider the role of salinity effects on the front stability. Our recent theory suggests that viscous fingering could be controlled, and even suppressed, by appropriately injecting electric currents. However, even in the absence of any external currents, strong electrokinetic coupling (present in small pores when the electric double layers overlap) can reduce viscous fingering by increasing the ``effective viscosity'' of the injected fluid. These findings suggest that it might be possible to improve extraction efficiencies by appropriately controlling the salt concentration of the injected fluid.

Heuristic extraction of rules in pruned artificial neural networks models used for quantifying highly overlapping chromatographic peaks.

PubMed

Hervás, César; Silva, Manuel; Serrano, Juan Manuel; Orejuela, Eva

2004-01-01

The suitability of an approach for extracting heuristic rules from trained artificial neural networks (ANNs) pruned by a regularization method and with architectures designed by evolutionary computation for quantifying highly overlapping chromatographic peaks is demonstrated. The ANN input data are estimated by the Levenberg-Marquardt method in the form of a four-parameter Weibull curve associated with the profile of the chromatographic band. To test this approach, two N-methylcarbamate pesticides, carbofuran and propoxur, were quantified using a classic peroxyoxalate chemiluminescence reaction as a detection system for chromatographic analysis. Straightforward network topologies (one and two outputs models) allow the analytes to be quantified in concentration ratios ranging from 1:7 to 5:1 with an average standard error of prediction for the generalization test of 2.7 and 2.3% for carbofuran and propoxur, respectively. The reduced dimensions of the selected ANN architectures, especially those obtained after using heuristic rules, allowed simple quantification equations to be developed that transform the input variables into output variables. These equations can be easily interpreted from a chemical point of view to attain quantitative analytical information regarding the effect of both analytes on the characteristics of chromatographic bands, namely profile, dispersion, peak height, and residence time. Copyright 2004 American Chemical Society

Cascade of kinetic energy and scalar variance in DC electrokinetic turbulence

NASA Astrophysics Data System (ADS)

Zhao, Wei; Wang, Guiren

2017-11-01

Turbulent flow can be generated by DC electrokinetic (EK) force based on the electric conductivity and permittivity variations in fluids, as have been demonstrated by Varshney et al (2016), where a -1.4 slope of velocity power spectrum is observed. Here, we theoretically found the scaling exponents of velocity and scalar structures in the electric-body-force (EBF) dominant subregion of DC EK turbulence were 2/5 (equivalent to the -7/5 slope of velocity power spectrum) and 4/5 respectively. The theory perfectly explains the experimental results of Varshney et al. (2016). Based on Kármán-Howarth equation with forcing terms, the energy cascade process of DC EK turbulence was also investigated. Depending on the electric Rayleigh number (Rae) , two different energy cascade processes may happen. When Rae is small, the kinetic energy cascades along inertial subregion and EBF dominant subregion in sequence, before it is dissipated by fluid viscosity. When Rae is sufficiently large, the inertial subregion may be absent with EBF dominant subregion left. This investigation is very important on understand EK turbulence, which could be widely existed in nature and applied in engineerings. The work was supported by NSFC (11672229), and NSF (CAREER CBET-0954977 and MRI CBET-1040227).

Derivatizing assay for the determination of aldehydes using micellar electrokinetic chromatography.

PubMed

Donegatti, Tiago Augusto; Gonçalves, Luís Moreira; Pereira, Elisabete Alves

2017-04-01

In this work, the use of a novel derivatization agent for the determination of aldehydes (in this particular case: formaldehyde, acetaldehyde, propionaldehyde, and valeraldehyde) using micellar electrokinetic chromatography is reported. The derivatization reaction is based on the reaction of aldehydes with benzhydrazide to form the corresponding derivates with maximum absorbance at 250 nm. The experimental conditions of the derivatization reaction as well of the separation were optimized. The adducts were separated with a +22 kV voltage at a temperature of 29°C. The adducts' separation was performed in less than 14 min using as the running buffer a mixture containing 110 mmol/L of sodium dodecyl sulfate and 27 mmol/L of sodium tetraborate at pH 9.45. Samples were injected using hydrodynamic mode (50 mbar × 5 s). The calibration curves were linear up to 15.0 mg/L with r 2 above 0.99. Intra and inter-day precisions were in average 3 and 4%, respectively, and recoveries were in average of 95%. Limits of detection and quantification were around 0.5 and 1.5 mg/L, respectively. The developed method was successfully applied in the analysis of low molar weight aldehydes in yogurt and vinegar samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-speed peak matching algorithm for retention time alignment of gas chromatographic data for chemometric analysis.

PubMed

Johnson, Kevin J; Wright, Bob W; Jarman, Kristin H; Synovec, Robert E

2003-05-09

A rapid retention time alignment algorithm was developed as a preprocessing utility to be used prior to chemometric analysis of large datasets of diesel fuel profiles obtained using gas chromatography (GC). Retention time variation from chromatogram-to-chromatogram has been a significant impediment against the use of chemometric techniques in the analysis of chromatographic data due to the inability of current chemometric techniques to correctly model information that shifts from variable to variable within a dataset. The alignment algorithm developed is shown to increase the efficacy of pattern recognition methods applied to diesel fuel chromatograms by retaining chemical selectivity while reducing chromatogram-to-chromatogram retention time variations and to do so on a time scale that makes analysis of large sets of chromatographic data practical. Two sets of diesel fuel gas chromatograms were studied using the novel alignment algorithm followed by principal component analysis (PCA). In the first study, retention times for corresponding chromatographic peaks in 60 chromatograms varied by as much as 300 ms between chromatograms before alignment. In the second study of 42 chromatograms, the retention time shifting exhibited was on the order of 10 s between corresponding chromatographic peaks, and required a coarse retention time correction prior to alignment with the algorithm. In both cases, an increase in retention time precision afforded by the algorithm was clearly visible in plots of overlaid chromatograms before and then after applying the retention time alignment algorithm. Using the alignment algorithm, the standard deviation for corresponding peak retention times following alignment was 17 ms throughout a given chromatogram, corresponding to a relative standard deviation of 0.003% at an average retention time of 8 min. This level of retention time precision is a 5-fold improvement over the retention time precision initially provided by a state

Development and validation of micellar liquid chromatographic methods for the determination of antibiotics in different matrixes.

PubMed

Rambla-Alegre, Maria; Esteve-Romero, Josep; Carda-Broch, Samuel

2011-01-01

Antibiotics are the most important bioactive and chemotherapeutic compounds to be produced by microbiological synthesis, and they have proved their worth in a variety of fields, such as medicinal chemistry, agriculture, and the food industry. Interest in antibiotics has grown in parallel with an increasingly high degree of productivity in the field of analytical applications. Therefore, it is necessary to develop chromatographic procedures capable of determining various drugs simultaneously in the shortest possible time. Micellar liquid chromatography (MLC) is an RP-HPLC technique that offers advantages over conventional HPLC as far as sample preparation, selectivity, and versatility are concerned. Its main advantage is that samples can be injected directly into the chromatographic system with no previous preparation step. This paper mainly focuses on the results of the authors' own recent research and reports the chromatographic conditions for determination of various antibiotics (penicillins, quinolones, and sulfonamides) in different matrixes (pharmaceuticals, biological fluids, and food). The work of other authors on MLC-based antibiotic determination has been included.

Rapid on-site sensing aflatoxin B1 in food and feed via a chromatographic time-resolved fluoroimmunoassay.

PubMed

Zhang, Zhaowei; Tang, Xiaoqian; Wang, Du; Zhang, Qi; Li, Peiwu; Ding, Xiaoxia

2015-01-01

Aflatoxin B1 poses grave threats to food and feed safety due to its strong carcinogenesis and toxicity, thus requiring ultrasensitive rapid on-site determination. Herein, a portable immunosensor based on chromatographic time-resolved fluoroimmunoassay was developed for sensitive and on-site determination of aflatoxin B1 in food and feed samples. Chromatographic time-resolved fluoroimmunoassay offered a magnified positive signal and low signal-to-noise ratio in time-resolved mode due to the absence of noise interference caused by excitation light sources. Compared with the immunosensing performance in previous studies, this platform demonstrated a wider dynamic range of 0.2-60 μg/kg, lower limit of detection from 0.06 to 0.12 µg/kg, and considerable recovery from 80.5% to 116.7% for different food and feed sample matrices. It was found to be little cross-reactivity with other aflatoxins (B2, G1, G2, and M1). In the case of determination of aflatoxin B1 in peanuts, corn, soy sauce, vegetable oil, and mouse feed, excellent agreement was found when compared with aflatoxin B1 determination via the conversational high-performance liquid chromatography method. The chromatographic time-resolved fluoroimmunoassay affords a powerful alternative for rapid on-site determination of aflatoxin B1 and holds a promise for food safety in consideration of practical food safety and environmental monitoring.

Rapid On-Site Sensing Aflatoxin B1 in Food and Feed via a Chromatographic Time-Resolved Fluoroimmunoassay

PubMed Central

Wang, Du; Zhang, Qi; Li, Peiwu; Ding, Xiaoxia

2015-01-01

Aflatoxin B1 poses grave threats to food and feed safety due to its strong carcinogenesis and toxicity, thus requiring ultrasensitive rapid on-site determination. Herein, a portable immunosensor based on chromatographic time-resolved fluoroimmunoassay was developed for sensitive and on-site determination of aflatoxin B1 in food and feed samples. Chromatographic time-resolved fluoroimmunoassay offered a magnified positive signal and low signal-to-noise ratio in time-resolved mode due to the absence of noise interference caused by excitation light sources. Compared with the immunosensing performance in previous studies, this platform demonstrated a wider dynamic range of 0.2-60 μg/kg, lower limit of detection from 0.06 to 0.12 µg/kg, and considerable recovery from 80.5% to 116.7% for different food and feed sample matrices. It was found to be little cross-reactivity with other aflatoxins (B2, G1, G2, and M1). In the case of determination of aflatoxin B1 in peanuts, corn, soy sauce, vegetable oil, and mouse feed, excellent agreement was found when compared with aflatoxin B1 determination via the conversational high-performance liquid chromatography method. The chromatographic time-resolved fluoroimmunoassay affords a powerful alternative for rapid on-site determination of aflatoxin B1 and holds a promise for food safety in consideration of practical food safety and environmental monitoring. PMID:25874803

Preliminary numerical analysis of improved gas chromatograph model

NASA Technical Reports Server (NTRS)

Woodrow, P. T.

1973-01-01

A mathematical model for the gas chromatograph was developed which incorporates the heretofore neglected transport mechanisms of intraparticle diffusion and rates of adsorption. Because a closed-form analytical solution to the model does not appear realizable, techniques for the numerical solution of the model equations are being investigated. Criteria were developed for using a finite terminal boundary condition in place of an infinite boundary condition used in analytical solution techniques. The class of weighted residual methods known as orthogonal collocation is presently being investigated and appears promising.

Detection system for a gas chromatograph

DOEpatents

Hayes, John M.; Small, Gerald J.

1984-01-01

A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam.

Electrokinetic Enhanced Delivery and Electrical Resistance Heating Activation of Persulfate for Low Permeability Soil Remediation

NASA Astrophysics Data System (ADS)

Chowdhury, A. I.; Gerhard, J.; Reynolds, D. A.; OCarroll, D.

2016-12-01

Remediation of low permeability soils is challenging because delivering remediants into these formations is difficult. Electrokinetics (EK) has been proposed as a new approach to overcome this difficulty, for example, to deliver oxidants such as persulfate into silts and clays. However, activation of the persulfate in such scenarios remains a challenge. The current study proposes a novel approach of combining (i) EK-assisted persulfate delivery with (ii) low temperature electrical resistance heating (ERH) to activate the persulfate. The advantage of this new approach that a single set of electrodes can be used for both oxidant delivery and oxidant activation in low permeability, contaminated soil. Proof-of-concept experiments were conducted in a two-dimensional sandbox packed with silt exhibiting high concentrations of aqueous phase tetrachloroethene (PCE). Results showed that (1) EK delivered the non-activated persulfate throughout the silt, (2) ERH was able to achieve and sustain the targeted temperatures to activate the persulfate, and (3) these resulted in complete PCE degradation at all locations. Activating persulfate at a temperature around 36 °C was better than at 42 °C (or higher), because the former more slowly generated the reactive SO4ˉ● radical which ensured more complete reaction with the contaminant. This study proved the concept of this novel, coupled approach for delivering and activating persulfate for remediating chlorinated solvents in low permeability soils.

Photochemically Activated Motors: From Electrokinetic to Diffusion Motion Control.

PubMed

Zhang, Kuan; Fraxedas, Jordi; Sepulveda, Borja; Esplandiu, Maria J

2017-12-27

Self-propelled micro/nanomotors that can transform chemical energy from the surrounding environment into mechanical motion are cutting edge nanotechnologies with potential applications in biomedicine and environmental remediation. These applications require full understanding of the propulsion mechanisms to improve the performance and controllability of the motors. In this work, we demonstrate that there are two competing chemomechanical mechanisms at semiconductor/metal (Si/Pt) micromotors in a pump configuration under visible light exposure. The first propulsion mechanism is driven by an electro-osmotic process stemmed from a photoactivation reaction mediated by H 2 O 2 , which takes place in two separated redox reactions at the Si and Pt interfaces. One reaction involves the oxidation of H 2 O 2 at the silicon side, and the other the H 2 O 2 reduction at the metal side. The second mechanism is not light responsive and is triggered by the redox decomposition of H 2 O 2 exclusively at the Pt surface. We show that it is possible to enhance/suppress one mechanism over the other by tuning the surface roughness of the micromotor metal. More specifically, the actuation mechanism can be switched from light-controlled electrokinetics to light-insensitive diffusio-osmosis by only increasing the metal surface roughness. The different actuation mechanisms yield strikingly different fluid flow velocities, electric fields, and light sensitivities. Consequently, these findings are very relevant and can have a remarkable impact on the design and optimization of photoactivated catalytic devices and, in general, on bimetallic or insulating-metallic motors.

Removal of oxyfluorfen from spiked soils using electrokinetic soil flushing with the surrounding arrangements of electrodes.

PubMed

Risco, C; Rubí-Juárez, H; Rodrigo, S; López-Vizcaíno, R; Saez, C; Cañizares, P; Barrera-Díaz, C; Navarro, V; Rodrigo, M A

2016-07-15

This work reports the results of a study in which the remediation of soil that undergoes an accidental discharge of oxyfluorfen is carried out by using electrokinetic soil flushing (EKSF). Two different electrode configurations were tested, consisting of several electrodes surrounding an electrode of different polarity (so-called 1A6C, one anode surrounded by six cathodes, and 1C6A, one cathode surrounded by six cathodes). A pilot plant scale was used (with a soil volume of 175dm(3)) to perform the studies. During the tests, different parameters were measured daily (flowrates, pH, electrical conductivity and herbicide concentration in different sampling positions). Furthermore, at the end of the test, a complete post-mortem analysis was carried out to obtain a 3-D map of the pollution, pH and electrical conductivity in the soil. The results demonstrate that electrode arrangement is a key factor for effective pollutant removal. In fact, the 1A6C configuration improves the removal rate by 41.3% versus the 27.0% obtained by the 1C6A configuration after a period of 35days. Finally, a bench mark comparison of this study of soil remediation polluted with 2,4-D allows for significant conclusions about the scale-up and full-scale application of this technology. Copyright © 2016 Elsevier B.V. All rights reserved.

Advanced hyphenated chromatographic-mass spectrometry in mycotoxin determination: current status and prospects.

PubMed

Li, Peiwu; Zhang, Zhaowei; Hu, Xiaofeng; Zhang, Qi

2013-01-01

Mass spectrometric techniques are essential for advanced research in food safety and environmental monitoring. These fields are important for securing the health of humans and animals, and for ensuring environmental security. Mycotoxins, toxic secondary metabolites of filamentous fungi, are major contaminants of agricultural products, food and feed, biological samples, and the environment as a whole. Mycotoxins can cause cancers, nephritic and hepatic diseases, various hemorrhagic syndromes, and immune and neurological disorders. Mycotoxin-contaminated food and feed can provoke trade conflicts, resulting in massive economic losses. Risk assessment of mycotoxin contamination for humans and animals generally depends on clear identification and reliable quantitation in diversified matrices. Pioneering work on mycotoxin quantitation using mass spectrometry (MS) was performed in the early 1970s. Now, unambiguous confirmation and quantitation of mycotoxins can be readily achieved with a variety hyphenated techniques that combine chromatographic separation with MS, including liquid chromatography (LC) or gas chromatography (GC). With the advent of atmospheric pressure ionization, LC-MS has become a routine technique. Recently, the co-occurrence of multiple mycotoxins in the same sample has drawn an increasing amount of attention. Thus, modern analyses must be able to detect and quantitate multiple mycotoxins in a single run. Improvements in tandem MS techniques have been made to achieve this purpose. This review describes the advanced research that has been done regarding mycotoxin determination using hyphenated chromatographic-MS techniques, but is not a full-circle survey of all the literature published on this topic. The present work provides an overview of the various hyphenated chromatographic-MS-based strategies that have been applied to mycotoxin analysis, with a focus on recent developments. The use of chromatographic-MS to measure levels of mycotoxins, including

Application of a Modified Gas Chromatograph to Analyze Space Experiment Combustion Gases on Space Shuttle Mission STS-94

NASA Technical Reports Server (NTRS)

Coho, William K.; Weiland, Karen J.; VanZandt, David M.

1998-01-01

A space experiment designed to study the behavior of combustion without the gravitational effects of buoyancy was launched aboard the Space Shuttle Columbia on July 1, 1997. The space experiment, designated as Combustion Module-1 (CM-1), was one of several manifested on the Microgravity Sciences Laboratory - 1 (MSL-1) mission. The launch, designated STS-94, had the Spacelab Module as the payload, in which the MSL-1 experiments were conducted by the Shuttle crewmembers. CM-1 was designed to accommodate two different combustion experiments during MSL-1. One experiment, the Structure of Flame Balls at Low Lewis-number experiment (SOFBALL), required gas chromatography analysis to verify the composition of the known, premixed gases prior to combustion, and to determine the remaining reactant and the products resulting from the combustion process in microgravity. A commercial, off-the-shelf, dual-channel micro gas chromatograph was procured and modified to interface with the CM-1 Fluids Supply Package and the CM-1 Combustion Chamber, to accommodate two different carrier gases, each flowing through its own independent column module, to withstand the launch environment of the Space Shuttle, to accept Spacelab electrical power, and to meet the Spacelab flight requirements for electromagnetic interference (EMI) and offgassing. The GC data was down linked to the Marshall Space Flight Center for near-real time analysis, and stored on-orbit for post-flight analysis. The gas chromatograph operated successfully during the entire SOFBALL experiment and collected 309 runs. Because of the constraints imposed upon the gas chromatograph by the CM-1 hardware, system and operations, it was unable to measure the gases to the required accuracy. Future improvements to the system for a re-flight of the SOFBALL experiment are expected to enable the gas chromatograph to meet all the requirements.

[Quantitative structure-gas chromatographic retention relationship of polycyclic aromatic sulfur heterocycles using molecular electronegativity-distance vector].

PubMed

Li, Zhenghua; Cheng, Fansheng; Xia, Zhining

2011-01-01

The chemical structures of 114 polycyclic aromatic sulfur heterocycles (PASHs) have been studied by molecular electronegativity-distance vector (MEDV). The linear relationships between gas chromatographic retention index and the MEDV have been established by a multiple linear regression (MLR) model. The results of variable selection by stepwise multiple regression (SMR) and the powerful predictive abilities of the optimization model appraised by leave-one-out cross-validation showed that the optimization model with the correlation coefficient (R) of 0.994 7 and the cross-validated correlation coefficient (Rcv) of 0.994 0 possessed the best statistical quality. Furthermore, when the 114 PASHs compounds were divided into calibration and test sets in the ratio of 2:1, the statistical analysis showed our models possesses almost equal statistical quality, the very similar regression coefficients and the good robustness. The quantitative structure-retention relationship (QSRR) model established may provide a convenient and powerful method for predicting the gas chromatographic retention of PASHs.

Remediation of Cd(II)-contaminated soil via humin-enhanced electrokinetic technology.

PubMed

Ding, Ling; Lv, Wenying; Yao, Kun; Li, Liming; Wang, Mengmeng; Liu, Guoguang

2017-02-01

Humin is the component of humic substances that is recalcitrant to extraction by either strong bases or strong acids, which contains a variety of functional groups that may combine with heavy metal ions. The present study employed humin as an adsorbent to investigate the efficacy of a remediation strategy under the effects of humin-enhanced electrokinetics. Because the cations gravitate toward cathode and anions are transferred to anode, humin was placed in close proximity to the cathode in the form of a package. The humin was taken out after the experiments to determine whether a target pollutant (cadmium) might be completely removed from soil. Acetic acid-sodium acetate was selected as the electrolyte for these experiments, which was circulated between the two electrode chambers via a peristaltic pump, in order to control the pH of the soil. The results indicated that when the remediation duration was extended to 240 h, the removal of acid extractable Cd(II) could be up to 43.86% efficiency, and the adsorption of the heavy metal within the humin was 86.15 mg/kg. Further, the recycling of the electrolyte exhibited a good control of the pH of the soil. When comparing the pH of the soil with the circulating electrolyte during remediation, in contrast to when it was not being recycled, the pH of the soil at the anode increased from 3.89 to 5.63, whereas the soil at the cathode decreased from 8.06 to 7.10. This indicated that the electrolyte recycling had the capacity to stabilize the pH of the soil.

Robust analysis of the hydrophobic basic analytes loratadine and desloratadine in pharmaceutical preparations and biological fluids by sweeping-cyclodextrin-modified micellar electrokinetic chromatography.

PubMed

El-Awady, Mohamed; Belal, Fathalla; Pyell, Ute

2013-09-27

The analysis of hydrophobic basic analytes by micellar electrokinetic chromatography (MEKC) is usually challenging because of the tendency of these analytes to be adsorbed onto the inner capillary wall in addition to the difficulty to separate these compounds as they exhibit extremely high retention factors. A robust and reliable method for the simultaneous determination of loratadine (LOR) and its major metabolite desloratadine (DSL) is developed based on cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with acidic sample matrix and basic background electrolyte (BGE). The influence of the sample matrix on the reachable focusing efficiency is studied. It is shown that the application of a low pH sample solution mitigates problems associated with the low solubility of the hydrophobic basic analytes in aqueous solution while having advantages with regard to on-line focusing. Moreover, the use of a basic BGE reduces the adsorption of these analytes in the separation compartment. The separation of the studied analytes is achieved in less than 7min using a BGE consisting of 10mmolL(-1) disodium tetraborate buffer, pH 9.30 containing 40mmolL(-1) SDS and 20mmolL(-1) hydroxypropyl-β-CD while the sample solution is composed of 10mmolL(-1) phosphoric acid, pH 2.15. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in tablets without interference of tablet additives as well as the analysis of spiked human urine without any sample pretreatment. Furthermore, DSL can be detected as an impurity in LOR bulk powder at the stated pharmacopeial limit (0.1%, w/w). The selectivity of the developed method allows the analysis of LOR and DSL in combination with the co-formulated drug pseudoephedrine. It is shown that in CD-MEKC with basic BGE, solute-wall interactions are effectively suppressed allowing the development of efficient and precise

[Gas chromatographic isolation of chloropicrin in drinking water].

PubMed

Malysheva, A G; Sotnikov, E E; Moskovkin, A S; Kamenetskaia, D B

2004-01-01

Gas chromatographic method has been developed to identify chloropicrin in the drinking water, which is based on its separation from water by statistic gas extraction and on the analysis of equilibrium vapor phase on a capillary column with electron-capture and nitrogen-phosphorus detectors connected in series. The method allows chloropicrin to be detected at the level of 5 mg/dm3 with a total measurement error of +/- 10% at a confidence probability of 0.95. The paper shows that the sensitivity of identification can be significantly increased.

A chromatographic objective function to characterise chromatograms with unknown compounds or without standards available.

PubMed

Alvarez-Segura, T; Gómez-Díaz, A; Ortiz-Bolsico, C; Torres-Lapasió, J R; García-Alvarez-Coque, M C

2015-08-28

Getting useful chemical information from samples containing many compounds is still a challenge to analysts in liquid chromatography. The highest complexity corresponds to samples for which there is no prior knowledge about their chemical composition. Computer-based methodologies are currently considered as the most efficient tools to optimise the chromatographic resolution, and further finding the optimal separation conditions. However, most chromatographic objective functions (COFs) described in the literature to measure the resolution are based on mathematical models fitted with the information obtained from standards, and cannot be applied to samples with unknown compounds. In this work, a new COF based on the automatic measurement of the protruding part of the chromatographic peaks (or peak prominences) that indicates the number of perceptible peaks and global resolution, without the need of standards, is developed. The proposed COF was found satisfactory with regard to the peak purity criterion when applied to artificial peaks and simulated chromatograms of mixtures built using the information of standards. The approach was applied to mixtures of drugs containing unknown impurities and degradation products and to extracts of medicinal herbs, eluted with acetonitrile-water mixtures using isocratic and gradient elution. Copyright © 2015 Elsevier B.V. All rights reserved.

[Analysis of phthalate esters in plastic-packaging bags on-line sample stacking-microemulsion electrokinetic chromatography].

PubMed

Xiao, Jia; Huang, Ying; Wang, Minyi; Chen, Guonan

2012-09-01

Two convenient, effective, and reproducible methods using microemulsion electrokinetic chromatography (MEEKC)-normal stacking mode (NSM) and reversed electrode polarity stacking mode (REPSM) were developed for the on-line sample stacking of phthalate esters (PAEs). REPSM coupled with MEEKC increased the sensitivity of 937.5 to 7,143 times for four PAEs compared to the conventional MEEKC. The separating conditions in the MEEKC method were studied, and many factors influencing the two sample stacking processes were investigated in detail. The optimum sample matrices for the two stacking methods were as follows: 30 mmol/L sodium cholate (SC) and 30.0 mmol/L borate (pH 8.5). Additionally, sample injections as large as 3.45 kPa x 40 s and 3.45 kPa x 90 s were applied for NSM-MEEKC and REPSM-MEEKC, respectively. The linear relationship and reproducibility were also examined. Under the optimum conditions, the detection limits (S/N = 3) of the PAEs were in the ranges of 0.021 - 0.33 mg/L and 0.7 - 4 microg/L for NSM-MEEKC and REPSM-MEEKC, respectively. The proposed REPSM-MEEKC has been successfully applied to determine PAEs in plastic-packaging bags, and the spiked recoveries were in the range of 89.1% - 105.6% with satisfactory results.

Advances in the Study of Aptamer-Protein Target Identification Using the Chromatographic Approach.

PubMed

Drabik, Anna; Ner-Kluza, Joanna; Mielczarek, Przemyslaw; Civit, Laia; Mayer, Günter; Silberring, Jerzy

2018-06-01

Ever since the development of the process known as the systematic evolution of ligands by exponential enrichment (SELEX), aptamers have been widely used in a variety of studies, including the exploration of new diagnostic tools and the discovery of new treatment methods. Aptamers' ability to bind to proteins with high affinity and specificity, often compared to that of antibodies, enables the search for potential cancer biomarkers and helps us understand the mechanisms of carcinogenesis. The blind spot of those investigations is usually the difficulty in the selective extraction of targets attached to the aptamer. There are many studies describing the cell SELEX for the prime choice of aptamers toward living cancer cells or even whole tumors in the animal models. However, a dilemma arises when a large number of proteins are being identified as potential targets, which is often the case. In this article, we present a new analytical approach designed to selectively target proteins bound to aptamers. During studies, we have focused on the unambiguous identification of the molecular targets of aptamers characterized by high specificity to the prostate cancer cells. We have compared four assay approaches using electrophoretic and chromatographic methods for "fishing out" aptamer protein targets followed by mass spectrometry identification. We have established a new methodology, based on the fluorescent-tagged oligonucleotides commonly used for flow-cytometry experiments or as optic aptasensors, that allowed the detection of specific aptamer-protein interactions by mass spectrometry. The use of atto488-labeled aptamers for the tracking of the formation of specific aptamer-target complexes provides the possibility of studying putative protein counterparts without needing to apply enrichment techniques. Significantly, changes in the hydrophobic properties of atto488-labeled aptamer-protein complexes facilitate their separation by reverse-phase chromatography combined with

Differentiation of Panax quinquefolius grown in United States and China using LC/MS-based chromatographic fingerprinting and metabolomic approaches

USDA-ARS?s Scientific Manuscript database

American ginseng (Panax quinquefolius) is one of the most commonly used herbal medicines in the world. Discriminating between P. quinquefolius grown in different countries is difficult using the traditional quantitation methods. In this study, a liquid chromatographic mass spectrometry (LC-MS) fing...

New method for evaluating irreversible adsorption and stationary phase bleed in gas chromatographic capillary columns.

PubMed

Wright, Bob W; Wright, Cherylyn W

2012-10-26

A novel method is described for the evaluation of irreversible adsorption and column bleed in gas chromatographic (GC) columns using a tandem GC approach. This work specifically determined the degree of irreversible adsorption behavior of specific sulfur and phosphorous containing test probe compounds at levels ranging from approximately 50 picograms (pg) to 1 nanogram (ng) on selected gas chromatographic columns. This method does not replace existing evaluation methods that characterize reversible adsorption but provides an additional tool. The test compounds were selected due to their ease of adsorption and their importance in the specific trace analytical detection methodology being developed. Replicate chromatographic columns with 5% phenylmethylpolysiloxane (PMS), polyethylene glycol (wax), trifluoropropylpolysiloxane (TFP), or 78% cyanopropylpolysiloxane stationary phases from a variety of vendors were evaluated. As expected, the results demonstrate that the different chromatographic phases exhibit differing degrees of irreversible adsorption behavior. The results also indicate that all manufacturers do not produce equally inert columns nor are columns from a given manufacturer identical. The wax-coated columns for the test probes used were more inert as a group than 5% PMS coated columns, and they were more reproducibly manufactured. Both TFP and 78% cyanopropylpolysiloxane columns displayed superior inertness to the test compounds compared to either 5% PMS- or wax-coated columns. Irreversible adsorption behavior was characterized for a limited range of stationary phase film thicknesses. In addition, the method was shown effective for characterizing column bleed and methods to remove bleed components. This method is useful in screening columns for demanding applications and to obtain diagnostic information related to improved preparation methods. Copyright © 2012 Elsevier B.V. All rights reserved.

[Quantitative relationship between gas chromatographic retention time and structural parameters of alkylphenols].

PubMed

Ruan, Xiaofang; Zhang, Ruisheng; Yao, Xiaojun; Liu, Mancang; Fan, Botao

2007-03-01

Alkylphenols are a group of permanent pollutants in the environment and could adversely disturb the human endocrine system. It is therefore important to effectively separate and measure the alkylphenols. To guide the chromatographic analysis of these compounds in practice, the development of quantitative relationship between the molecular structure and the retention time of alkylphenols becomes necessary. In this study, topological, constitutional, geometrical, electrostatic and quantum-chemical descriptors of 44 alkylphenols were calculated using a software, CODESSA, and these descriptors were pre-selected using the heuristic method. As a result, three-descriptor linear model (LM) was developed to describe the relationship between the molecular structure and the retention time of alkylphenols. Meanwhile, the non-linear regression model was also developed based on support vector machine (SVM) using the same three descriptors. The correlation coefficient (R(2)) for the LM and SVM was 0.98 and 0. 92, and the corresponding root-mean-square error was 0. 99 and 2. 77, respectively. By comparing the stability and prediction ability of the two models, it was found that the linear model was a better method for describing the quantitative relationship between the retention time of alkylphenols and the molecular structure. The results obtained suggested that the linear model could be applied for the chromatographic analysis of alkylphenols with known molecular structural parameters.

Potentiometric and electrokinetic signatures of iron(II) interactions with (α,γ)-Fe2O3.

PubMed

Toczydłowska, Diana; Kędra-Królik, Karolina; Nejbert, Krzysztof; Preočanin, Tajana; Rosso, Kevin M; Zarzycki, Piotr

2015-10-21

The electrochemical signatures of Fe(II) interactions with iron(III) oxides are poorly understood, despite their importance in controlling the amount of mobilized iron. Here, we report the potentiometric titration of α,γ-Fe2O3 oxides exposed to Fe(II) ions. We monitored in situ surface and ζ potentials, the ratio of mobilized ferric to ferrous, and the periodically analyzed nanoparticle crystal structure using X-ray diffraction. Electrokinetic potential reveals weak but still noticeable specific sorption of Fe(II) to the oxide surface under acidic conditions, and pronounced adsorption under alkaline conditions that results in a surface potential reversal. By monitoring the aqueous iron(II/III) fraction, we found that the addition of Fe(II) ions produces platinum electrode response consistent with the iron solubility-activity curve. Although, XRD analysis showed no evidence of γ-Fe2O3 transformations along the titration pathway despite iron cycling between aqueous and solid reservoirs, the magnetite formation cannot be ruled out.

Electrokinetic and hydrodynamic properties of charged-particles systems. From small electrolyte ions to large colloids

NASA Astrophysics Data System (ADS)

Nägele, G.; Heinen, M.; Banchio, A. J.; Contreras-Aburto, C.

2013-11-01

Dynamic processes in dispersions of charged spherical particles are of importance both in fundamental science, and in technical and bio-medical applications. There exists a large variety of charged-particles systems, ranging from nanometer-sized electrolyte ions to micron-sized charge-stabilized colloids. We review recent advances in theoretical methods for the calculation of linear transport coefficients in concentrated particulate systems, with the focus on hydrodynamic interactions and electrokinetic effects. Considered transport properties are the dispersion viscosity, self- and collective diffusion coefficients, sedimentation coefficients, and electrophoretic mobilities and conductivities of ionic particle species in an external electric field. Advances by our group are also discussed, including a novel mode-coupling-theory method for conduction-diffusion and viscoelastic properties of strong electrolyte solutions. Furthermore, results are presented for dispersions of solvent-permeable particles, and particles with non-zero hydrodynamic surface slip. The concentration-dependent swelling of ionic microgels is discussed, as well as a far-reaching dynamic scaling behavior relating colloidal long- to short-time dynamics.

[Fluorescent signal detection of chromatographic chip by algorithms of pyramid connection and Gaussian mixture model].

PubMed

Hu, Beibei; Zhang, Xueqing; Chen, Haopeng; Cui, Daxiang

2011-03-01

We proposed a new algorithm for automatic identification of fluorescent signal. Based on the features of chromatographic chips, mathematic morphology in RGB color space was used to filter and enhance the images, pyramid connection was used to segment the areas of fluorescent signal, and then the method of Gaussian Mixture Model was used to detect the fluorescent signal. Finally we calculated the average fluorescent intensity in obtained fluorescent areas. Our results show that the algorithm has a good efficacy to segment the fluorescent areas, can detect the fluorescent signal quickly and accurately, and finally realize the quantitative detection of fluorescent signal in chromatographic chip.

Evaluation of Comprehensive 2-D Gas Chromatography-Time-Of-Flight Mass Spectrometry for 209 Chlorinated Biphenyl Congeners in Two Chromatographic Runs

EPA Science Inventory

This research evaluates a recently developed comprehensive 2-D GC coupled with a time-of-flight (TOF) mass spectrometer for the potential separation of 209 PCB congeners, using a sequence of 1-D and 2-D chromatographic modes. In two consecutive chromatographic runs, using a 40 m,...

Comprehensive two-dimensional liquid chromatographic analysis of poloxamers.

PubMed

Malik, Muhammad Imran; Lee, Sanghoon; Chang, Taihyun

2016-04-15

Poloxamers are low molar mass triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), having number of applications as non-ionic surfactants. Comprehensive one and two-dimensional liquid chromatographic (LC) analysis of these materials is proposed in this study. The separation of oligomers of both types (PEO and PPO) is demonstrated for several commercial poloxamers. This is accomplished at the critical conditions for one of the block while interaction for the other block. Reversed phase LC at CAP of PEO allowed for oligomeric separation of triblock copolymers with regard to PPO block whereas normal phase LC at CAP of PPO renders oligomeric separation with respect to PEO block. The oligomeric separation with regard to PEO and PPO are coupled online (comprehensive 2D-LC) to reveal two-dimensional contour plots by unconventional 2D IC×IC (interaction chromatography) coupling. The study provides chemical composition mapping of both PEO and PPO, equivalent to combined molar mass and chemical composition mapping for several commercial poloxamers. Copyright © 2016 Elsevier B.V. All rights reserved.

DEVELOPMENT AND VALIDATION OF AN ION CHROMATOGRAPHIC METHOD FOR DETERMINING PERCHLORATE IN FERTILIZERS

EPA Science Inventory

A method has been developed for the determination of perchlorate in fertilizers. Materials are leached with deionized water to dissolve any soluble perchlorate compounds. Ion chromatographic separation is followed by suppressed conductivity for detection. Perchlorate is retained ...