Double injection/single detection asymmetric flow injection manifold for spectrophotometric determination of ascorbic acid and uric acid: Selection the optimal conditions by MCDM approach based on different criteria weighting methods

NASA Astrophysics Data System (ADS)

Boroumand, Samira; Chamjangali, Mansour Arab; Bagherian, Ghadamali

2017-03-01

A simple and sensitive double injection/single detector flow injection analysis (FIA) method is proposed for the simultaneous kinetic determination of ascorbic acid (AA) and uric acid (UA). This method is based upon the difference between the rates of the AA and UA reactions with Fe3 + in the presence of 1, 10-phenanthroline (phen). The absorbance of Fe2 +/1, 10-phenanthroline (Fe-phen) complex obtained as the product was measured spectrophotometrically at 510 nm. To reach a good accuracy in the differential kinetic determination via the mathematical manipulations of the transient signals, different criteria were considered in the selection of the optimum conditions. The multi criteria decision making (MCDM) approach was applied for the selection of the optimum conditions. The importance weights of the evaluation criteria were determined using the analytic hierarchy process, entropy method, and compromised weighting (CW). The experimental conditions (alternatives) were ranked by the technique for order preference by similarity to an ideal solution. Under the selected optimum conditions, the obtained analytical signals were linear in the ranges of 0.50-5.00 and 0.50-4.00 mg L- 1 for AA and UA, respectively. The 3σ detection limits were 0.07 mg L- 1 for AA and 0.12 mg L- 1 for UA. The relative standard deviations for four replicate determinations of AA and UA were 2.03% and 3.30% respectively. The method was also applied for the analysis of analytes in the blood serum, Vitamine C tablets, and tap water with satisfactory results.

Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography

NASA Astrophysics Data System (ADS)

Chen, Shujuan; Li, Nan; Zhang, Xinshen; Yang, Dongjing; Jiang, Heimei

2015-03-01

A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515 nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040-1.0 mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55 μg/L, the relative standard deviation (n = 10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5 mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1 h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples.

Reverse flow injection spectrophotometric determination of ciprofloxacin in pharmaceuticals using iron from soil as a green reagent

NASA Astrophysics Data System (ADS)

Palamy, Sysay; Ruengsitagoon, Wirat

2018-02-01

A novel reverse flow injection spectrophotometric method for the determination of ciprofloxacin was successfully combined with the on-line introduction of an iron solution extracted from soil as green reagent. The assay was optimized by a univariate method to select the optimum conditions for the highest absorbance and highest stability of the complex. Beer-Lambert's law (λmax = 440 nm) is obeyed in the range 0.5-50 μg mL- 1 with a correlation coefficient (r2) of 0.9976 and 0.9996 using soil as green reagent from Khon Kaen, Thailand and Vientiane, Laos, respectively. The average percentage recoveries were in the range of 98.55-102.14% and the precision was in the range of 0.80-1.73%. The limit of detection and the limit of quantitation were 0.20 and 0.69 μg mL- 1, respectively, with a sampling rate of over 46 samples h- 1. The method was successfully applied to the determination of ciprofloxacin in commercial pharmaceutical formulations. The results were in good agreement with those obtained by the reference HPLC method using a t-test at 95% of confidence level for comparison. This method is suitable for laboratories looking for alternative analytical methods using green reagents.

Spectrophotometric determination of zinc and copper in a multi-syringe flow injection analysis system using a liquid waveguide capillary cell: application to natural waters.

PubMed

Páscoa, Ricardo N M J; Tóth, Ildikó V; Rangel, António O S S

2011-06-15

This work exploits a multi-syringe injection analysis (MSFIA) system coupled with a long liquid waveguide capillary cell for the spectrophotometric determination of zinc and copper in waters. A liquid waveguide capillary cell (1.0m pathlength, 550 μm i.d. and 250 μL internal volume) was used to enhance the sensitivity of the detection. The determination for both ions is based on a colorimetric reaction with zincon at different pH values. The developed methodology compares favourably with other previously described procedures, as it allows to reach low detection limits for both cations (LODs of 0.1 and 2 μg L(-1), for copper and zinc, respectively), without the need for any pre-concentration step. The system also provided a linear response up to 100 μg L(-1) with a high throughput (43 h(-1)) and low reagent consumption and effluent production. The developed work was applied to natural waters and three certified reference water samples. Copyright © 2011 Elsevier B.V. All rights reserved.

Determination of Trace Amounts of Chromium(III) in Water Samples Using Online Flow Injection Catalytic Spectrophotometry

NASA Astrophysics Data System (ADS)

Zhao, Z. X.; Zhang, X. S.

2017-01-01

A new online flow injection spectrophotometric method for the determination of trivalent chromium was developed. This method is based on the property of trivalent chromium to be a catalyst for the oxidation of Indigo Carmine (IC) with potassium periodate and to lose its color in the presence of ethylenediaminetetraacetic acid and sodium tripolyphosphate. It was shown that Tween-20 serves as an additional accelerator of the catalytic oxidation. The linear dynamic range of the determination of Cr(III) was 1-40.0 μg/L, while the limit of detection was 0.05 μg/L. The correlation coefficient r was 0.998, while the relative standard deviation for 5 μg/L of the Cr(III) solution was 3.83%. The feasibility of this method was checked by its application to trivalent chromium determination in real water samples.

The facile flow-injection spectrophotometric detection of gold(III) in water and pharmaceutical samples using 3,5-dimethoxy-4-hydroxy-2-aminoacetophenone isonicotinoyl hydrazone (3,5-DMHAAINH).

PubMed

Babu, S Hari; Suvardhan, K; Kumar, K Suresh; Reddy, K M; Rekha, D; Chiranjeevi, P

2005-04-11

A simple, sensitive and rapid flow-injection spectrophotometric method was developed for the determination of trace amounts of Au(III) in aqueous dimethylformamide (DMF). The method is based on formation of Au(III)-(3,5-DMHAAINH)3 complex. The optimum conditions for the chromogenic reaction of Au(III) with 3,5-DMHAAINH is studied and the colored (reddish brown) complex is selectively monitored at lambda(max) 490 nm at pH 6.0. The reaction and flow conditions of the full experimental design were optimized. The detection limit (2 s) of 0.1 microg l-1 Au(III) was obtained at a sampling rate of 15 samples h-1. Beer's law is obeyed over the range of 0.30-4.00 microg ml-1. The molar absorptivity and Sandell's sensitivity were 3.450x10(4) M and 0.0050 microg ml-1, respectively. Job's method of continuous variation and stability constants corresponding to these maxima was determined and found to be 9.3x10(15) (1:3, M:R) (M, metal; R, reagent). The detailed study of various interferences confirmed the high selectivity of the developed method. The method was successfully applied for the determination of trace amount of Au(III) in water and pharmaceutical samples. The results obtained were in agreement with the reported methods at the 95% confidence level.

Quantitation of glycerophosphorylcholine by flow injection analysis using immobilized enzymes.

PubMed

Mancini, A; Del Rosso, F; Roberti, R; Caligiana, P; Vecchini, A; Binaglia, L

1996-09-20

A method for quantitating glycerophosphorylcholine by flow injection analysis is reported in the present paper. Glycerophosphorylcholine phosphodiesterase and choline oxidase, immobilized on controlled porosity glass beads, are packed in a small reactor inserted in a flow injection manifold. When samples containing glycerophosphorylcholine are injected, glycerophosphorylcholine is hydrolyzed into choline and sn-glycerol-3-phosphate. The free choline produced in this reaction is oxidized to betain and hydrogen peroxide. Hydrogen peroxide is detected amperometrically. Quantitation of glycerophosphorylcholine in samples containing choline and phosphorylcholine is obtained inserting ahead of the reactor a small column packed with a mixed bed ion exchange resin. The time needed for each determination does not exceed one minute. The present method, applied to quantitate glycerophosphorylcholine in samples of seminal plasma, gave results comparable with those obtained using the standard enzymatic-spectrophotometric procedure. An alternative procedure, making use of co-immobilized glycerophosphorylcholine phosphodiesterase and glycerol-3-phosphate oxidase for quantitating glycerophosphorylcholine, glycerophosphorylethanolamine and glycerophosphorylserine is also described.

Flow injection spectrophotometry using natural reagent from Morinda citrifolia root for determination of aluminium in tea.

PubMed

Tontrong, Sopa; Khonyoung, Supada; Jakmunee, Jaroon

2012-05-01

A flow injection (FI) spectrophotometric method with using natural reagent extracted from Morinda citrifolia root has been developed for determination of aluminium. The extract contained anthraquinone compounds which could react with Al(3+) to form reddish complexes which had maximum absorption wavelength at 499.0nm. The extract could be used as a reagent in FI system without further purification to obtain pure compound. A sensitive method for determination of aluminium in concentration range of 0.1-1.0mgL(-1), with detection limit of 0.05mgL(-1) was achieved. Relative standard deviations of 1.2% and 1.7% were obtained for the determination of 0.1 and 0.6mgL(-1) Al(3+) (n=11). Sample throughput of 35h(-1) was achieved with the consumption of 3mL each of carrier and reagent solutions per injection. The developed method was successfully applied to tea samples, validated by the FAAS standard method. The method is simple, fast, economical and could be classified as a greener analytical method. Copyright © 2011 Elsevier Ltd. All rights reserved.

Flow injection spectrophotometric determination of V(V) involving on-line separation using a poly(vinylidene fluoride-co-hexafluoropropylene)-based polymer inclusion membrane.

PubMed

Yaftian, Mohammad Reza; Almeida, M Inês G S; Cattrall, Robert W; Kolev, Spas D

2018-05-01

A poly(vinylidene fluoride-co-hexafluoropropylene)-based polymer inclusion membrane (PIM) using Cyphos® IL 101 (i.e. trihexyl(tetradecyl)phosphonium chloride) as the carrier and 2-nitrophenyl octyl ether as a plasticizer in a mass ratio of 55/35/10 was employed for the on-line extractive separation of V(V) prior to its spectrophotometric determination in a flow injection analysis (FIA) system using xylenol orange as the colorimetric reagent. The selectivity of the membrane allowed the determination of V(V) in sulfate solutions in the presence of a variety of cations and anions. The interference of molybdenum(VI) was eliminated by off-line extraction using the same PIM. A univariate sequential optimization of the newly developed FIA system was conducted and under optimal conditions the system is characterized by a linear concentration range of 0.5-8.0mgL -1 , detection limit of 0.08mgL -1 and sample throughput of 4h -1 . The relative standard deviation at the 3mgL -1 level of V(V) was 2.9% based on 8 replicate determinations. The membrane was stable, which was reflected by the standard deviation value for determinations over three consecutive days (24 determinations of 3mgL -1 V(V)) of 3.6%. The newly developed FIA system was applied to the determination of V(V) in water and dietary supplements samples and a good agreement with inductively coupled plasma optical emission spectrometry was observed. Copyright © 2018 Elsevier B.V. All rights reserved.

Simple and clean determination of tetracyclines by flow injection analysis

NASA Astrophysics Data System (ADS)

Rodríguez, Michael Pérez; Pezza, Helena Redigolo; Pezza, Leonardo

2016-01-01

An environmentally reliable analytical methodology was developed for direct quantification of tetracycline (TC) and oxytetracycline (OTC) using continuous flow injection analysis with spectrophotometric detection. The method is based on the diazo coupling reaction between the tetracyclines and diazotized sulfanilic acid in a basic medium, resulting in the formation of an intense orange azo compound that presents maximum absorption at 434 nm. Experimental design was used to optimize the analytical conditions. The proposed technique was validated over the concentration range of 1 to 40 μg mL- 1, and was successfully applied to samples of commercial veterinary pharmaceuticals. The detection (LOD) and quantification (LOQ) limits were 0.40 and 1.35 μg mL- 1, respectively. The samples were also analyzed by an HPLC method, and the results showed agreement with the proposed technique. The new flow injection method can be immediately used for quality control purposes in the pharmaceutical industry, facilitating monitoring in real time during the production processes of tetracycline formulations for veterinary use.

Exploiting an automated microfluidic hydrodynamic sequential injection system for determination of phosphate.

PubMed

Khongpet, Wanpen; Pencharee, Somkid; Puangpila, Chanida; Kradtap Hartwell, Supaporn; Lapanantnoppakhun, Somchai; Jakmunee, Jaroon

2018-01-15

A microfluidic hydrodynamic sequential injection (μHSI) spectrophotometric system was designed and fabricated. The system was built by laser engraving a manifold pattern on an acrylic block and sealing with another flat acrylic plate to form a microfluidic channel platform. The platform was incorporated with small solenoid valves to obtain a portable setup for programmable control of the liquid flow into the channel according to the HSI principle. The system was demonstrated for the determination of phosphate using a molybdenum blue method. An ascorbic acid, standard or sample, and acidic molybdate solutions were sequentially aspirated to fill the channel forming a stack zone before flowing to the detector. Under the optimum condition, a linear calibration graph in the range of 0.1-6mg P L -1 was obtained. The detection limit was 0.1mgL -1 . The system is compact (5.0mm thick, 80mm wide × 140mm long), durable, portable, cost-effective, and consumes little amount of chemicals (83μL each of molybdate and ascorbic acid, 133μL of the sample solution and 1.7mL of water carrier/run). It was applied for the determination of phosphate content in extracted soil samples. The percent recoveries of the analysis were obtained in the range of 91.2-107.3. The results obtained agreed well with those of the batch spectrophotometric method. Copyright © 2017 Elsevier B.V. All rights reserved.

Determination of nitrite and nitrate in water samples by an automated hydrodynamic sequential injection method.

PubMed

Somnam, Sarawut; Jakmunee, Jaroon; Grudpan, Kate; Lenghor, Narong; Motomizu, Shoji

2008-12-01

An automated hydrodynamic sequential injection (HSI) system with spectrophotometric detection was developed. Thanks to the hydrodynamic injection principle, simple devices can be used for introducing reproducible microliter volumes of both sample and reagent into the flow channel to form stacked zones in a similar fashion to those in a sequential injection system. The zones were then pushed to the detector and a peak profile was recorded. The determination of nitrite and nitrate in water samples by employing the Griess reaction was chosen as a model. Calibration graphs with linearity in the range of 0.7 - 40 muM were obtained for both nitrite and nitrate. Detection limits were found to be 0.3 muM NO(2)(-) and 0.4 muM NO(3)(-), respectively, with a sample throughput of 20 h(-1) for consecutive determination of both the species. The developed system was successfully applied to the analysis of water samples, employing simple and cost-effective instrumentation and offering higher degrees of automation and low chemical consumption.

Matrix isolation with an ion transfer device for interference-free simultaneous spectrophotometric determinations of hexavalent and trivalent chromium in a flow-based system.

PubMed

Ohira, Shin-Ichi; Nakamura, Koretaka; Chiba, Mitsuki; Dasgupta, Purnendu K; Toda, Kei

2017-03-01

Chromium speciation by spectrophotometric determination of hexavalent chromium (Cr(VI)) with diphenylcarbazide (DPC) has several problems. These include: (1) the inability to directly detect trivalent chromium (Cr(III)) with DPC, (2) positive interference in Cr(VI) determination by other metal cations and (3) negative interference by any reducing agent present in the sample. These are addressed with an ion transfer device (ITD) in a flow injection analysis system. We previously developed the ITD for electrodialytic separations. Here we separate oppositely charged Cr(III) and Cr(VI) species by the ITD into two different acceptor solutions within ~5 s. The acceptor solutions consist of buffered H 2 O 2 to oxidize the Cr(III) to Cr(VI). Then DPC is added to either acceptor to measure Cr(III) and Cr(VI) spectrophotometrically. The system was optimized to provide the same response for Cr(VI) and Cr(III) with limits of detection (LODs, S/N=3) of 0.5 μg L -1 for each and a throughput rate of 30 samples h -1 . The ITD separation was also effective for matrix isolation and reduction of interferences. Potential cationic interferences were not transferred into the anionic Cr(VI) acceptor stream. Much of the organic compounds in soil extracts were also eliminated as evidenced from standard addition and recovery studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Multisyringe flow injection analysis hyphenated with liquid core waveguides for the development of cleaner spectroscopic analytical methods: improved determination of chloride in waters.

PubMed

Maya, Fernando; Estela, José Manuel; Cerdà, Víctor

2009-07-01

In this work, the hyphenation of the multisyringe flow injection analysis technique with a 100-cm-long pathlength liquid core waveguide has been accomplished. The Cl-/Hg(SCN)2/Fe3+ reaction system for the spectrophotometric determination of chloride (Cl(-)) in waters was used as chemical model. As a result, this classic analytical methodology has been improved, minimizing dramatically the consumption of reagents, in particular, that of the highly biotoxic chemical Hg(SCN)2. The proposed method features a linear dynamic range composed of two steps between (1) 0.2-2 and (2) 2-8 mg Cl- L(-1), thus extended applicability due to on-line sample dilution (up to 400 mg Cl- L(-1)). It also presents improved limits of detection and quantification of 0.06 and 0.20 mg Cl- L(-1), respectively. The coefficient of variation and the injection throughput were 1.3% (n = 10, 2 mg Cl- L(-1)) and 21 h(-1). Furthermore, a very low consumption of reagents per Cl- determination of 0.2 microg Hg(II) and 28 microg Fe3+ has been achieved. The method was successfully applied to the determination of Cl- in different types of water samples. Finally, the proposed system is critically compared from a green analytical chemistry point of view against other flow systems for the same purpose.

Validated flow-injection method for rapid aluminium determination in anti-perspirants.

PubMed

López-Gonzálvez, A; Ruiz, M A; Barbas, C

2008-09-29

A flow-injection (FI) method for the rapid determination of aluminium in anti-perspirants has been developed. The method is based on the spectrophotometric detection at 535nm of the complex formed between Al ions and the chromogenic reagent eriochrome cyanine R. Both the batch and FI methods were validated by checking the parameters included in the ISO-3543-1 regulation. Variables involved in the FI method were optimized by using appropriate statistical tools. The method does not exhibit interference from other substances present in anti-perspirants and it shows a high precision with a R.S.D. value (n=6) of 0.9%. Moreover, the accuracy of the method was evaluated by comparison with a back complexometric titration method, which is currently used for routine analysis in pharmaceutical laboratories. The Student's t-test showed that the results obtained by both methods were not significantly different for a significance level of 95%. A response time of 12s and a sample analysis time, by performing triplicate injections, of 60s were achieved. The analytical figures of merit make the method highly appropriate to substitute the time-consuming complexometric method for this kind of analysis.

Application of hydrocyanic acid vapor generation via focused microwave radiation to the preparation of industrial effluent samples prior to free and total cyanide determinations by spectrophotometric flow injection analysis.

PubMed

Quaresma, Maria Cristina Baptista; de Carvalho, Maria de Fátima Batista; Meirelles, Francis Assis; Santiago, Vânia Maria Junqueira; Santelli, Ricardo Erthal

2007-02-01

A sample preparation procedure for the quantitative determination of free and total cyanides in industrial effluents has been developed that involves hydrocyanic acid vapor generation via focused microwave radiation. Hydrocyanic acid vapor was generated from free cyanides using only 5 min of irradiation time (90 W power) and a purge time of 5 min. The HCN generated was absorbed into an accepting NaOH solution using very simple glassware apparatus that was appropriate for the microwave oven cavity. After that, the cyanide concentration was determined within 90 s using a well-known spectrophotometric flow injection analysis system. Total cyanide analysis required 15 min irradiation time (90 W power), as well as chemical conditions such as the presence of EDTA-acetate buffer solution or ascorbic acid, depending on the effluent to be analyzed (petroleum refinery or electroplating effluents, respectively). The detection limit was 0.018 mg CN l(-1) (quantification limit of 0.05 mg CN l(-1)), and the measured RSD was better than 8% for ten independent analyses of effluent samples (1.4 mg l(-1) cyanide). The accuracy of the procedure was assessed via analyte spiking (with free and complex cyanides) and by performing an independent sample analysis based on the standard methodology recommended by the APHA for comparison. The sample preparation procedure takes only 10 min for free and 20 min for total cyanide, making this procedure much faster than traditional methodologies (conventional heating and distillation), which are time-consuming (they require at least 1 h). Samples from oil (sour and stripping tower bottom waters) and electroplating effluents were analyzed successfully.

Determination of yeast assimilable nitrogen content in wine fermentations by sequential injection analysis with spectrophotometric detetection.

PubMed

Muik, Barbara; Edelmann, Andrea; Lendl, Bernhard; Ayora-Cañada, María José

2002-09-01

An automated method for measuring the primary amino acid concentration in wine fermentations by sequential injection analysis with spectrophotometric detection was developed. Isoindole-derivatives from the primary amino acid were formed by reaction with o-phthaldialdehyde and N-acetyl- L-cysteine and measured at 334 nm with respect to a baseline point at 700 nm to compensate the observed Schlieren effect. As the reaction kinetic was strongly matrix dependent the analytical readout at the final reaction equilibrium has been evaluated. Therefore four parallel reaction coils were included in the flow system to be capable of processing four samples simultaneously. Using isoleucine as the representative primary amino acid in wine fermentations a linear calibration curve from 2 to 10 mM isoleucine, corresponding to 28 to 140 mg nitrogen/L (N/L) was obtained. The coefficient of variation of the method was 1.5% at a throughput of 12 samples per hour. The developed method was successfully used to monitor two wine fermentations during alcoholic fermentation. The results were in agreement with an external reference method based on high performance liquid chromatography. A mean-t-test showed no significant differences between the two methods at a confidence level of 95%.

Iodine speciation in coastal and inland bathing waters and seaweeds extracts using a sequential injection standard addition flow-batch method.

PubMed

Santos, Inês C; Mesquita, Raquel B R; Bordalo, Adriano A; Rangel, António O S S

2015-02-01

The present work describes the development of a sequential injection standard addition method for iodine speciation in bathing waters and seaweeds extracts without prior sample treatment. Iodine speciation was obtained by assessing the iodide and iodate content, the two inorganic forms of iodine in waters. For the determination of iodide, an iodide ion selective electrode (ISE) was used. The indirect determination of iodate was based on the spectrophotometric determination of nitrite (Griess reaction). For the iodate measurement, a mixing chamber was employed (flow batch approach) to explore the inherent efficient mixing, essential for the indirect determination of iodate. The application of the standard addition method enabled detection limits of 0.14 µM for iodide and 0.02 µM for iodate, together with the direct introduction of the target water samples, coastal and inland bathing waters. The results obtained were in agreement with those obtained by ICP-MS and a colorimetric reference procedure. Recovery tests also confirmed the accuracy of the developed method which was effectively applied to bathing waters and seaweed extracts. Copyright © 2014 Elsevier B.V. All rights reserved.

[Flow injection-spectrophotometric determination of total dissolved nitrogen in seawater based on quantificational solenoid valves].

PubMed

Han, Bin; Cao, Lei; Zheng, Li; Zang, Jia-ye; Wang, Xiao-ru

2012-01-01

Using three pipe clamp solenoid valves to replace the traditional six-port valve for sample quota, a set of multi-channel flow injection analyzer was designed in the present paper. The authors optimized optimum instrumental testing condition, and realized determination and analysis of total dissolved nitrogen in seawaters. The construction of apparatus is simple and it has the potential to be used for analysis of total dissolved nitrogen. The sample throughput of total dissolved nitrogen was 27 samples per hour. The linear range of total dissolved nitrogen was 50.0-1 000.0 microgN x L(-3) (r > or = 0.999). The detection limit was 7.6 microgN x L(-3). The recovery of total dissolved nitrogen was 87.3%-107.2%. The relative standard deviation for total dissolved nitrogen was 1.35%-6.32% (n = 6). After the t-test analysis, it does not have the significance difference between this method and national standard method. It is suitable for fast analysis of total dissolved nitrogen in seawater.

Spectrophotometric determination of sulphate in automotive fuel ethanol by sequential injection analysis using dimethylsulphonazo(III) reaction.

PubMed

de Oliveira, Fabio Santos; Korn, Mauro

2006-01-15

A sensitive SIA method was developed for sulphate determination in automotive fuel ethanol. This method was based on the reaction of sulphate with barium-dimethylsulphonazo(III) leading to a decrease on the magnitude of analytical signal monitored at 665 nm. Alcohol fuel samples were previously burned up to avoid matrix effects for sulphate determinations. Binary sampling and stop-flow strategies were used to increase the sensitivity of the method. The optimization of analytical parameter was performed by response surface method using Box-Behnker and central composite designs. The proposed sequential flow procedure permits to determine up to 10.0mg SO(4)(2-)l(-1) with R.S.D. <2.5% and limit of detection of 0.27 mg l(-1). The method has been successfully applied for sulphate determination in automotive fuel alcohol and the results agreed with the reference volumetric method. In the optimized condition the SIA system carried out 27 samples per hour.

Fully automated analytical procedure for propofol determination by sequential injection technique with spectrophotometric and fluorimetric detections.

PubMed

Šrámková, Ivana; Amorim, Célia G; Sklenářová, Hana; Montenegro, Maria C B M; Horstkotte, Burkhard; Araújo, Alberto N; Solich, Petr

2014-01-01

In this work, an application of an enzymatic reaction for the determination of the highly hydrophobic drug propofol in emulsion dosage form is presented. Emulsions represent a complex and therefore challenging matrix for analysis. Ethanol was used for breakage of a lipid emulsion, which enabled optical detection. A fully automated method based on Sequential Injection Analysis was developed, allowing propofol determination without the requirement of tedious sample pre-treatment. The method was based on spectrophotometric detection after the enzymatic oxidation catalysed by horseradish peroxidase and subsequent coupling with 4-aminoantipyrine leading to a coloured product with an absorbance maximum at 485 nm. This procedure was compared with a simple fluorimetric method, which was based on the direct selective fluorescence emission of propofol in ethanol at 347 nm. Both methods provide comparable validation parameters with linear working ranges of 0.005-0.100 mg mL(-1) and 0.004-0.243 mg mL(-1) for the spectrophotometric and fluorimetric methods, respectively. The detection and quantitation limits achieved with the spectrophotometric method were 0.0016 and 0.0053 mg mL(-1), respectively. The fluorimetric method provided the detection limit of 0.0013 mg mL(-1) and limit of quantitation of 0.0043 mg mL(-1). The RSD did not exceed 5% and 2% (n=10), correspondingly. A sample throughput of approx. 14 h(-1) for the spectrophotometric and 68 h(-1) for the fluorimetric detection was achieved. Both methods proved to be suitable for the determination of propofol in pharmaceutical formulation with average recovery values of 98.1 and 98.5%. © 2013 Elsevier B.V. All rights reserved.

Simultaneous determination of Cr(III) and Cr(VI) in tannery wastewater using low pressure ion chromatography combined with flow injection spectrophotometry

NASA Astrophysics Data System (ADS)

Chen, Shujuan; Zhang, Xinshen; Yu, Lingyun; Wang, Li; Li, Hui

2012-03-01

Trivalent and hexavalent chromium have been successfully separated and determined using low pressure ion chromatography combined with flow injection spectrophotometric analysis (LPIC-FIA). A column packed with crosslinking starch microspheres was used for on-line separation of Cr(III) from Cr(VI) in a flow-injection system because of its absorptive effect on Cr(III). To determine the concentration of Cr(III) and Cr(VI) in samples, we used 3.0 mmol/L nitric acid to elute adsorbed Cr(III) from the column and then used ceric sulfate-sulfuric acid as oxidant to convert all Cr(III) into Cr(VI). Then, Cr(VI) directly came from the samples and Cr(VI) came from Cr(III) successively formed a amaranthine complex with diphenycarbazide and the complex shows a maximum absorption at 530 nm. Analytical parameters including the concentration of eluent and oxidant solution, oxidizing temperature, length of oxidizing reaction coil, reaction coil and injection coil, interfering effects, etc., were optimized. The limit of detection was 1.25 μg/L for Cr(VI) and 3.76 μg/L for Cr(III). The linear relationship between absorption with the concentration of Cr(VI) and Cr(III) was 0.001-1.000 mg/L and 0.030-1.000 mg/L with correlation coefficients of 0.9995 and 0.9994, respectively. The relative standard deviation of Cr(VI) and Cr(III) was 1.21% and 1.66%, respectively (n = 10). Major cations and anions did not show any interference. We validated this method through certified reference materials and through measuring the recovery in tannery wastewater.

Redesigning flow injection after 40 years of development: Flow programming.

PubMed

Ruzicka, Jaromir Jarda

2018-01-01

Automation of reagent based assays, by means of Flow Injection (FI), is based on sample processing, in which a sample flows continuously towards and through a detector for quantification of the target analyte. The Achilles heel of this methodology, the legacy of Auto Analyzer®, is continuous reagent consumption, and continuous generation of chemical waste. However, flow programming, assisted by recent advances in precise pumping, combined with the lab-on-valve technique, allows the FI manifold to be designed around a single confluence point through which sample and reagents are sequentially directed by means of a series of flow reversals. This approach results in sample/reagent mixing analogous to the traditional FI, reduces sample and reagent consumption, and uses the stop flow technique for enhancement of the yield of chemical reactions. The feasibility of programmable Flow Injection (pFI) is documented by example of commonly used spectrophotometric assays of, phosphate, nitrate, nitrite and glucose. Experimental details and additional information are available in online tutorial http://www.flowinjectiontutorial.com/. Copyright © 2017 Elsevier B.V. All rights reserved.

Stopped-in-loop flow analysis system for successive determination of trace vanadium and iron in drinking water using their catalytic reactions.

PubMed

Ayala Quezada, Alejandro; Ohara, Keisuke; Ratanawimarnwong, Nuanlaor; Nacapricha, Duangjai; Murakami, Hiroya; Teshima, Norio; Sakai, Tadao

2015-11-01

An automated stopped-in-loop flow analysis (SILFA) system is proposed for the successive catalytic determination of vanadium and iron. The determination of vanadium was based on the p-anisidine oxidation by potassium bromate in the presence of Tiron as an activator to form a reddish dye, which has an absorption maximum at 510 nm. The selectivity of the vanadium determination was greatly improved by adding diphosphate as a masking agent of iron. For the iron determination, an iron-catalyzed oxidative reaction of p-anisidine by hydrogen peroxide with 1,10-phenanthroline as an activator to produce a reddish dye (510 nm) was employed. The SILFA system consisted of two peristaltic pumps, two six-port injection valves, a four-port selection valve, a heater device, a spectrophotometric detector and a data acquisition device. One six-port injection valve was used for the isolation of a mixed solution of standard/sample and reagent to promote each catalytic reaction, and another six-port injection valve was used for switching the reagent for vanadium or iron to achieve selective determination of each analyte. The above mentioned four-port selection valve was used to select standard solutions or sample. These three valves and the two peristaltic pumps were controlled by a built-in programmable logic controller in a touchscreen controller. The obtained results showed that the proposed SILFA monitoring system constituted an effective approach for the selective determination of vanadium and iron. The limits of detection, 0.052 and 0.55 µg L(-1), were obtained for vanadium and iron, respectively. The proposed system was successfully applied to drinking water samples without any preconcentration procedures. Copyright © 2015 Elsevier B.V. All rights reserved.

The use of a polymer inclusion membrane in flow injection analysis for the on-line separation and determination of zinc.

PubMed

Zhang, Lujia L; Cattrall, Robert W; Kolev, Spas D

2011-06-15

This paper reports the first use of a polymer inclusion membrane (PIM) for on-line separation in flow injection analysis (FIA) involving simultaneous extraction and back-extraction. The FIA system containing the PIM separation module was used for the determination of Zn(II) in aqueous samples in the presence of Mg(II), Ca(II), Cd(II), Co(II), Ni(II), Cu(II), and Fe(III). The Fe(III) and Cu(II) interferences were eliminated by off-line precipitation with phosphate and on-line complexation with chloride, respectively. The concentration of Zn(II) was determined spectrophotometrically using 4-(2-pyridylazo) resorcinol (PAR). The optimal composition of the PIM consisted of 40% (m/m) di(2-ethlyhexyl) phosphoric acid (D2EHPA) as carrier, 10% (m/m) dioctyl phthalate (DOP) as plasticizer and 50% (m/m) poly(vinyl chloride) (PVC) as the base polymer. The optimized FIA system was characterized by a linear calibration curve in the range from 1.0 to 30.0 mg L(-1) Zn(II), a detection limit of 0.05 mg L(-1) and a relative standard deviation of 3.4% with a sampling rate of 4h(-1). Reproducible results were obtained for 20 replicate injections over a 5h period which demonstrated a good membrane stability. The FIA system was applied to the determination of Zn(II) in pharmaceuticals and samples from the galvanizing industry and very good agreement with atomic absorption spectrometry was obtained. Copyright © 2011 Elsevier B.V. All rights reserved.

[Determination of aluminum in sediments by atomic absorption spectrophotometer without FIA spectrophotometric analysis].

PubMed

Zhao, Zhen-yi; Han, Guang-xi; Song, Xi-ming; Luo, Zhi-xiong

2008-06-01

To search for a new method of determining, we developed a new flow injection analyzer, applied to the atomic absorption spectrophotometer, relying on it without flame in place of visible spectrophotometer, and studied the appropriate condition for the determination of aluminum in sediments, thus built up a kind of new analytical test technique. Three peak and two valley absorption values (A1, A2, A3, A4 and A5) can be continuously obtained simultaneously that all can be used for quantitative analysis, then we discussed its theory and experiment technique. Based on the additivity of absorbance (A = A1+A2+A3+A4+ A5), the sensitivity of FIA is enhanced, and its precision and linear relation are also good, raising the efficiency of AAS. The simple method has been applied to determining Al in sediments, and the results are satisfactory.

Single peak parameters technique for simultaneous measurements: Spectrophotometric sequential injection determination of Fe(II) and Fe(III).

PubMed

Kozak, J; Paluch, J; Węgrzecka, A; Kozak, M; Wieczorek, M; Kochana, J; Kościelniak, P

2016-02-01

Spectrophotometric sequential injection system (SI) is proposed to automate the method of simultaneous determination of Fe(II) and Fe(III) on the basis of parameters of a single peak. In the developed SI system, sample and mixture of reagents (1,10-phenanthroline and sulfosalicylic acid) are introduced into a vessel, where in an acid environment (pH≅3) appropriate compounds of Fe(II) and Fe(III) with 1,10-phenanthroline and sulfosalicylic acid are formed, respectively. Then, in turn, air, sample, EDTA and sample again, are introduced into a holding coil. After the flow reversal, a segment of air is removed from the system by an additional valve and as EDTA replaces sulfosalicylic acid forming a more stable colorless compound with Fe(III), a complex signal is registered. Measurements are performed at wavelength 530 nm. The absorbance measured at minimum of the negative peak and the area or the absorbance measured at maximum of the signal can be used as measures corresponding to Fe(II) and Fe(III) concentrations, respectively. The time of the peak registration is about 2 min. Two-component calibration has been applied to analysis. Fe(II) and Fe(III) can be determined within the concentration ranges of 0.04-4.00 and 0.1-5.00 mg L(-1), with precision less than 2.8% and 1.7% (RSD), respectively and accuracy better than 7% (RE). The detection limit is 0.04 and 0.09 mg L(-1) for Fe(II) and Fe(III), respectively. The method was applied to analysis of artesian water samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Sequential determination of multi-nutrient elements in natural water samples with a reverse flow injection system.

PubMed

Lin, Kunning; Ma, Jian; Yuan, Dongxing; Feng, Sichao; Su, Haitao; Huang, Yongming; Shangguan, Qipei

2017-05-15

An integrated system was developed for automatic and sequential determination of NO 2 - , NO 3 - , PO 4 3- , Fe 2+ , Fe 3+ and Mn 2+ in natural waters based on reverse flow injection analysis combined with spectrophotometric detection. The system operation was controlled by a single chip microcomputer and laboratory-programmed software written in LabVIEW. The experimental parameters for each nutrient element analysis were optimized based on a univariate experimental design, and interferences from common ions were evaluated. The upper limits of the linear range (along with detection limit, µmolL -1 ) of the proposed method was 20 (0.03), 200 (0.7), 12 (0.3), 5 (0.03), 5 (0.03), 9 (0.2) µmolL -1 , for NO 2 - , NO 3 - , PO 4 3- , Fe 2+ , Fe 3+ and Mn 2+ , respectively. The relative standard deviations were below 5% (n=9-13) and the recoveries varied from 88.0±1.0% to 104.5±1.0% for spiked water samples. The sample throughput was about 20h -1 . This system has been successfully applied for the determination of multi-nutrient elements in different kinds of water samples and showed good agreement with reference methods (slope 1.0260±0.0043, R 2 =0.9991, n=50). Copyright © 2017 Elsevier B.V. All rights reserved.

Fast batch injection analysis of H(2)O(2) using an array of Pt-modified gold microelectrodes obtained from split electronic chips.

PubMed

Pacheco, Bruno D; Valério, Jaqueline; Angnes, Lúcio; Pedrotti, Jairo J

2011-06-24

A fast and robust analytical method for amperometric determination of hydrogen peroxide (H(2)O(2)) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n=14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H(2)O(2) amperometric determination in the concentration range from 0.8 μmolL(-1) to 100 μmolL(-1). The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 μmolL(-1) (3σ). The anodic current peaks obtained after a series of 23 successive injections of 50 μL of 25 μmolL(-1) H(2)O(2) showed an RSD<0.9%. To ensure the good selectivity to detect H(2)O(2), its determination was performed in a differential mode, with selective destruction of the H(2)O(2) with catalase in 10 mmolL(-1) phosphate buffer solution. Practical application of the analytical procedure involved H(2)O(2) determination in rainwater of São Paulo City. A comparison of the results obtained by the proposed amperometric method with another one which combines flow injection analysis (FIA) with spectrophotometric detection showed good agreement. Copyright © 2011 Elsevier B.V. All rights reserved.

Novel approaches to analysis by flow injection gradient titration.

PubMed

Wójtowicz, Marzena; Kozak, Joanna; Kościelniak, Paweł

2007-09-26

Two novel procedures for flow injection gradient titration with the use of a single stock standard solution are proposed. In the multi-point single-line (MP-SL) method the calibration graph is constructed on the basis of a set of standard solutions, which are generated in a standard reservoir and subsequently injected into the titrant. According to the single-point multi-line (SP-ML) procedure the standard solution and a sample are injected into the titrant stream from four loops of different capacities, hence four calibration graphs are able to be constructed and the analytical result is calculated on the basis of a generalized slope of these graphs. Both approaches have been tested on the example of spectrophotometric acid-base titration of hydrochloric and acetic acids with using bromothymol blue and phenolphthalein as indicators, respectively, and sodium hydroxide as a titrant. Under optimized experimental conditions the analytical results of precision less than 1.8 and 2.5% (RSD) and of accuracy less than 3.0 and 5.4% (relative error (RE)) were obtained for MP-SL and SP-ML procedures, respectively, in ranges of 0.0031-0.0631 mol L(-1) for samples of hydrochloric acid and of 0.1680-1.7600 mol L(-1) for samples of acetic acid. The feasibility of both methods was illustrated by applying them to the total acidity determination in vinegar samples with precision lower than 0.5 and 2.9% (RSD) for MP-SL and SP-ML procedures, respectively.

Ceramic microsystem incorporating a microreactor with immobilized biocatalyst for enzymatic spectrophotometric assays.

PubMed

Baeza, Mireia; López, Carmen; Alonso, Julián; López-Santín, Josep; Alvaro, Gregorio

2010-02-01

Low-temperature cofired ceramics (LTCC) technology is a versatile fabrication technique used to construct microflow systems. It permits the integration of several unitary operations (pretreatment, separation, (bio)chemical reaction, and detection stage) of an analytical process in a modular or monolithic way. Moreover, because of its compatibility with biological material, LTCC is adequate for analytical applications based on enzymatic reactions. Here we present the design, construction, and evaluation of a LTCC microfluidic system that integrates a microreactor (internal volume, 24.28 microL) with an immobilized beta-galactosidase from Escherichia coli (0.479 activity units) and an optical flow cell to measure the product of the enzymatic reaction. The enzyme was immobilized on a glyoxal-agarose support, maintaining its activity along the time of the study. As a proof of concept, the LTCC-beta-galactosidase system was tested by measuring the conversion of ortho-nitrophenyl beta-D-galactopyranoside, the substrate usually employed for activity determinations. Once packed in a monolithically integrated microcolumn, the miniaturized flow system was characterized, the operational conditions optimized (flow rate and injection volume), and its performance successfully evaluated by determining the beta-galactosidase substrate concentration at the millimolar level.

A sensitive and rapid assay for 4-aminophenol in paracetamol drug and tablet formulation, by flow injection analysis with spectrophotometric detection.

PubMed

Bloomfield, M S

2002-12-06

4-Aminophenol (4AP) is the primary degradation product of paracetamol which is limited at a low level (50 ppm or 0.005% w/w) in the drug substance by the European, United States, British and German Pharmacopoeias, employing a manual colourimetric limit test. The 4AP limit is widened to 1000 ppm or 0.1% w/w for the tablet product monographs, which quote the use of a less sensitive automated HPLC method. The lower drug substance specification limit is applied to our products, (50 ppm, equivalent to 25 mug 4AP in a tablet containing 500-mg paracetamol) and the pharmacopoeial HPLC assay was not suitable at this low level due to matrix interference. For routine analysis a rapid, automated assay was required. This paper presents a highly sensitive, precise and automated method employing the technique of Flow Injection (FI) analysis to quantitatively assay low levels of this degradant. A solution of the drug substance, or an extract of the tablets, containing 4AP and paracetamol is injected into a solvent carrier stream and merged on-line with alkaline sodium nitroprusside reagent, to form a specific blue derivative which is detected spectrophotometrically at 710 nm. Standard HPLC equipment is used throughout. The procedure is fully quantitative and has been optimised for sensitivity and robustness using a multivariate experimental design (multi-level 'Central Composite' response surface) model. The method has been fully validated and is linear down to 0.01 mug ml(-1). The approach should be applicable to a range of paracetamol products.

Structural and spectrophotometric characterization of 2-[4-(dimethylamino)styryl]-1-ethylquinolinium iodide as a reagent for sequential injection determination of tungsten

NASA Astrophysics Data System (ADS)

Bazel, Yaroslav; Lešková, Martina; Rečlo, Michal; Šandrejová, Jana; Simon, András; Fizer, Maksym; Sidey, Vasyl

2018-05-01

Structure, spectrophotometric and protolytic properties of the styryl dye 2-[4-(dimethylamino)styryl]-1-ethylquinolinium iodide (R) as well as its complex with tungsten were studied. The selective protonation of dimethylamino group was confirmed by density functional theory investigation through the computation of Fukui function, NPA partial atomic charges, and NICS(0) aromaticity indexes. The TD-DFT study explains the experimental change of color by excluding the dimethylamino group from HOMO orbital upon protonation. The acid dissociation constant, the optimum wavelength and the molar absorptivity of R were found to be: 3.02, 501 nm and 4.0 × 104 L mol-1 cm-1, respectively. The protolytic properties of the reagent were found to change significantly in the presence of tungsten(VI). Analysis of bond critical points between the anions and Quinaldine Red cation gives the selectivity raw HWO4- > MoO4-> H2VO4- > ReO4- > ClO4-, that perfectly match with the experimental data. Based on this observation, a non-extractive sequential-injection spectrophotometric method for the determination of tungsten was developed. The absorbance of the colored extracts obeys Beer's law up to 55.2 mg L-1 of W at 520 nm wavelength. The limit of detection calculated from a blank test (n = 10) based on 3 s was 0.96 mg L-1. The developed method was applied for the determination of tungsten in model samples.

Flow injection chemiluminescence determination of the total phenolics levels in plant-derived beverages using soluble manganese(IV).

PubMed

Nalewajko-Sieliwoniuk, Edyta; Tarasewicz, Iwona; Kojło, Anatol

2010-05-23

This study established a flow injection (FI) methodology for the determination of the total phenolic content in plant-derived beverages based on soluble manganese(IV) chemiluminescence (CL) detection. It was found that mixing polyphenols with acidic soluble manganese(IV) in the presence of formaldehyde evoked chemiluminescence. Based on this finding, a new FI-CL method was developed for the estimation of the total content of phenolic compounds (expressed as milligrams of gallic acid equivalent per litre of drink) in a variety of wine, tea and fruit juice samples. The proposed method is sensitive with a detection limit of 0.02 ng mL(-1) (gallic acid), offers a wide linear dynamic range (0.5-400 ng mL(-1)) and high sample throughput (247 samples h(-1)). The relative standard deviation for 15 measurements was 3.8% for 2 ng mL(-1) and 0.45% for 10 ng mL(-1) of gallic acid. Analysis of 36 different samples showed that the results obtained by the proposed FI-CL method correlate highly with those obtained by spectrophotometric methods commonly used for the evaluation of the total phenolic/antioxidant level. However, the FI-CL method was found to be far simpler, more rapid and selective, with almost no interference from non-phenolic components of the samples examined. Copyright 2010 Elsevier B.V. All rights reserved.

Sub-1min separation in sequential injection chromatography for determination of synthetic water-soluble dyes in pharmaceutical formulation.

PubMed

Davletbaeva, Polina; Chocholouš, Petr; Bulatov, Andrey; Šatínský, Dalibor; Solich, Petr

2017-09-05

Sequential Injection Chromatography (SIC) evolved from fast and automated non-separation Sequential Injection Analysis (SIA) into chromatographic separation method for multi-element analysis. However, the speed of the measurement (sample throughput) is due to chromatography significantly reduced. In this paper, a sub-1min separation using medium polar cyano monolithic column (5mm×4.6mm) resulted in fast and green separation with sample throughput comparable with non-separation flow methods The separation of three synthetic water-soluble dyes (sunset yellow FCF, carmoisine and green S) was in a gradient elution mode (0.02% ammonium acetate, pH 6.7 - water) with flow rate of 3.0mLmin -1 corresponding with sample throughput of 30h -1 . Spectrophotometric detection wavelengths were set to 480, 516 and 630nm and 10Hz data collection rate. The performance of the separation was described and discussed (peak capacities 3.48-7.67, peak symmetries 1.72-1.84 and resolutions 1.42-1.88). The method was represented by validation parameters: LODs of 0.15-0.35mgL -1 , LOQs of 0.50-1.25mgL -1 , calibration ranges 0.50-150.00mgL -1 (r>0.998) and repeatability at 10.0mgL -1 of RSD≤0.98% (n=6). The method was used for determination of the dyes in "forest berries" colored pharmaceutical cough-cold formulation. The sample matrix - pharmaceuticals and excipients were not interfering with vis determination because of no retention in the separation column and colorless nature. The results proved the concept of fast and green chromatography approach using very short medium polar monolithic column in SIC. Copyright © 2017 Elsevier B.V. All rights reserved.

Automated stopped-in-dual-loop flow analysis system for catalytic determination of vanadium in drinking water.

PubMed

Teshima, Norio; Kuno, Masami; Ueda, Minoru; Ueda, Hisashi; Ohno, Shinsuke; Sakai, Tadao

2009-07-15

An automated stopped-in-dual-loop flow analysis (SIDL-FA) system is proposed for the determination of vanadium in drinking water. The chemistry is based on the vanadium-catalyzed oxidation reaction of p-anisidine by bromate in the presence of Tiron as an activator to produce a dye (lambda(max)=510 nm). A SIDL-FA system basically consists of a selection valve, three pumps (one is for delivering of standard/sample, and others are for reagents), two six-way injection valves, a spectrophotometric detector and a data acquisition device. A 100-microL coiled loop around a heated device is fitted onto each six-way injection valve. A well-mixed solution containing reagents and standard/sample is loaded into the first loop on a six-way valve, and then the same solution is loaded into the second loop on another six-way valve. The solutions are isolated by switching these two six-way valves, so that the catalytic reaction can be promoted. The net waste can be zero in this stage, because all pumps are turned off. Then each resulting solution is dispensed to the detector with suitable time lag. A touchscreen controller is developed to automatically carry out the original SIDL-FA protocol. The proposed SIDL-FA method allows vanadium to be quantified in the range of 0.1-2 microg L(-1) and is applied to the determination of vanadium in drinking water samples.

Additional studies for the spectrophotometric measurement of iodine in water

NASA Technical Reports Server (NTRS)

1972-01-01

Previous work in iodine spectroscopy is briefly reviewed. Continued studies of the direct spectrophotometric determination of aqueous iodine complexed with potassium iodide show that free iodine is optimally determined at the isosbestic point for these solutions. The effects on iodine determinations of turbidity and chemical substances (in trace amounts) is discussed and illustrated. At the levels tested, iodine measurements are not significantly altered by such substances. A preliminary design for an on-line, automated iodine monitor with eventual capability of operating also as a controller was analyzed and developed in detail with respect single beam colorimeter operating at two wavelengths (using a rotating filter wheel). A flow-through sample cell allows the instrument to operate continuously, except for momentary stop flow when measurements are made. The timed automatic cycling of the system may be interrupted whenever desired, for manual operation. An analog output signal permits controlling an iodine generator.

Validation of HPLC and UV spectrophotometric methods for the determination of meropenem in pharmaceutical dosage form.

PubMed

Mendez, Andreas S L; Steppe, Martin; Schapoval, Elfrides E S

2003-12-04

A high-performance liquid chromatographic method and a UV spectrophotometric method for the quantitative determination of meropenem, a highly active carbapenem antibiotic, in powder for injection were developed in present work. The parameters linearity, precision, accuracy, specificity, robustness, limit of detection and limit of quantitation were studied according to International Conference on Harmonization guidelines. Chromatography was carried out by reversed-phase technique on an RP-18 column with a mobile phase composed of 30 mM monobasic phosphate buffer and acetonitrile (90:10; v/v), adjusted to pH 3.0 with orthophosphoric acid. The UV spectrophotometric method was performed at 298 nm. The samples were prepared in water and the stability of meropenem in aqueous solution at 4 and 25 degrees C was studied. The results were satisfactory with good stability after 24 h at 4 degrees C. Statistical analysis by Student's t-test showed no significant difference between the results obtained by the two methods. The proposed methods are highly sensitive, precise and accurate and can be used for the reliable quantitation of meropenem in pharmaceutical dosage form.

[Studies on a sequential injection renewable surface reflectance spectrophotometric system using a microchip flow cell].

PubMed

Wang, Jian-ya; Fang, Zhao-lun

2002-02-01

A microchip flow cell was developed for flow injection renewable surface assay by reflectance spectrophotometry. The flow cell was coupled to a sequential injection system and optical fiber photometric detection system. The flow cell featured a three-layer structure. The flow channel was cut into a silicone rubber membrance which formed the middle layer, and a porous filter was inlayed across a widened section of the channel to trap microbeads introduced into the flow cell. The area of the detection window of the flow cell was approximately 3.6 mm2, the volume of the bead trapped in the flow cell was 2.2 microL, the depth of the bead layer was 600 microns. A multistrand bifurcated optical fiber was coupled with incident light, detector and flow cell. The chromogenic reaction of Cr(VI) with 1,5-diphenylcarbohydrazide (DPC) which was adsorbed on trapped Polysorb C-18 beads was used as a model reaction to optimize the flow cell design and the experimental system. The reflectance of the renewable reaction surface was monitored at 540 nm. With 100 microL sample loaded and 1.0 mL.min-1 carrier flow rate, the linear response range was 0-0.6 microgram.mL-1 Cr(VI). A detection limit (3 sigma) of 6 ng.mL-1, precision of 1.5% RSD(n = 11), and a throughput of 64 samples per hour were achieved. Considerations in system and flow cell design, the influence of depth of the bead layer, weight of beads used, and the flow rates of carrier stream on the performance were discussed.

Spectrophotometric determination of norepinephrine with sodium iodate and determination of its acidity constants

NASA Astrophysics Data System (ADS)

Hashem, E. Y.; Youssef, A. K.

2013-05-01

A spectrophotometric method is proposed for the determination of norepinephrine (NE) and its bitartrate salts. The method was based on the development of a red color (λmax = 495 nm) with sodium iodate in aqueous alcoholic medium at pH 5. The color was stable for at least 4 hrs. The molar reacting ratio of NE to sodium iodate was 1:4. A linear relationship was obtained between the absorption intensity and NE concentration in the range of 3.384-37.224 μg/ml with detection limit of 0.067 μg/ml and correlation coefficient of 0.9972. The present work facilitated the determination of the three acidity constants, 7.564 ± 0.02, 9.036 ± 0.034, and 10.761 ± 0.023. The reaction mechanism was also described. The proposed method was successfully applied for the determination of NE in pharmaceutical formulations. Results for analysis of bulk drugs and injections agree with those of official methods.

Determination of ammonium ion by fluorometry or spectrophotometry after on-line derivatization with o-phthalaldehyde

NASA Technical Reports Server (NTRS)

Goyal, S. S.; Rains, D. W.; Huffaker, R. C.

1988-01-01

A fast, sensitive, simple, and highly reproducible method for routine assay of ammonium ion (NH4+) was developed by using HPLC equipment. The method is based on the reaction of NH4+ with o-phthalaldehyde (OPA) in the presence of 2-mercaptoethanol. After an on-line derivatization, the resulting NH4(+)-OPA product was quantified by using fluorometric or spectrophotometric detection. For fluorometric detection, the excitation and emission wavelengths were 410 and 470 nm, respectively. The spectrophotometric detection was made by measuring absorbance at 410 nm. Results on the effects of OPA-reagent composition and pH, reaction temperature, sample matrix, and linearity of the assay are presented. Even though it took about 2 min from the time of sample injection to the appearance of sample peak, sample injections could be overlapped at an interval of about 1 min. Thus, the actual time needed for analysis was about 1 min per assay. The method can be used in a fully automated mode by using an autosampler injector.

A novel dual-valve sequential injection manifold (DV-SIA) for automated liquid-liquid extraction. Application for the determination of picric acid.

PubMed

Skrlíková, Jana; Andruch, Vasil; Sklenárová, Hana; Chocholous, Petr; Solich, Petr; Balogh, Ioseph S

2010-05-07

A novel dual-valve sequential injection system (DV-SIA) for online liquid-liquid extraction which resolves the main problems of LLE utilization in SIA has been designed. The main idea behind this new design was to construct an SIA system by connecting two independent units, one for aqueous-organic mixture flow and the second specifically for organic phase flow. As a result, the DV-SIA manifold consists of an Extraction unit and a Detection unit. Processing a mixture of aqueous-organic phase in the Extraction unit and a separated organic phase in the Detection unit solves the problems associated with the change of phases having different affinities to the walls of the Teflon tubing used in the SI-system. The developed manifold is a simple, user-friendly and universal system built entirely from commercially available components. The system can be used for a variety of samples and organic solvents and is simple enough to be easily handled by operators less familiar with flow systems. The efficiency of the DV-SIA system is demonstrated by the extraction of picric acid in the form of an ion associate with 2-[2-(4-methoxy-phenylamino)-vinyl]-1,3,3-trimethyl-3H-indolium reagent, with subsequent spectrophotometric detection. The suggested DV-SIA concept can be expected to stimulate new experiments in analytical laboratories and can be applied to the elaboration of procedures for the determination of other compounds extractable by organic solvents. It could thus form a basis for the design of simple, single-purpose commercial instruments used in LLE procedures. 2010 Elsevier B.V. All rights reserved.

A multisyringe flow-based system for kinetic-catalytic determination of cobalt(II).

PubMed

Chaparro, Laura; Ferrer, Laura; Leal, Luz; Cerdà, Víctor

2015-02-01

A kinetic-catalytic method for cobalt determination based on the catalytic effect of cobalt(II) on the oxidative coupling of 1,2-dihydroxyanthraquinone (alizarin) was automated exploiting multisyringe flow injection analysis (MSFIA). The proposed method was performed at pH 9.2, resulting in a discoloration process in the presence of hydrogen peroxide. The fixed-time approach was employed for analytical signal measurement. The spectrophotometric detection was used exploiting a liquid waveguide capillary cell (LWCC), of 1m optical length at 465 nm. The optimization was carried out by a multivariate approach, reaching critical values of 124 µmol L(-1) and 0.22 mol L(-1) for alizarin and hydrogen peroxide, respectively, and 67°C of reagent temperature. A sample volume of 150 µL was used allowing a sampling rate of 30h(-1). Under optimal conditions, calibration curve was linear in the range of 1-200 µg L(-1) Co, achieving a DL of 0.3 µg L(-1) Co. The repeatability, expressed as relative standard deviation (RSD) was lower than 1%. The proposed analytical procedure was applied to the determination of cobalt in cobalt gluconate and different forms of vitamin B12, cyanocobalamin and hydroxicobalamin with successful results showing recoveries around 95%. Copyright © 2014 Elsevier B.V. All rights reserved.

3D-printed flow system for determination of lead in natural waters.

PubMed

Mattio, Elodie; Robert-Peillard, Fabien; Branger, Catherine; Puzio, Kinga; Margaillan, André; Brach-Papa, Christophe; Knoery, Joël; Boudenne, Jean-Luc; Coulomb, Bruno

2017-06-01

The development of 3D printing in recent years opens up a vast array of possibilities in the field of flow analysis. In the present study, a new 3D-printed flow system has been developed for the selective spectrophotometric determination of lead in natural waters. This system was composed of three 3D-printed units (sample treatment, mixing coil and detection) that might have been assembled without any tubing to form a complete flow system. Lead was determined in a two-step procedure. A preconcentration of lead was first carried out on TrisKem Pb Resin located in a 3D-printed column reservoir closed by a tapped screw. This resin showed a high extraction selectivity for lead over many tested potential interfering metals. In a second step, lead was eluted by ammonium oxalate in presence of 4-(2-pyridylazo)-resorcinol (PAR), and spectrophotometrically detected at 520nm. The optimized flow system has exhibited a linear response from 3 to 120µgL -1 . Detection limit, coefficient of variation and sampling rate were evaluated at 2.7µgL -1 , 5.4% (n=6) and 4 sampleh -1 , respectively. This flow system stands out by its fully 3D design, portability and simplicity for low cost analysis of lead in natural waters. Copyright © 2017 Elsevier B.V. All rights reserved.

Determination of Caffeine in Beverages by Capillary Zone Electrophoresis: An Experiment for the Undergraduate Analytical Laboratory

NASA Astrophysics Data System (ADS)

Conte, Eric D.; Barry, Eugene F.; Rubinstein, Harry

1996-12-01

Certain individuals may be sensitive to specific compounds in comsumer products. It is important to quantify these analytes in food products in order to monitor their intake. Caffeine is one such compound. Determination of caffeine in beverages by spectrophotometric procedures requires an extraction procedure, which can prove time-consuming. Although the corresponding determination by HPLC allows for a direct injection, capillary zone electrophoresis provides several advantages such as extremely low solvent consumption, smaller sample volume requirements, and improved sensitivity.

Simple, fast and reliable liquid chromatographic and spectrophotometric methods for the determination of theophylline in urine, saliva and plasma samples.

PubMed

Charehsaz, Mohammad; Gürbay, Aylin; Aydin, Ahmet; Sahin, Gönül

2014-01-01

In this study, a high-performance liquid chromatographic method (HPLC) and UV spectrophotometric method were developed, validated and applied for the determination of theophylline in biological fluids. Liquid- liquid extraction is performed for isolation of the drug and elimination of plasma and saliva interferences. Urine samples were applied without any extraction. The chromatographic separation was achieved on a C18 column by using 60:40 methanol:water as mobile phase under isocratic conditions at a flow rate of 0.75 mL/min with UV detection at 280 nm in HPLC method. UV spectrophotometric analysis was performed at 275 nm. the limit of quantification: 1.1 µg/mL for urine, 1.9 µg/mL for saliva, 3.1 µg/mL for plasma; recovery: 94.85% for plasma, 100.45% for saliva, 101.39% for urine; intra-day precision: 0.22-2.33%, inter-day precision: 3.17-13.12%. Spectrophotometric analysis results were as follows: the limit of quantitation: 5.23 µg/mL for plasma, 8.7 µg/mL for urine; recovery: 98.27% for plasma, 95.25% for urine; intra-day precision: 2.37 - 3.00%, inter-day precision: 5.43-7.91%. It can be concluded that this validated HPLC method is easy, precise, accurate, sensitive and selective for determination of theophylline in biological samples. Also spectrophotometric analysis can be used where it can be applicable.

Liquid-liquid microextraction in a multicommuted flow system for direct spectrophotometric determination of iodine value in biodiesel.

PubMed

Pereira, Andréia C; Rocha, Fábio R P

2014-06-04

A flow-based procedure was developed for the direct spectrophotometric determination of the iodine value (IV) in biodiesel. The procedure was based on the microextraction/reaction of unsaturated compounds with triiodide ions in an aqueous medium by inserting the reagent solution between the aliquots of biodiesel without any pretreatment. The interaction occurred through the biodiesel film formed on the inner walls of the hydrophobic tube used as the reactor and at the aqueous/biodiesel interfaces. The spectrophotometric detection was based on the discoloration of the I3(-) reagent in the aqueous phase by using a glass tube coupled to a fiber-optic spectrophotometer as the detection cell. Reference solutions were prepared by dilution of biodiesel samples with previously determined IV in hexane. The analytical response was linear for IV from 13 to 135 g I2/100 g with a detection limit of 5 g I2/100 g. A coefficient of variation of 1.7% (n=10) and a sampling rate of 108 determinations per hour were achieved by consuming 224 μL of the sample and 200 μg of I2 per determination. The slopes of analytical curves obtained with three different biodiesel samples were in agreement (variations in slopes lower than 3.1%), thus indicating an absence of any matrix effects. Results for biodiesel samples from different sources agreed with the volumetric official procedure at the 95% confidence level. The proposed procedure is therefore a simple, fast, and reliable alternative for estimating the iodine value of biodiesel. Copyright © 2014. Published by Elsevier B.V.

Sequential injection titration method using second-order signals: determination of acidity in plant oils and biodiesel samples.

PubMed

del Río, Vanessa; Larrechi, M Soledad; Callao, M Pilar

2010-06-15

A new concept of flow titration is proposed and demonstrated for the determination of total acidity in plant oils and biodiesel. We use sequential injection analysis (SIA) with a diode array spectrophotometric detector linked to chemometric tools such as multivariate curve resolution-alternating least squares (MCR-ALS). This system is based on the evolution of the basic specie of an acid-base indicator, alizarine, when it comes into contact with a sample that contains free fatty acids. The gradual pH change in the reactor coil due to diffusion and reaction phenomenona allows the sequential appearance of both species of the indicator in the detector coil, recording a data matrix for each sample. The SIA-MCR-ALS method helps to reduce the amounts of sample, the reagents and the time consumed. Each determination consumes 0.413ml of sample, 0.250ml of indicator and 3ml of carrier (ethanol) and generates 3.333ml of waste. The frequency of the analysis is high (12 samples h(-1) including all steps, i.e., cleaning, preparing and analysing). The utilized reagents are of common use in the laboratory and it is not necessary to use the reagents of perfect known concentration. The method was applied to determine acidity in plant oil and biodiesel samples. Results obtained by the proposed method compare well with those obtained by the official European Community method that is time consuming and uses large amounts of organic solvents.

Different Spectrophotometric and Chromatographic Methods for Determination of Mepivacaine and Its Toxic Impurity.

PubMed

Abdelwahab, Nada S; Fared, Nehal F; Elagawany, Mohamed; Abdelmomen, Esraa H

2017-09-01

Stability-indicating spectrophotometric, TLC-densitometric, and ultra-performance LC (UPLC) methods were developed for the determination of mepivacaine HCl (MEP) in the presence of its toxic impurity, 2,6-dimethylanaline (DMA). Different spectrophotometric methods were developed for the determination of MEP and DMA. In a dual-wavelength method combined with direct spectrophotometric measurement, the absorbance difference between 221.4 and 240 nm was used for MEP measurements, whereas the absorbance at 283 nm was used for measuring DMA in the binary mixture. In the second-derivative method, amplitudes at 272.2 and 232.6 nm were recorded and used for the determination of MEP and DMA, respectively. The developed TLC-densitometric method depended on chromatographic separation using silica gel 60 F254 TLC plates as a stationary phase and methanol-water-acetic acid (9 + 1 + 0.1, v/v/v) as a developing system, with UV scanning at 230 nm. The developed UPLC method depended on separation using a C18 column (250 × 4.6 mm id, 5 μm particle size) as a stationary phase and acetonitrile-water (40 + 60, v/v; pH 4 with phosphoric acid) as a mobile phase at a flow rate of 0.4 mL/min, with UV detection at 215 nm. The chromatographic run time was approximately 1 min. The proposed methods were validated with respect to International Conference on Harmonization guidelines regarding precision, accuracy, ruggedness, robustness, and specificity.

Polyphenols Determination in Olive Oil Samples Based on a Thick Film Voltammetric Sensor and a Tyrosinase Biosensor

NASA Astrophysics Data System (ADS)

Capannesi, Cecilia; Palchetti, Ilaria; Mascini, Marco

2000-12-01

The aim of the present work was to compare different techniques to evaluate the variation with the storage time and storage conditions in the phenolic content of an extra-virgin olive oil. A disposable screen-printed sensor (SPE) was coupled with differential pulse voltammetry (DPV) to determine the phenolic fractions after extraction with glycine buffer; DPV parameters were chosen in order to study oxidation peak of oleuropein, that was used as reference compound. Moreover a tyrosinase based biosensor operating in organic solvent (hexane) was assembled, using an amperometric oxygen probe as transducer. Calibration curves were realised in flow injection analysis (F.I.A.) using phenol as substrate. Both of these methods are easy to operate, require no extraction (biosensor) or a rapid extraction procedure (SPE), and the analysis time is short (min.). The results obtained with these two innovative procedures were compared with classical spectrophotometric assay using the Folin-Ciocalteau reagent. Other extra-virgin olive oil quality parameters were investigated with classical methods in order to better define the alteration process and results are reported.

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

PubMed

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

2005-12-15

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

Micro solid phase spectrophotometry in a sequential injection lab-on-valve platform for cadmium, zinc, and copper determination in freshwaters.

PubMed

Santos, Inês C; Mesquita, Raquel B R; Rangel, António O S S

2015-09-03

This work describes the development of a solid phase spectrophotometry method in a μSI-LOV system for cadmium, zinc, and copper determination in freshwaters. NTA (Nitrilotriacetic acid) beads with 60-160 μm diameter were packed in the flow cell of the LOV for a μSPE column of 1 cm length. The spectrophotometric determination is based on the colourimetric reaction between dithizone and the target metals, previously retained on NTA resin. The absorbance of the coloured product formed is measured, at 550 nm, on the surface of the NTA resin beads in a solid phase spectrophotometry approach. The developed method presented preconcentration factors in the range of 11-21 for the metal ions. A LOD of 0.23 μg L(-1) for cadmium, 2.39 μg L(-1) for zinc, and 0.11 μg L(-1) for copper and a sampling rate of 12, 13, and 15 h(-1) for cadmium, zinc, and copper were obtained, respectively. The proposed method was successfully applied to freshwater samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Development and validation of liquid chromatographic and UV derivative spectrophotometric methods for the determination of famciclovir in pharmaceutical dosage forms.

PubMed

Srinubabu, Gedela; Sudharani, Batchu; Sridhar, Lade; Rao, Jvln Seshagiri

2006-06-01

A high-performance liquid chromatographic method and a UV derivative spectrophotometric method for the determination of famciclovir, a highly active antiviral agent, in tablets were developed in the present work. The various parameters, such as linearity, precision, accuracy, specificity, robustness, limit of detection and limit of quantitation were studied according to International Conference on Harmonization guidelines. HPLC was carried out by using the reversed-phase technique on an RP-18 column with a mobile phase composed of 50 mM monobasic phosphate buffer and methanol (50 : 50; v/v), adjusted to pH 3.05 with orthophosphoric acid. The mobile phase was pumped at a flow rate of 1 ml/min and detection was made at 242 nm with UV dual absorbance detector. The first derivative UV spectrophotometric method was performed at 226.5 nm. Statistical analysis was done by Student's t-test and F-test, which showed no significant difference between the results obtained by the two methods. The proposed methods are highly sensitive, precise and accurate and therefore can be used for its Intended purpose.

Elevated Skin Blood Flow Influences Near Infrared Spectroscopy Measurements During Supine Rest

NASA Technical Reports Server (NTRS)

Lee, Stuart M. C.; Clarke, Mark S. F.

2004-01-01

Near infrared spectroscopy is a non-invasive technique that allows determination of tissue oxygenation/blood flow based on spectrophotometric quantitation of oxy- and deoxyhemoglobin present within a tissue. This technique has gained acceptance as a means of detecting and quantifying changes in tissue blood flow due to physiological perturbation, such as that which is elicited in skeletal muscle during exercise. Since the NIRS technique requires light to penetrate the skin and subcutaneous fat in order to reach the muscle of interest, changes in skin blood flow may alter the NIRS signal in a fashion unrelated to blood flow in the muscle of interest. The aim of this study was to determine the contribution of skin blood flow to the NIRS signal obtained from resting vastus lateralis muscle of the thigh.

Injection flow during steam condensation in silicon microchannels

NASA Astrophysics Data System (ADS)

Wu, Huiying; Yu, Mengmeng; Cheng, Ping; Wu, Xinyu

2007-08-01

An experimental investigation with the combined use of visualization and measurement techniques was performed on flow pattern transitions and wall temperature distributions in the condensation of steam in silicon microchannels. Three sets of trapezoidal silicon microchannels, having hydraulic diameters of 53.0 µm, 77.5 µm and 128.5 µm, respectively, were tested under different flow and cooling conditions. It was found that during the transitions from the annular flow to the slug/bubbly flow, a peculiar flow pattern injection flow appeared in silicon microchannels. The location at which the injection flow occurred was dependent on the Reynolds number, condensation number and hydraulic diameter. With increase in the Reynolds number, or decrease in the condensation number and hydraulic diameter, the injection flow moved towards the channel outlet. Based on the experimental results, a dimensionless correlation for the location of injection flow in functions of the Reynolds number, condensation number and hydraulic diameter was proposed for the first time. This correlation can be used to determine the annular flow zone and the slug/bubbly flow zone, and further to determine the dominating condensation flow pattern in silicon microchannels. Wall temperature distributions were also explored in this paper. It was found that near the injection flow, wall temperatures have a rapid decrease in the flow direction, while upstream and downstream far away from the injection flow, wall temperatures decreased mildly. Thus, the location of injection flow can also be determined based on the wall temperature distributions. The results presented in this paper help us to better understand the condensation flow and heat transfer in silicon microchannels.

Methods of automatic nucleotide-sequence analysis. Multicomponent spectrophotometric analysis of mixtures of nucleic acid components by a least-squares procedure

PubMed Central

Lee, Sheila; McMullen, D.; Brown, G. L.; Stokes, A. R.

1965-01-01

1. A theoretical analysis of the errors in multicomponent spectrophotometric analysis of nucleoside mixtures, by a least-squares procedure, has been made to obtain an expression for the error coefficient, relating the error in calculated concentration to the error in extinction measurements. 2. The error coefficients, which depend only on the `library' of spectra used to fit the experimental curves, have been computed for a number of `libraries' containing the following nucleosides found in s-RNA: adenosine, guanosine, cytidine, uridine, 5-ribosyluracil, 7-methylguanosine, 6-dimethylaminopurine riboside, 6-methylaminopurine riboside and thymine riboside. 3. The error coefficients have been used to determine the best conditions for maximum accuracy in the determination of the compositions of nucleoside mixtures. 4. Experimental determinations of the compositions of nucleoside mixtures have been made and the errors found to be consistent with those predicted by the theoretical analysis. 5. It has been demonstrated that, with certain precautions, the multicomponent spectrophotometric method described is suitable as a basis for automatic nucleotide-composition analysis of oligonucleotides containing nine nucleotides. Used in conjunction with continuous chromatography and flow chemical techniques, this method can be applied to the study of the sequence of s-RNA. PMID:14346087

Control of manganese dioxide particles resulting from in situ chemical oxidation using permanganate.

PubMed

Crimi, Michelle; Ko, Saebom

2009-02-01

In situ chemical oxidation using permanganate is an approach to organic contaminant site remediation. Manganese dioxide particles are products of permanganate reactions. These particles have the potential to deposit in the subsurface and impact the flow-regime in/around permanganate injection, including the well screen, filter pack, and the surrounding subsurface formation. Control of these particles can allow for improved oxidant injection and transport and contact between the oxidant and contaminants of concern. The goals of this research were to determine if MnO(2) can be stabilized/controlled in an aqueous phase, and to determine the dependence of particle stabilization on groundwater characteristics. Bench-scale experiments were conducted to study the ability of four stabilization aids (sodium hexametaphosphate (HMP), Dowfax 8390, xanthan gum, and gum arabic) in maintaining particles suspended in solution under varied reaction conditions and time. Variations included particle and stabilization aid concentrations, ionic content, and pH. HMP demonstrated the most promising results, as compared to xanthan gum, gum arabic, and Dowfax 8390 based on results of spectrophotometric studies of particle behavior, particle filtration, and optical measurements of particle size and zeta potential. HMP inhibited particle settling, provided for greater particle stability, and resulted in particles of a smaller average size over the range of experimental conditions evaluated compared to results for systems that did not include HMP. Additionally, HMP did not react unfavorably with permanganate. These results indicate that the inclusion of HMP in a permanganate oxidation system improves conditions that may facilitate particle transport.

Tracer-monitored flow titrations.

PubMed

Sasaki, Milton K; Rocha, Diogo L; Rocha, Fábio R P; Zagatto, Elias A G

2016-01-01

The feasibility of implementing tracer-monitored titrations in a flow system is demonstrated. A dye tracer is used to estimate the instant sample and titrant volumetric fractions without the need for volume, mass or peak width measurements. The approach was applied to spectrophotometric flow titrations involving variations of sample and titrant flow-rates (i.e. triangle programmed technique) or concentration gradients established along the sample zone (i.e. flow injection system). Both strategies required simultaneous monitoring of two absorbing species, namely the titration indicator and the dye tracer. Mixing conditions were improved by placing a chamber with mechanical stirring in the analytical path aiming at to minimize diffusional effects. Unlike most of flow-based titrations, the innovation is considered as a true titration, as it does not require a calibration curve thus complying with IUPAC definition. As an application, acidity evaluation in vinegars involving titration with sodium hydroxide was selected. Phenolphthalein and brilliant blue FCF were used as indicator and dye tracer, respectively. Effects of sample volume, titrand/titrant concentrations and flow rates were investigated aiming at improved accuracy and precision. Results were reliable and in agreement with those obtained by a reference titration procedure. Copyright © 2015 Elsevier B.V. All rights reserved.

Development and Validation of Eco-Friendly Liquid Chromatographic and Spectrophotometric Methods for Simultaneous Determination of Coformulated Drugs: Phenylephrine Hydrochloride and Prednisolone Acetate.

PubMed

Mostafa, Nadia M; Elsayed, Ghada M; Hassan, Nagiba Y; El Mously, Dina A

2017-11-01

Five simple, sensitive, and eco-friendly LC and UV spectrophotometric methods have been developed for the simultaneous determination of phenylephrine hydrochloride (PHE) and prednisolone acetate (PRD) in their combined dosage form. The first method was reversed-phase (RP) LC using methanol-water-heptane-1-sulfonic acid sodium salt (75 + 25 + 0.1, v/v/w) as a mobile phase. Separation was achieved using an XSelect HSS reversed-phase C18 analytical column (250 × 4.6 mm, 5µm). The flow rate was 1.0 mL/min and UV detection was done at 230 nm. Quantification was achieved over the concentration ranges of 5-50 µg/mL for PHE and 2-90 µg/mL for PRD. Four spectrophotometric methods were proposed, namely dual wavelength, first derivative of ratio spectra, ratio difference, and mean-centering of ratio spectra. Linearity was observed in the concentration ranges of 10-120 and 5-35 µg/mL for PHE and PRD, respectively, for the spectrophotometric methods. Green solvents were used in the proposed methods because they play a vital role in the analytical methods' influence on the environment. The suggested methods were validated regarding linearity, accuracy, and precision according to the International Conference on Harmonization guidelines, with satisfactory results. These methods could be used as harmless substitutes for routine analysis of the mentioned drugs, with no interference from excipients.

From thermometric to spectrophotometric kinetic-catalytic methods of analysis. A review.

PubMed

Cerdà, Víctor; González, Alba; Danchana, Kaewta

2017-05-15

Kinetic-catalytic analytical methods have proved to be very easy and highly sensitive strategies for chemical analysis, that rely on simple instrumentation [1,2]. Molecular absorption spectrophotometry is commonly used as the detection technique. However, other detection systems, like electrochemical or thermometric ones, offer some interesting possibilities since they are not affected by the color or turbidity of the samples. In this review some initial experience with thermometric kinetic-catalytic methods is described, up to our current experience exploiting spectrophotometric flow techniques to automate this kind of reactions, including the use of integrated chips. Procedures for determination of inorganic and organic species in organic and inorganic matrices are presented. Copyright © 2017 Elsevier B.V. All rights reserved.

Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation.

PubMed

Cordeiro, Thiago G; Hidalgo, Pilar; Gutz, Ivano G R; Pedrotti, Jairo J

2010-07-15

A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(2)(-) at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate, EtX(-), with 2.0 mol L(-1) HCl generating ethanol and carbon disulfide, CS(2). A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS(2) is selectively detected by UV absorbance at 206 nm (epsilon=65,000 L mol(-1) cm(-1)). The measured absorbance is directly proportional to EtX(-) concentration present in the sample solutions. The Beer's law is obeyed in a 1x10(-6) to 2x10(-4) mol L(-1) concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r=0.999) and a detection limit of 3.1x10(-7) mol L(-1), corresponding to 38 microg L(-1). At flow rates of 200 microL min(-1) of the donor stream and 100 microL min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD<2.3% (n=10, 300 microL injections of 1x10(-5) mol L(-1) EtX(-)). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX(-) concentration during a laboratory study of the EtX(-) adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX(-) at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore. Copyright 2010 Elsevier B.V. All rights reserved.

Simultaneous determination of atorvastatin calcium and olmesartan medoxomil in a pharmaceutical formulation by reversed phase high-performance liquid chromatography, high-performance thin-layer chromatography, and UV spectrophotometric methods.

PubMed

Soni, Hiral; Kothari, Charmy; Khatri, Deepak; Mehta, Priti

2014-01-01

Validated RP-HPLC, HPTLC, and UV spectrophotometric methods have been developed for the simultaneous determination of atorvastatin calcium (ATV) and olmesartan medoxomil (OLM) in a pharmaceutical formulation. The RP-HPLC separation was achieved on a Kromasil C18 column (250 x 4.6 mm, 5 microm particle size) using 0.01 M potassium dihydrogen o-phosphate (pH 4 adjusted with o-phosphoric acid)-acetonitrile (50 + 50, v/v) as the mobile phase at a flow rate of 1.5 mL/min. Quantification was achieved by UV detection at 276 nm. The HPTLC separation was achieved on precoated silica gel 60F254 plates using chloroform-methanol-acetonitrile (4 + 2+ 4, v/v/v) mobile phase. Quantification was achieved with UV detection at 276 nm. The UV-Vis spectrophotometric method was based on the simultaneous equation method that involves measurement of absorbance at two wavelengths, i.e., 255 nm (lambda max of OLM) and 246.2 nm (lambda max of ATV) in methanol. All three methods were validated as per International Conference on Harmonization guidelines. The proposed methods were simple, precise, accurate, and applicable for the simultaneous determination of ATV and OLM in a marketed formulation. The results obtained by applying the proposed methods were statistically analyzed and were found satisfactory.

Validation of different spectrophotometric methods for determination of vildagliptin and metformin in binary mixture

NASA Astrophysics Data System (ADS)

Abdel-Ghany, Maha F.; Abdel-Aziz, Omar; Ayad, Miriam F.; Tadros, Mariam M.

New, simple, specific, accurate, precise and reproducible spectrophotometric methods have been developed and subsequently validated for determination of vildagliptin (VLG) and metformin (MET) in binary mixture. Zero order spectrophotometric method was the first method used for determination of MET in the range of 2-12 μg mL-1 by measuring the absorbance at 237.6 nm. The second method was derivative spectrophotometric technique; utilized for determination of MET at 247.4 nm, in the range of 1-12 μg mL-1. Derivative ratio spectrophotometric method was the third technique; used for determination of VLG in the range of 4-24 μg mL-1 at 265.8 nm. Fourth and fifth methods adopted for determination of VLG in the range of 4-24 μg mL-1; were ratio subtraction and mean centering spectrophotometric methods, respectively. All the results were statistically compared with the reported methods, using one-way analysis of variance (ANOVA). The developed methods were satisfactorily applied to analysis of the investigated drugs and proved to be specific and accurate for quality control of them in pharmaceutical dosage forms.

Sustained modelling ability of artificial neural networks in the analysis of two pharmaceuticals (dextropropoxyphene and dipyrone) present in unequal concentrations.

PubMed

Cámara, María S; Ferroni, Félix M; De Zan, Mercedes; Goicoechea, Héctor C

2003-07-01

An improvement is presented on the simultaneous determination of two active ingredients present in unequal concentrations in injections. The analysis was carried out with spectrophotometric data and non-linear multivariate calibration methods, in particular artificial neural networks (ANNs). The presence of non-linearities caused by the major analyte concentrations which deviate from Beer's law was confirmed by plotting actual vs. predicted concentrations, and observing curvatures in the residuals for the estimated concentrations with linear methods. Mixtures of dextropropoxyphene and dipyrone have been analysed by using linear and non-linear partial least-squares (PLS and NPLSs) and ANNs. Notwithstanding the high degree of spectral overlap and the occurrence of non-linearities, rapid and simultaneous analysis has been achieved, with reasonably good accuracy and precision. A commercial sample was analysed by using the present methodology, and the obtained results show reasonably good agreement with those obtained by using high-performance liquid chromatography (HPLC) and a UV-spectrophotometric comparative methods.

[Prevention of the brain neurodegeneration in rats with experimental Alzheimer's disease by adaptation to hypoxia].

PubMed

Manukhina, E B; Goriacheva, A V; Barskov, I V; Viktorov, I V; Guseva, A A; Pshennikova, M G; Khomenko, I P; Mashina, S Iu; Pokidyshev, D A; Malyshev, I Iu

2009-07-01

The study focused on a possibility of preventing brain neurodegeneration by adaptation to intermittent hypoxia (AH) in rats with experimental Alzheimer's disease (AD) modeled by injection of a neurotoxic bert-amyloid peptide fragment (Ab) into n. basalis magnocellularis. AH was produ- ced in an altitude chamber (4.000 m; 4 hours daily; 14 days). The following results were obtained after fifteen days of the Ab injection: (1) AH substantially prevented the memory impairment induced by Ab, which was determined using the conditioned avoidance reflex test; (2) the AH significantly restricted the enhanced oxidative stress, which was determined spectrophotometrically by thiobarbituric acid-reactive substance level in the hippocampus; (3) the AH completely prevented Ab-induced nitric oxide (NO) overproduction in brain, which was measured by tissue level of nitrite and nitrate; (4) pathologically changed and dead neurons (Niessle staining) were absent in the brain cortex of rats exposed to AH before the Ab injection. Therefore AH seems to effectively prevent oxidative and nitrosative stress thereby providing protection of brain against neurodegeneration and preservation of cognitive function in experimental AD.

Monitoring of pyrocatechol indoor air pollution

NASA Astrophysics Data System (ADS)

Eškinja, I.; Grabarić, Z.; Grabarić, B. S.

Spectrophotometric and electrochemical methods for monitoring of pyrocatechol (PC) indoor air pollution have been investigated. Spectrophotometric determination was performed using Fe(III) and iodine methods. The adherence to Beer's law was found in the concentration range between 0 and 12 μg ml - for iodine method at pH = 5.7 measuring absorbance at 725 nm, and in the range 0-30 μg ml - for Fe(III) method at pH = 9.5 measuring absorbance at 510 nm. The former method showed greater sensitivity than the latter one. Differential pulse voltammetry (DPV) and chronoamperometric (CA) detection in flow injection analysis (FIA) using carbon paste electrode in phosphate buffer solution of pH = 6.5 was also used for pyrocatechol determination. The electrochemical methods allowed pyrocatechol quantitation in submicromolar concentration level with an overall reproducibility of ± 1%. The efficiency of pyrocatechol sampling collection was investigated at two temperatures (27 and 40°C) in water, 0.1 M NaOH and 0.1 M HCl solutions. Solution of 0.1 M HCl gave the best collection efficiency (95.5-98.5%). A chamber testing simulating the indoor pollution has been performed. In order to check the reliability of the proposed methods for monitoring of the indoor pyrocatechol pollution, the air in working premises with pyrocatechol released from meteorological charts during mapping and paper drying was analyzed using proposed methods. The concentration of pyrocatechol in the air during mapping was found to be 1.8 mg m -3 which is below the hygienic standard of permissible exposure of 20 mg m -3 (≈ 5 ppm). The release of pyrocatechol from the paper impregnated with pyrocatechol standing at room temperature during one year was also measured. The proposed methods can be used for indoor pyrocatechol pollution monitoring in working premises of photographic, rubber, oil and dye industries, fur and furniture dyeing and cosmetic or pharmaceutical premises where pyrocatechol and related compounds are in use.

Enhanced capabilities of separation in Sequential Injection Chromatography--fused-core particle column and its comparison with narrow-bore monolithic column.

PubMed

Chocholouš, Petr; Kosařová, Lucie; Satínský, Dalibor; Sklenářová, Hana; Solich, Petr

2011-08-15

In the Sequential Injection Chromatography (SIC) only monolithic columns for chromatographic separations have been used so far. This article presents the first use of fused-core particle packed column in an attempt to extend of the chromatographic capabilities of the SIC system. A new fused-core particle column (2.7 μm) Ascentis(®) Express C18 (Supelco™ Analytical) 30 mm × 4.6 mm brings high separation efficiency within flow rates and pressures comparable to monolithic column Chromolith(®) Performance RP-18e 100-3 (Merck(®)) 100 mm × 3 mm. Both columns matches the conditions of the commercially produced SIC system - SIChrom™ (8-port high-pressure selection valve and medium-pressure Sapphire™ syringe pump with 4 mL reservoir - maximal work pressure 1000 PSI) (FIAlab(®), USA). The system was tested by the separation of four estrogens with similar structure and an internal standard - ethylparaben. The mobile phase composed of acetonitrile/water (40/60 (v/v)) was pumped isocratic at flow rate 0.48 mL min(-1). Spectrophotometric detection was performed at wavelength of 225 nm and injected volume of sample solutions was 10 μL. The chromatographic characteristics of both columns were compared. Obtained results and conclusions have shown that both fused-core particle column and longer narrow shaped monolithic column bring benefits into the SIC method. Copyright © 2011 Elsevier B.V. All rights reserved.

An Ion-Selective Electrode/Flow-Injection Analysis Experiment: Determination of Potassium in Serum.

ERIC Educational Resources Information Center

Meyerhoff, Mark E.; Kovach, Paul M.

1983-01-01

Describes a low-cost, senior-level, instrumental analysis experiment in which a home-made potassium tubular flow-through electrode is constructed and incorporated into a flow injection analysis system (FIA). Also describes experiments for evaluating the electrode's response properties, examining basic FIA concepts, and determining potassium in…

Evaluation of the nitrate content in leaf vegetables produced through different agricultural systems.

PubMed

Guadagnin, S G; Rath, S; Reyes, F G R

2005-12-01

The nitrate content of leafy vegetables (watercress, lettuce and arugula) produced by different agricultural systems (conventional, organic and hydroponic) was determined. The daily nitrate intake from the consumption of these crop species by the average Brazilian consumer was also estimated. Sampling was carried out between June 2001 to February 2003 in Campinas, São Paulo State, Brazil. Nitrate was extracted from the samples using the procedure recommended by the AOAC. Flow injection analysis with spectrophotometric detection at 460 nm was used for nitrate determination through the ternary complex FeSCNNO+. For lettuce and arugula, the average nitrate content varied (p < 0.05) between the three agricultural systems with the nitrate level in the crops produced by the organic system being lower than in the conventional system that, in turn, was lower than in the hydroponic system. For watercress, no difference (p < 0.05) was found between the organic and hydroponic samples, both having higher nitrate contents (p < 0.05) than conventionally cultivated samples. The nitrate content for each crop species varied among producers, between different parts of the plant and in relation to the season. The estimated daily nitrate intake, calculated from the consumption of the crops produced by the hydroponic system, represented 29% of the acceptable daily intake established for this ion.

Spectrophotometric reading of EUCAST antifungal susceptibility testing of Aspergillus fumigatus.

PubMed

Meletiadis, J; Leth Mortensen, K; Verweij, P E; Mouton, J W; Arendrup, M C

2017-02-01

Given the increasing number of antifungal drugs and the emergence of resistant Aspergillus isolates, objective, automated and high-throughput antifungal susceptibility testing is important. The EUCAST E.Def 9.3 reference method for MIC determination of Aspergillus species relies on visual reading. Spectrophotometric reading was not adopted because of concern that non-uniform filamentous growth might lead to unreliable and non-reproducible results. We therefore evaluated spectrophotometric reading for the determination of MICs of antifungal azoles against Aspergillus fumigatus. Eighty-eight clinical isolates of A. fumigatus were tested against four medical azoles (posaconazole, voriconazole, itraconazole, isavuconazole) and one agricultural azole (tebuconazole) with EUCAST E.Def 9.3. The visually determined MICs (complete inhibition of growth) were compared with spectrophotometrically determined MICs and essential (±1 twofold dilution) and categorical (susceptible/intermediate/resistant or wild-type/non-wild-type) agreement was calculated. Spectrophotometric data were analysed with regression analysis using the E max model, and the effective concentration corresponding to 5% (EC 5 ) was estimated. Using the 5% cut-off, high essential (92%-97%) and categorical (93%-99%) agreement (<6% errors) was found between spectrophotometric and visual MICs. The EC 5 also correlated with the visually determined MICs with an essential agreement of 83%-96% and a categorical agreement of 90%-100% (<5% errors). Spectrophotometric determination of MICs of antifungal drugs may increase objectivity, and allow automation and high-throughput of EUCAST E.Def 9.3 antifungal susceptibility testing of Aspergillus species. Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Comparison of UV spectrophotometry and high performance liquid chromatography methods for the determination of repaglinide in tablets.

PubMed

Dhole, Seema M; Khedekar, Pramod B; Amnerkar, Nikhil D

2012-07-01

Repaglinide is a miglitinide class of antidiabetic drug used for the treatment of type 2 diabetes mellitus. A fast and reliable method for the determination of repaglinide was highly desirable to support formulation screening and quality control. UV spectrophotometric and reversed-phase high performance liquid chromatography (RP-HPLC) methods were developed for determination of repaglinide in the tablet dosage form. The UV spectrum recorded between 200 400 nm using methanol as solvent and the wavelength 241 nm was selected for the determination of repaglinide. RP-HPLC analysis was carried out using Agilent TC-C18 (2) column and mobile phase composed of methanol and water (80:20 v/v, pH adjusted to 3.5 with orthophosphoric acid) at a flow rate of 1.0 ml/min. Parameters such as linearity, precision, accuracy, recovery, specificity and ruggedness are studied as reported in the International Conference on Harmonization (ICH) guidelines. The developed methods illustrated excellent linearity (r(2) > 0.999) in the concentration range of 5-30 μg/ml and 5-50 μg/ml for UV spectrophotometric and HPLC methods, respectively. Precision (%R.S.D < 1.50) and mean recoveries were found in the range of 99.63-100.45% for UV spectrophotometric method and 99.71-100.25% for HPLC method which shows accuracy of the methods. The developed methods were found to be reliable, simple, fast, accurate and successfully used for the quality control of repaglinide as a bulk drug and in pharmaceutical formulations.

Comparison of UV spectrophotometry and high performance liquid chromatography methods for the determination of repaglinide in tablets

PubMed Central

Dhole, Seema M.; Khedekar, Pramod B.; Amnerkar, Nikhil D.

2012-01-01

Background: Repaglinide is a miglitinide class of antidiabetic drug used for the treatment of type 2 diabetes mellitus. A fast and reliable method for the determination of repaglinide was highly desirable to support formulation screening and quality control. Objective: UV spectrophotometric and reversed-phase high performance liquid chromatography (RP-HPLC) methods were developed for determination of repaglinide in the tablet dosage form. Materials and Methods: The UV spectrum recorded between 200 400 nm using methanol as solvent and the wavelength 241 nm was selected for the determination of repaglinide. RP-HPLC analysis was carried out using Agilent TC-C18 (2) column and mobile phase composed of methanol and water (80:20 v/v, pH adjusted to 3.5 with orthophosphoric acid) at a flow rate of 1.0 ml/min. Parameters such as linearity, precision, accuracy, recovery, specificity and ruggedness are studied as reported in the International Conference on Harmonization (ICH) guidelines. Results: The developed methods illustrated excellent linearity (r2 > 0.999) in the concentration range of 5-30 μg/ml and 5-50 μg/ml for UV spectrophotometric and HPLC methods, respectively. Precision (%R.S.D < 1.50) and mean recoveries were found in the range of 99.63-100.45% for UV spectrophotometric method and 99.71-100.25% for HPLC method which shows accuracy of the methods. Conclusion: The developed methods were found to be reliable, simple, fast, accurate and successfully used for the quality control of repaglinide as a bulk drug and in pharmaceutical formulations. PMID:23781481

Determination of Hypochlorite in Bleaching Products with Flower Extracts to Demonstrate the Principles of Flow Injection Analysis

ERIC Educational Resources Information Center

Ramos, Luiz Antonio; Prieto, Katia Roberta; Carvalheiro, Eder Tadeu Gomes; Carvalheiro, Carla Cristina Schmitt

2005-01-01

The use of crude flower extracts to the principle of analytical chemistry automation, with the flow injection analysis (FIA) procedure developed to determine hypochlorite in household bleaching products was performed. The FIA comprises a group of techniques based on injection of a liquid sample into a moving, nonsegmented carrier stream of a…

Determination of tannin in green tea infusion by flow-injection analysis based on quenching the fluorescence of 3-aminophthalate.

PubMed

Chen, Richie L C; Lin, Chun-Hsun; Chung, Chien-Yu; Cheng, Tzong-Jih

2005-11-02

A flow-injection analytical system was developed to determine tannin content in green tea infusions. The flow-injection system is based on measuring the quenching effect of tannin on the fluorescence of 3-aminophthalate. Fluorophore was obtained by auto-oxidation of luminol during solution preparation. System performance was satisfactory for routine analysis (sample throughput >20 h(-1); linear dynamic range for tannic acid, 0.005-0.3 mg/mL; linear dynamic range for green tea tannin, 0.02-1.0 mg/mL; CV < 3%). The flow-injection method is immune from interference by coexisting ascorbate in green tea infusion. Analytical results were verified by the ferrous tartrate method, the Japanese official analytical method.

Determination of albumin in bronchoalveolar lavage fluid by flow-injection fluorometry using chromazurol S.

PubMed

Sato, Takaji; Saito, Yoshihiro; Chikuma, Masahiko; Saito, Yutaka; Nagai, Sonoko

2008-03-01

A highly sensitive flow injection fluorometry for the determination of albumin was developed and applied to the determination of albumin in human bronchoalveolar lavage fluids (BALF). This method is based on binding of chromazurol S (CAS) to albumin. The calibration curve was linear in the range of 5-200 microg/ml of albumin. A highly linear correlation (r=0.986) was observed between the albumin level in BALF samples (n=25) determined by the proposed method and by a conventional fluorometric method using CAS (CAS manual method). The IgG interference was lower in the CAS flow injection method than in the CAS manual method. The albumin level in BALF collected from healthy volunteers (n=10) was 58.5+/-13.1 microg/ml. The albumin levels in BALF samples obtained from patients with sarcoidosis and idiopathic pulmonary fibrosis were increased. This finding shows that the determination of albumin levels in BALF samples is useful for investigating lung diseases and that CAS flow injection method is promising in the determination of trace albumin in BALF samples, because it is sensitive and precise.

Investigation of Thrust Augmentation of a 1600-pound Thrust Centrifugal-flow-type Turbojet Engine by Injection of Refrigerants at Compressor Inlets

NASA Technical Reports Server (NTRS)

Jones, William L.; Dowman, Harry W.

1947-01-01

Investigations were conducted to determine effectiveness of refrigerants in increasing thrust of turbojet engines. Mixtures of water an alcohol were injected for a range of total flows up to 2.2 lb/sec. Kerosene was injected into inlets covering a range of injected flows up to approximately 30% of normal engine fuel flow. Injection of 2.0 lb/sec of water alone produced an increase in thrust of 35.8% of rate engine conditions and kerosene produced a negligible increase in thrust. Carbon dioxide increased thrust 23.5 percent.

Determination of dasatinib in the tablet dosage form by ultra high performance liquid chromatography, capillary zone electrophoresis, and sequential injection analysis.

PubMed

Gonzalez, Aroa Garcia; Taraba, Lukáš; Hraníček, Jakub; Kozlík, Petr; Coufal, Pavel

2017-01-01

Dasatinib is a novel oral prescription drug proposed for treating adult patients with chronic myeloid leukemia. Three analytical methods, namely ultra high performance liquid chromatography, capillary zone electrophoresis, and sequential injection analysis, were developed, validated, and compared for determination of the drug in the tablet dosage form. The total analysis time of optimized ultra high performance liquid chromatography and capillary zone electrophoresis methods was 2.0 and 2.2 min, respectively. Direct ultraviolet detection with detection wavelength of 322 nm was employed in both cases. The optimized sequential injection analysis method was based on spectrophotometric detection of dasatinib after a simple colorimetric reaction with folin ciocalteau reagent forming a blue-colored complex with an absorbance maximum at 745 nm. The total analysis time was 2.5 min. The ultra high performance liquid chromatography method provided the lowest detection and quantitation limits and the most precise and accurate results. All three newly developed methods were demonstrated to be specific, linear, sensitive, precise, and accurate, providing results satisfactorily meeting the requirements of the pharmaceutical industry, and can be employed for the routine determination of the active pharmaceutical ingredient in the tablet dosage form. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel spectrophotometric methods for simultaneous determination of timolol and dorzolamide in their binary mixture.

PubMed

Lotfy, Hayam Mahmoud; Hegazy, Maha A; Rezk, Mamdouh R; Omran, Yasmin Rostom

2014-05-21

Two smart and novel spectrophotometric methods namely; absorbance subtraction (AS) and amplitude modulation (AM) were developed and validated for the determination of a binary mixture of timolol maleate (TIM) and dorzolamide hydrochloride (DOR) in presence of benzalkonium chloride without prior separation, using unified regression equation. Additionally, simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of the binary mixture namely; simultaneous ratio subtraction (SRS), ratio difference (RD), ratio subtraction (RS) coupled with extended ratio subtraction (EXRS), constant multiplication method (CM) and mean centering of ratio spectra (MCR). The proposed spectrophotometric procedures do not require any separation steps. Accuracy, precision and linearity ranges of the proposed methods were determined and the specificity was assessed by analyzing synthetic mixtures of both drugs. They were applied to their pharmaceutical formulation and the results obtained were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there is no significant difference between the proposed methods and the reported one regarding both accuracy and precision. Copyright © 2014 Elsevier B.V. All rights reserved.

Determination of free formaldehyde in cosmetics containing formaldehyde-releasing preservatives by reversed-phase dispersive liquid-liquid microextraction and liquid chromatography with post-column derivatization.

PubMed

Miralles, Pablo; Chisvert, Alberto; Alonso, M José; Hernandorena, Sandra; Salvador, Amparo

2018-03-30

An analytical method for the determination of traces of formaldehyde in cosmetic products containing formaldehyde-releasing preservatives has been developed. The method is based on reversed-phase dispersive liquid-liquid microextraction (RP-DLLME), that allows the extraction of highly polar compounds, followed by liquid chromatography-ultraviolet/visible (LC-UV/vis) determination with post-column derivatization. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the selected conditions, a mixture of 500 μL of acetonitrile (disperser solvent) and 50 μL of water (extraction solvent) was rapidly injected into 5 mL of toluene sample solution. The extracts were injected into the LC-UV/vis system using phosphate buffer 6 mmol L -1 at pH 2 as mobile phase. After chromatographic separation, the eluate merged with a flow stream of pentane-2,4-dione in ammonium acetate solution as derivatizing reagent and passed throughout a post-column reactor at 85 °C in order to derivatize formaldehyde into 3,5-diacetyl-1,4-dihydrolutidine, according to Hantzsch reaction, which was finally measured spectrophotometrically at 407 nm. The method was successfully validated showing good linearity, an enrichment factor of 86 ± 2, limits of detection and quantification of 0.7 and 2.3 ng mL -1 , respectively, and good repeatability (RSD < 9.2%). Finally, the proposed analytical method was applied to the determination of formaldehyde in different commercial cosmetic samples containing formaldehyde-releasing preservatives, such as bronopol, diazolidinyl urea, imidazolidinyl urea, and DMDM hydantoin, with good relative recovery values (91-113%) thus showing that matrix effects were negligible. The good analytical features of the proposed method besides of its simplicity and affordability, make it useful to carry out the quality control of cosmetic products containing formaldehyde-releasing preservatives. Copyright © 2018 Elsevier B.V. All rights reserved.

Quantitative determination of ambroxol in tablets by derivative UV spectrophotometric method and HPLC.

PubMed

Dinçer, Zafer; Basan, Hasan; Göger, Nilgün Günden

2003-04-01

A derivative UV spectrophotometric method for the determination of ambroxol in tablets was developed. Determination of ambroxol in tablets was conducted by using first-order derivative UV spectrophotometric method at 255 nm (n = 5). Standards for the calibration graph ranging from 5.0 to 35.0 microg/ml were prepared from stock solution. The proposed method was accurate with 98.6+/-0.4% recovery value and precise with coefficient of variation (CV) of 1.22. These results were compared with those obtained by reference methods, zero-order UV spectrophotometric method and reversed-phase high-performance liquid chromatography (HPLC) method. A reversed-phase C(18) column with aqueous phosphate (0.01 M)-acetonitrile-glacial acetic acid (59:40:1, v/v/v) (pH 3.12) mobile phase was used and UV detector was set to 252 nm. Calibration solutions used in HPLC were ranging from 5.0 to 20.0 microg/ml. Results obtained by derivative UV spectrophotometric method was comparable to those obtained by reference methods, zero-order UV spectrophotometric method and HPLC, as far as ANOVA test, F(calculated) = 0.762 and F(theoretical) = 3.89, was concerned. Copyright 2003 Elsevier Science B.V.

Spectroflourometric and spectrophotometric methods for the determination of sitagliptin in binary mixture with metformin and ternary mixture with metformin and sitagliptin alkaline degradation product.

PubMed

El-Bagary, Ramzia I; Elkady, Ehab F; Ayoub, Bassam M

2011-03-01

Simple, accurate and precise spectroflourometric and spectrophotometric methods have been developed and validated for the determination of sitagliptin phosphate monohydrate (STG) and metformin HCL (MET). Zero order, first derivative, ratio derivative spectrophotometric methods and flourometric methods have been developed. The zero order spectrophotometric method was used for the determination of STG in the range of 50-300 μg mL(-1). The first derivative spectrophotometric method was used for the determination of MET in the range of 2-12 μg mL(-1) and STG in the range of 50-300 μg mL(-1) by measuring the peak amplitude at 246.5 nm and 275 nm, respectively. The first derivative of ratio spectra spectrophotometric method used the peak amplitudes at 232 nm and 239 nm for the determination of MET in the range of 2-12 μg mL(-1). The flourometric method was used for the determination of STG in the range of 0.25-110 μg mL(-1). The proposed methods used to determine each drug in binary mixture with metformin and ternary mixture with metformin and sitagliptin alkaline degradation product that is obtained after alkaline hydrolysis of sitagliptin. The results were statistically compared using one-way analysis of variance (ANOVA). The methods developed were satisfactorily applied to the analysis of the pharmaceutical formulations and proved to be specific and accurate for the quality control of the cited drugs in pharmaceutical dosage forms.

Spectroflourometric and Spectrophotometric Methods for the Determination of Sitagliptin in Binary Mixture with Metformin and Ternary Mixture with Metformin and Sitagliptin Alkaline Degradation Product

PubMed Central

El-Bagary, Ramzia I.; Elkady, Ehab F.; Ayoub, Bassam M.

2011-01-01

Simple, accurate and precise spectroflourometric and spectrophotometric methods have been developed and validated for the determination of sitagliptin phosphate monohydrate (STG) and metformin HCL (MET). Zero order, first derivative, ratio derivative spectrophotometric methods and flourometric methods have been developed. The zero order spectrophotometric method was used for the determination of STG in the range of 50-300 μg mL-1. The first derivative spectrophotometric method was used for the determination of MET in the range of 2–12 μg mL-1 and STG in the range of 50-300 μg mL-1 by measuring the peak amplitude at 246.5 nm and 275 nm, respectively. The first derivative of ratio spectra spectrophotometric method used the peak amplitudes at 232 nm and 239 nm for the determination of MET in the range of 2–12 μg mL-1. The flourometric method was used for the determination of STG in the range of 0.25-110 μg mL-1. The proposed methods used to determine each drug in binary mixture with metformin and ternary mixture with metformin and sitagliptin alkaline degradation product that is obtained after alkaline hydrolysis of sitagliptin. The results were statistically compared using one-way analysis of variance (ANOVA). The methods developed were satisfactorily applied to the analysis of the pharmaceutical formulations and proved to be specific and accurate for the quality control of the cited drugs in pharmaceutical dosage forms. PMID:23675222

SPECTROPHOTOMETRIC DETERMINATION OF CALCIUM WITH GLYOXAL BIS (2-HYDROXY- ANIL)

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

Florence, T.M.; Morgan, J.

1961-03-01

A selective method is described for the spectrophotometric determination of calcium using glyoxal bis(2hydroxy-anil) as the chromogenic agent. A comprehensive study of interferences and reagent variables was made. (auth)

Portable device and method for determining permeability characteristics of earth formations

DOEpatents

Shuck, Lowell Z.

1977-01-01

The invention is directed to a device which is used for determining permeability characteristics of earth formations at the surface thereof. The determination of the maximum permeability direction and the magnitude of permeability are achieved by employing a device comprising a housing having a central fluid-injection port surrounded by a plurality of spaced-apart fluid flow and pressure monitoring ports radially extending from the central injection port. With the housing resting on the earth formation in a relatively fluid-tight manner as provided by an elastomeric pad disposed therebetween, fluid is injected through the central port into the earth formation and into registry with the fluid-monitoring ports disposed about the injection port. The fluid-monitoring ports are selectively opened and the flow of the fluid through the various fluid ports is measured so as to provide a measurement of flow rates and pressure distribution about the center hole which is indicative on the earth formation permeability direction and magnitude. For example, the azimuthal direction of the fluid-monitoring ports in the direction through which the greatest amount of injected fluid flows as determined by the lowest pressure distribution corresponds to the direction of maximum permeability in the earth formation.

Simultaneous spectrophotometric determination of trace copper, nickel, and cobalt ions in water samples using solid phase extraction coupled with partial least squares approaches

NASA Astrophysics Data System (ADS)

Guo, Yugao; Zhao, He; Han, Yelin; Liu, Xia; Guan, Shan; Zhang, Qingyin; Bian, Xihui

2017-02-01

A simultaneous spectrophotometric determination method for trace heavy metal ions based on solid-phase extraction coupled with partial least squares approaches was developed. In the proposed method, trace metal ions in aqueous samples were adsorbed by cation exchange fibers and desorbed by acidic solution from the fibers. After the ion preconcentration process, the enriched solution was detected by ultraviolet and visible spectrophotometer (UV-Vis). Then, the concentration of heavy metal ions were quantified by analyzing ultraviolet and visible spectrum with the help of partial least squares (PLS) approaches. Under the optimal conditions of operation time, flow rate and detection parameters, the overlapped absorption peaks of mixed ions were obtained. The experimental data showed that the concentration, which can be calculated through chemometrics method, of each metal ion increased significantly. The heavy metal ions can be enriched more than 80-fold. The limits of detection (LOD) for the target analytes of copper ions (Cu2 +), cobalt ions (Co2 +) and nickel ions (Ni2 +) mixture was 0.10 μg L- 1, 0.15 μg L- 1 and 0.13 μg L- 1, respectively. The relative standard deviations (RSD) were less than 5%. The performance of the solid-phase extraction can enrich the ions efficiently and the combined method of spectrophotometric detection and PLS can evaluate the ions concentration accurately. The work proposed here is an interesting and promising attempt for the trace ions determination in water samples and will have much more applied field.

Simultaneous spectrophotometric determination of trace copper, nickel, and cobalt ions in water samples using solid phase extraction coupled with partial least squares approaches.

PubMed

Guo, Yugao; Zhao, He; Han, Yelin; Liu, Xia; Guan, Shan; Zhang, Qingyin; Bian, Xihui

2017-02-15

A simultaneous spectrophotometric determination method for trace heavy metal ions based on solid-phase extraction coupled with partial least squares approaches was developed. In the proposed method, trace metal ions in aqueous samples were adsorbed by cation exchange fibers and desorbed by acidic solution from the fibers. After the ion preconcentration process, the enriched solution was detected by ultraviolet and visible spectrophotometer (UV-Vis). Then, the concentration of heavy metal ions were quantified by analyzing ultraviolet and visible spectrum with the help of partial least squares (PLS) approaches. Under the optimal conditions of operation time, flow rate and detection parameters, the overlapped absorption peaks of mixed ions were obtained. The experimental data showed that the concentration, which can be calculated through chemometrics method, of each metal ion increased significantly. The heavy metal ions can be enriched more than 80-fold. The limits of detection (LOD) for the target analytes of copper ions (Cu 2+ ), cobalt ions (Co 2+ ) and nickel ions (Ni 2+ ) mixture was 0.10μgL -1 , 0.15μgL -1 and 0.13μgL -1 , respectively. The relative standard deviations (RSD) were less than 5%. The performance of the solid-phase extraction can enrich the ions efficiently and the combined method of spectrophotometric detection and PLS can evaluate the ions concentration accurately. The work proposed here is an interesting and promising attempt for the trace ions determination in water samples and will have much more applied field. Copyright © 2016 Elsevier B.V. All rights reserved.

Flow injection method for sulphide determination using an organic mercury compound

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

Yaqoob, M.; Anwar, M.; Masood, A.S.

1991-04-01

A simple flow injection analysis method is described for the determination of soluble sulfide, based on the complexation of sulfide with p-hydroxymercurbenzoic acid, in the presence of dithizone used as an indicator. The reaction is very rapid, with a sampling rate of 90/hr. and requires a very short length post injection reaction coil. The detection limit and precision are 0.01 mM and 0.7%, respectively.

Application of potassium permanganate to spectrophotometric assay of metoclopramide hydrochloride in pharmaceuticals

NASA Astrophysics Data System (ADS)

Devi, O. Zenita; Basavaiah, K.; Vinay, K. B.

2012-01-01

Two simple, sensitive, and cost-effective spectrophotometric methods are described for the determination of metoclopramide hydrochloride (MCP) in pharmaceutical dosage forms. The methods are based on a redox reaction between MCP and KMnO4 in alkaline and acid media. Direct spectrophotometry (method A) involves treating MCP with permanganate in an NaOH medium and measuring a bluish green product at 610 nm. In indirect spectrophotometry (method B), MCP is treated with a fixed concentration of KMnO4 in an H2SO4 medium, and after a specified time, the unreacted KMnO4 is measured at 545 nm. Under optimum assay conditions, Beer's law is obeyed over the ranges of 0.75-12.0 and 2.5-30.0 g/ml for methods A and B, respectively. Molar absorptivity values are calculated to be 2.33•104 and 2.66•104 l/mol cm for methods A and B, respectively, and corresponding Sandell's sensitivity values are 0.015 and 0.013 g/cm2. Limits of detection (LOD) and quantification (LOQ) are also reported. The applicability of the developed methods was demonstrated by the determination of MCP in tablet and injection forms. The accuracy and reliability of the proposed methods were further ascertained by recovery studies via standard addition technique.

Comparative study on the selectivity of various spectrophotometric techniques for the determination of binary mixture of fenbendazole and rafoxanide.

PubMed

Saad, Ahmed S; Attia, Ali K; Alaraki, Manal S; Elzanfaly, Eman S

2015-11-05

Five different spectrophotometric methods were applied for simultaneous determination of fenbendazole and rafoxanide in their binary mixture; namely first derivative, derivative ratio, ratio difference, dual wavelength and H-point standard addition spectrophotometric methods. Different factors affecting each of the applied spectrophotometric methods were studied and the selectivity of the applied methods was compared. The applied methods were validated as per the ICH guidelines and good accuracy; specificity and precision were proven within the concentration range of 5-50 μg/mL for both drugs. Statistical analysis using one-way ANOVA proved no significant differences among the proposed methods for the determination of the two drugs. The proposed methods successfully determined both drugs in laboratory prepared and commercially available binary mixtures, and were found applicable for the routine analysis in quality control laboratories. Copyright © 2015 Elsevier B.V. All rights reserved.

Application of spectrophotometric, densitometric, and HPLC techniques as stability indicating methods for determination of Zaleplon in pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Metwally, Fadia H.; Abdelkawy, M.; Abdelwahab, Nada S.

2007-12-01

Spectrophotometric, spectrodensitometric and HPLC are stability indicating methods described for determination of Zaleplon in pure and dosage forms. As Zaleplon is easily degradable, the proposed techniques in this manuscript are adopted for its determination in presence of its alkaline degradation product, namely N-[4-(3-cyano-pyrazolo[1,5a]pyridin-7-yl)-phenyl]- N-ethyl-acetamide. These approaches are successfully applied to quantify Zaleplon using the information included in the absorption spectra of appropriate solutions. The second derivative (D 2) spectrophotometric method, allows determination of Zaleplon without interference of its degradate at 235.2 nm using 0.01N HCl as a solvent with obedience to Beer's law over a concentration range of 1-10 μg ml -1 with mean percentage recovery 100.24 ± 0.86%. The first derivative of the ratio spectra ( 1DD) based on the simultaneous use of ( 1DD) and measurement at 241.8 nm using the same solvent and over the same concentration range as (D 2) spectrophotometric method, with mean percentage recovery 99.9 ± 1.07%. The spectrodensitometric analysis allows the separation and quantitation of Zaleplon from its degradate on silica gel plates using chloroform:acetone:ammonia solution (9:1:0.2 by volume) as a mobile phase. This method depends on quantitave densitometric evaluation of thin layer chromatogram of Zaleplon at 338 nm over a concentration range of 0.2-1 μg band -1, with mean percentage recovery 99.73 ± 1.35. Also a reversed-phase liquid chromatographic method using 5-C8 (22 cm × 4.6 mm i.d. 5 μm particle size) column was described and validated for quantitation of Zaleplon using acetonitrile:deionised water (35:65, v/v) as a mobile phase using Paracetamol as internal standard and a flow rate of 1.5 ml min -1 with UV detection of the effluent at 232 nm at ambient temperature over a concentration range of 2-20 μg ml -1 with mean percentage recovery 100.19 ± 1.15%. The insignificance difference of the proposed methods results with those of the reference one proved their accuracy and precision.

Sequential injection redox or acid-base titration for determination of ascorbic acid or acetic acid.

PubMed

Lenghor, Narong; Jakmunee, Jaroon; Vilen, Michael; Sara, Rolf; Christian, Gary D; Grudpan, Kate

2002-12-06

Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence of peak area obtained with ascorbic acid concentration up to 1200 mg l(-1) was achieved. The relative standard deviation for 11 replicate determinations of 400 mg l(-1) ascorbic acid was 2.9%. The second system, for acetic acid determination, was based on acid-base titration of acetic acid with sodium hydroxide using phenolphthalein as an indicator. The decrease in color intensity of the indicator was proportional to the acid content. A linear calibration graph in the range of 2-8% w v(-1) of acetic acid with a relative standard deviation of 4.8% (5.0% w v(-1) acetic acid, n=11) was obtained. Sample throughputs of 60 h(-1) were achieved for both systems. The systems were successfully applied for the assays of ascorbic acid in vitamin C tablets and acetic acid content in vinegars, respectively.

Novel spectrophotometric determination of flumethasone pivalate and clioquinol in their binary mixture and pharmaceutical formulation.

PubMed

Abdel-Aleem, Eglal A; Hegazy, Maha A; Sayed, Nour W; Abdelkawy, M; Abdelfatah, Rehab M

2015-02-05

This work is concerned with development and validation of three simple, specific, accurate and precise spectrophotometric methods for determination of flumethasone pivalate (FP) and clioquinol (CL) in their binary mixture and ear drops. Method A is a ratio subtraction spectrophotometric one (RSM). Method B is a ratio difference spectrophotometric one (RDSM), while method C is a mean center spectrophotometric one (MCR). The calibration curves are linear over the concentration range of 3-45 μg/mL for FP, and 2-25 μg/mL for CL. The specificity of the developed methods was assessed by analyzing different laboratory prepared mixtures of the FP and CL. The three methods were validated as per ICH guidelines; accuracy, precision and repeatability are found to be within the acceptable limits. Copyright © 2014 Elsevier B.V. All rights reserved.

Spectrophotometric methods for the determination of urea in real samples using silver nanoparticles by standard addition and 2nd order derivative methods

NASA Astrophysics Data System (ADS)

Ali, Nauman; Ismail, Muhammad; Khan, Adnan; Khan, Hamayun; Haider, Sajjad; Kamal, Tahseen

2018-01-01

In this work, we have developed simple, sensitive and inexpensive methods for the spectrophotometric determination of urea in urine samples using silver nanoparticles (AgNPs). The standard addition and 2nd order derivative methods were adopted for this purpose. AgNPs were prepared by chemical reduction of AgNO3 with hydrazine using 1,3-di-(1H-imidazol-1-yl)-2-propanol (DIPO) as a stabilizing agent in aqueous medium. The proposed methods were based on the complexation of AgNPs with urea. Using this concept, urea in the urine samples was successfully determined spectrophotometric methods. The results showed high percent recovery with ± RSD. The recoveries of urea in the three urine samples by spectrophotometric standard addition were 99.2% ± 5.37, 96.3% ± 4.49, 104.88% ± 4.99 and that of spectrophotometric 2nd order derivative method were 115.3% ± 5.2, 103.4% ± 2.6, 105.93% ± 0.76. The results show that these methods can open doors for a potential role of AgNPs in the clinical determination of urea in urine, blood, biological, non-biological fluids.

Determination of niobium in the parts per million range in rocks

USGS Publications Warehouse

Grimaldi, F.S.

1960-01-01

A modified niobium thiocyanate spectrophotometric procedure relatively insensitive to titanium interference is presented. Elements such as tungsten, molybdenum, vanadium, and rhenium, which seriously interfere in the spectrophotometric determination of niobium, are separated by simple sodium hydroxide fusion and leach; iron and magnesium are used as carriers for the niobium. Tolerance limits are given for 28 elements in the spectrophotometric method. Specific application is made to the determination of niobium in the parts per million range in rocks. The granite G-1 contains 0.0022% niobium and the diabase W-1 0.00096% niobium.

Simultaneous determination of the brand new two-drug combination for the treatment of hepatitis C: Sofosbuvir/ledipasvir using smart spectrophotometric methods manipulating ratio spectra

NASA Astrophysics Data System (ADS)

Eissa, Maya S.

2017-08-01

In this work, various sensitive and selective spectrophotometric methods were first introduced for the simultaneous determination of sofosbuvir and ledipasvir in their binary mixture without preliminary separation. Ledipasvir was determined simply by zero-order spectrophotometric method at its λmax = 333.0 nm in a linear range of 2.5-30.0 μg/ml without any interference of sofosbuvir even in low or high concentrations and with mean percentage recovery of 100.05 ± 0.632. Sofosbuvir can be quantitatively estimated by one of the following smart spectrophotometric methods based on ratio spectra developed for the resolution of the overlapped spectra of their binary mixture; ratio difference spectrophotometric method (RD) by computing the difference between the amplitudes of sofosbuvir ratio spectra at 228 nm and 270 nm, first derivative (DD1) of ratio spectra by measuring the sum of amplitude of trough and peak at 265 nm and 277 nm, respectively, ratio subtraction (RS) spectrophotometric method in which sofosbuvir can be successfully determined at its λmax = 261.0 nm and mean centering (MC) of ratio spectra by measuring the mean centering values at 270 nm. All of the above mentioned spectrophotometric methods can estimate sofosbuvir in a linear range of 7.5-90.0 μg/ml with mean percentage recoveries of 100.57 ± 0.810, 99.92 ± 0.759, 99.51 ± 0.475 and 100.75 ± 0.672, respectively. These methods were successfully applied to the analysis of their combined dosage form and bulk powder. The adopted methods were also validated as per ICH guidelines and statistically compared to an in-house HPLC method.

Simultaneous determination of the brand new two-drug combination for the treatment of hepatitis C: Sofosbuvir/ledipasvir using smart spectrophotometric methods manipulating ratio spectra.

PubMed

Eissa, Maya S

2017-08-05

In this work, various sensitive and selective spectrophotometric methods were first introduced for the simultaneous determination of sofosbuvir and ledipasvir in their binary mixture without preliminary separation. Ledipasvir was determined simply by zero-order spectrophotometric method at its λ max =333.0nm in a linear range of 2.5-30.0μg/ml without any interference of sofosbuvir even in low or high concentrations and with mean percentage recovery of 100.05±0.632. Sofosbuvir can be quantitatively estimated by one of the following smart spectrophotometric methods based on ratio spectra developed for the resolution of the overlapped spectra of their binary mixture; ratio difference spectrophotometric method (RD) by computing the difference between the amplitudes of sofosbuvir ratio spectra at 228nm and 270nm, first derivative (DD 1 ) of ratio spectra by measuring the sum of amplitude of trough and peak at 265nm and 277nm, respectively, ratio subtraction (RS) spectrophotometric method in which sofosbuvir can be successfully determined at its λ max =261.0nm and mean centering (MC) of ratio spectra by measuring the mean centering values at 270nm. All of the above mentioned spectrophotometric methods can estimate sofosbuvir in a linear range of 7.5-90.0μg/ml with mean percentage recoveries of 100.57±0.810, 99.92±0.759, 99.51±0.475 and 100.75±0.672, respectively. These methods were successfully applied to the analysis of their combined dosage form and bulk powder. The adopted methods were also validated as per ICH guidelines and statistically compared to an in-house HPLC method. Copyright © 2017 Elsevier B.V. All rights reserved.

Spectrophotometric determination of dopaminergic drugs used for Parkinson's disease, cabergoline and ropinirole, in pharmaceutical preparations.

PubMed

Onal, Armağan; Cağlar, Sena

2007-04-01

Simple and reproducible spectrophotometric methods have been developed for determination of dopaminergic drugs used for Parkinson's disease, cabergoline (CAB) and ropinirole hydrochloride (ROP), in pharmaceutical preparations. The methods are based on the reactions between the studied drug substances and ion-pair agents [methyl orange (MO), bromocresol green (BCG) and bromophenol blue (BPB)] producing yellow colored ion-pair complexes in acidic buffers, after extracting in dichloromethane, which are spectrophotometrically determined at the appropriate wavelength of ion-pair complexes. Beer's law was obeyed within the concentration range from 1.0 to 35 microg ml(-1). The developed methods were applied successfully for the determination of these drugs in tablets.

A Sensitive Photometric Procedure for Cobalt Determination in Water Employing a Compact Multicommuted Flow Analysis System.

PubMed

da Silva Magalhães, Ticiane; Reis, Boaventura F

2017-09-01

In this work, a multicommuted flow analysis procedure is proposed for the spectrophotometric determination of cobalt in fresh water, employing an instrument setup of downsized dimension and improved cost-effectiveness. The method is based on the catalytic effect of Co(II) on the Tiron oxidation by hydrogen peroxide in alkaline medium, forming a complex that absorbs radiation at 425 nm. The photometric detection was accomplished using a homemade light-emitting-diode (LED)-based photometer designed to use a flow cell with an optical path-length of 100 mm to improve sensitivity. After selecting adequate values for the flow system variables, adherence to the Beer-Lambert-Bouguer law was observed for standard solution concentrations in the range of 0.13-1.5 µg L -1 Co(II). Other useful features including a relative standard deviation of 2.0% (n = 11) for a sample with 0.49 µg L -1 Co(II), a detection limit of 0.06 µg L -1 Co(II) (n = 20), an analytical frequency of 42 sample determinations per hour, and waste generation of 1.5 mL per determination were achieved.

Spectrophotometric determination of 4-acetamidophenyl N'-(sulphanilamide) acetate in biological fluids.

PubMed

Shah, Bhavna; Patil, Pravin; Shah, Hirva

2014-01-01

A simple, accurate and low cost spectrophotometric method is proposed for the determination of the synthesized paracetamol derivative; 4-acetamidophenyl N'-(sulphanilamide) acetate (APSA) in biological fluids. The spectrophotometric method is based on a condensation reaction between the alcoholic solution of APSA and acidic solution of p-dimethylaminobenzaldeyde (DPMK) to generate a yellow colored product. The linear range for the determination of APSA was 1-10 µg mL(-1) with molar absorptivity of 3.6877 × 10(4) L mol(-1) cm(-1) and Sandell's sensitivity of 0.001 µg cm-2/0.001 absorbance unit. During the inter-day and intra-day analysis, the relative standard deviation for replicated determination of APSA was found to be less than 2.0% and accuracy was 99.20-101.60% and 99.10-101.30% in blood and urine samples, respectively. There was no interference with commonly used blood and urine sample. The developed spectrophotometric method was successfully applied to assess APSA in biological fluids.

Fast determination of phosphorus in honey, milk and infant formulas by electrothermal atomic absorption spectrometry using a slurry sampling procedure

NASA Astrophysics Data System (ADS)

López-García, I.; Viñas, P.; Romero-Romero, R.; Hernández-Córdoba, M.

2007-01-01

A procedure for the electrothermal atomic absorption spectrometric determination of phosphorus in honey, milk and infant formulas using slurried samples is described. Suspensions prepared in a medium containing 50% v/v concentrated hydrogen peroxide, 1% v/v concentrated nitric acid, 10% m/v glucose, 5% m/v sucrose and 100 mg l - 1 of potassium were introduced directly into the furnace. For the honey samples, multiple injection of the sample was necessary. The modifier selected was a mixture of 20 μg palladium and 5 μg magnesium nitrate, which was injected after the sample and before proceeding with the drying and calcination steps. Calibration was performed using aqueous standards prepared in the same suspension medium and the graph was linear between 5 and 80 mg l - 1 of phosphorus. The reliability of the procedure was checked by comparing the results obtained by the new developed method with those found when using a reference spectrophotometric method after a mineralization step, and by analyzing several certified reference materials.

Sequential injection system with in-line solid phase extraction and soil mini-column for determination of zinc and copper in soil leachates.

PubMed

Paluch, Justyna; Mesquita, Raquel B R; Cerdà, Víctor; Kozak, Joanna; Wieczorek, Marcin; Rangel, António O S S

2018-08-01

A sequential injection (SI) system equipped with in-line solid phase extraction column and in-line soil mini-column is proposed for determination of zinc and copper in soil leachates. The spectrophotometric determination (560 nm) is based on the reaction of both analytes with 1-(2-Pyridylazo)-2-naphthol (PAN). Zinc is determined after retaining copper on a cationic resin (Chelex100) whereas copper is determined from the difference of the absorbance measured for both analytes, introduced into the system with the use of a different channel, and zinc absorbance. The influence of several potential interferences was studied. Using the developed method, zinc and copper were determined within the concentration ranges of 0.005-0.300 and 0.011-0.200 mg L -1 , and with a relative standard deviation lower than 6.0% and 5.1%, respectively. The detection limits are 1.4 and 3.0 µg/L for determination of zinc and copper, respectively. The developed SI method was verified by the determination of both analytes in synthetic and certified reference materials of water samples, and applied to the determination of the analytes in rain water and soil leachates from laboratory scale soil core column and in-line soil mini-column. Copyright © 2018 Elsevier B.V. All rights reserved.

Determination of cyanide by a highly sensitive indirect spectrophotometric method.

PubMed

Blanco, M; Maspoch, S

1984-01-01

Complexation of Pd(2+) with cyanide inhibits the extraction of the palladium complex of 5-phenylazo-8-aminoquinoline. This effect is used for the indirect spectrophotometric determination of cyanide at the mug level. Cyanide in industrial waste water and in sea-water is determined after distillation as HCN from the sample and collection in sodium hydroxide solution.

Determination of cyanide by an indirect spectrophotometric method using 5-Br-PADAP.

PubMed

Fu-Sheng, W; Yu-Qin, L; Fang, Y; Nai-Kui, S

1981-09-01

Complexation of Ni(2+) with cyanide inhibits its colour reaction with 5-Br-PADAP and this reaction is used in the spectrophotometric determination of cyanide at the ug level. Cyanide in industrial waste waters is determined after an initial transfer as hydrogen cyanide from the sample into sodium hydroxide solution with a stream of air.

Spectrophotometric and high performance liquid chromatographic methods for sensitive determination of bisphenol A

NASA Astrophysics Data System (ADS)

Zhuang, Yafeng; Zhou, Meng; Gu, Jia; Li, Xiangmei

2014-03-01

A new spectrophotometric method for the determination of trace amounts of bisphenol A based on a diazotization-coupling reaction was developed. In acidic solution, clenbuterol was first diazotized with sodium nitrite, then coupled with bisphenol A to from an azo-compound [I] in NH3-NH4Cl buffer, which shows a maximum absorption at 410 nm. The effects of the amount of sodium nitrite, diazo reaction time, the amount of clenbuterol, coupling reaction time and coupling reaction temperature have been examined. Under the optional conditions, the determination of the linear range of bisphenol A is 0.24-8.4 μg/mL, correlation coefficient is 0.9905 and detection limit of this method is 0.15 μg/mL. The spectrophotometric method is simple, rapid, high sensitivity with better accuracy. High performance liquid chromatography (HPLC) technique combined with this new spectrophotometric method has been also developed for the measurement of bisphenol A. The analysis was achieved on a C18 column using water and methanol as a mobile phase and the detection was done spectrophotometrically at 410 nm. These reported methods were applied to the determination of bisphenol A in hot water in contact with commercially available table-water bottle samples.

Spectrophotometric determination of triclosan based on diazotization reaction: response surface optimization using Box-Behnken design.

PubMed

Kaur, Inderpreet; Gaba, Sonal; Kaur, Sukhraj; Kumar, Rajeev; Chawla, Jyoti

2018-05-01

A spectrophotometric method based on diazotization of aniline with triclosan has been developed for the determination of triclosan in water samples. The diazotization process involves two steps: (1) reaction of aniline with sodium nitrite in an acidic medium to form diazonium ion and (2) reaction of diazonium ion with triclosan to form a yellowish-orange azo compound in an alkaline medium. The resulting yellowish-orange product has a maximum absorption at 352 nm which allows the determination of triclosan in aqueous solution in the linear concentration range of 0.1-3.0 μM with R 2 = 0.998. The concentration of hydrochloric acid, sodium nitrite, and aniline was optimized for diazotization reaction to achieve good spectrophotometric determination of triclosan. The optimization of experimental conditions for spectrophotometric determination of triclosan in terms of concentration of sodium nitrite, hydrogen chloride and aniline was also carried out by using Box-Behnken design of response surface methodology and results obtained were in agreement with the experimentally optimized values. The proposed method was then successfully applied for analyses of triclosan content in water samples.

[Determination of mercury in Boletus impolitus by flow injection-atomic absorption spectrometry].

PubMed

Li, Tao; Wang, Yuan-Zhong

2008-04-01

Various test conditions and effect factors for the determination of mercury by flow injection-atomic absorption spectrometry were discussed, and a method for the determination of mercury in Boletus impolitus has been developed. The linear range for mercury is 0-60 microg x L(-1). The relative standard deviation is less than 3.0%, and the recovery is 96%-107%. This method is simple, rapid and has been applied to the determination of mercury in Boletus impolitus samples with satisfactory results.

Flow in a porous nozzle with massive wall injection

NASA Technical Reports Server (NTRS)

Kinney, R. B.

1973-01-01

An analytical and experimental investigation has been conducted to determine the effect of massive wall injection on the flow characteristics in a nozzle. The experiments were performed on a water table with a porous-nozzle test section. This had 45 deg and 15 deg half angles of convergence and divergence, respectively, throat radius of 2.5 inches, and throat width of 3 inches. The hydraulic analogy was employed to qualitatively extend the results to a compressible gas flow through the nozzle. An analysis of the water table flow was made using a one-dimensional flow assumption in the continuity and momentum equations. An analysis of a compressible flow in a nozzle was made in a manner analogous to that for the water flow. It is shown that the effect of blowing is to move the sonic position downstream of the geometric throat. Similar results were determined for the incompressible water table flow. Limited photographic results are presented for an injection of air, CO2, and Freon-12 into a main-stream air flow in a convergent-divergent nozzle. Schlieren photographs were used to visualize the flow.

Flow analysis techniques for phosphorus: an overview.

PubMed

Estela, José Manuel; Cerdà, Víctor

2005-04-15

A bibliographical review on the implementation and the results obtained in the use of different flow analytical techniques for the determination of phosphorus is carried out. The sources, occurrence and importance of phosphorus together with several aspects regarding the analysis and terminology used in the determination of this element are briefly described. A classification as well as a brief description of the basis, advantages and disadvantages of the different existing flow techniques, namely; segmented flow analysis (SFA), flow injection analysis (FIA), sequential injection analysis (SIA), all injection analysis (AIA), batch injection analysis (BIA), multicommutated FIA (MCFIA), multisyringe FIA (MSFIA) and multipumped FIA (MPFIA) is also carried out. The most relevant manuscripts regarding the analysis of phosphorus by means of flow techniques are herein classified according to the detection instrumental technique used with the aim to facilitate their study and obtain an overall scope. Finally, the analytical characteristics of numerous flow-methods reported in the literature are provided in the form of a table and their applicability to samples with different matrixes, namely water samples (marine, river, estuarine, waste, industrial, drinking, etc.), soils leachates, plant leaves, toothpaste, detergents, foodstuffs (wine, orange juice, milk), biological samples, sugars, fertilizer, hydroponic solutions, soils extracts and cyanobacterial biofilms are tabulated.

Determination of pK(a) of felodipine using UV-Visible spectroscopy.

PubMed

Pandey, M M; Jaipal, A; Kumar, A; Malik, R; Charde, S Y

2013-11-01

In the present study, for the first time, experimental pKa value of felodipine is reported. Dissociation constant, pKa, is one of the very important physicochemical properties of drugs. It is of paramount significance from the perspective of pharmaceutical analysis and dosage form design. The method used for the pKa determination of felodipine was essentially a UV-Visible spectrophotometric method. The spectrophotometric method for the pKa determination was opted by acknowledging the established fact that spectrophotometric determination of pKa produces most precise values. The pKa of felodipine was found to be 5.07. Furthermore, the ruggedness of the determined value is also validated in this study in order to produce exact pKa of the felodipine. Copyright © 2013 Elsevier B.V. All rights reserved.

Determination of chloride in admixtures and aggregates for cement by a simple flow injection potentiometric system.

PubMed

Junsomboon, Jaroon; Jakmunee, Jaroon

2008-07-15

A simple flow injection system using three 3-way solenoid valves as an electric control injection valve and with a simple home-made chloride ion selective electrode based on Ag/AgCl wire as a sensor for determination of water soluble chloride in admixtures and aggregates for cement has been developed. A liquid sample or an extract was injected into a water carrier stream which was then merged with 0.1M KNO(3) stream and flowed through a flow cell where the solution will be in contact with the sensor, producing a potential change recorded as a peak. A calibration graph in range of 10-100 mg L(-1) was obtained with a detection limit of 2 mg L(-1). Relative standard deviations for 7 replicates injecting of 20, 60 and 90 mg L(-1) chloride solutions were 1.0, 1.2 and 0.6%, respectively. Sample throughput of 60 h(-1) was achieved with the consumption of 1 mL each of electrolyte solution and water carrier. The developed method was validated by the British Standard methods.

Determination of Reaction Stoichiometries by Flow Injection Analysis.

ERIC Educational Resources Information Center

Rios, Angel; And Others

1986-01-01

Describes a method of flow injection analysis intended for calculation of complex-formation and redox reaction stoichiometries based on a closed-loop configuration. The technique is suitable for use in undergraduate laboratories. Information is provided for equipment, materials, procedures, and sample results. (JM)

Chemiluminescence determination of ferulic acid by flow-injection analysis using cerium(IV) sensitized by rhodamine 6G.

PubMed

Wang, Ju Peng; Li, Nian Bing; Luo, Hong Qun

2008-11-01

A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with rhodamine 6G and ceric sulfate in sulphuric acid medium. Strong chemiluminescence signal was observed when ferulic acid was injected into the acidic ceric sulfate solution in a flow-cell. The present method allowed the determination of ferulic acid in the concentration range of 8.0 x 10(-6) to 1.0 x 10(-4) mol l(-1) and the detection limit for ferulic acid was 8.7 x 10(-9) mol l(-1). The relative standard deviation was 2.4% for 10 replicate analyses of 1.0 x 10(-5) mol l(-1) ferulic acid. The proposed method was applied to the determination of ferulic acid in Taita Beauty Essence samples with satisfactory results.

Chemiluminescence determination of ferulic acid by flow-injection analysis using cerium(IV) sensitized by rhodamine 6G

NASA Astrophysics Data System (ADS)

Wang, Ju Peng; Li, Nian Bing; Luo, Hong Qun

2008-11-01

A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with rhodamine 6G and ceric sulfate in sulphuric acid medium. Strong chemiluminescence signal was observed when ferulic acid was injected into the acidic ceric sulfate solution in a flow-cell. The present method allowed the determination of ferulic acid in the concentration range of 8.0 × 10 -6 to 1.0 × 10 -4 mol l -1 and the detection limit for ferulic acid was 8.7 × 10 -9 mol l -1. The relative standard deviation was 2.4% for 10 replicate analyses of 1.0 × 10 -5 mol l -1 ferulic acid. The proposed method was applied to the determination of ferulic acid in Taita Beauty Essence samples with satisfactory results.

Spectrophotometric determination of fluorine in silicate rocks

USGS Publications Warehouse

Peck, L.C.; Smith, V.C.

1964-01-01

The rock powder is sintered with a sodium carbonate flux containing zinc oxide and magnesium carbonate, the sinter-cake leached with water and the resulting solution filtered. Fluorine is separated from the acidified filtrate by steam distillation and determined spectrophotometrically by means of a zirconium-SPADNS reagent. If a multiple-unit distillation apparatus is used, 12 determinations can be completed per man-day. ?? 1964.

Simultaneous Estimation of Amlodipine Besilate and Olmesartan Medoxomil in Pharmaceutical Dosage Form

PubMed Central

Wankhede, S. B.; Wadkar, S. B.; Raka, K. C.; Chitlange, S. S.

2009-01-01

Two UV Spectrophotometric and one reverse phase high performance liquid chromatography methods have been developed for the simultaneous estimation of amlodipine besilate and olmesartan medoxomil in tablet dosage form. First UV spectrophotometric method was a determination using the simultaneous equation method at 237.5 nm and 255.5 nm over the concentration range 10-50 μg/ml and 10-50 μg/ml, for amlodipine besilate and olmesartan medoxomil with accuracy 100.09%, and 100.22% respectively. Second UV spectrophotometric method was a determination using the area under curve method at 242.5-232.5 nm and 260.5-250.5 nm over the concentration range of 10-50 μg/ml and 10-50 μg/ml, for amlodipine besilate and olmesartan medoxomil with accuracy 100.10%, and 100.48%, respectively. In reverse phase high performance liquid chromatography analysis carried out using 0.05M potassuim dihydrogen phosphate buffer:acetonitrile (50:50 v/v) as the mobile phase and Kromasil C18 (4.6 mm i.d.×250 mm) column as the stationery phase with detection wavelength of 238 nm. Flow rate was 1.0 ml/min. Retention time for amlodipine besilate and olmesartan medoxomil were 3.69 and 5.36 min, respectively. Linearity was obtained in the concentration range of 4-20 μg/ml and 10-50 μg/ml for amlodipine besilate and olmesartan medoxomil, respectively. Proposed methods can be used for the estimation of amlodipine besilate and olmesartan medoxomil in tablet dosage form provided all the validation parameters are met. PMID:20502580

Application of the ratio difference spectrophotometry to the determination of ibuprofen and famotidine in their combined dosage form: comparison with previously published spectrophotometric methods.

PubMed

Zaazaa, Hala E; Elzanfaly, Eman S; Soudi, Aya T; Salem, Maissa Y

2015-05-15

Ratio difference spectrophotometric method was developed for the determination of ibuprofen and famotidine in their mixture form. Ibuprofen and famotidine were determined in the presence of each other by the ratio difference spectrophotometric (RD) method where linearity was obtained from 50 to 600μg/mL and 2.5 to 25μg/mL for ibuprofen and famotidine, respectively. The suggested method was validated according to ICH guidelines and successfully applied for the analysis of ibuprofen and famotidine in their pharmaceutical dosage forms without interference from any additives or excipients. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel Methods of Determining Urinary Calculi Composition: Petrographic Thin Sectioning of Calculi and Nanoscale Flow Cytometry Urinalysis

PubMed Central

Gavin, Carson T; Ali, Sohrab N; Tailly, Thomas; Olvera-Posada, Daniel; Alenezi, Husain; Power, Nicholas E; Hou, Jinqiang; St. Amant, Andre H; Luyt, Leonard G; Wood, Stephen; Wu, Charles; Razvi, Hassan; Leong, Hon S

2016-01-01

Accurate determination of urinary stone composition has significant bearing on understanding pathophysiology, choosing treatment modalities and preventing recurrence. A need exists for improved methods to determine stone composition. Urine of 31 patients with known renal calculi was examined with nanoscale flow cytometry and the calculi collected during surgery subsequently underwent petrographic thin sectioning with polarized and fluorescent microscopy. Fluorescently labeled bisphosphonate probes (Alendronate-fluorescein/Alendronate-Cy5) were developed for nanoscale flow cytometry to enumerate nanocrystals that bound the fluorescent probes. Petrographic sections of stones were also imaged by fluorescent and polarized light microscopy with composition analysis correlated to alendronate +ve nanocrystal counts in corresponding urine samples. Urine samples from patients with Ca2+ and Mg2+ based calculi exhibited the highest alendronate +ve nanocrystal counts, ranging from 100–1000 nm in diameter. This novel urine based assay was in agreement with composition determined by petrographic thin sections with Alendronate probes. In some cases, high alendronate +ve nanocrystal counts indicated a Ca2+ or Mg2+ composition, as confirmed by petrographic analysis, overturning initial spectrophotometric diagnosis of stone composition. The combination of nanoscale flow cytometry and petrographic thin sections offer an alternative means for determining stone composition. Nanoscale flow cytometry of alendronate +ve nanocrystals alone may provide a high-throughput means of evaluating stone burden. PMID:26771074

Forced-flow chromatographic determination of calcium and magnesium with continuous spectrophotometric detection

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

Arguello, M.D.

1977-12-01

Modifications to the forced-flow chromatograph include a flow-through pH monitor to continuously monitor the pH of the final effluent and an active low-pass filter to eliminate noise in the spectrophotometric detector. All separations are performed using partially sulfonated XAD-2 as the ion exchanger. Elution of calcium and magnesium is accomplished using ammonium chloride and ethylenediammonium chloride solutions. Calcium and magnesium are detected by means of Arsenazo I and PAR-ZnEDTA color-forming reagents. Other metal ions are detected by means of PAR and Chromazurol S color-forming reagents. Calcium and magnesium distribution coefficients on partially sulfonated XAD-2 as functions of ammonium chloride andmore » ethylenediammonium chloride concentration are given together with distribution coefficients of other metal ions. Methods for the selective elution of interfering metal ions prior to the elution of calcium and magnesium are described. Beryllium and aluminum are selectively eluted with sulfosalicylic acid. Those elements forming anionic chloride complexes are selectively eluted with HCl-acetone. Nickel is selectively eluted with HCl-acetone-dimethylglyoxime. Synthetic samples containing calcium and magnesium, both alone and in combination with alkali metals, strontium, barium, beryllium, aluminum, transition metals, and rare earths, are analyzed. Hard water samples are analyzed for calcium and magnesium and the results compared to those obtained by EDTA titration, atomic absorption spectroscopy, and plasma emission spectroscopy. Several clinical serum samples are analyzed for calcium and magnesium and the results compared to those obtained by atomic absorption spectroscopy.« less

How Much Cranberry Juice Is in Cranberry-Apple Juice? A General Chemistry Spectrophotometric Experiment

ERIC Educational Resources Information Center

Edionwe, Etinosa; Villarreal, John R.; Smith, K. Christopher

2011-01-01

A laboratory experiment that spectrophotometrically determines the percent of cranberry juice in cranberry-apple juice is described. The experiment involves recording an absorption spectrum of cranberry juice to determine the wavelength of maximum absorption, generating a calibration curve, and measuring the absorbance of cranberry-apple juice.…

An improved leaping detector for flow analysis applied to iron speciation in drugs

PubMed Central

Santos, Sérgio R. B.; Araújo, Mário C. U.; Honorato, Ricardo S.; Zagatto, Elias A. G.; Lima, José F. C.; Lapa, Rui A. S.

2000-01-01

A low inner volume (ca. 64 ml) probe was built up in an injector-commutator in order to behave as a photometric leaping detector in flow analysis. It comprises a bicolour light-emitting diode (BLED), as a source of pulsed radiation in the red and green visible region, and two phototransistors as transducers. Sample injection, detector relocation, analytical signal recording, data treatment and definition of the spectral working range were computer-controlled. The feasibility of the system was initially demonstrated in the flow-injection speciation of iron, and the overall standard deviation of results was estimated as ± 1.6 and ± 1.4% for 1.6–4.0 mg l−1 Fe(II) or total iron after eightfold processing of synthetic samples. The system was further applied to drug analysis: the mean deviations of results for typical samples were estimated as ± 5.2 and ± 3.3%, and the relative standard deviation as ± 1.6 and ± 1.3% for Fe(II) and total iron, respectively. Results were compared with those obtained by a conventional spectrophotometric procedure and no statistic differences at the 95% confidence level were found. In relation to an earlier system with multi-site detection, the proposed system is more stable, presenting low drift with a relative standard deviation of 0.026% and 0.039% for measurements (n=120 during 4 h of observation) with green and red emission. It is also faster with a sampling rate of 133 h−1 and carryover problems are not found. The possibility of compensating the Schlieren noise by dual-wavelength spectrophotometry is discussed. PMID:18924860

Effect of feeding protein supplements of differing degradability on omasal flow of microbial and undegraded protein.

PubMed

Reynal, S M; Broderick, G A; Ahvenjärvi, S; Huhtanen, P

2003-04-01

Ten ruminally cannulated lactating Holstein cows that were part of a larger trial studying the effects of feeding different proteins on milk production were used in a replicated 5 x 5 Latin square to quantify flows of microbial and rumen-undegradable protein (RUP) in omasal digesta. Cows were fed total mixed rations containing (dry matter basis) 44% corn silage, 22% alfalfa silage, 2% urea, and 31% concentrate. The basal diet contained 31% high-moisture corn; equal N from one of four protein supplements was added to the other diets at the expense of corn: 9% solvent soybean meal (SSBM), 10% expeller soybean meal (ESBM), 5.5% blood meal (BM), and 7% corn gluten meal (CGM). Omasal sampling was used to quantify total AA N (TAAN) and nonammonia N (NAN) flows from the rumen. Estimates of RUP were made from differences between total and microbial N flows, including a correction for RUP in the basal diet. Modifying a spectrophotometric assay improved total purine recovery from isolated bacteria and omasal samples and gave estimates of microbial TAAN and NAN flows that were similar to a standard HPLC method. Linear programming, based on AA patterns of the diet and isolated omasal bacteria and ruminal protozoa, appeared to overestimate microbial TAAN and NAN flows compared to the purine assays. Yields of microbial TAAN and NAN determined using any method was not affected by diet and averaged 32 to 35 g NAN per kilogram of organic matter truly digested in the rumen. On average, National Research Council (NRC) equations underpredicted microbial N flows by 152 g/d (vs. HPLC), 168 g/d (vs. spectrophotometry), and 244 g/d (vs. linear programming). Estimates of RUP (means from the HPLC and spectrophotometric methods) were: SSBM, 27%, ESBM, 45%, BM, 60%, and CGM, 73%. Except for CGM, RUP values averaged about 20 percentage units lower than those reported by the NRC.

Velocity field of a round jet in a cross flow for various jet injection angles and velocity ratios. [Langley V/STOL tunnel

NASA Technical Reports Server (NTRS)

Fearn, R. L.; Weston, R. P.

1979-01-01

A subsonic round jet injected from a flat plate into a subsonic crosswind of the same temperature was investigated. Velocity and pressure measurements in planes perpendicular to the path of the jet were made for nominal jet injection angles of 45 deg, 60 deg, 75 deg, 90 deg, and 105 deg and for jet/cross flow velocity ratios of four and eight. The velocity measurements were obtained to infer the properties of the vortex pair associated with a jet in a cross flow. Jet centerline and vortex trajectories were determined and fit with an empirical equation that includes the effects of jet injection angle, jet core length, and jet/cross flow velocity ratios.

Sensitized spectrophotometric determination of Cr(III) ion for speciation of chromium ion in surfactant media using alpha-benzoin oxime.

PubMed

Ghaedi, Mehrorang; Asadpour, Enayat; Vafaie, Azam

2006-01-01

A simple and accurate micellanized spectrophotometric method for determination of trace amounts of Cr(III) ion in tab and top water and a synthetic mixture has been described. The micellar method is based on effect of organized molecular assemblies such as micelles in spectrophotometric measurement due to their effect on the systems of interest. The ability of micellar system in solubilizing of sparingly soluble ligand or complexes has been used for increasing figures of merit of an analytical method. Due to solubility increasing in aqueous media requirement for a primary extraction can be eliminated. Using the alpha-benzoin oxime (alpha-BO) spectrophotometric determination of Cr(III) ion has been performed and results are compared. The spectrophotometric determination of Cr(III) ion using alpha-BO in the presence of non-ionic surfactant Triton X-100 has been performed. The influence of type and amount of surfactant, pH, complexation time and amount of ligand were examined. Finally, the repeatability, accuracy and the effect of interfering ions on the determination of Cr(III) ion was evaluated. The proposed methods successfully with recovery yield of almost 100% have been applied to the rapid and simple determination of Cr(III) ion in the real samples. There is a good agreement between methods and atomic absorption spectrometry. The Beers law is obeyed over the concentration range of 0.1-13.7 microg mL(-1) for micellar media. The detection limit is 0.8 ng mL(-1). The molar absorptivity of complex is 5350 L mol(-1) cm(-1).

Sensitized spectrophotometric determination of Cr(III) ion for speciation of chromium ion in surfactant media using α-benzoin oxime

NASA Astrophysics Data System (ADS)

Ghaedi, Mehrorang; Asadpour, Enayat; Vafaie, Azam

2006-01-01

A simple and accurate micellanized spectrophotometric method for determination of trace amounts of Cr(III) ion in tab and top water and a synthetic mixture has been described. The micellar method is based on effect of organized molecular assemblies such as micelles in spectrophotometric measurement due to their effect on the systems of interest. The ability of micellar system in solubilizing of sparingly soluble ligand or complexes has been used for increasing figures of merit of an analytical method. Due to solubility increasing in aqueous media requirement for a primary extraction can be eliminated. Using the α-benzoin oxime (α-BO) spectrophotometric determination of Cr(III) ion has been performed and results are compared. The spectrophotometric determination of Cr(III) ion using α-BO in the presence of non-ionic surfactant Triton X-100 has been performed. The influence of type and amount of surfactant, pH, complexation time and amount of ligand were examined. Finally, the repeatability, accuracy and the effect of interfering ions on the determination of Cr(III) ion was evaluated. The proposed methods successfully with recovery yield of almost 100% have been applied to the rapid and simple determination of Cr(III) ion in the real samples. There is a good agreement between methods and atomic absorption spectrometry. The Beers law is obeyed over the concentration range of 0.1-13.7 μg mL-1 for micellar media. The detection limit is 0.8 ng mL-1. The molar absorptivity of complex is 5350 L mol-1 cm-1.

A volumetric flow sensor for automotive injection systems

NASA Astrophysics Data System (ADS)

Schmid, U.; Krötz, G.; Schmitt-Landsiedel, D.

2008-04-01

For further optimization of the automotive power train of diesel engines, advanced combustion processes require a highly flexible injection system, provided e.g. by the common rail (CR) injection technique. In the past, the feasibility to implement injection nozzle volumetric flow sensors based on the thermo-resistive measurement principle has been demonstrated up to injection pressures of 135 MPa (1350 bar). To evaluate the transient behaviour of the system-integrated flow sensors as well as an injection amount indicator used as a reference method, hydraulic simulations on the system level are performed for a CR injection system. Experimentally determined injection timings were found to be in good agreement with calculated values, especially for the novel sensing element which is directly implemented into the hydraulic system. For the first time pressure oscillations occurring after termination of the injection pulse, predicted theoretically, could be verified directly in the nozzle. In addition, the injected amount of fuel is monitored with the highest resolution ever reported in the literature.

Spectrophotometric and HPLC determinations of anti-diabetic drugs, rosiglitazone maleate and metformin hydrochloride, in pure form and in pharmaceutical preparations.

PubMed

Onal, Armağan

2009-12-01

In this study, three spectrophotometric methods and one HPLC method were developed for analysis of anti-diabetic drugs in tablets. The two spectrophotometric methods were based on the reaction of rosiglitazone (RSG) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and bromocresol green (BCG). Linear relationship between the absorbance at lambda(max) and the drug concentration was found to be in the ranges 6.0-50.0 and 1.5-12 microg ml(-1) for DDQ and BCG methods, respectively. The third spectrophotometric method consists of a zero-crossing first-derivative spectrophotometric method for simultaneous analysis of RSG and metformin (MTF) in tablets. The calibration curves were linear within the concentration ranges of 5.0-50 microg ml(-1) for RSG and 1.0-10.0 microg ml(-1) for MTF. The fourth method is a rapid stability-indicating HPLC method developed for the determination of RSG. A linear response was observed within the concentration range of 0.25-2.5 microg ml(-1). The proposed methods have been successfully applied to the tablet analysis.

Spectrophotometric and Spectrofluorimetric Studies on Azilsartan Medoxomil and Chlorthalidone to Be Utilized in Their Determination in Pharmaceuticals

PubMed Central

Ebeid, Walid M; Elkady, Ehab F; El-Zaher, Asmaa A; El-Bagary, Ramzia I; Patonay, Gabor

2014-01-01

The recently approved angiotensin II receptor blocker, azilsartan medoxomil (AZL), was determined spectrophotometrically and spectrofluorimetrically in its combination with chlorthalidone (CLT) in their combined dosage form. The UV-spectrophotometric technique depends on simultaneous measurement of the first derivative spectra for AZL and CLT at 286 and 257 nm, respectively, in methanol. The spectrofluorimetric technique depends on measurement of the fourth derivative of the synchronous spectra intensities of AZL in presence of CLT at 298 nm in methanol. The effects of different solvents on spectrophotometric and spectrofluorimetric responses were studied. For, the spectrofluorimetric study, the effect of pH and micelle-assisted fluorescence enhancement were also studied. Linearity, accuracy, and precision were found to be satisfactory over the concentration ranges of 8–50 μg mL−1 and 2–20 μg mL−1 for AZL and CLT, respectively, in the spectrophotometric method as well as 0.01–0.08 μg mL−1 for AZL in the spectrofluorimetric method. The methods were successfully applied for the determination of the studied drugs in their co-formulated tablets. The developed methods are inexpensive and simple for the quality control and routine analysis of the cited drugs in bulk and in pharmaceuticals. PMID:24855334

New Spectrophotometric and Fluorimetric Methods for Determination of Fluoxetine in Pharmaceutical Formulations

PubMed Central

Darwish, Ibrahim A.; Amer, Sawsan M.; Abdine, Heba H.; Al-Rayes, Lama I.

2009-01-01

New simple and sensitive spectrophotometric and fluorimetric methods have been developed and validated for the determination of fluoxetine hydrochloride (FLX) in its pharmaceutical formulations. The spectrophotometric method was based on the reaction of FLX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium (pH 11) to form an orange-colored product that was measured at 490 nm. The fluorimetric method was based on the reaction of FLX with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in an alkaline medium (pH 8) to form a highly fluorescent product that was measured at 545 nm after excitation at 490 nm. The variables affecting the reactions of FLX with both NQS and NBD-Cl were carefully studied and optimized. The kinetics of the reactions were investigated, and the reaction mechanisms were presented. Under the optimum reaction conditions, good linear relationships were found between the readings and the concentrations of FLX in the ranges of 0.3–6 and 0.035–0.5 μg mL−1 for the spectrophotometric and fluorimetric methods, respectively. The limits of detection were 0.1 and 0.01 μg mL−1 for the spectrophotometric and fluorimetric methods, respectively. Both methods were successfully applied to the determination of FLX in its pharmaceutical formulations. PMID:20107560

AAS and spectrophotometric methods for the determination metoprolol tartrate in tablets

NASA Astrophysics Data System (ADS)

Alpdoğan, Güzin; Sungur, Sidika

1999-11-01

Sensitive and specific atomic adsorption spectroscopy (AAS) and spectrophotometric methods have been developed for the determination of beta adrenergic blocking drug, metoprolol tartrate.The method is based on the formation of Cu(II) dithiocarbamate complex by derivatization of the secondary amino group of metoprolol with CS 2 and CuCl 2 in the presence of ammonia.The copper-bis(dithiocarbamate) complex was extracted into chloroform and the concentration of metoprolol tartrate was determined directly by spectrophotometric and indirectly by AAS measurement of copper.The two methods developed were applied to the assay of metoprolol tartrate in commercial tablet formulations.The methods were compared statistically with each other and with the high performance liquid chromatography (HPLC) method of USPXXII using t- and F-tests.

Net analyte signal standard addition method (NASSAM) as a novel spectrofluorimetric and spectrophotometric technique for simultaneous determination, application to assay of melatonin and pyridoxine

NASA Astrophysics Data System (ADS)

Asadpour-Zeynali, Karim; Bastami, Mohammad

2010-02-01

In this work a new modification of the standard addition method called "net analyte signal standard addition method (NASSAM)" is presented for the simultaneous spectrofluorimetric and spectrophotometric analysis. The proposed method combines the advantages of standard addition method with those of net analyte signal concept. The method can be applied for the determination of analyte in the presence of known interferents. The accuracy of the predictions against H-point standard addition method is not dependent on the shape of the analyte and interferent spectra. The method was successfully applied to simultaneous spectrofluorimetric and spectrophotometric determination of pyridoxine (PY) and melatonin (MT) in synthetic mixtures and in a pharmaceutical formulation.

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

PubMed

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

2012-01-01

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

"Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification

NASA Technical Reports Server (NTRS)

Akse, J. R.; Thompson, J. O.; Sauer, R. L.; Atwater, J. E.

1998-01-01

Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

Piezoelectric detection of ion pairs between sulphonate and catecholamines for flow injection analysis of pharmaceutical preparations.

PubMed

Mo, Z; Long, X; Zhang, M

1999-03-01

Fundamentals of ion-pair flow injection with piezoelectric detection were investigated experimentally and theoretically for the adsorption of dodecyl phenylsulfonate and interfacial ion-pair formation with epinephrine and l-dopa on silver electrode of quartz crystal microbalance. The influences of sulfonate concentration and operating parameters on the frequency response were demonstrated and provided the possibility for the discriminating determination of mixtures. The selected system of ion-pair flow injection with piezoelectric detection was applied to the determination of epinephrine and l-dopa. Calibration curves were linear in ranges 4.00-850 and 3.50-730 mug ml(-1), with detection limits of 1.22 and 1.05 mug ml(-1) and sampling frequencies of 120 samples h(-1), for epinephrine and l-dopa, respectively. The method has been satisfactorily applied to the determination of catecholamines in pharmaceutical preparations.

Spectrophotometric determination of ketoprofen and its application in pharmaceutical analysis.

PubMed

Kormosh, Zholt; Hunka, Iryna; Basel, Yaroslav

2009-01-01

A new simple rapid and sensitive spectrophotometric method has been developed for the determination of ketoprofen in pharmaceutical preparations. The method is based on the reaction of ketoprofen with an analytical reagent--Astra Phloxin FF--at pH 8.0-10.8 and followed by the extraction of formed ion associate in toluene with spectrophotometric detection (it has an absorption maximum at 563 nm, epsilon = 7.6 x 10(4) L x mol(-1) x cm(-1)). The calibration plot was linear from 0.8-16.0 microg x mL(-1) of ketoprofen, and the detection limit was 0.037 microg x mL(-1).

Flow behaviour of negatively buoyant jets in immiscible ambient fluid

NASA Astrophysics Data System (ADS)

Geyer, A.; Phillips, J. C.; Mier-Torrecilla, M.; Idelsohn, S. R.; Oñate, E.

2012-01-01

In this paper we investigate experimentally the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid. Experiments are carried out by injecting a jet of dyed fresh water through a nozzle in the base of a cylindrical tank containing rapeseed oil. The fountain inlet flow rate and nozzle diameter were varied to cover a wide range of Richardson Ri (8 × 10-4 < Ri < 1.98), Reynolds Re (467 < Re < 5,928) and Weber We (2.40 < We < 308.56) numbers. Based on the Re, Ri and We values for the experiments, we have determined a regime map to define how these values may control the occurrence of the observed flow types. Whereas Ri plays a stronger role when determining the maximum penetration height, the effect of the Reynolds number is stronger predicting the flow behaviour for a specific nozzle diameter and injection velocity.

Simultaneous determination of some cholesterol-lowering drugs in their binary mixture by novel spectrophotometric methods

NASA Astrophysics Data System (ADS)

Lotfy, Hayam Mahmoud; Hegazy, Maha Abdel Monem

2013-09-01

Four simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of simvastatin (SM) and ezetimibe (EZ) namely; extended ratio subtraction (EXRSM), simultaneous ratio subtraction (SRSM), ratio difference (RDSM) and absorption factor (AFM). The proposed spectrophotometric procedures do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined, and the methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the cited drugs. The four methods were applied for the determination of the cited drugs in tablets and the obtained results were statistically compared with each other and with those of a reported HPLC method. The comparison showed that there is no significant difference between the proposed methods and the reported method regarding both accuracy and precision.

21 CFR 177.1050 - Acrylonitrile/styrene copoly-mer modified with butadiene/styrene elastomer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... parts by weight of a grafted rubber consisting of (i) 8-12 parts of butadiene/styrene elastomer... limitations are determined by an infrared spectro-photo-metric method titled “Infrared Spectro-photo-metric...

Numerical prediction of flow induced fibers orientation in injection molded polymer composites

NASA Astrophysics Data System (ADS)

Oumer, A. N.; Hamidi, N. M.; Mat Sahat, I.

2015-12-01

Since the filling stage of injection molding process has important effect on the determination of the orientation state of the fibers, accurate analysis of the flow field for the mold filling stage becomes a necessity. The aim of the paper is to characterize the flow induced orientation state of short fibers in injection molding cavities. A dog-bone shaped model is considered for the simulation and experiment. The numerical model for determination of the fibers orientation during mold-filling stage of injection molding process was solved using Computational Fluid Dynamics (CFD) software called MoldFlow. Both the simulation and experimental results showed that two different regions (or three layers of orientation structures) across the thickness of the specimen could be found: a shell region which is near to the mold cavity wall, and a core region at the middle of the cross section. The simulation results support the experimental observations that for thin plates the probability of fiber alignment to the flow direction near the mold cavity walls is high but low at the core region. It is apparent that the results of this study could assist in decisions regarding short fiber reinforced polymer composites.

Insights on Flow Behavior of Foam in Unsaturated Porous Media during Soil Flushing.

PubMed

Zhao, Yong S; Su, Yan; Lian, Jing R; Wang, He F; Li, Lu L; Qin, Chuan Y

2016-11-01

  One-dimensional column and two-dimensional tank experiments were carried out to determine (1) the physics of foam flow and propagation of foaming gas, foaming liquid, and foam; (2) the pressure distribution along foam flow and the effect of media permeability, foam flow rate and foam quality on foam injection pressure; and (3) the migration and distribution property of foam flow in homogeneous and heterogeneous sediments. The results demonstrated that: (1) gas and liquid front were formed ahead of the foam flow front, the transport speed order is foaming gas > foaming liquid > foam flowing; (2) injection pressure mainly comes from the resistance to bubble migration. Effect of media permeability on foam injection pressure mainly depends on the physics and behavior of foam flow; (3) foam has a stronger capacity of lateral spreading, besides, foam flow was uniformly distributed across the foam-occupied region, regardless of the heterogeneity of porous media.

Migration rates and formation injectivity to determine containment time scales of sequestered carbon dioxide

USGS Publications Warehouse

Burke, Lauri

2012-01-01

Additionally, this research establishes a methodology to calculate the injectivity of a target formation. Because injectivity describes the pressure increase due to the introduction of fluids into a formation, the relevant application of injectivity is to determine the pressure increase, due to an injection volume and flow rate, that will induce fractures in the reservoir rocks. This quantity is defined mathematically as the maximum pressure differential between the hydrostatic gradient and the fracture gradient of the target formation. Injectivity is mathematically related to the maximum pressure differential of the formation, and can be used to determine the upper limit for the pressure increase that an injection target can withstand before fracturing.

Validated derivative and ratio derivative spectrophotometric methods for the simultaneous determination of levocetirizine dihydrochloride and ambroxol hydrochloride in pharmaceutical dosage form

NASA Astrophysics Data System (ADS)

Ali, Omnia I. M.; Ismail, Nahla S.; Elgohary, Rasha M.

2016-01-01

Three simple, precise, accurate and validated derivative spectrophotometric methods have been developed for the simultaneous determination of levocetirizine dihydrochloride (LCD) and ambroxol hydrochloride (ABH) in bulk powder and in pharmaceutical formulations. The first method is a first derivative spectrophotometric method (1D) using a zero-crossing technique of measurement at 210.4 nm for LCD and at 220.0 nm for ABH. The second method employs a second derivative spectrophotometry (2D) where the measurements were carried out at 242.0 and 224.4 nm for LCD and ABH, respectively. In the third method, the first derivative of the ratio spectra was calculated and the first derivative of the ratio amplitudes at 222.8 and 247.2 nm was selected for the determination of LCD and ABH, respectively. Calibration graphs were established in the ranges of 1.0-20.0 μg mL- 1 for LCD and 4.0-20.0 μg mL- 1 for ABH using derivative and ratio first derivative spectrophotometric methods with good correlation coefficients. The developed methods have been successfully applied to the simultaneous determination of both drugs in commercial tablet dosage form.

Flow in a discrete slotted nozzle with massive injection. [water table tests

NASA Technical Reports Server (NTRS)

Perkins, H. C.

1974-01-01

An experimental investigation has been conducted to determine the effect of massive wall injection on the flow characteristics in a slotted nozzle. Some of the experiments were performed on a water table with a slotted-nozzle test section. This has 45 deg and 15 deg half angles of convergence and divergence, respectively, throat radius of 2.5 inches, and throat width of 3 inches. The hydraulic analogy was employed to qualitatively extend the results to a compressible gas flow through the nozzle. Experimental results from the water table include contours of constant Froude and Mach number with and without injection. Photographic results are also presented for the injection through slots of CO2 and Freon-12 into a main-stream air flow in a convergent-divergent nozzle in a wind tunnel. Schlieren photographs were used to visualize the flow, and qualititative agreement between the results from the gas tunnel and water table is good.

Indirect spectrophotometric determination of cyanide by means of the colour reaction of silver with cadion 2B in presence of triton X-100.

PubMed

Yu-Rui, Z; Fu-Sheng, W; Fang, Y

1983-10-01

Silver gives a colour reaction with cadion 2B in the presence of the non-ionic surfactant Triton X-100, and the suppression of the colour by competitive complexation of the silver can be used for the spectrophotometric determination of cyanide. Cyanide in waste water can be separated by distillation from other ions that also interfere, and then determined.

SPECTROPHOTOMETRIC DETERMINATION OF TRACES OF BORON IN THORIUM

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

Onishi, H.; Ishiwatari, N.; Nagai, H.

1960-12-01

A procedure is described for the spectrophotometric determination of a few tenths of a pant per million of boron ia thorium oxide or thorium. The sample is dissolved in strong phosphoric acid. After diluting the solution with water, boron is separated by distillation as methyl borate and finally determined by the curcumin method. The error is not likely to exceed plus or minus O.l ppm for 0.2 to 1 ppm of boron. (auth)

A comparative study of smart spectrophotometric methods for simultaneous determination of a skeletal muscle relaxant and an analgesic in combined dosage form

NASA Astrophysics Data System (ADS)

Salem, Hesham; Mohamed, Dalia

2015-04-01

Six simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the analgesic drug; paracetamol (PARA) and the skeletal muscle relaxant; dantrolene sodium (DANT). Three methods are manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and mean centering (MC). The other three methods are utilizing the isoabsorptive point either at zero order namely; absorbance ratio (AR) and absorbance subtraction (AS) or at ratio spectrum namely; amplitude modulation (AM). The proposed spectrophotometric procedures do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the drugs and their combined dosage form. Standard deviation values are less than 1.5 in the assay of raw materials and capsules. The obtained results were statistically compared with each other and with those of reported spectrophotometric ones. The comparison showed that there is no significant difference between the proposed methods and the reported methods regarding both accuracy and precision.

Determination of lead and cadmium in soils, sludges, and fertilizers by an ion-exchange/spectrophotometric method

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

Heinzig, M.; DeYong, G.D.; Anglin, R.J.

1993-12-01

The MetalTrace method, which consists of an anion-exchange separation coupled with a spectrophotometric quantification, was used to determine lead and cadmium in sulfuric acid-hydrogen peroxide digests of soils and sludges and hydrobromic acid extracts of soils. Cadmium only was determined in sulfuric acid-hydrogen peroxide digests of fertilizers because no standards were available with certified lead contents. The selectivity provided by the anion-exchange separation allowed the use of a spectrophotometric indicator with an extremely high extinction coefficient so that detection limits in the low parts per million range could be attained. The results obtained using this method compared favorably with thosemore » obtained using much more expensive methods requiring more specialized training and equipment.« less

Gene delivery by direct injection (microinjection) using a controlled-flow system.

PubMed

Dean, David A

2006-12-01

INTRODUCTIONThis protocol describes a method for constant-flow microinjection using the Pneumatic PicoPump (World Precision Instruments). This type of system is very simple and can be assembled on a relatively low budget. In this method, a constant flow of sample is delivered from the tip of the pipette, and the amount of sample injected into the cell is determined by how long the pipette remains in the cell. A typical system is composed of a pressure regulator that can be adjusted for two pressures (back pressure and injection pressure), a capillary holder, and a coarse and fine micromanipulator.

Calculation method of water injection forward modeling and inversion process in oilfield water injection network

NASA Astrophysics Data System (ADS)

Liu, Long; Liu, Wei

2018-04-01

A forward modeling and inversion algorithm is adopted in order to determine the water injection plan in the oilfield water injection network. The main idea of the algorithm is shown as follows: firstly, the oilfield water injection network is inversely calculated. The pumping station demand flow is calculated. Then, forward modeling calculation is carried out for judging whether all water injection wells meet the requirements of injection allocation or not. If all water injection wells meet the requirements of injection allocation, calculation is stopped, otherwise the demand injection allocation flow rate of certain step size is reduced aiming at water injection wells which do not meet requirements, and next iterative operation is started. It is not necessary to list the algorithm into water injection network system algorithm, which can be realized easily. Iterative method is used, which is suitable for computer programming. Experimental result shows that the algorithm is fast and accurate.

Simultaneous determination of choline and acetylcholine based on a trienzyme chemiluminometric biosensor in a single line flow injection system.

PubMed

Kiba, Nobutoshi; Ito, Seiji; Tachibana, Masaki; Tani, Kazue; Koizumi, Hitoshi

2003-12-01

A detector for the simultaneous determination of choline (Ch) and acetylcholine (ACh) based on a sensitive trienzyme chemiluminometric biosensor in a single line flow injection (FI) system is described. Immobilized choline oxidase (ChOx), immobilized peroxidase (POx), immobilized acetylcholinesterase, and coimmobilized ChOx/POx were packed, in turn, in a transparent ETFE tube (1 mm i.d., 75 cm) and the tube was placed in front of a photomultipier tube as a flow cell. Two-peak response was obtained by one injection of the sample solution. The first and second peaks were dependent on the concentrations of Ch and ACh, respectively. The influence of some experimental parameters such as flow rate, amounts of immobilized enzymes on the behavior of the sensor was studied in order to optimize the sensitivity, sample throughput and resolution. Calibration curves were linear at 1 - 1000 nM for Ch and 3 - 3000 nM for ACh. The sample throughput was 25/h without carryover. The FI system was applied to the simultaneous determination of Ch and ACh in rabbit brain tissue homogenates.

Spectrophotometric and Reversed-Phase High-Performance Liquid Chromatographic Method for the Determination of Doxophylline in Pharmaceutical Formulations

PubMed Central

Joshi, HR; Patel, AH; Captain, AD

2010-01-01

Two methods are described for determination of Doxophylline in a solid dosage form. The first method was based on ultraviolet (UV)-spectrophotometric determination of the drug. It involves absorbance measurement at 274 nm (λmax of Doxophylline) in 0.1 N hydrochloric acid. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.20–30 mg/ml for the drug. The second method was based on high-performance liquid chromatography (HPLC) separation of the drug in reverse-phase mode using the Hypersil ODS C18 column (250 × 4.6 mm, 5 mm). The mobile phase constituted of buffer acetonitrile (80:20) and pH adjusted to 3.0, with dilute orthophosphoric acid delivered at a flow rate 1.0 ml/min. Detection was performed at 210 nm. Separation was completed within 7 min. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.165–30 mg/ml for the drug. The relative standard deviation was found to be <2.0% for the UV-spectrophotometry and HPLC methods. Both these methods have been successively applied to the solid dosage pharmaceutical formulation, and were fully validated according to ICH guidelines. PMID:21042488

Gas-assisted dispersive liquid-phase microextraction using ionic liquid as extracting solvent for spectrophotometric speciation of copper.

PubMed

Akhond, Morteza; Absalan, Ghodratollah; Pourshamsi, Tayebe; Ramezani, Amir M

2016-07-01

Gas-assisted dispersive liquid-phase microextraction (GA-DLPME) has been developed for preconcentration and spectrophotometric determination of copper ion in different water samples. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate and argon gas, respectively, were used as the extracting solvent and disperser. The procedure was based on direct reduction of Cu(II) to Cu(I) by hydroxylamine hydrochloride, followed by extracting Cu(I) into ionic liquid phase by using neocuproine as the chelating agent. Several experimental variables that affected the GA-DLPME efficiency were investigated and optimized. Under the optimum experimental conditions (IL volume, 50µL; pH, 6.0; acetate buffer, 1.5molL(-1); reducing agent concentration, 0.2molL(-1); NC concentration, 120µgmL(-1); Ar gas bubbling time, 6min; argon flow rate, 1Lmin(-1); NaCl concentration, 6% w/w; and centrifugation time, 3min), the calibration graph was linear over the concentration range of 0.30-2.00µgmL(-1) copper ion with a limit of detection of 0.07µgmL(-1). Relative standard deviation for five replicate determinations of 1.0µgmL(-1) copper ion was found to be 3.9%. The developed method was successfully applied to determination of both Cu(I) and Cu(II) species in water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectrophotometric Methods for Simultaneous Determination of Oxytetracycline HCl and Flunixin Meglumine in Their Veterinary Pharmaceutical Formulation.

PubMed

Merey, Hanan A; Abd-Elmonem, Mahmmoud S; Nazlawy, Hagar N; Zaazaa, Hala E

2017-01-01

Four precise, accurate, selective, and sensitive UV-spectrophotometric methods were developed and validated for the simultaneous determination of a binary mixture of Oxytetracycline HCl (OXY) and Flunixin Meglumine (FLU). The first method, dual wavelength (DW), depends on measuring the difference in absorbance (ΔA 273.4-327 nm) for the determination of OXY where FLU is zero while FLU is determined at ΔA 251.7-275.7 nm. The second method, first-derivative spectrophotometric method (1D), depends on measuring the peak amplitude of the first derivative selectively at 377 and 266.7 nm for the determination of OXY and FLU, respectively. The third method, ratio difference method, depends on the difference in amplitudes of the ratio spectra at ΔP 286.5-324.8 nm and ΔP 249.6-286.3 nm for the determination of OXY and FLU, respectively. The fourth method, first derivative of ratio spectra method (1DD), depends on measuring the amplitude peak to peak of the first derivative of ratio spectra at 296.7 to 369 nm and 259.1 to 304.7 nm for the determination of OXY and FLU, respectively. Different factors affecting the applied spectrophotometric methods were studied. The proposed methods were validated according to ICH guidelines. Satisfactory results were obtained for determination of both drugs in laboratory prepared mixture and pharmaceutical dosage form. The developed methods are compared favourably with the official ones.

Determination of moclobemide in human plasma by high-performance liquid chromatography with spectrophotometric detection.

PubMed

Amini, Hossein; Shahmir, Badri; Ahmadiani, Abolhassan

2004-08-05

A simple and sensitive high-performance liquid chromatographic (HPLC) method with spectrophotometric detection was developed for the determination of moclobemide in human plasma. Plasma samples were extracted under basic conditions with dichloromethane followed by back-extraction into diluted phosphoric acid. Isocratic separation was employed on an ODS column (250 mm x 4.6 mm, 5 microm) at room temperature. The mobile phase consisted of 5 mM NaH2PO4-acetonitrile-triethylamine (1000:350:10 (v/v/v), pH 3.4). Analyses were run at a flow-rate of 1.0 ml/min and ultraviolet (UV) detection was carried out at 240 nm. The method was specific and sensitive with a quantification limit of 15.6 ng/ml and a detection limit of 5 ng/ml at a signal-to-noise ratio of 3:1. The mean absolute recovery was about 98.2%, while the intra- and inter-day coefficient of variation and percent error values of the assay method were all at acceptable levels. Linearity was assessed in the range of 15.6-2000 ng/ml in plasma with a correlation coefficient of greater than 0.999. This method has been used to analyze several hundred human plasma samples for bioavailibility studies.

Complexation equilibria and spectrophotometric determination of iron(III) with 1-amino-4-hydroxyanthraquinone.

PubMed

Abu-Bakr, M S; Sedaira, H; Hashem, E Y

1994-10-01

The complex equilibria of iron(III) with 1-amino-4-hydroxyanthraquinone (AMHA) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaClO(4)). The complexation reactions were demonstrated and characterized using graphical logarithmic analysis of the absorbance-pH graphs. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of Fe(III) is developed based on the formation of Fe(AMHA) complex at pH 2.5 (lambda(max) = 640 nm, epsilon approximately = 2.1 x 10(4) L. mol(-1) . cm(-1)) in the presence of a large number of foreign ions. Interferences caused by palladium(II) was masked by the addition of cyanide ions. The method has been applied to the determination of iron in some synthetic samples and polymetallic iron ores.

Comparison of Series of Vugs and Non-vuggy Synthetic Porous Media on Formation Damage

NASA Astrophysics Data System (ADS)

Khan, H.; DiCarlo, D. A.; Prodanovic, M.

2017-12-01

Produced water reinjection (PWRI) is an established cost-effective oil field practice where produced water is injected without any cleanup, for water flooding or disposal. Resultantly the cost of fresh injection fluid and/or processing produced water is saved. A common problem with injection of unprocessed water is formation damage in the near injection zone due to solids (fines) entrapment, causing a reduction in permeability and porosity of the reservoir. Most studies have used homogeneous porous media with unimodal grain sizes, while real world porous media often has a wide range of pores, up to and including vugs in carbonaceous rocks. Here we fabricate a series of vugs in synthetic porous media by sintering glass beads with large dissolvable inclusions. The process is found to be repeatable, allowing a similar vug configuration to be tested for different flow conditions. Bi-modal glass bead particles (25 & 100 micron) are injected at two different flow rates and three different injection concentrations. Porosity, permeability and effluent concentration are determined using CT scanning, pressure measurements and particle counting (Coulter counter), respectively. Image analysis is performed on the CT images to determine the change in vug size for each flow condition. We find that for the same flow conditions, heterogeneous media with series of vugs have an equal or greater permeability loss compared to homogeneous porous media. A significant change in permeability is observed at the highest concentration and flow rate as more particles approach the filter quickly, resulting in a greater loss in permeability in the lower end of the core. Image analysis shows the highest loss in vug size occurs at the low flow rate and highest concentration. The lower vug is completely blocked for this flow case. For all flow cases lower values of porosity are observed after the core floods. At low flow rate and medium concentration, a drastic loss in porosity is observed in the lower part of the core, after the vuggy zone. This trough is also distinctly clear in the homogeneous core for the same flow conditions. This study focuses on understanding the effect of pore heterogeneity on formation damage. We conclude that more damage is done deeper in vuggy formations at high flow rates, resulting in shorter injection cycle prior to clean up.

A study of the methods for the production and confinement of high energy plasmas. [injection of dense plasma into long magnetic field

NASA Technical Reports Server (NTRS)

Cheng, D. Y.; Wang, P.

1972-01-01

The injection of dense plasmas into a B sub z long magnetic field from both ends of the field coil was investigated. Deflagration plasma guns and continuous flow Z-pinch are discussed along with the possibility of a continuous flow Z-pinch fusion reactor. The injection experiments are described with emphasis on the synchronization of the two plasma deflagration guns, the collision of the two plasma beams, and the determination of plasma density.

Flow injection analysis simulations and diffusion coefficient determination by stochastic and deterministic optimization methods.

PubMed

Kucza, Witold

2013-07-25

Stochastic and deterministic simulations of dispersion in cylindrical channels on the Poiseuille flow have been presented. The random walk (stochastic) and the uniform dispersion (deterministic) models have been used for computations of flow injection analysis responses. These methods coupled with the genetic algorithm and the Levenberg-Marquardt optimization methods, respectively, have been applied for determination of diffusion coefficients. The diffusion coefficients of fluorescein sodium, potassium hexacyanoferrate and potassium dichromate have been determined by means of the presented methods and FIA responses that are available in literature. The best-fit results agree with each other and with experimental data thus validating both presented approaches. Copyright © 2013 The Author. Published by Elsevier B.V. All rights reserved.

Determination of the Flow Field in the Propellant Tank of a Rocket Engine on Completion of the Mission

NASA Astrophysics Data System (ADS)

Fedorov, A. V.; Bedarev, I. A.; Lavruk, S. A.; Trushlyakov, V. I.; Kudentsov, V. Yu.

2018-03-01

In the present work, a method of mathematical simulation is employed to describe processes occurring in the specimens of new equipment and using the remaining propellant in rocket-engine tanks. Within the framework of certain turbulence models, the authors perform a calculation of the flow field in the volume of the tank of the launch-vehicle stage when a hot gas jet is injected into it. A vortex flow structure is revealed; the characteristics of heat transfer for different angles of injection of the jet are determined. The obtained correlation Nu = Nu(Re) satisfactorily describes experimental data.

Determination of the Flow Field in the Propellant Tank of a Rocket Engine on Completion of the Mission

NASA Astrophysics Data System (ADS)

Fedorov, A. V.; Bedarev, I. A.; Lavruk, S. A.; Trushlyakov, V. I.; Kudentsov, V. Yu.

2018-05-01

In the present work, a method of mathematical simulation is employed to describe processes occurring in the specimens of new equipment and using the remaining propellant in rocket-engine tanks. Within the framework of certain turbulence models, the authors perform a calculation of the flow field in the volume of the tank of the launch-vehicle stage when a hot gas jet is injected into it. A vortex flow structure is revealed; the characteristics of heat transfer for different angles of injection of the jet are determined. The obtained correlation Nu = Nu(Re) satisfactorily describes experimental data.

Spectrophotometric determination of molybdenum in rocks with thiocyanate

USGS Publications Warehouse

Lillie, E.G.; Greenland, L.P.

1974-01-01

A rapid procedure for the determination of microgram amounts of molybdenum in rocks is described. After acid decomposition, molybdenum is extracted from a hydrochloric acid solution into xylene with tributyl phosphate. After back-extraction with water, molybdenum is extracted as the ??-benzoinoximate into chloroform, stripped into hydrochloric acid extracted as the thiocyanate into amyl alcohol, and determined spectrophotometrically. The molybdenum thiocyanate color produced is stable, sensitive, and reproducible. Results of analyses of several of the U.S. Geological Survey standard rocks are given. ?? 1974.

Flow visualization study of the effect of injection hole geometry on an inclined jet in crossflow

NASA Technical Reports Server (NTRS)

Simon, F. F.; Ciancone, M. L.

1985-01-01

A flow visualization was studied by using neutrally buoyant, helium-filled soap bubbles, to determine the effect of injection hole geometry on the trajectory of an air jet in a crossflow and to investigate the mechanisms involved in jet deflection. Experimental variables were the blowing rate, and the injection hole geometry cusp facing upstream (CUS), cusp facing downstream (CDS), round, swirl passage, and oblong. It is indicated that jet deflection is governed by both the pressure drag forces and the entrainment of free-stream fluid into the jet flow. For injection hole geometries with similar cross-sectional areas and similar mass flow rates, the jet configuration with the larger aspect ratio experienced a greater deflection. Entrainment arises from lateral shearing forces on the sides of the jet, which set up a dual vortex motion within the jet and thereby cause some of the main-stream fluid momentum to be swept into the jet flow. This additional momentum forces the jet nearer the surface. Of the jet configurations, the oblong, CDS, and CUS configutations exhibited the largest deflections. The results correlate well with film cooling effectiveness data, which suggests a need to determine the jet exit configuration of optimum aspect ratio to provide maximum film cooling effectiveness.

Flow visualization study of the effect of injection hole geometry on an inclined jet in crossflow

NASA Technical Reports Server (NTRS)

Simon, Frederick F.; Ciancone, Michael L.

1987-01-01

A flow visualization was studied by using neutrally buoyant, helium-filled soap bubbles, to determine the effect of injection hole geometry on the trajectory of an air jet in a crossflow and to investigate the mechanisms involved in jet deflection. Experimental variables were the blowing rate, and the injection hole geometry cusp facing upstream (CUS), cusp facing downstream (CDS), round, swirl passage, and oblong. It is indicated that jet deflection is governed by both the pressure drag forces and the entrainment of free-stream fluid into the jet flow. For injection hole geometries with similar cross-sectional areas and similar mass flow rates, the jet configuration with the larger aspect ratio experienced a greater deflection. Entrainment arises from lateral shearing forces on the sides of the jet, which set up a dual vortex motion within the jet and thereby cause some of the main-stream fluid momentum to be swept into the jet flow. This additional momentum forces the jet nearer the surface. Of the jet configurations, the oblong, CDS, and CUS configurations exhibited the largest deflections. The results correlate well with film cooling effectiveness data, which suggests a need to determine the jet exit configuration of optimum aspect ratio to provide maximum film cooling effectiveness.

[Spectrophotometric determination of prodigiozan in ampule solutions].

PubMed

Shchedrina, L E; Brutko, L I; Rastunova, G A; Shcherbakova, E G

1984-06-01

Based on a study of the absorption properties of prodigiosan it has been shown that its UV absorption spectrum is characterized by an arm at 250-260 nm with an inflection point at 260 nm. The concentration ranges within which the optical density of prodigiosan solution obeyed the Bouguer-Lambert-Beer law were measured. This allowed the development of a quantitative spectrophotometric method for determination of prodigiosan in ampouled solutions.

Spectrophotometric Determination of Iron(III)-Glycine Formation Constant in Aqueous Medium Using Competitive Ligand Binding

ERIC Educational Resources Information Center

Prasad, Rajendra; Prasad, Surendra

2009-01-01

The formation constant of iron(III) complex with glycine (Gly) ligand in aqueous acidic medium (0.2 M HNO[subscript 3], I = 0.2 M at 28 plus or minus 1 degree C) was determined spectrophotometrically in which a competing color reaction between Fe(III) and SCN[superscript -] was used as an indicator reaction. Under the specified conditions Fe(III)…

Microscale determination of the spectral characteristics and carbon-isotopic compositions of porphyrins

NASA Technical Reports Server (NTRS)

Popp, B. N.; Hayes, J. M.; Boreham, C. J.

1993-01-01

Molar extinction coefficients for band III of Ni porphyrins are calculated from results of spectrophotometric and manometric analyses of individual etioporphyrins, DPEP, cyclic, and diDPEP porphyrins known to initially be pure from mass spectrometry, 1H NMR, and analytical HPLC studies. A method for determining carbon-isotopic compositions and purity of micromolar quantities of individual porphyrins using combined spectrophotometric and manometric techniques is presented.

Flow-batch analysis of clenbuterol based on analyte extraction on molecularly imprinted polymers coupled to an in-system chromogenic reaction. Application to human urine and milk substitute samples.

PubMed

González, Natalia; Grünhut, Marcos; Šrámková, Ivana; Lista, Adriana G; Horstkotte, Burkhard; Solich, Petr; Sklenářová, Hana; Acebal, Carolina C

2018-02-01

A fully automated spectrophotometric method based on flow-batch analysis has been developed for the determination of clenbuterol including an on-line solid phase extraction using a molecularly imprinted polymer (MIP) as the sorbent. The molecularly imprinted solid phase extraction (MISPE) procedure allowed analyte extraction from complex matrices at low concentration levels and with high selectivity towards the analyte. The MISPE procedure was performed using a commercial MIP cartridge that was introduced into a guard column holder and integrated in the analyzer system. Optimized parameters included the volume of the sample, the type and volume of the conditioning and washing solutions, and the type and volume of the eluent. Quantification of clenbuterol was carried out by spectrophotometry after in-system post-elution analyte derivatization based on azo-coupling using N- (1-Naphthyl) ethylenediamine as the coupling agent to yield a red-colored compound with maximum absorbance at 500nm. Both the chromogenic reaction and spectrophotometric detection were performed in a lab-made flow-batch mixing chamber that replaced the cuvette holder of the spectrophotometer. The calibration curve was linear in the 0.075-0.500mgL -1 range with a correlation coefficient of 0.998. The precision of the proposed method was evaluated in terms of the relative standard deviation obtaining 1.1% and 3.0% for intra-day precision and inter-day precision, respectively. The detection limit was 0.021mgL -1 and the sample throughput for the entire process was 3.4h -1 . The proposed method was applied for the determination of CLB in human urine and milk substitute samples obtaining recoveries values within a range of 94.0-100.0%. Copyright © 2017 Elsevier B.V. All rights reserved.

Spectrophotometric determination of ternary mixtures of thiamin, riboflavin and pyridoxal in pharmaceutical and human plasma by least-squares support vector machines.

PubMed

Niazi, Ali; Zolgharnein, Javad; Afiuni-Zadeh, Somaie

2007-11-01

Ternary mixtures of thiamin, riboflavin and pyridoxal have been simultaneously determined in synthetic and real samples by applications of spectrophotometric and least-squares support vector machines. The calibration graphs were linear in the ranges of 1.0 - 20.0, 1.0 - 10.0 and 1.0 - 20.0 microg ml(-1) with detection limits of 0.6, 0.5 and 0.7 microg ml(-1) for thiamin, riboflavin and pyridoxal, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graph concentrations of vitamins. The simultaneous determination of these vitamin mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. The partial least squares (PLS) modeling and least-squares support vector machines were used for the multivariate calibration of the spectrophotometric data. An excellent model was built using LS-SVM, with low prediction errors and superior performance in relation to PLS. The root mean square errors of prediction (RMSEP) for thiamin, riboflavin and pyridoxal with PLS and LS-SVM were 0.6926, 0.3755, 0.4322 and 0.0421, 0.0318, 0.0457, respectively. The proposed method was satisfactorily applied to the rapid simultaneous determination of thiamin, riboflavin and pyridoxal in commercial pharmaceutical preparations and human plasma samples.

Validated derivative and ratio derivative spectrophotometric methods for the simultaneous determination of levocetirizine dihydrochloride and ambroxol hydrochloride in pharmaceutical dosage form.

PubMed

Ali, Omnia I M; Ismail, Nahla S; Elgohary, Rasha M

2016-01-15

Three simple, precise, accurate and validated derivative spectrophotometric methods have been developed for the simultaneous determination of levocetirizine dihydrochloride (LCD) and ambroxol hydrochloride (ABH) in bulk powder and in pharmaceutical formulations. The first method is a first derivative spectrophotometric method ((1)D) using a zero-crossing technique of measurement at 210.4 nm for LCD and at 220.0 nm for ABH. The second method employs a second derivative spectrophotometry ((2)D) where the measurements were carried out at 242.0 and 224.4 nm for LCD and ABH, respectively. In the third method, the first derivative of the ratio spectra was calculated and the first derivative of the ratio amplitudes at 222.8 and 247.2 nm was selected for the determination of LCD and ABH, respectively. Calibration graphs were established in the ranges of 1.0-20.0 μg mL(-1) for LCD and 4.0-20.0 μg mL(-1) for ABH using derivative and ratio first derivative spectrophotometric methods with good correlation coefficients. The developed methods have been successfully applied to the simultaneous determination of both drugs in commercial tablet dosage form. Copyright © 2015 Elsevier B.V. All rights reserved.

Programmable flow system for automation of oxygen radical absorbance capacity assay using pyrogallol red for estimation of antioxidant reactivity.

PubMed

Ramos, Inês I; Gregório, Bruno J R; Barreiros, Luísa; Magalhães, Luís M; Tóth, Ildikó V; Reis, Salette; Lima, José L F C; Segundo, Marcela A

2016-04-01

An automated oxygen radical absorbance capacity (ORAC) method based on programmable flow injection analysis was developed for the assessment of antioxidant reactivity. The method relies on real time spectrophotometric monitoring (540 nm) of pyrogallol red (PGR) bleaching mediated by peroxyl radicals in the presence of antioxidant compounds within the first minute of reaction, providing information about their initial reactivity against this type of radicals. The ORAC-PGR assay under programmable flow format affords a strict control of reaction conditions namely reagent mixing, temperature and reaction timing, which are critical parameters for in situ generation of peroxyl radical from 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). The influence of reagent concentrations and programmable flow conditions on reaction development was studied, with application of 37.5 µM of PGR and 125 mM of AAPH in the flow cell, guaranteeing first order kinetics towards peroxyl radicals and pseudo-zero order towards PGR. Peroxyl-scavenging reactivity of antioxidants, bioactive compounds and phenolic-rich beverages was estimated employing the proposed methodology. Recovery assays using synthetic saliva provided values of 90 ± 5% for reduced glutathione. Detection limit calculated using the standard antioxidant compound Trolox was 8 μM. RSD values were <3.4 and <4.9%, for intra and inter-assay precision, respectively. Compared to previous batch automated ORAC assays, the developed system also accounted for high sampling frequency (29 h(-1)), low operating costs and low generation of waste. Copyright © 2015 Elsevier B.V. All rights reserved.

Flow injection analysis-flame atomic absorption spectrometry system for indirect determination of sulfite after on-line reduction of solid-phase manganese (IV) dioxide reactor.

PubMed

Zare-Dorabei, Rouholah; Boroun, Shokoufeh; Noroozifar, Meissam

2018-02-01

A new and simple flow injection method followed by atomic absorption spectrometry was developed for indirect determination of sulfite. The proposed method is based on the oxidation of sulfite to sulphate ion using solid-phase manganese dioxide (30% W/W suspended on silica gel beads) reactor. MnO 2 will be reduced to Mn(II) by sample injection in to the column under acidic carrier stream of HNO 3 (pH 2) with flow rate of 3.5mLmin -1 at room temperature. Absorption measurement of Mn(II) which is proportional to the concentration of sulfite in the sample was carried out by atomic absorption spectrometry. The calibration curve was linear up to 25mgL -1 with a detection limit (DL) of 0.08mgL -1 for 400µL injection sample volume. The presented method is efficient toward sulfite determination in sugar and water samples with a relative standard deviation (RSD) less than 1.2% and a sampling rate of about 60h -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

Determination of solid mass fraction in partially frozen hydrocarbon fuels

NASA Technical Reports Server (NTRS)

Cotterell, E. M.; Mossadegh, R.; Bruce, A. J.; Moynihan, C. T.

1986-01-01

Filtration procedures alone are insufficient to determine the amounts of crystalline solid in a partially frozen hydrocarbon distillate fraction. This is due to the nature of the solidification process by which a large amount of liquid becomes entrapped within an interconnected crystalline structure. A technique has been developed to supplement filtration methods with an independent determination of the amount of liquid in the precipitate thereby revealing the actual value of mass percent crystalline solid, %S. A non-crystallizing dye is injected into the fuel and used as a tracer during the filtration. The relative concentrations of the dye in the filtrate and precipitate fractions is subsequently detected by a spectrophotometric comparison. The filtration apparatus was assembled so that the temperature of the sample is recorded immediately above the filter. Also, a second method of calculation has been established which allows significant reduction in test time while retaining acceptable accuracy of results. Data have been obtained for eight different kerosene range hydrocarbon fuels.

Bivariate versus multivariate smart spectrophotometric calibration methods for the simultaneous determination of a quaternary mixture of mosapride, pantoprazole and their degradation products.

PubMed

Hegazy, M A; Yehia, A M; Moustafa, A A

2013-05-01

The ability of bivariate and multivariate spectrophotometric methods was demonstrated in the resolution of a quaternary mixture of mosapride, pantoprazole and their degradation products. The bivariate calibrations include bivariate spectrophotometric method (BSM) and H-point standard addition method (HPSAM), which were able to determine the two drugs, simultaneously, but not in the presence of their degradation products, the results showed that simultaneous determinations could be performed in the concentration ranges of 5.0-50.0 microg/ml for mosapride and 10.0-40.0 microg/ml for pantoprazole by bivariate spectrophotometric method and in the concentration ranges of 5.0-45.0 microg/ml for both drugs by H-point standard addition method. Moreover, the applied multivariate calibration methods were able for the determination of mosapride, pantoprazole and their degradation products using concentration residuals augmented classical least squares (CRACLS) and partial least squares (PLS). The proposed multivariate methods were applied to 17 synthetic samples in the concentration ranges of 3.0-12.0 microg/ml mosapride, 8.0-32.0 microg/ml pantoprazole, 1.5-6.0 microg/ml mosapride degradation products and 2.0-8.0 microg/ml pantoprazole degradation products. The proposed bivariate and multivariate calibration methods were successfully applied to the determination of mosapride and pantoprazole in their pharmaceutical preparations.

Synthesis and Characterization of Potassium Tris(oxalato)ferrate(III) Trihydrate: A Spectrophotometric Method of Iron Analysis

NASA Astrophysics Data System (ADS)

Dallinger, Richard F.

1995-10-01

A previous Journal article [J. Chem. Educ. 1984, 61, 1098--1099] described a potassium tris(oxalato)ferrate(III) trihydrate empirical formula experiment that offered an excellent integrative experience in synthesis and characterization for general chemistry laboratory students. However, we have introduced a fast and accurate spectrophotometric method for the determination of iron in the product that takes the place of the photochemical-gravimetric procedure described in the article. Besides the pedagogic interest of bringing three different types of chemical analysis (titrimetric, gravimetric, and spectrophotometric) to bear on one compound, the new iron determination allows students to complete the experiment in 2, 3-hr laboratory periods rather than the 5 periods allotted in the original experiment.

Experiment T001: Entry communication on the Gemini 3 mission

NASA Technical Reports Server (NTRS)

Schroeder, L. C.; Sims, T. E.; Cuddihy, W. F.

1971-01-01

Water addition to the Gemini 3 exhaust plasma was studied to determine its effectiveness in the establishment of communication links during the entry portion of the flight. Attenuation levels were measured with and without water injection at uhf frequencies of 230.4 and 296.8 megahertz and at the C-band frequency of 5690 megahertz. Ultrahigh frequency signals that had been blacked out were restored to significant levels, during early portions of the water-injection sequence, by the high flow rate injection. The C-band signal was enhanced by medium and high flow rate injections during the latter portion of the injection period. The uhf signal recovered during water injection resulted in an antenna pattern that was beamed in the radial direction of injection from the spacecraft. Postflight analysis showed that the uhf recovery data were consistent with injection-penetration theory.

Development and validation of an analytical method for the separation and determination of major bioactive curcuminoids in Curcuma longa rhizomes and herbal products using non-aqueous capillary electrophoresis.

PubMed

Anubala, S; Sekar, R; Nagaiah, K

2014-06-01

A simple, fast and efficient non-aqueous capillary electrophoresis method (NACE) was developed for the simultaneous determination of three major bioactive curcuminoids (CMNs) in Curcuma longa rhizomes and its herbal products. Good separation, resolution and reproducibility were achieved with the background electrolyte (BGE) consisting a mixture of 15.0 mM sodium tetraborate and 7.4 mM sodium hydroxide (NaOH) in 2:10:15 (v/v/v) of water, 1-propanol, and methanol. The influences of background electrolyte, sodium hydroxide, water, sodium dodecyl sulfate and hydroxylpropyl-β-cyclodextrin on separations were investigated. The separation was carried out in a fused-silica capillary tube with reverse polarity. Hydrodynamic injection of 25mbar for 12s was used for injecting samples and a voltage of 28 kV was applied for separation. The ultrasonication method was used for the extraction of CMNs from the turmeric herbal products and the extract was filtered and directly injected without any further treatments. The limits of detection and quantification were less than 5.0 and 14.6 µg/ml respectively for all CMNs. The percentage recoveries for CMNs were >97.2% (%RSD, <2.62). The results obtained by the method were compared with existing spectrophotometric and HPLC methods. The related compounds in the extract did not interfere in the determination of CMNs. The proposed NACE method is better than existing chromatographic and electrophoretic methods in terms of simple electrophoretic medium, fast analysis and good resolution. Copyright © 2014 Elsevier B.V. All rights reserved.

A comparative study of smart spectrophotometric methods for simultaneous determination of a skeletal muscle relaxant and an analgesic in combined dosage form.

PubMed

Salem, Hesham; Mohamed, Dalia

2015-04-05

Six simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the analgesic drug; paracetamol (PARA) and the skeletal muscle relaxant; dantrolene sodium (DANT). Three methods are manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and mean centering (MC). The other three methods are utilizing the isoabsorptive point either at zero order namely; absorbance ratio (AR) and absorbance subtraction (AS) or at ratio spectrum namely; amplitude modulation (AM). The proposed spectrophotometric procedures do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the drugs and their combined dosage form. Standard deviation values are less than 1.5 in the assay of raw materials and capsules. The obtained results were statistically compared with each other and with those of reported spectrophotometric ones. The comparison showed that there is no significant difference between the proposed methods and the reported methods regarding both accuracy and precision. Copyright © 2015 Elsevier B.V. All rights reserved.

Rapid and Automated Analytical Methods for Redox Species Based on Potentiometric Flow Injection Analysis Using Potential Buffers

PubMed Central

Ohura, Hiroki; Imato, Toshihiko

2011-01-01

Two analytical methods, which prove the utility of a potentiometric flow injection technique for determining various redox species, based on the use of some redox potential buffers, are reviewed. The first is a potentiometric flow injection method in which a redox couple such as Fe(III)-Fe(II), Fe(CN)6 3−-Fe(CN)(CN)6 4−, and bromide-bromine and a redox electrode or a combined platinum-bromide ion selective electrode are used. The analytical principle and advantages of the method are discussed, and several examples of its application are reported. Another example is a highly sensitive potentiometric flow injection method, in which a large transient potential change due to bromine or chlorine as an intermediate, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing bromide or chloride, is utilized. The analytical principle and details of the proposed method are described, and examples of several applications are described. The determination of trace amounts of hydrazine, based on the detection of a transient change in potential caused by the reaction with a Ce(IV)-Ce(III) potential buffer, is also described. PMID:21584280

Determination of mercury by multisyringe flow injection system with cold-vapor atomic absorption spectrometry.

PubMed

Leal, L O; Elsholz, O; Forteza, R; Cerdà, V

2006-07-28

A new software-controlled time-based multisyringe flow injection system for mercury determination by cold-vapor atomic absorption spectrometry is proposed. Precise known volumes of sample, reducing agent (1.1% SnCl2 in 3% HCl) and carrier (3% HCl) are dispensed into a gas-liquid separation cell with a multisyringe burette coupled with one three-way solenoid valve. An argon flow delivers the reduced mercury to the spectrometer. The optimization of the system was carried out testing reaction coils and gas-liquid separators of different design as well as changing parameters, such as sample and reagents volumes, reagent concentrations and carrier gas flow rate, among others. The analytical curves were obtained within the range 50-5000 ng L(-1). The detection limit (3sigma(b)/S) achieved is 5 ng L(-1). The relative standard deviation (R.S.D.) was 1.4%, evaluated from 16 successive injections of 250 ng L(-1) Hg standard solution. The injection and sample throughput per hour were 44 and 11, respectively. This technique was validated by means of solid and water reference materials with good agreement with the certified values and was successfully applied to fish samples.

Thoron-tartaric acid systems for spectrophotometric determination of thorium

USGS Publications Warehouse

Grimaldi, F.S.; Fletcher, M.H.

1956-01-01

Thoron is commonly used for the spectrophotometric determination of thorium. An undesirable feature of its use is its high sensitivity to zirconium. This study describes the use of tartaric acid as a masking reagent for zirconium. Three tartaric acid-thoron systems, developed for the determination of thorium, differ with respect to the concentrations of thoron and tartaric acid. Mesotartaric acid, used in one of the systems, is most effective in masking zirconium. The behavior of rarer elements, usually associated with thorium ores, is determined in two systems, and a dilution method is described for the direct determination of thorium in monazite concentrates.

Modeling GPR data to interpret porosity and DNAPL saturations for calibration of a 3-D multiphase flow simulation

USGS Publications Warehouse

Sneddon, Kristen W.; Powers, Michael H.; Johnson, Raymond H.; Poeter, Eileen P.

2002-01-01

Dense nonaqueous phase liquids (DNAPLs) are a pervasive and persistent category of groundwater contamination. In an effort to better understand their unique subsurface behavior, a controlled and carefully monitored injection of PCE (perchloroethylene), a typical DNAPL, was performed in conjunction with the University of Waterloo at Canadian Forces Base Borden in 1991. Of the various geophysical methods used to monitor the migration of injected PCE, the U.S. Geological Survey collected 500-MHz ground penetrating radar (GPR) data. These data are used in determining calibration parameters for a multiphase flow simulation. GPR data were acquired over time on a fixed two-dimensional surficial grid as the DNAPL was injected into the subsurface. Emphasis is on the method of determining DNAPL saturation values from this time-lapse GPR data set. Interactive full-waveform GPR modeling of regularized field traces resolves relative dielectric permittivity versus depth profiles for pre-injection and later-time data. Modeled values are end members in recursive calculations of the Bruggeman-Hanai-Sen (BHS) mixing formula, yielding interpreted pre-injection porosity and post-injection DNAPL saturation values. The resulting interpreted physical properties of porosity and DNAPL saturation of the Borden test cell, defined on a grid spacing of 50 cm with 1-cm depth resolution, are used as observations for calibration of a 3-D multiphase flow simulation. Calculated values of DNAPL saturation in the subsurface at 14 and 22 hours after the start of injection, from both the GPR and the multiphase flow modeling, are interpolated volumetrically and presented for visual comparison.

On the Distance Measurements toward Young Milky Way Objects. I. Study of IC 2944

NASA Astrophysics Data System (ADS)

Krełowski, J.; Strobel, A.; Godunova, V.; Bondar, A.

2017-12-01

We compare distances to a very young stellar aggregate, IC 2944, using three methods: direct parallaxes of Gaia, spectrophotometric parallax and our method based on intensities of interstellar CaII lines. The discrepancies between spectrophotometric distances and those, based on CaII K and H lines, were already reported. The interstellar CaII H and K lines allow one to determine both distances and radial velocities of the intervening clouds. Thus, these data allow us to check the aggregate membership. It is also possible to check the spectral classification of considered targets which is necessary for spectrophotometric parallaxes. Using three methods, we determined distances to IC 2944 stars. We demonstrate that CaII based distances agree very well with the kinematic ones but are generally much smaller than the spectrophotometric ones. We conclude that the majority of IC 2944 objects is obscured by clouds producing neutral ("gray") extinction which diminishes their brightness exactly like extended distances. This influences spectrophotometric parallaxes while those, based on the CaII lines, do not depend on extinction and this method seems to be the most reliable one inside the thin disk of our Galaxy. The Gaia trigonometric parallaxes lead to distances similar to those obtained using the CaII method if their errors are reasonably small.

Determination of inorganic arsenic and its organic metabolites in urine by flow-injection hydride generation atomic absorption spectrometry.

PubMed

Hanna, C P; Tyson, J F; McIntosh, S

1993-08-01

A method has been developed for the determination of inorganic arsenic [As(III) and As(V)] and its organic metabolites (monomethylarsenic and dimethylarsenic) in urine by flow-injection hydride generation atomic absorption spectrometry. The nontoxic seafood-derived arsenobetaine and arsenocholine species were first separated by a solid-phase extraction procedure. The remaining sample was digested with a mixture of nitric and sulfuric acids and potassium dichromate, followed by attack with hydrogen peroxide. The resulting As(V) was reduced to As(III) with potassium iodide in hydrochloric acid before injection into the flow-injection manifold. The percentage analytical recoveries (mean +/- 95% confidence interval) of various arsenic species added to a urine specimen at 250 micrograms/L were 108 +/- 2, 112 +/- 11, 104 +/- 7, and 95 +/- 5 for As(III), As(V), monomethylarsenic, and dimethylarsenic, respectively. For the determination of arsenic in Standard Reference Material 2670 (toxic metals in human urine), results agreed with the certified value (480 +/- 100 micrograms/L). Analyses of samples for the Centre de Toxicologie du Quebec, containing seafood-derived species, demonstrated the viability of the separation procedure. Detection limits were between 0.1 and 0.2 microgram/L in the solution injected into the manifold, and precision at 10 micrograms/L was between 2% and 3% (CV). These preliminary results show that the method might be applicable to determinations of arsenic in a range of clinical urine specimens.

Spectrophotometric Methods for Simultaneous Determination of Oxytetracycline HCl and Flunixin Meglumine in Their Veterinary Pharmaceutical Formulation

PubMed Central

Abd-Elmonem, Mahmmoud S.; Nazlawy, Hagar N.; Zaazaa, Hala E.

2017-01-01

Four precise, accurate, selective, and sensitive UV-spectrophotometric methods were developed and validated for the simultaneous determination of a binary mixture of Oxytetracycline HCl (OXY) and Flunixin Meglumine (FLU). The first method, dual wavelength (DW), depends on measuring the difference in absorbance (ΔA 273.4–327 nm) for the determination of OXY where FLU is zero while FLU is determined at ΔA 251.7–275.7 nm. The second method, first-derivative spectrophotometric method (1D), depends on measuring the peak amplitude of the first derivative selectively at 377 and 266.7 nm for the determination of OXY and FLU, respectively. The third method, ratio difference method, depends on the difference in amplitudes of the ratio spectra at ΔP 286.5–324.8 nm and ΔP 249.6–286.3 nm for the determination of OXY and FLU, respectively. The fourth method, first derivative of ratio spectra method (1DD), depends on measuring the amplitude peak to peak of the first derivative of ratio spectra at 296.7 to 369 nm and 259.1 to 304.7 nm for the determination of OXY and FLU, respectively. Different factors affecting the applied spectrophotometric methods were studied. The proposed methods were validated according to ICH guidelines. Satisfactory results were obtained for determination of both drugs in laboratory prepared mixture and pharmaceutical dosage form. The developed methods are compared favourably with the official ones. PMID:28811956

A comparative study of smart spectrophotometric methods for simultaneous determination of sitagliptin phosphate and metformin hydrochloride in their binary mixture.

PubMed

Lotfy, Hayam M; Mohamed, Dalia; Mowaka, Shereen

2015-01-01

Simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of the oral antidiabetic drugs; sitagliptin phosphate (STG) and metformin hydrochloride (MET) in combined pharmaceutical formulations. Three methods were manipulating ratio spectra namely; ratio difference (RD), ratio subtraction (RS) and a novel approach of induced amplitude modulation (IAM) methods. The first two methods were used for determination of STG, while MET was directly determined by measuring its absorbance at λmax 232 nm. However, (IAM) was used for the simultaneous determination of both drugs. Moreover, another three methods were developed based on derivative spectroscopy followed by mathematical manipulation steps namely; amplitude factor (P-factor), amplitude subtraction (AS) and modified amplitude subtraction (MAS). In addition, in this work the novel sample enrichment technique named spectrum addition was adopted. The proposed spectrophotometric methods did not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined. The selectivity of the developed methods was investigated by analyzing laboratory prepared mixtures of the drugs and their combined pharmaceutical formulations. Standard deviation values were less than 1.5 in the assay of raw materials and tablets. The obtained results were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there was no significant difference between the proposed methods and the reported one regarding both accuracy and precision. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of an automated flow injection analysis system for determination of phosphate in nutrient solutions.

PubMed

Karadağ, Sevinç; Görüşük, Emine M; Çetinkaya, Ebru; Deveci, Seda; Dönmez, Koray B; Uncuoğlu, Emre; Doğu, Mustafa

2018-01-25

A fully automated flow injection analysis (FIA) system was developed for determination of phosphate ion in nutrient solutions. This newly developed FIA system is a portable, rapid and sensitive measuring instrument that allows on-line analysis and monitoring of phosphate ion concentration in nutrient solutions. The molybdenum blue method, which is widely used in FIA phosphate analysis, was adapted to the developed FIA system. The method is based on the formation of ammonium Mo(VI) ion by reaction of ammonium molybdate with the phosphate ion present in the medium. The Mo(VI) ion then reacts with ascorbic acid and is reduced to the spectrometrically measurable Mo(V) ion. New software specific for flow analysis was developed in the LabVIEW development environment to control all the components of the FIA system. The important factors affecting the analytical signal were identified as reagent flow rate, injection volume and post-injection flow path length, and they were optimized using Box-Behnken experimental design and response surface methodology. The optimum point for the maximum analytical signal was calculated as 0.50 mL min -1 reagent flow rate, 100 µL sample injection volume and 60 cm post-injection flow path length. The proposed FIA system had a sampling frequency of 100 samples per hour over a linear working range of 3-100 mg L -1 (R 2  = 0.9995). The relative standard deviation (RSD) was 1.09% and the limit of detection (LOD) was 0.34 mg L -1 . Various nutrient solutions from a tomato-growing hydroponic greenhouse were analyzed with the developed FIA system and the results were found to be in good agreement with vanadomolybdate chemical method findings. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Hollow-Fiber Cartridges: Model Systems for Virus Removal from Blood

NASA Astrophysics Data System (ADS)

Jacobitz, Frank; Menon, Jeevan

2005-11-01

Aethlon Medical is developing a hollow-fiber hemodialysis device designed to remove viruses and toxins from blood. Possible target viruses include HIV and pox-viruses. The filter could reduce virus and viral toxin concentration in the patient's blood, delaying illness so the patient's immune system can fight off the virus. In order to optimize the design of such a filter, the fluid mechanics of the device is both modeled analytically and investigated experimentally. The flow configuration of the proposed device is that of Starling flow. Polysulfone hollow-fiber dialysis cartridges were used. The cartridges are charged with water as a model fluid for blood and fluorescent latex beads are used in the experiments as a model for viruses. In the experiments, properties of the flow through the cartridge are determined through pressure and volume flow rate measurements of water. The removal of latex beads, which are captured in the porous walls of the fibers, was measured spectrophotometrically. Experimentally derived coefficients derived from these experiments are used in the analytical model of the flow and removal predictions from the model are compared to those obtained from the experiments.

Standard test method for nitrogen dioxide content of the atmosphere (Griess--Saltzman reaction)

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

Not Available

1977-01-01

A spectrophotometric method for the determination of NO/sub 2/ in the atmosphere is described. The NO/sub 2/ is absorbed in an azo-dye forming reagent, and a red-violet color is measured spectrophotometrically at 550 nm. The NO/sub 2/ is sampled through fritted-tip bubblers, and concentrations of NO/sub 2/ in the atmosphere from 4 to 10,000 ..mu..g/m/sup 3/ can be determined.

Rapid spectrophotometric method for determining surface free energy of microalgal cells.

PubMed

Zhang, Xinru; Jiang, Zeyi; Li, Mengyin; Zhang, Xinxin; Wang, Ge; Chou, Aihui; Chen, Liang; Yan, Hai; Zuo, Yi Y

2014-09-02

Microalgae are one of the most promising renewable energy sources with environmental sustainability. The surface free energy of microalgal cells determines their biofouling and bioflocculation behavior and hence plays an important role in microalgae cultivation and harvesting. To date, the surface energetic properties of microalgal cells are still rarely studied. We developed a novel spectrophotometric method for directly determining the surface free energy of microalgal cells. The principles of this method are based on analyzing colloidal stability of microalgae suspensions. We have shown that this method can effectively differentiate the surface free energy of four microalgal strains, i.e., marine Chlorella sp., marine Nannochloris oculata, freshwater autotrophic Chlorella sp., and freshwater heterotrophic Chlorella sp. With advantages of high-throughput and simplicity, this new spectrophotometric method has the potential to evolve into a standard method for measuring the surface free energy of cells and abiotic particles.

A comparative study of the novel spectrophotometric methods versus conventional ones for the simultaneous determination of Esomeprazole magnesium trihydrate and Naproxen in their binary mixture.

PubMed

Lotfy, Hayam M; Amer, Sawsan M; Zaazaa, Hala E; Mostafa, Noha S

2015-01-01

Two novel simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra are developed and validated for simultaneous determination of Esomeprazole magnesium trihydrate (ESO) and Naproxen (NAP) namely; absorbance subtraction and ratio difference. The results were compared to that of the conventional spectrophotometric methods namely; dual wavelength and isoabsorptive point coupled with first derivative of ratio spectra and derivative ratio. The suggested methods were validated in compliance with the ICH guidelines and were successfully applied for determination of ESO and NAP in their laboratory prepared mixtures and pharmaceutical preparation. No preliminary separation steps are required for the proposed spectrophotometeric procedures. The statistical comparison showed that there is no significant difference between the proposed methods and the reported method with respect to both accuracy and precision. Copyright © 2015 Elsevier B.V. All rights reserved.

Spectrophotometric determination of flucloxacillin in pharmaceutical preparations using some nitrophenols as a complexing agent

NASA Astrophysics Data System (ADS)

El-Mammli, Magda Y.

2003-03-01

Some nitrophenols are proposed as chromogenic reagents for the spectrophotometric determination of flucloxacillin. The reagent forms a greenish yellow 1:1 complex with flucloxacillin at pH 9.0. This complex is stable for at least 3.0 h after its formation. The greenish yellow charge transfer complex species has an absorption maximum at 446, 435, 442, 473 and 439 nm for p-nitrophenol (I), 2,4-dinitrophenol (II), 3,5-dinitrosalycilic acid (III), picramic acid (IV) and picric acid (V), respectively, with a molar absorptivity between 1.43×10 4 and 2.59×10 4 l mol -1 cm -1. Beer's low is valid over the concentration range 2.0-40 μg ml -1 of flucloxacillin. The detection and quantitation limits as well as relative standard deviation were also calculated. The reagents have been successfully used for the spectrophotometric determination of flucloxacillin in pure form and in pharmaceutical preparations.

Measurement of bronchial blood flow in the sheep by video dilution technique.

PubMed Central

Link, D P; Parsons, G H; Lantz, B M; Gunther, R A; Green, J F; Cross, C E

1985-01-01

Bronchial blood flow was determined in five adult anaesthetised sheep by the video dilution technique. This is a new fluoroscopic technique for measuring blood flow that requires only arterial catheterisation. Catheters were placed into the broncho-oesophageal artery and ascending aorta from the femoral arteries for contrast injections and subsequent videotape recording. The technique yields bronchial blood flow as a percentage of cardiac output. The average bronchial artery blood flow was 0.6% (SD 0.20%) of cardiac output. In one sheep histamine (90 micrograms) injected directly into the bronchial artery increased bronchial blood flow by a factor of 6 and histamine (90 micrograms) plus methacholine (4.5 micrograms) augmented flow by a factor of 7.5 while leaving cardiac output unchanged. This study confirms the high degree of reactivity of the bronchial circulation and demonstrates the feasibility of using the video dilution technique to investigate the determinants of total bronchial artery blood flow in a stable animal model avoiding thoracotomy. Images PMID:3883564

Evaluation of spectrophotometric and HPLC methods for shikimic acid determination in plants: models in glyphosate-resistant and -susceptible crops.

PubMed

Zelaya, Ian A; Anderson, Jennifer A H; Owen, Micheal D K; Landes, Reid D

2011-03-23

Endogenous shikimic acid determinations are routinely used to assess the efficacy of glyphosate in plants. Numerous analytical methods exist in the public domain for the detection of shikimic acid, yet the most commonly cited comprise spectrophotometric and high-pressure liquid chromatography (HPLC) methods. This paper compares an HPLC and two spectrophotometric methods (Spec 1 and Spec 2) and assesses the effectiveness in the detection of shikimic acid in the tissues of glyphosate-treated plants. Furthermore, the study evaluates the versatility of two acid-based shikimic acid extraction methods and assesses the longevity of plant extract samples under different storage conditions. Finally, Spec 1 and Spec 2 are further characterized with respect to (1) the capacity to discern between shikimic acid and chemically related alicyclic hydroxy acids, (2) the stability of the chromophore (t1/2), (3) the detection limits, and (4) the cost and simplicity of undertaking the analytical procedure. Overall, spectrophotometric methods were more cost-effective and simpler to execute yet provided a narrower detection limit compared to HPLC. All three methods were specific to shikimic acid and detected the compound in the tissues of glyphosate-susceptible crops, increasing exponentially in concentration within 24 h of glyphosate application and plateauing at approximately 72 h. Spec 1 estimated more shikimic acid in identical plant extract samples compared to Spec 2 and, likewise, HPLC detection was more effective than spectrophotometric determinations. Given the unprecedented global adoption of glyphosate-resistant crops and concomitant use of glyphosate, an effective and accurate assessment of glyphosate efficacy is important. Endogenous shikimic acid determinations are instrumental in corroborating the efficacy of glyphosate and therefore have numerous applications in herbicide research and related areas of science as well as resolving many commercial issues as a consequence of glyphosate utilization.

Portable electrochemical system using screen-printed electrodes for monitoring corrosion inhibitors.

PubMed

Squissato, André L; Silva, Weberson P; Del Claro, Augusto T S; Rocha, Diego P; Dornellas, Rafael M; Richter, Eduardo M; Foster, Christopher W; Banks, Craig E; Munoz, Rodrigo A A

2017-11-01

This work presents a portable electrochemical system for the continuous monitoring of corrosion inhibitors in a wide range of matrices including ethanol, seawater and mineral oil following simple dilution of the samples. Proof-of-concept is demonstrated for the sensing of 2,5-dimercapto-1,3,5-thiadiazole (DMCT), an important corrosion inhibitor. Disposable screen-printed graphitic electrodes (SPGEs) associated with a portable batch-injection cell are proposed for the amperometric determination of DMCT following sample dilution with electrolyte (95% v/v ethanol + 5% v/v 0.1molL -1 H 2 SO 4 solution). This electrolyte was compatible with all samples and the organic-resistant SPGE could be used continuously for more than 200 injections (100µL injected at 193µLs -1 ) free from effects of adsorption of DMCT, which have a great affinity for metallic surfaces, and dissolution of the other reported SPGE inks which has hampered prior research efforts. Fast (180h -1 ) and precise responses (RSD < 3% n = 10) with a detection limit of 0.3µmolL -1 was obtained. The accuracy of the proposed method was attested through recovery tests (93-106%) and the reasonable agreement of results of DMCT concentrations in samples analyzed by both proposed and spectrophotometric (comparative) methods. Copyright © 2017 Elsevier B.V. All rights reserved.

Studies on the injection molding of polyvinyl chloride: Analysis of viscous heating and degradation in simple geometries

NASA Astrophysics Data System (ADS)

Garcia, Jose Luis

2000-10-01

In injection molding processes, computer aided engineering (CAE) allows processors to evaluate different process parameters in order to achieve complete filling of a cavity and, in some cases, it predicts shrinkage and warpage. However, because commercial computational packages are used to design complex geometries, detail in the thickness direction is limited. Approximations in the thickness direction lead to the solution of a 2½-D problem instead of a 3-D problem. These simplifications drastically reduce computational times and memory requirements. However, these approximations hinder the ability to predict thermal and/or mechanical degradation. The goal of this study was to determine the degree of degradation during PVC injection molding and to compare the results with a computational model. Instead of analyzing degradation in complex geometries, the computational analysis and injection molding trials were performed on typical sections found in complex geometries, such as flow in a tube, flow in a rectangular channel, and radial flow. This simplification reduces the flow problem to a 1-D problem and allows one to develop a computational model with a higher level of detail in the thickness direction, essential for the determination of degradation. Two different geometries were examined in this study: a spiral mold, in order to approximate the rectangular channel, and a center gated plate for the radial flow. Injection speed, melt temperature, and shot size were varied. Parts varying in degree of degradation, from no to severe degradation, were produced to determine possible transition points. Furthermore, two different PVC materials were used, low and high viscosity, M3800 and M4200, respectively (The Geon Company, Avon Lake, OH), to correlate the degree of degradation with the viscous heating observed during injection. It was found that a good agreement between experimental and computational results was obtained only if the reaction was assumed to be more thermally sensitive than found in literature. The results from this study show that, during injection, the activation energy for degradation was 65 kcal/mol, compared to 17--30 kcal/mol found in literature for quiescent systems.

A rapid and accurate method for determining protein content in dairy products based on asynchronous-injection alternating merging zone flow-injection spectrophotometry.

PubMed

Liang, Qin-Qin; Li, Yong-Sheng

2013-12-01

An accurate and rapid method and a system to determine protein content using asynchronous-injection alternating merging zone flow-injection spectrophotometry based on reaction between coomassie brilliant blue G250 (CBBG) and protein was established. Main merit of our approach is that it can avoid interferences of other nitric-compounds in samples, such as melamine and urea. Optimized conditions are as follows: Concentrations of CBBG, polyvinyl alcohol (PVA), NaCl and HCl are 150 mg/l, 30 mg/l, 0.1 mol/l and 1.0% (v/v), respectively; volumes of the sample and reagent are 150 μl and 30 μl, respectively; length of a reaction coil is 200 cm; total flow rate is 2.65 ml/min. The linear range of the method is 0.5-15 mg/l (BSA), its detection limit is 0.05 mg/l, relative standard deviation is less than 1.87% (n=11), and analytical speed is 60 samples per hour. Copyright © 2013 Elsevier Ltd. All rights reserved.

Determination of triclosan in antiperspirant gels by first-order derivative spectrophotometry.

PubMed

Du, Lina; Li, Miao; Jin, Yiguang

2011-10-01

A first-order derivative UV spectrophotometric method was developed to determine triclosan, a broad-spectrum antimicrobial agent, in health care products containing fragrances which could interfere the determination as impurities. Different extraction methods were compared. Triclosan was extracted with chloroform and diluted with ethanol followed by the derivative spectrophotometric measurement. The interference of fragrances was completely eliminated. The calibration graph was found to be linear in the range of 7.5-45 microg x mL(-1). The method is simple, rapid, sensitive and proper to determine triclosan in fragrance-containing health care products.

SPECTROPHOTOMETRIC DETERMINATION OF ULTRA-SMALL QUANTITIES OF NICKEL IN INDIUM (in Russian)

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

Peshkova, V.M.; Bochkova, V.M.; Astakhova, E.K.

1961-09-01

alpha -Benzil doxime permits the determination of nickel by measuring optical density in the region of maximum absortption (at 275 m mu ), after the reagent excess is removed by washing the extract with alkali. Conditions were found for the spectrophotometric determination of ultra-small quantities (down to 0.005 gamma ) of nickel with alpha -benzil dioxime in the soultion of its pure salt, in the presence of cobalt and copper. A method was developed for the determination of traces of nickel down to 5 x 10 /sup -7%/ in metallic indium. The reproducibility of method is +25%. (auth)

Validation of a spectrophotometric assay method for bisoprolol using picric acid.

PubMed

Panainte, Alina-Diana; Bibire, Nela; Tântaru, Gladiola; Apostu, M; Vieriu, Mădălina

2013-01-01

Bisoprolol is a drug belonging to beta blockers drugs used primarily for the treatment of cardiovascular diseases. A spectrophotometric method for quantitative determination of bisoprolol was developed based on the formation of a complex combination between bisoprolol and picric acid. The complex combination of bisoprolol and picric acid has a maximum absorbance peak at 420 nm. Optimum working conditions were established and the method was validated. The method presented a good linearity in the concentration range 5-120 microg/ml (regression coefficient r2 = 0.9992). The RSD for the precision of the method was 1.74 and for the intermediate precision 1.43, and recovery values ranged between 98.25-101.48%. The proposed and validated spectrophotometric method for the determination of bisoprolol is simple and cost effective.

Development of an underwater in-situ spectrophotometric sensor for seawater pH

NASA Astrophysics Data System (ADS)

Waterbury, Robert D.; Byrne, Robert H.; Kelly, John; Leader, Bram; McElligott, Sean; Russell, Randy

1996-12-01

A pH sensor based upon spectrophotometric techniques has been developed for in-situ analysis of surface seawater. This sensor utilizes a spectrophotometric pH indicator (Thymol Blue) which has been calibrated for use in seawater as a function of temperature and salinity. Shipboard spectrophotometric pH analyses routinely demonstrate a precision on the order of plus or minus 0.0004 pH units. In- situ analysis of seawater pH has demonstrated a precision on the order of plus or minus 0.001 and an accuracy, using shipboard measurements as a standard, on the order of plus or minus 0.01. The sensor is a self-contained system which pumps seawater, meters in indicator, spectrophotometrically determines indicator absorbance and stores data with a 1 Hz acquisition frequency. The sensor employs two absorbance cells, each with three wavelength channels, to obtain the spectrophotometric absorbance. The sensor system, rated for depths up to 500 m, provides pH, conductivity, temperature and can be operated via computer or in a standalone mode with internal data storage. The sensor utilizes less than 12 watts of power and is packaged in a 29' long by 4.5' diameter aluminum housing.

Spectrophotometric Calibration of pH Electrodes in Seawater Using Purified m-Cresol Purple

PubMed Central

2012-01-01

This work examines the use of purified meta-cresol purple (mCP) for direct spectrophotometric calibration of glass pH electrodes in seawater. The procedures used in this investigation allow for simple, inexpensive electrode calibrations over salinities of 20–40 and temperatures of 278.15–308.15 K without preparation of synthetic Tris seawater buffers. The optimal pH range is ∼7.0–8.1. Spectrophotometric calibrations enable straightforward, quantitative distinctions between Nernstian and non-Nernstian electrode behavior. For the electrodes examined in this study, both types of behavior were observed. Furthermore, calibrations performed in natural seawater allow direct determination of the influence of salinity on electrode performance. The procedures developed in this study account for salinity-induced variations in liquid junction potentials that, if not taken into account, would create pH inconsistencies of 0.028 over a 10-unit change in salinity. Spectrophotometric calibration can also be used to expeditiously determine the intercept potential (i.e., the potential corresponding to pH 0) of an electrode that has reliably demonstrated Nernstian behavior. Titrations to ascertain Nernstian behavior and salinity effects can be undertaken relatively infrequently (∼weekly to monthly). One-point determinations of intercept potential should be undertaken frequently (∼daily) to monitor for stable electrode behavior and ensure accurate potentiometric pH determinations. PMID:22463815

Use of two sulfonthalein dyes in the extraction-free spectrophotometric assay of tramadol in dosage forms and in spiked human urine based on ion-pair reaction.

PubMed

Vinay, Kanakapura B; Revannasiddappa, Hosakere D; Rajendraprasad, Nagaraju; Ramesh, Pavagada J; Xavier, Cijo M; Basavaiah, Kanakapura

2012-02-01

Tramadol is a centrally acting analgesic used in the prevention and treatment of moderate to severe pain. Two sensitive, selective, and rapid spectrophotometric methods are described for the determination of tramadol in its dosage forms and in spiked human urine. The methods are based on formation of yellow ion-pairs between tramadol and two sulfonthalein dyes; bromocresol purple (BCP) and bromocresol green (BCG) in dichloromethane medium followed by absorbance measurement at 400 and 410 nm, respectively. Under the optimum conditions, tramadol could be assayed in the concentration ranges, 1-15 and 1-16 µg ml(-1) with correlation coefficient greater than 0.999 in both cases. The molar absorptivity values are calculated to be 1.84 × 10(4) and 1.97 × 10(4) l mol(-1) cm(-1) for BCP and BCG methods, respectively; and the corresponding Sandell sensitivity values are 0.0143 and 0.0134 µg cm(-2). The limits of detection (LOD) and quantification (LOQ) have also been reported. The stoichiometry of the reaction was found to be 1:1 in both cases and the conditional stability constant (K(f)) values of the ion pairs have been calculated. The within-day and between-day RSD were 0.9-1.96% and 1.56-3.21%, respectively. The methods were successfully applied to the determination of tramadol in tablets and injections and also in spiked human urine with good recoveries. The procedures are simple, accurate, and suitable for quality control application. Copyright © 2011 John Wiley & Sons, Ltd.

Real-time redox speciation of iron in estuarine and coastal surface waters.

PubMed

Huang, Yongming; Yuan, Dongxing; Zhu, Yong; Feng, Sichao

2015-03-17

An automated, shipboard-use system was developed for real-time speciation of iron in coastal surface waters. It comprised a towed Fish underway sampler and a modified reverse flow injection analysis system with a liquid waveguide capillary flow cell-spectrophotometric detection device. The detection was based on the reaction between ferrozine and Fe(II). The detection limits of 0.3 and 0.7 nM were achieved for Fe(II) and Fe(II+III), together with their respective dynamic linear ranges of 0.5-250 and 0.9-250 nM. The system was successfully deployed and run consecutively for about 1 week during a cruise in August 2009 to the East China Sea off the Changjiang Estuary. The distribution of operationally defined field dissolvable Fe(II) and Fe(II+III) (expressed as Fea(II) and Fea(II+III)) in these areas was obtained, which showed that both Fea(II) and Fea(II+III) concentrations decreased with salinity when there were relatively high Fea(II) concentrations (up to about 120 nM) near shore. A distinct distribution of Fea(II) to Fea(II+III) ratios was also revealed, with a ratio of 0.58 in the water off Changjiang Estuary and 0.19 in the open ocean.

Assessment of Current Process Modeling Approaches to Determine Their Limitations, Applicability and Developments Needed for Long-Fiber Thermoplastic Injection Molded Composites

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

Nguyen, Ba Nghiep; Holbery, Jim; Smith, Mark T.

2006-11-30

This report describes the status of the current process modeling approaches to predict the behavior and flow of fiber-filled thermoplastics under injection molding conditions. Previously, models have been developed to simulate the injection molding of short-fiber thermoplastics, and an as-formed composite part or component can then be predicted that contains a microstructure resulting from the constituents’ material properties and characteristics as well as the processing parameters. Our objective is to assess these models in order to determine their capabilities and limitations, and the developments needed for long-fiber injection-molded thermoplastics (LFTs). First, the concentration regimes are summarized to facilitate the understandingmore » of different types of fiber-fiber interaction that can occur for a given fiber volume fraction. After the formulation of the fiber suspension flow problem and the simplification leading to the Hele-Shaw approach, the interaction mechanisms are discussed. Next, the establishment of the rheological constitutive equation is presented that reflects the coupled flow/orientation nature. The decoupled flow/orientation approach is also discussed which constitutes a good simplification for many applications involving flows in thin cavities. Finally, before outlining the necessary developments for LFTs, some applications of the current orientation model and the so-called modified Folgar-Tucker model are illustrated through the fiber orientation predictions for selected LFT samples.« less

Spectrophotometric and spectrofluorimetric methods for analysis of tramadol, acebutolol and dothiepin in pharmaceutical preparations

NASA Astrophysics Data System (ADS)

Abdellatef, Hisham E.; El-Henawee, Magda M.; El-Sayed, Heba M.; Ayad, Magda M.

2006-12-01

Sensitive spectrophotometric and spectrofluorimetric methods are described for the determination of tramadol, acebutolol and dothiepin (dosulepin) hydrochlorides. The two methods are based on the condensation of the cited drugs with the mixed anhydrides of malonic and acetic acids at 60 °C for 25-40 min. The coloured condensation products are suitable for the spectrophotometric and spectrofluorimetric determination at 329-333 and 431-434 nm (excitation at 389 nm), respectively. For the spectrophotometric method, Beer's law was obeyed from 0.5 to 2.5 μg ml -1 for tramadol, dothiepin and 5-25 μg ml -1 for acebutolol. Using the spectrofluorimetric method linearity ranged from 0.25 to 1.25 μg ml -1 for tramadol, dothiepin and 1-5 μg ml -1 for acebutolol. Mean percentage recoveries for the spectrophotometric method were 99.68 ± 1.00, 99.95 ± 1.11 and 99.72 ± 1.01 for tramadol, acebutolol and dothiepin, respectively and for the spectrofluorimetric method, recoveries were 99.5 ± 0.844, 100.32 ± 0.969 and 99.82 ± 1.15 for the three drugs, respectively. The optimum experimental parameters for the reaction has been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed methods were successfully applied for the determination of the selected drugs in their pharmaceutical preparations with good recoveries. The procedures were accurate, simple and suitable for quality control application.

Computation of geometric representation of novel spectrophotometric methods used for the analysis of minor components in pharmaceutical preparations.

PubMed

Lotfy, Hayam M; Saleh, Sarah S; Hassan, Nagiba Y; Salem, Hesham

2015-01-01

Novel spectrophotometric methods were applied for the determination of the minor component tetryzoline HCl (TZH) in its ternary mixture with ofloxacin (OFX) and prednisolone acetate (PA) in the ratio of (1:5:7.5), and in its binary mixture with sodium cromoglicate (SCG) in the ratio of (1:80). The novel spectrophotometric methods determined the minor component (TZH) successfully in the two selected mixtures by computing the geometrical relationship of either standard addition or subtraction. The novel spectrophotometric methods are: geometrical amplitude modulation (GAM), geometrical induced amplitude modulation (GIAM), ratio H-point standard addition method (RHPSAM) and compensated area under the curve (CAUC). The proposed methods were successfully applied for the determination of the minor component TZH below its concentration range. The methods were validated as per ICH guidelines where accuracy, repeatability, inter-day precision and robustness were found to be within the acceptable limits. The results obtained from the proposed methods were statistically compared with official ones where no significant difference was observed. No difference was observed between the obtained results when compared to the reported HPLC method, which proved that the developed methods could be alternative to HPLC techniques in quality control laboratories. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel green analytical procedure for monitoring of azoxystrobin in water samples by a flow injection chemiluminescence method with off-line ultrasonic treatment.

PubMed

Yang, Xin-an; Zhang, Wang-bing

2013-01-01

A simple and green flow injection chemiluminescence (FI-CL) method for determination of the fungicide azoxystrobin was described for the first time. CL signal was generated when azoxystrobin was injected into a mixed stream of luminol and KMnO4 . The CL signal of azoxystrobin could be greatly improved when an off-line ultrasonic treatment was adopted. Meanwhile, the signal intensity increases with the analyte concentration proportionally. Several variables, such as the ultrasonic parameters, flow rate of reagents, concentrations of sodium hydroxide solution and CL reagents (potassium permanganate, luminol) were investigated, and the optimal CL conditions were obtained. Under optimal conditions, the linear range of 1-100 ng/mL for azoxystrobin was obtained and the detection limit (3σ) was determined as 0.13 ng/mL. The relative standard deviation was 1.5% for 10 consecutive measurements of 20 ng/mL azoxystrobin. The method has been applied to the determination of azoxystrobin residues in water samples. Copyright © 2012 John Wiley & Sons, Ltd.

Determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride by flow-injection analysis based on a specific condensation reaction between malonic acid and ethylenediamine.

PubMed

Seno, Kunihiko; Matumura, Kazuki; Oshita, Koji; Oshima, Mitsuko; Motomizu, Shoji

2009-03-01

A sensitive and rapid flow-injection analysis was developed for the determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC.HCl), which was used for the formation of amide (peptide) and esters as a dehydration or condensation reagent. The EDC.HCl could be determined by the flow-injection analysis based on a specific condensation reaction between malonic acid and ethylenediamine in aquatic media. The reaction was accelerated at 60 degrees C, and the absorbance of the product was detected at 262 nm. The calibration graph of EDC.HCl showed good linearity in the range from 0 to 0.1% (0 to 0.0005 M), whose regression equation was y = 1.52 x 10(9)x (y, peak area; x, % concentration of EDC.HCl). The proposed method allowed high-throughput analysis; the sample throughput was 12 samples per hour. The limit of detection (LOD) and the relative standard deviation (RSD) were 2 x 10(-6) M and 1.0%, respectively. This reaction is proceeded in aqueous solution and specific for EDC.HCl.

Compatible validated spectrofluorimetric and spectrophotometric methods for determination of vildagliptin and saxagliptin by factorial design experiments.

PubMed

Abdel-Aziz, Omar; Ayad, Miriam F; Tadros, Mariam M

2015-04-05

Simple, selective and reproducible spectrofluorimetric and spectrophotometric methods have been developed for the determination of vildagliptin and saxagliptin in bulk and their pharmaceutical dosage forms. The first proposed spectrofluorimetric method is based on the dansylation reaction of the amino group of vildagliptin with dansyl chloride to form a highly fluorescent product. The formed product was measured spectrofluorimetrically at 455 nm after excitation at 345 nm. Beer's law was obeyed in a concentration range of 100-600 μg ml(-1). The second proposed spectrophotometric method is based on the charge transfer complex of saxagliptin with tetrachloro-1,4-benzoquinone (p-chloranil). The formed charge transfer complex was measured spectrophotometrically at 530 nm. Beer's law was obeyed in a concentration range of 100-850 μg ml(-1). The third proposed spectrophotometric method is based on the condensation reaction of the primary amino group of saxagliptin with formaldehyde and acetyl acetone to form a yellow colored product known as Hantzsch reaction, measured at 342.5 nm. Beer's law was obeyed in a concentration range of 50-300 μg ml(-1). All the variables were studied to optimize the reactions' conditions using factorial design. The developed methods were validated and proved to be specific and accurate for quality control of vildagliptin and saxagliptin in their pharmaceutical dosage forms. Copyright © 2015. Published by Elsevier B.V.

Compatible validated spectrofluorimetric and spectrophotometric methods for determination of vildagliptin and saxagliptin by factorial design experiments

NASA Astrophysics Data System (ADS)

Abdel-Aziz, Omar; Ayad, Miriam F.; Tadros, Mariam M.

2015-04-01

Simple, selective and reproducible spectrofluorimetric and spectrophotometric methods have been developed for the determination of vildagliptin and saxagliptin in bulk and their pharmaceutical dosage forms. The first proposed spectrofluorimetric method is based on the dansylation reaction of the amino group of vildagliptin with dansyl chloride to form a highly fluorescent product. The formed product was measured spectrofluorimetrically at 455 nm after excitation at 345 nm. Beer's law was obeyed in a concentration range of 100-600 μg ml-1. The second proposed spectrophotometric method is based on the charge transfer complex of saxagliptin with tetrachloro-1,4-benzoquinone (p-chloranil). The formed charge transfer complex was measured spectrophotometrically at 530 nm. Beer's law was obeyed in a concentration range of 100-850 μg ml-1. The third proposed spectrophotometric method is based on the condensation reaction of the primary amino group of saxagliptin with formaldehyde and acetyl acetone to form a yellow colored product known as Hantzsch reaction, measured at 342.5 nm. Beer's law was obeyed in a concentration range of 50-300 μg ml-1. All the variables were studied to optimize the reactions' conditions using factorial design. The developed methods were validated and proved to be specific and accurate for quality control of vildagliptin and saxagliptin in their pharmaceutical dosage forms.

Load flows and faults considering dc current injections

NASA Technical Reports Server (NTRS)

Kusic, G. L.; Beach, R. F.

1991-01-01

The authors present novel methods for incorporating current injection sources into dc power flow computations and determining network fault currents when electronic devices limit fault currents. Combinations of current and voltage sources into a single network are considered in a general formulation. An example of relay coordination is presented. The present study is pertinent to the development of the Space Station Freedom electrical generation, transmission, and distribution system.

Dual-phase gas-permeation flow-injection thermometric analysis for the determination of carbon dioxide.

PubMed

Liu, S J; Tubino, M

1998-11-01

A flow-injection configuration based on a dual-phase gas-permeation system from a liquid donor to a gas acceptor stream with a thermistor flow-through detector is proposed for the direct analysis of the gas in the acceptor. This system was applied for the determination of carbon dioxide (in the form of carbonate) using the following chemical reaction: CO(2)(g)+2NH(3)(g)+H(2)O(g)=(NH(4))(2)CO(3)(s), with a linear response from 1x10(-3) to 50x10(-3) mol l(-1) of CO(3)(2-). Carbon dioxide was produced in the liquid donor and permeated into the gaseous acceptor stream of air/water vapor. The detection limit is 1x10(-3) mol l(-1) of carbonate, and a sampling frequency of 60 h(-1) is achieved with a relative standard deviation of 4.1% for replicate injections. The dual-phase gas-permeation flow-injection manifold, along with the membrane and phase separations, as well as the chemical reaction, provides enhanced selectivity when compared with the system employing a liquid acceptor stream, as serious interferents in this system, for instance, acetate and formate, among others, do not interfere in the proposed system.

Flow injection method for the determination of silver concentration in drinking water for spacecrafts.

PubMed

Bruzzoniti, Maria Concetta; Kobylinska, Dorota Korte; Franko, Mladen; Sarzanini, Corrado

2010-04-14

A flow injection method has been developed for determination of silver. The method is based on a reduction reaction with sodium borohydride which leads to the formation of a colloidal species which is monitored at a wavelength of 390 nm. The reaction variables flow rate, sodium borohydride concentration and pH, which affect sensitivity, were investigated and their effects were established using a two-levels, three-factor experimental design. Further optimization of manifold variables (reaction coil and injection volume) allowed us to determine silver in the range 0.050-5.0 mg L(-1) with a minimum detectable concentration of 0.050 mg L(-1). Silver is added, as biocide, to drinking water for spacecrafts. The chemical species of silver, present in this kind of sample, were characterized by a procedure based on the selective retention of Ag(+) onto a 2.2.2. cryptand based substrate followed by determination of the non-bound and bound (after elution) Ag(+) by the FIA method. The method optimized was applied to a drinking water sample provided for the launch with the Automated Transfer Vehicle (ATV) module Jule Verne to the International Space Station (March 9, 2008). Copyright 2010 Elsevier B.V. All rights reserved.

In situ sensor technology for simultaneous spectrophotometric measurements of seawater total dissolved inorganic carbon and pH.

PubMed

Wang, Zhaohui Aleck; Sonnichsen, Frederick N; Bradley, Albert M; Hoering, Katherine A; Lanagan, Thomas M; Chu, Sophie N; Hammar, Terence R; Camilli, Richard

2015-04-07

A new, in situ sensing system, Channelized Optical System (CHANOS), was recently developed to make high-resolution, simultaneous measurements of total dissolved inorganic carbon (DIC) and pH in seawater. Measurements made by this single, compact sensor can fully characterize the marine carbonate system. The system has a modular design to accommodate two independent, but similar measurement channels for DIC and pH. Both are based on spectrophotometric detection of hydrogen ion concentrations. The pH channel uses a flow-through, sample-indicator mixing design to achieve near instantaneous measurements. The DIC channel adapts a recently developed spectrophotometric method to achieve flow-through CO2 equilibration between an acidified sample and an indicator solution with a response time of only ∼ 90 s. During laboratory and in situ testing, CHANOS achieved a precision of ±0.0010 and ± 2.5 μmol kg(-1) for pH and DIC, respectively. In situ comparison tests indicated that the accuracies of the pH and DIC channels over a three-week time-series deployment were ± 0.0024 and ± 4.1 μmol kg(-1), respectively. This study demonstrates that CHANOS can make in situ, climatology-quality measurements by measuring two desirable CO2 parameters, and is capable of resolving the CO2 system in dynamic marine environments.

A Microscale Spectrophotometric Determination of Water Hardness

NASA Astrophysics Data System (ADS)

Gordon, James S.

2001-08-01

A spectrophotometric titration was performed to determine water hardness. The titration incorporated the traditional titration method employing EDTA as the titrant and calmagite as the indicator. The microscale experiment was carried out in a spectrometer cuvette and made use of a Texas Instruments (TI-83) calculator interfaced through a TI Calculator-Based Laboratory system to a Vernier colorimeter as the detector. Monitoring at 635 nm, one of the colorimeter's fixed wavelengths, was well suited for this analysis. Agreement was found with results from traditional titrations.

Spectrophotometric determination of vanadium and its application to gas-turbine fuel-oils.

PubMed

Banerjee, S; Sinha, B P; Dutta, R K

1975-08-01

A very sensitive spectrophotometric method for the determination of vanadium in furnace oils is described. The intense indigo-blue colour developed by the reaction of vanadium with tannin and thioglycollic acid is measured at a wavelength of 600 nm at pH 4 and obeys Beer's law between 0.5 and 5 ppm vanadium. The method is applicable to gas-turbine fuel-oil and special navy fuel-oils. The common mineral constituents usually present in such oils do not interfere.

Profiling Sugars in Tall Fescue and Kentucky Bluegrass Extracts Assayed for Total Water- and Ethanol-Soluble Carbohydrates: Relationship of Chromatographic to Spectrophotometric Data

USDA-ARS?s Scientific Manuscript database

Water-soluble carbohydrates (WSC) and ethanol-soluble carbohydrates (ESC) of herbage are often quantified by spectrophotometric assays. To determine if quantifying individual sugars from chromatograms could yield results comparable to those obtained by the assays, WSC and ESC were extracted from fr...

Validation of a spectrophotometric procedure for determining nitrate in water samples

USDA-ARS?s Scientific Manuscript database

A single-reagent spectrophotometric procedure using vanadium (III) chloride (VCl3) was found to provide accurate and robust measurement of low levels of nitrate (lNO3-N) in agricultural runoff. Results of the VCl3 method produced data that correlated well (r=0.86; p<0.001) with NO3-N concentrations ...

Chemical Analysis through CL-Detection Assisted by Periodate Oxidation

PubMed Central

Evmiridis, Nicholaos P.; Vlessidis, Athanasios G.; Thanasoulias, Nicholas C.

2007-01-01

The progress of the research work of the author and his colleagues on the field of CL-emission generated by pyrogallol oxidation and further application for the direct determination of periodate and indirect or direct determination of other compounds through flow-injection manifold/CL-detection set up is described. The instrumentation used for these studies was a simple flow-injection manifold that provides good reproducibility, coupled to a red sensitive photomultiplier that gives sensitive CL-detection. In addition, recent reports on studies and analytical methods based on CL-emission generated by periodate oxidation by other authors are included. PMID:17611611

Spectrophotometric determination of H2O2-generating oxidases using oxyhemoglobin as oxygen donor and indicator.

PubMed

Bârzu, O; Dânşoreanu, M

1980-01-01

1. Spectrophotometric determination of oxygen uptake using oxyhemoglobin as oxygen donor and indicator was used for assay of H2O2-generating oxidases like monoamine oxidase and glucose oxidase. 2. In order to decompose H2O2 formed during the oxygen uptake, catalase and methanol (or ethanol) was added to the respiratory system. At pH values higher than 7.5 the oxydation of deoxygenated hemoglobin to methemoglobin was less than 3%. 2. Oxidases with low Km for oxygen can be assayed using the spectrophotometric method if suitable correction factors are introduced into the calculation of oxygen uptake. The correction factor represents the ratio of the rate of formation (or disappearance) of one of the reactants and the rate of oxyhemoglobin deoxygenation, measured under identical experimental conditions.

Determination of niobium in rocks by an isotope dilution spectrophotometric method

USGS Publications Warehouse

Greenland, L.P.; Campbell, E.Y.

1970-01-01

Rocks and minerals are fused with sodium peroxide in the presence of carrierfree 95Nb. The fusion cake is leached with water and the precipitate dissolved in hydrofluoric-sulfuric acid mixture. Niobium is extracted into methyl isobutyl ketone and further purified by ion exchange. The amount of niobium is determined spectrophotometrically with 4-(2-pyridylazo)-resorcinol, and the chemical yield of the separations determined by counting 95Nb. This procedure is faster and less sensitive to interferences than previously proposed methods for determining niobium in rocks.The high purity of the separated niobium makes the method applicable to nearly all matrices. ?? 1970.

Spectrophotometric determination of bacitracin in bulk drug as dabsyl derivative in a range of visible light.

PubMed

Krzek, Jan; Piotrowska, Joanna

2011-01-01

A fast spectrophotometric method has been developed for bacitracin identification and determination after condensation reaction with dabsyl chloride. In addition, determination of dye stability of sulfonamide derivative and identification of the molar ratio of reagents was done at various time-points. The developed method has a good linearity with very broad spectrum, correlation coefficient of r = 0.9972, good precision (RSD = 1.54 +/- 0.11%), and recovery at three different levels of concentration was found between 98.33% and 103.47%. Usefulness of the method was demonstrated by positive results obtained during determination of bacitracin concentration in bulk drug.

Two spectrophotometric methods for simultaneous determination of some antihyperlipidemic drugs

PubMed Central

Abdelwahab, Nada S.; El-Zeiny, Badr A.; Tohamy, Salwa I.

2012-01-01

Two simple, accurate, precise and economic spectrophotometric methods have been developed for simultaneous determination of Atorvastatin calcium (ATR) and Ezetimibe (EZ) in their bulk powder and pharmaceutical dosage form. Method (I) is based on dual wavelength analysis while method (II) is the mean centering of ratio spectra spectrophotometric (MCR) method. In method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the second drug. At wavelengths 226.6 and 244 nm EZ had equal absorbance values; therefore, these two wavelengths have been used to determine ATR; on a similar basis 228.6 and 262.8 nm were selected to determine EZ in their binary mixtures. In method II, the absorption spectra of both ATR and EZ with different concentrations were recorded over the range 200–350, divided by the spectrum of suitable divisor of both ATR and EZ and then the obtained ratio spectra were mean centered. The concentrations of active components were then determined from the calibration graphs obtained by measuring the amplitudes at 215–260 nm (peak to peak) for both ATR and EZ. Accuracy and precision of the developed methods have been tested; in addition recovery studies have been carried out in order to confirm their accuracy. On the other hand, selectivities of the methods were tested by application for determination of different synthetic mixtures containing different ratios of the studied drugs. The developed methods have been successfully used for determination of ATR and EZ in their combined dosage form and statistical comparison of the developed methods with the reported spectrophotometric one using F and Student's t-tests showed no significant difference regarding both accuracy and precision. PMID:29403754

Two spectrophotometric methods for simultaneous determination of some antihyperlipidemic drugs.

PubMed

Abdelwahab, Nada S; El-Zeiny, Badr A; Tohamy, Salwa I

2012-08-01

Two simple, accurate, precise and economic spectrophotometric methods have been developed for simultaneous determination of Atorvastatin calcium (ATR) and Ezetimibe (EZ) in their bulk powder and pharmaceutical dosage form. Method (I) is based on dual wavelength analysis while method (II) is the mean centering of ratio spectra spectrophotometric (MCR) method. In method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the second drug. At wavelengths 226.6 and 244 nm EZ had equal absorbance values; therefore, these two wavelengths have been used to determine ATR; on a similar basis 228.6 and 262.8 nm were selected to determine EZ in their binary mixtures. In method II, the absorption spectra of both ATR and EZ with different concentrations were recorded over the range 200-350, divided by the spectrum of suitable divisor of both ATR and EZ and then the obtained ratio spectra were mean centered. The concentrations of active components were then determined from the calibration graphs obtained by measuring the amplitudes at 215-260 nm (peak to peak) for both ATR and EZ. Accuracy and precision of the developed methods have been tested; in addition recovery studies have been carried out in order to confirm their accuracy. On the other hand, selectivities of the methods were tested by application for determination of different synthetic mixtures containing different ratios of the studied drugs. The developed methods have been successfully used for determination of ATR and EZ in their combined dosage form and statistical comparison of the developed methods with the reported spectrophotometric one using F and Student's t -tests showed no significant difference regarding both accuracy and precision.

Spectrophotometric method for the determination of paraquat in water, grain and plant materials.

PubMed

Shivhare, P; Gupta, V K

1991-04-01

A sensitive spectrophotometric method for the determination of paraquat using ascorbic acid (an easily available reducing agent) is described. Paraquat is reduced with ascorbic acid in alkaline solution to give a blue radical ion with an absorbance maximum at 600 nm. Beer's law is obeyed in the range 12-96 micrograms of paraquat in 10 ml of the final solution (1.2-9.6 ppm). The important analytical parameters and the optimum reaction conditions were evaluated. The method was applied successfully to the determination of paraquat in water, grain and plant materials.

Determining Glutathione Levels in Plants.

PubMed

Sahoo, Smita; Awasthi, Jay Prakash; Sunkar, Ramanjulu; Panda, Sanjib Kumar

2017-01-01

Upon exposure to abiotic stresses, plants tend to accumulate excessive amounts of reactive oxygen species (ROS) that inturn react with cellular lipids, proteins, and DNA. Therefore, decreasing ROS accumulation is indispensible to survive under stress, which is accomplished by inducing enzymatic and nonenzymatic antioxidant defense pathways. Glutathione, particularly reduced glutathione (GSH), represents a principal anitioxidant that could decrease ROS through scavenging them directly or indirectly through ascorbate-glutathione cycle or GSH peroxidases. Glutathione content can be determined using HPLC or spectrophotometric assays. In this chapter, we provided detailed assays to determine total, reduced, and oxidized gluathione using spectrophotometric method.

Jet mixing into a heated cross flow in a cylindrical duct: Influence of geometry and flow variations

NASA Technical Reports Server (NTRS)

Hatch, M. S.; Sowa, W. A.; Samuelsen, G. S.; Holdeman, J. D.

1992-01-01

To examine the mixing characteristics of jets in an axi-symmetric can geometry, temperature measurements were obtained downstream of a row of cold jets injected into a heated cross stream. Parametric, non-reacting experiments were conducted to determine the influence of geometry and flow variations on mixing patterns in a cylindrical configuration. Results show that jet to mainstream momentum flux ratio and orifice geometry significantly impact the mixing characteristics of jets in a can geometry. For a fixed number of orifices, the coupling between momentum flux ratio and injector determines (1) the degree of jet penetration at the injection plane, and (2) the extent of circumferential mixing downstream of the injection plane. The results also show that, at a fixed momentum flux ratio, jet penetration decreases with (1) an increase in slanted slot aspect ratio, and (2) an increase in the angle of the slots with respect to the mainstream direction.

Validated spectrophotometric method for the determination, spectroscopic characterization and thermal structural analysis of duloxetine with 1,2-naphthoquinone-4-sulphonate

NASA Astrophysics Data System (ADS)

Ulu, Sevgi Tatar; Elmali, Fikriye Tuncel

2012-03-01

A novel, selective, sensitive and simple spectrophotometric method was developed and validated for the determination of the antidepressant duloxetine hydrochloride in pharmaceutical preparation. The method was based on the reaction of duloxetine hydrochloride with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline media to yield orange colored product. The formation of this complex was also confirmed by UV-visible, FTIR, 1H NMR, Mass spectra techniques and thermal analysis. This method was validated for various parameters according to ICH guidelines. Beer's law is obeyed in a range of 5.0-60 μg/mL at the maximum absorption wavelength of 480 nm. The detection limit is 0.99 μg/mL and the recovery rate is in a range of 98.10-99.57%. The proposed methods was validated and applied to the determination of duloxetine hydrochloride in pharmaceutical preparation. The results were statistically analyzed and compared to those of a reference UV spectrophotometric method.

Mechanised flow system for on-line microwave digestion of food samples with off-line catalytic spectrophotometric determination of cobalt at ng l-1 levels.

PubMed

Pereira-Filho, E R; Arruda, M A

1999-12-01

A mechanised system for on-line slurry food sample digestion was developed and an off-line cobalt determination was performed. The stabilised slurry sample was introduced into an air carrier stream until reaching the digestion coils located inside a household microwave oven. Software written in Visual Basic 3.0 was developed to permit the transport of the slurry samples and the programming of the microwave oven and also the control of the mineralization valve. The proposed system was optimized for determination of cobalt in certified samples such as mussels, bovine liver and fish and also uncertified fish samples. The digestion parameters were established as 3 mol l-1 HNO3 for mussels, 3 mol l-1 HNO3 plus 0.16% v/v H2O2 for bovine liver and 12 mol l-1 HNO3 for fish employing maximum power for 5 min of microwave actuation. In the subsequent spectrophotometric method for the catalytic determination of cobalt, the Tiron and hydrogen peroxide concentrations were 1.8 x 10(-3) and 3.0 x 10(-4) mol l-1, respectively, and the sample residence time was 300 s as determined by an optimisation process. The proposed method features a linear range from 10 to 200 ng l-1 Co (r > 0.996) with detection and quantification limits of 1.7 and 5.5 ng l-1 Co, respectively. The precision, expressed as RSD, was 2.4% (n = 12) for repeatability and 5.2% (n = 10) for reproducibility and the accuracy of the proposed method was assessed by using certified samples and an alternative technique (ETAAS).

On-line lab-in-syringe cloud point extraction for the spectrophotometric determination of antimony.

PubMed

Frizzarin, Rejane M; Portugal, Lindomar A; Estela, José M; Rocha, Fábio R P; Cerdà, Victor

2016-02-01

Most of the procedures for antimony determination require time-consuming sample preparation (e.g. liquid-liquid extraction with organic solvents), which are harmful to the environment. Because of the high antimony toxicity, a rapid, sensitive and greener procedure for its determination becomes necessary. The goal of this work was to develop an analytical procedure exploiting for the first time the cloud point extraction on a lab-in-syringe flow system aiming at the spectrophotometric determination of antimony. The procedure was based on formation of an ion-pair between the antimony-iodide complex and H(+) followed by extraction with Triton X-114. The factorial design showed that the concentrations of ascorbic acid, H2SO4 and Triton X-114, as well as second and third order interactions were significant at the 95% confidence level. A Box-Behnken design was applied to obtain the response surfaces and to identify the critical values. System is robust at the 95% confidence level. A linear response was observed from 5 to 50 µg L(-1), described by the equation A=0.137+0.050C(Sb) (r=0.998). The detection limit (99.7% confidence level), the coefficient of variation (n=5; 15 µg L(-1)) and the sampling rate was estimated at 1.8 µg L(-1), 1.6% and 16 h(-1), respectively. The procedure allows quantification of antimony in the concentrations established by environmental legislation (6 µg L(-1)) and it was successfully applied to the determination of antimony in freshwater samples and antileishmanial drugs, yielding results in agreement with those obtained by HGFAAS at the 95% confidence level. Copyright © 2015 Elsevier B.V. All rights reserved.

The thoron-tartaric acid systems for the spectrophotometric determination of thorium

USGS Publications Warehouse

Grimaldi, F.S.; Fletcher, Mary H.

1955-01-01

Thoron is popularly used for the spectrophotometric determination of thorium.  An undesirable feature of its use is the high sensitivity of the reagent toward zirconium. This study describes the use of tartaric acid as a masking reagent for zirconium. Three tartaric acid-thoron systems, developed for the determination of thorium, differ with respect to the concentrations of thoron and tartaric acid. Mesotataric acid, used in one of the systems, is found to be most effective in masking zirconium. The behavior of various rarer elements, usually found associated with thorium ores, is determined in two of the systems, and a dilution method is described for the direct determination of thorium in monazite concentrates.

Extraction-spectrophotometric determination of traces of gold in copper in silver, lead, blister copper, copper concentrate and anode slime with 4,4'-bis(dimethylamino)-thiobenzophenone.

PubMed

Tsukahara, I

1977-10-01

A sensitive spectrophotometric method has been developed for the determination of gold in copper, silver, lead, blister copper, copper concentrate and anode slime. Optimal conditions have been established for the extraction and determination of gold. Gold is extracted as its bromo complex with tri-n-octylamine and determined photometrically with 4,4'-bis(dimethylamino)thiobenzophenone; the absorbance of the organic phase is measured at 540 nm and the apparent molar absorptivity is about 1.2 x 10(5) 1.mole(-1). cm(-1). As little as 0.1 or 0.2 ppm of gold in these materials can be determined.

Dispersion of a Nanoliter Bolus in Microfluidic Co-Flow.

PubMed

Conway, A J; Saadi, W M; Sinatra, F L; Kowalski, G; Larson, D; Fiering, J

2014-03-01

Microfluidic systems enable reactions and assays on the scale of nanoliters. However, at this scale nonuniformities in sample delivery become significant. To determine the fundamental minimum sample volume required for a particular device, a detailed understanding of mass transport is required. Co-flowing laminar streams are widely used in many devices, but typically only in the steady-state. Because establishing the co-flow steady-state consumes excess sample volume and time, there is a benefit to operating devices in the transient state, which predominates as the volume of the co-flow reactor decreases. Analysis of the co-flow transient has been neglected thus far. In this work we describe the fabrication of a pneumatically controlled microfluidic injector constructed to inject a discrete 50nL bolus into one side of a two-stream co-flow reactor. Using dye for image analysis, injections were performed at a range of flow rates from 0.5-10μL/min, and for comparison we collected the co-flow steady-state data for this range. The results of the image analysis were also compared against theory and simulations for device validation. For evaluation, we established a metric that indicates how well the mass distribution in the bolus injection approximates steady-state co-flow. Using such analysis, transient-state injections can approximate steady-state conditions within predefined errors, allowing straight forward measurements to be performed with reduced reagent consumption.

Catalytic spectrophotometric determination of iodide in pharmaceutical preparations and edible salt.

PubMed

El-Ries, M A; Khaled, Elmorsy; Zidane, F I; Ibrahim, S A; Abd-Elmonem, M S

2012-02-01

The catalytic effect of iodide on the oxidation of four dyes: viz. variamine blue (VB), methylene blue (MB), rhodamine B (RB), and malachite green (MG) with different oxidizing agents was investigated for the kinetic spectrophotometric determination of iodide. The above catalyzed reactions were monitored spectrophotometrically by following the change in dye absorbances at 544, 558, 660, or 617 nm for the VB, RB, MB, or MG catalyzed reactions, respectively. Under optimum conditions, iodide can be determined within the concentration levels 0.064-1.27 µg mL(-1) for VB method, 3.20-9.54 µg mL(-1) for RB method, 5.00-19.00 µg mL(-1) for the MB method, and 6.4-19.0 µg mL(-1) for the MG one, with detection limit reaching 0.004 µg mL(-1) iodide. The reported methods were highly sensitive, selective, and free from most interference. Applying the proposed procedures, trace amounts of iodide in pharmaceutical and edible salt samples were successfully determined without separation or pretreatment steps. Copyright © 2011 John Wiley & Sons, Ltd.

Comparison of the acetyl bromide spectrophotometric method with other analytical lignin methods for determining lignin concentration in forage samples.

PubMed

Fukushima, Romualdo S; Hatfield, Ronald D

2004-06-16

Present analytical methods to quantify lignin in herbaceous plants are not totally satisfactory. A spectrophotometric method, acetyl bromide soluble lignin (ABSL), has been employed to determine lignin concentration in a range of plant materials. In this work, lignin extracted with acidic dioxane was used to develop standard curves and to calculate the derived linear regression equation (slope equals absorptivity value or extinction coefficient) for determining the lignin concentration of respective cell wall samples. This procedure yielded lignin values that were different from those obtained with Klason lignin, acid detergent acid insoluble lignin, or permanganate lignin procedures. Correlations with in vitro dry matter or cell wall digestibility of samples were highest with data from the spectrophotometric technique. The ABSL method employing as standard lignin extracted with acidic dioxane has the potential to be employed as an analytical method to determine lignin concentration in a range of forage materials. It may be useful in developing a quick and easy method to predict in vitro digestibility on the basis of the total lignin content of a sample.

Automation of flow injection gas diffusion-ion chromatography for the nanomolar determination of methylamines and ammonia in seawater and atmospheric samples

PubMed Central

Gibb, Stuart W.; Wood, John W.; Fauzi, R.; Mantoura, C.

1995-01-01

The automation and improved design and performance of Flow Injection Gas Diffusion-Ion Chromatography (FIGD-IC), a novel technique for the simultaneous analysis of trace ammonia (NH3) and methylamines (MAs) in aqueous media, is presented. Automated Flow Injection Gas Diffusion (FIGD) promotes the selective transmembrane diffusion of MAs and NH3 from aqueous sample under strongly alkaline (pH > 12, NaOH), chelated (EDTA) conditions into a recycled acidic acceptor stream. The acceptor is then injected onto an ion chromatograph where NH3 and the MAs are fully resolved as their cations and detected conductimetrically. A versatile PC interfaced control unit and data capture unit (DCU) are employed in series to direct the selonoid valve switching sequence, IC operation and collection of data. Automation, together with other modifications improved both linearily (R2 > 0.99 MAs 0-100 nM, NH3 0-1000 nM) and precision (<8%) of FIGD-IC at nanomolar concentrations, compared with the manual procedure. The system was successfully applied to the determination of MAs and NH3 in seawater and in trapped particulate and gaseous atmospheric samples during an oceanographic research cruise. PMID:18925047

A spectrophotometric screening method for avermectin oxidizing microorganisms.

PubMed

Wang, Yuan-Shan; Hu, Qi-Wei; Zheng, Xing-Chang; Zhang, Jian-Fen; Zheng, Yu-Guo

2017-04-01

A spectrophotometric screening method for avermectin oxidizing microbes by determination of 4″-oxo-avermectin was established based on the reaction between 4″-oxo-avermectin and 2,4-dinitrophenylhydrazine. Combined with a gradient HPLC assay, microorganisms capable of regioselectively oxidizing avermectin to 4″-oxo-avermectin were successfully obtained by this method. Copyright © 2017 Elsevier B.V. All rights reserved.

A comparative study of progressive versus successive spectrophotometric resolution techniques applied for pharmaceutical ternary mixtures

NASA Astrophysics Data System (ADS)

Saleh, Sarah S.; Lotfy, Hayam M.; Hassan, Nagiba Y.; Salem, Hesham

2014-11-01

This work represents a comparative study of a novel progressive spectrophotometric resolution technique namely, amplitude center method (ACM), versus the well-established successive spectrophotometric resolution techniques namely; successive derivative subtraction (SDS); successive derivative of ratio spectra (SDR) and mean centering of ratio spectra (MCR). All the proposed spectrophotometric techniques consist of several consecutive steps utilizing ratio and/or derivative spectra. The novel amplitude center method (ACM) can be used for the determination of ternary mixtures using single divisor where the concentrations of the components are determined through progressive manipulation performed on the same ratio spectrum. Those methods were applied for the analysis of the ternary mixture of chloramphenicol (CHL), dexamethasone sodium phosphate (DXM) and tetryzoline hydrochloride (TZH) in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the official BP methods, showing no significant difference with respect to accuracy and precision.

Recovery of injected freshwater to differentiate fracture flow in a low-permeability brackish aquifer

NASA Astrophysics Data System (ADS)

Miotliński, Konrad; Dillon, Peter J.; Pavelic, Paul; Cook, Peter G.; Page, Declan W.; Levett, Kerry

2011-10-01

SummaryA low-permeability weathered siltstone-sandstone aquifer containing brackish water was investigated to measure recoverability of injected freshwater with the aim of determining the significance of secondary porosity in contributing to groundwater flow and transport. Examination of the core, borehole geophysics, Radon-222, electromagnetic flowmeter (EMF) profiles and step-drawdown pumping tests did not identify whether fractures contribute to groundwater flow. A number of injection and recovery tests lasting from 3 days to 3 months using potable water showed a large degree of mixing with native groundwater. Withdrawal greater than 12-17% of the injected volume resulted in recovered water containing more native groundwater than injected water. A finite element solute transport model was set up to reproduce the observed salinity in recovered water. Without the inclusion of discrete fractures in the model it was not possible to get a fit between the observed and modelled salinity of recovered water within a realistic range of dispersivity values. The model was subsequently verified by using data from long-term injection and recovery trials. This evaluation of mixing conclusively demonstrated that the aquifer behaved as a fractured rock aquifer and not as an aquifer with primary porosity alone. Therefore, aquifer storage and recovery can be a very useful hydrogeological method to identify the occurrence of fracture flow in aquifers where there is a measurable concentration difference between the injected water and ambient groundwater.

The measurement of skin lymph flow by isotope clearance--reliability, reproducibility, injection dynamics, and the effect of massage

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

Mortimer, P.S.; Simmonds, R.; Rezvani, M.

1990-12-01

The measurement of skin lymph flow was investigated using an isotope clearance technique (ICT). Multiple lymph flow determinations were undertaken in the skin of anaesthetized large white pigs to test for reproducibility, ascertain the most suitable tracer, study the influence of injection dynamics, and observe the effect of massage as a stimulus to lymph flow. Blood clearance of tracer was also investigated. Results demonstrated that lymphatic clearance is a monoexponential function with good reproducibility under controlled laboratory conditions. 99mTc-colloid (TCK17 Cis) compared favorably with 131I-human serum albumin as a tracer and both performed better than colloid gold (198Au). Lymph flowmore » was significantly faster in one pig than in the other. No difference existed between left and right sides or between caudal and rostral sites on each flank, but clearance was significantly slower in thigh than flank skin. Sub-epidermal injections cleared faster and more consistently than either deep or subcutaneous injections. Neither injection volume nor needle tract backflow of tracer influenced results, but local massage significantly enhanced clearance. Escape of 99mTc-colloid by the blood was negligible. These results indicate that skin lymph flow can be reliably measured when conditions are controlled. Extrinsic factors such as massage strongly influence lymph flow. Greater sensitivity in detecting degrees of lymphatic insufficiency may be achieved if a standardized stimulus to lymph flow is administered during isotope clearance measurement.« less

Impact of Air Injection on Jet Noise

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Norum, Tom

2007-01-01

The objective of this viewgraph presentation is to review the program to determine impact of core fluidic chevrons on noise produced by dual stream jets (i.e., broadband shock noise - supersonic, and mixing noise - subsonic and supersonic). The presentation reviews the sources of jet noise. It shows designs of Generation II Fluidic Chevrons. The injection impacts shock structure and stream disturbances through enhanced mixing. This may impact constructive interference between acoustic sources. The high fan pressures may inhibit mixing produced by core injectors. A fan stream injection may be required for better noise reduction. In future the modification of Gen II nozzles to allow for some azimuthal control: will allow for higher mass flow rates and will allow for shallower injection angles A Flow field study is scheduled for spring, 2008 The conclusions are that injection can reduce well-defined shock noise and injection reduces mixing noise near peak jet noise angle

Polymeric microchip for the simultaneous determination of anions and cations by hydrodynamic injection using a dual-channel sequential injection microchip electrophoresis system.

PubMed

Gaudry, Adam J; Nai, Yi Heng; Guijt, Rosanne M; Breadmore, Michael C

2014-04-01

A dual-channel sequential injection microchip capillary electrophoresis system with pressure-driven injection is demonstrated for simultaneous separations of anions and cations from a single sample. The poly(methyl methacrylate) (PMMA) microchips feature integral in-plane contactless conductivity detection electrodes. A novel, hydrodynamic "split-injection" method utilizes background electrolyte (BGE) sheathing to gate the sample flows, while control over the injection volume is achieved by balancing hydrodynamic resistances using external hydrodynamic resistors. Injection is realized by a unique flow-through interface, allowing for automated, continuous sampling for sequential injection analysis by microchip electrophoresis. The developed system was very robust, with individual microchips used for up to 2000 analyses with lifetimes limited by irreversible blockages of the microchannels. The unique dual-channel geometry was demonstrated by the simultaneous separation of three cations and three anions in individual microchannels in under 40 s with limits of detection (LODs) ranging from 1.5 to 24 μM. From a series of 100 sequential injections the %RSDs were determined for every fifth run, resulting in %RSDs for migration times that ranged from 0.3 to 0.7 (n = 20) and 2.3 to 4.5 for peak area (n = 20). This system offers low LODs and a high degree of reproducibility and robustness while the hydrodynamic injection eliminates electrokinetic bias during injection, making it attractive for a wide range of rapid, sensitive, and quantitative online analytical applications.

Vertical gas injection into liquid cross-stream beneath horizontal surfaces

NASA Astrophysics Data System (ADS)

Lee, In-Ho; Makiharju, Simo; Lee, Inwon; Perlin, Marc; Ceccio, Steve

2013-11-01

Skin friction drag reduction on flat bottomed ships and barges can be achieved by creating an air layer immediately beneath the horizontal surface. The simplest way of introducing the gas is through circular orifices; however the dynamics of gas injection into liquid cross-streams under horizontal surfaces is not well understood. Experiments were conducted to investigate the development of the gas topology following its vertical injection through a horizontal surface. The liquid cross-flow, orifice diameter and gas flow rate were varied to investigate the effect of different ratios of momentum fluxes. The testing was performed on a 4.3 m long and 0.73 m wide barge model with air injection through a hole in the transparent bottom hull. The incoming boundary layer was measured via a pitot tube. Downstream distance based Reynolds number at the injection location was 5 × 105 through 4 × 106 . To observe the flow topology, still images and video were recorded from above the model (i.e. through the transparent hull), from beneath the bottom facing upward, and from the side at an oblique angle. The transition point of the flow topology was determined and analyzed.

New spectrofluorimetric and spectrophotometric methods for the determination of the analgesic drug, nalbuphine in pharmaceutical and biological fluids.

PubMed

El-Didamony, Akram M; Ali, Ismail I

2013-01-01

We describe the first studies of a simple and sensitive spectrofluorimetric and spectrophotometric methods for the analysis of nalbuphine (NLB) in dosage form and biological fluids. The spectrofluorimetric method was based on the oxidation of NLB with Ce(IV) to produce Ce(III) and its fluorescence was monitored at 352 nm after excitation at 250 nm. The spectrophotometric method involves addition of a known excess of Ce(IV) to NLB in acid medium, followed by determination of residual Ce(IV) by reacting with a fixed amount of methyl orange and measuring absorbance at 510 nm. In both methods, the amount of Ce(IV) reacted corresponds to the amount of NLB and measured fluorescence or absorbance were found to increase linearly with the concentration of NLB, which are corroborated by correlation coefficients of 0.9997 and 0.9999 for spectrofluorimetric and spectrophotometric methods, respectively. Different variables affecting the reaction conditions such as concentrations of Ce(IV), type and concentration of acid medium, reaction time, temperature, and diluting solvents were carefully studied and optimized. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis. The proposed methods were successfully applied for the determination of NLB in pharmaceutical formulation and biological samples with good recoveries. Copyright © 2012 John Wiley & Sons, Ltd.

Pressure-controlled injection of guar gum stabilized microscale zerovalent iron for groundwater remediation.

PubMed

Luna, M; Gastone, F; Tosco, T; Sethi, R; Velimirovic, M; Gemoets, J; Muyshondt, R; Sapion, H; Klaas, N; Bastiaens, L

2015-10-01

The paper reports a pilot injection test of microsized zerovalent iron (mZVI) dispersed in a guar gum shear thinning solution. The test was performed in the framework of the EU research project AQUAREHAB in a site in Belgium contaminated by chlorinated aliphatic hydrocarbons (CAHs). The field application was aimed to overcome those critical aspects which hinder mZVI field injection, mainly due to the colloidal instability of ZVI-based suspensions. The iron slurry properties (iron particles size and concentration, polymeric stabilizer type and concentration, slurry viscosity) were designed in the laboratory based on several tests (reactivity tests towards contaminants, sedimentation tests and rheological measurements). The particles were delivered into the aquifer through an injection well specifically designed for controlled-pressure delivery (approximately 10 bars). The well characteristics and the critical pressure of the aquifer (i.e. the injection pressure above which fracturing occurs) were assessed via two innovative injection step rate tests, one performed with water and the other one with guar gum. Based on laboratory and field preliminary tests, a flow regime at the threshold between permeation and preferential flow was selected for mZVI delivery, as a compromise between the desired homogeneous distribution of the mZVI around the injection point (ensured by permeation flow) and the fast and effective injection of the slurry (guaranteed by high discharge rates and injection pressure, resulting in the generation of preferential flow paths). A monitoring setup was designed and installed for the real-time monitoring of relevant parameters during injection, and for a fast determination of the spatial mZVI distribution after injection via non-invasive magnetic susceptibility measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

Spectrophotometric and spectrofluorimetric methods for determination of certain biologically active phenolic drugs in their bulk powders and different pharmaceutical formulations

NASA Astrophysics Data System (ADS)

Omar, Mahmoud A.; Badr El-Din, Kalid M.; Salem, Hesham; Abdelmageed, Osama H.

2018-03-01

Two simple and sensitive spectrophotometric and spectrofluorimetric methods for the determination of terbutaline sulfate, fenoterol hydrobromide, etilefrine hydrochloride, isoxsuprine hydrochloride, ethamsylate, doxycycline hyclate have been developed. Both methods were based on the oxidation of the cited drugs with cerium (IV) in acid medium. The spectrophotometric method was based on measurement of the absorbance difference (ΔA), which represents the excess cerium (IV), at 317 nm for each drug. On the other hand, the spectrofluorimetric method was based on measurement of the fluorescent of the produced cerium (III) at emission wavelength 354 nm (λexcitation = 255 nm) for the concentrations studied for each drug. For both methods, the variables affecting the reactions were carefully investigated and the conditions were optimized. Linear relationships were found between either ΔA or the fluorescent of the produced cerium (III) values and the concentration of the studied drugs in a general concentration range of 2.0-24.0 μg mL- 1, 20.0-24.0 ng mL- 1 with good correlation coefficients in the following range 0.9990-0.9999, 0.9990-0.9993 for spectrophotometric and spectrofluorimetric methods respectively. The limits of detection and quantitation of spectrophotometric method were found in general concentration range 0.190-0.787 and 0.634-2.624 μg mL- 1respectively. For spectrofluorimetric method, the limits of detection and quantitation were found in general concentration range 4.77-9.52 and 15.91-31.74 ng mL- 1 respectively. The stoichiometry of the reaction was determined, and the reactions pathways were postulated. The analytical performance of the methods, in terms of accuracy and precision, were statistically validated and the results obtained were satisfactory. The methods have been successfully applied to the determination of the cited drugs in their commercial pharmaceutical formulations. Statistical comparison of the results with the reference methods showed excellent agreement and proved that no significant difference in the accuracy and precision.

Validated univariate and multivariate spectrophotometric methods for the determination of pharmaceuticals mixture in complex wastewater

NASA Astrophysics Data System (ADS)

Riad, Safaa M.; Salem, Hesham; Elbalkiny, Heba T.; Khattab, Fatma I.

2015-04-01

Five, accurate, precise, and sensitive univariate and multivariate spectrophotometric methods were developed for the simultaneous determination of a ternary mixture containing Trimethoprim (TMP), Sulphamethoxazole (SMZ) and Oxytetracycline (OTC) in waste water samples collected from different cites either production wastewater or livestock wastewater after their solid phase extraction using OASIS HLB cartridges. In univariate methods OTC was determined at its λmax 355.7 nm (0D), while (TMP) and (SMZ) were determined by three different univariate methods. Method (A) is based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method followed by ratio difference method for determination of TMP and SMZ. Method (B) is successive derivative ratio technique (SDR). Method (C) is mean centering of the ratio spectra (MCR). The developed multivariate methods are principle component regression (PCR) and partial least squares (PLS). The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs. The obtained results are statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Validated univariate and multivariate spectrophotometric methods for the determination of pharmaceuticals mixture in complex wastewater.

PubMed

Riad, Safaa M; Salem, Hesham; Elbalkiny, Heba T; Khattab, Fatma I

2015-04-05

Five, accurate, precise, and sensitive univariate and multivariate spectrophotometric methods were developed for the simultaneous determination of a ternary mixture containing Trimethoprim (TMP), Sulphamethoxazole (SMZ) and Oxytetracycline (OTC) in waste water samples collected from different cites either production wastewater or livestock wastewater after their solid phase extraction using OASIS HLB cartridges. In univariate methods OTC was determined at its λmax 355.7 nm (0D), while (TMP) and (SMZ) were determined by three different univariate methods. Method (A) is based on successive spectrophotometric resolution technique (SSRT). The technique starts with the ratio subtraction method followed by ratio difference method for determination of TMP and SMZ. Method (B) is successive derivative ratio technique (SDR). Method (C) is mean centering of the ratio spectra (MCR). The developed multivariate methods are principle component regression (PCR) and partial least squares (PLS). The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures containing different ratios of the three drugs. The obtained results are statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision at p=0.05. Copyright © 2015 Elsevier B.V. All rights reserved.

Indirect spectrophotometric determination of arbutin, whitening agent through oxidation by periodate and complexation with ferric chloride

NASA Astrophysics Data System (ADS)

Barsoom, B. N.; Abdelsamad, A. M. E.; Adib, N. M.

2006-07-01

A simple and accurate spectrophotometric method for the determination of arbutin (glycosylated hydroquinone) is described. It is based on the oxidation of arbutin by periodate in presence of iodate. Excess periodate causes liberation of iodine at pH 8.0. The unreacted periodate is determined by measurement of the liberated iodine spectrophotometrically in the wavelength range (300-500 nm). A calibration curve was constructed for more accurate results and the correlation coefficient of linear regression analysis was -0.9778. The precision of this method was better than 6.17% R.S.D. ( n = 3). Regression analysis of Bear-Lambert plot shows good correlation in the concentration range 25-125 ug/ml. The identification limit was determined to be 25 ug/ml a detailed study of the reaction conditions was carried out, including effect of changing pH, time, temperature and volume of periodate. Analyzing pure and authentic samples containing arbutin tested the validity of the proposed method which has an average percent recovery of 100.86%. An alternative method is also proposed which involves a complexation reaction between arbutin and ferric chloride solution. The produced complex which is yellowish-green in color was determined spectophotometrically.

Pneumatic testing in 45-degree-inclined boreholes in ash-flow tuff near Superior, Arizona

USGS Publications Warehouse

LeCain, G.D.

1995-01-01

Matrix permeability values determined by single-hole pneumatic testing in nonfractured ash-flow tuff ranged from 5.1 to 20.3 * 1046 m2 (meters squared), depending on the gas-injection rate and analysis method used. Results from the single-hole tests showed several significant correlations between permeability and injection rate and between permeability and test order. Fracture permeability values determined by cross-hole pneumatic testing in fractured ash-flow tuff ranged from 0.81 to 3.49 * 1044 m2, depending on injection rate and analysis method used. Results from the cross-hole tests monitor intervals showed no significant correlation between permeability and injection rate; however, results from the injection interval showed a significant correlation between injection rate and permeability. Porosity estimates from the 'cross-hole testing range from 0.8 to 2.0 percent. The maximum temperature change associated with the pneumatic testing was 1.2'(2 measured in the injection interval during cross-hole testing. The maximum temperature change in the guard and monitor intervals was O.Ip C. The maximum error introduced into the permeability values due to temperature fluctuations is approximately 4 percent. Data from temperature monitoring in the borehole indicated a positive correlation between the temperature decrease in the injection interval during recovery testing and the gas-injection rate. The thermocouple psychrometers indicated that water vapor was condensing in the boreholes during testing. The psychrometers in the guard and monitor intervals detected the drier injected gas as an increase in the dry bulb reading. The relative humidity in the test intervals was always higher than the upper measurement limit of the psychrometers. Although the installation of the packer system may have altered the water balance of the borehole, the gas-injection testing resulted in minimal or no changes in the borehole relative humidity.

Evaluation of Flow-Injection Tandem Mass Spectrometry for Rapid and High-Throughput Quantitative Determination of B-Vitamins in Nutritional Supplements

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

Bhandari, Deepak; Van Berkel, Gary J

2012-01-01

The use of flow-injection electrospray ionization tandem mass spectrometry for rapid and high-throughput mass spectral analysis of selected B-vitamins, viz. B1, B2, B3, B5, and B6, in nutritional formulations was demonstrated. A simple and rapid (~5 min) in-tube sample preparation was performed by adding extraction solvent to a powdered sample aliquot followed by agitation, centrifugation, and filtration to recover an extract for analysis. Automated flow injection introduced 1 L of the extracts directly into the mass spectrometer ion source without chromatographic separation. Sample-to-sample analysis time was 60 s representing significant improvement over conventional liquid chromatography approaches which typically require 25-45more » min, and often require more significant sample preparation procedures. Quantitative capabilities of the flow-injection analysis were tested using the method of standard additions and NIST standard reference material (SRM 3280) multivitamin/multielement tablets. The quantity determined for each B-vitamin in SRM 3280 was within the statistical range provided for the respective certified values. The same sample preparation and analysis approach was also applied to two different commercial vitamin supplement tablets and proved to be successful in the quantification of the selected B-vitamins as evidenced by an agreement with the labels values and the results obtained using isotope dilution liquid chromatography/mass spectrometry.« less

Feasibility of diffuse reflectance infrared Fourier spectroscopy (DRIFTS) to quantify iron-cyanide (Fe-CN) complexes in soil

NASA Astrophysics Data System (ADS)

Sut-Lohmann, Magdalena; Raab, Thomas

2017-04-01

Contaminated sites create a significant risk to human health, by poisoning drinking water, soil, air and as a consequence food. Continuous release of persistent iron-cyanide (Fe-CN) complexes from various industrial sources poses a high hazard to the environment and indicates the necessity to analyze considerable amount of samples. At the present time quantitative determination of Fe-CN concentration in soil usually requires a time consuming two step process: digestion of the sample (e.g., micro distillation system) and its analytical detection performed, e.g., by automated spectrophotometrical flow injection analysis (FIA). In order to determine the feasibility of diffuse reflectance infrared Fourier spectroscopy (DRIFTS) to quantify the Fe-CN complexes in soil matrix, 42 soil samples were collected (8 to 12.520 mg kg-1CN) indicating single symmetrical CN band in the range 2092 - 2084 cm-1. Partial least squares (PLS) calibration-validation model revealed IR response to CNtot exceeding 1268 mg kg-1 (limit of detection, LOD). Subsequently, leave-one-out cross-validation (LOO-CV) was performed on soil samples containing low CNtot (<900 mg kg-1), which improved the sensitivity of the model by reducing the LOD to 154 mg kg-1. Finally, the LOO-CV conducted on the samples with CNtot >900 mg kg-1 resulted in LOD equal to 3494 mg kg-1. Our results indicate that spectroscopic data in combination with PLS statistics can efficiently be used to predict Fe-CN concentrations in soil. We conclude that the protocol applied in this study can strongly reduce the time and costs essential for the spatial and vertical screening of the site affected by complexed Fe-CN.

Modeling and flow analysis of pure nylon polymer for injection molding process

NASA Astrophysics Data System (ADS)

Nuruzzaman, D. M.; Kusaseh, N.; Basri, S.; Oumer, A. N.; Hamedon, Z.

2016-02-01

In the production of complex plastic parts, injection molding is one of the most popular industrial processes. This paper addresses the modeling and analysis of the flow process of the nylon (polyamide) polymer for injection molding process. To determine the best molding conditions, a series of simulations are carried out using Autodesk Moldflow Insight software and the processing parameters are adjusted. This mold filling commercial software simulates the cavity filling pattern along with temperature and pressure distributions in the mold cavity. In the modeling, during the plastics flow inside the mold cavity, different flow parameters such as fill time, pressure, temperature, shear rate and warp at different locations in the cavity are analyzed. Overall, this Moldflow is able to perform a relatively sophisticated analysis of the flow process of pure nylon. Thus the prediction of the filling of a mold cavity is very important and it becomes useful before a nylon plastic part to be manufactured.

Simultaneous Determination of Iron, Copper and Cobalt in Food Samples by CCD-diode Array Detection-Flow Injection Analysis with Partial Least Squares Calibration Model

NASA Astrophysics Data System (ADS)

Mi, Jiaping; Li, Yuanqian; Zhou, Xiaoli; Zheng, Bo; Zhou, Ying

2006-01-01

A flow injection-CCD diode array detection spectrophotometry with partial least squares (PLS) program for simultaneous determination of iron, copper and cobalt in food samples has been established. The method was based on the chromogenic reaction of the three metal ions and 2- (5-Bromo-2-pyridylazo)-5-diethylaminophenol, 5-Br-PADAP in acetic acid - sodium acetate buffer solution (pH5) with Triton X-100 and ascorbic acid. The overlapped spectra of the colored complexes were collected by charge-coupled device (CCD) - diode array detector and the multi-wavelength absorbance data was processed using partial least squares (PLS) algorithm. Optimum reaction conditions and parameters of flow injection analysis were investigated. The samples of tea, sesame, laver, millet, cornmeal, mung bean and soybean powder were determined by the proposed method. The average recoveries of spiked samples were 91.80%~100.9% for Iron, 92.50%~108.0% for Copper, 93.00%~110.5% for Cobalt, respectively with relative standard deviation (R.S.D) of 1.1%~12.1%. The sampling rate is 45 samples h-1. The determination results of the food samples were in good agreement between the proposed method and ICP-AES.

Extraction-spectrophotometric determination of tris(2-chloroethyl)amine using phthaleins.

PubMed

Rozsypal, Tomas; Halamek, Emil

2017-06-01

Procedures for the extraction-spectrophotometric determination of tris(2-chloroethyl)amine, an alkylating agent known as a drug as well as a chemical warfare agent (nitrogen mustard HN-3), with 7 acid-base indicators of a triphenylmethane lactone type, phthaleins, were developed. Representatives of phthaleins without an oxygen bridge (thymolphthalein, o-cresolphthalein, naphtholphthalein) and with an oxygen bridge (fluorescein, 2',7'-dichlorofluorescein, eosin B and eosin Y) were used. The methods were based on the formation of ion pair complexes. Chloroform was used as a non-polar solvent for an extraction. The conditions to determine were optimized for the optimal pH of the buffer and the concentration of a phthalein as a reagent. The dependence on the reaction time in a water phase and the stoichiometry of extraction products were studied. The detection limits and the limits of the determination of separate procedures and conditional extraction constants were determined. Comparison with the spectrophotometric method of the group determination of alkyl halides and acyl halides using alkaline ethanol-water solution of thymolphthalein, the so-called T-135 agent, was conducted. While studying the selectivity, the possible interference of bis(2-chloroethyl)sulphide and 3 nitrogen mustards in the proposed procedures were verified. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Development of a Low Cost, Compact, Spectrophotometric pH Sensor

NASA Astrophysics Data System (ADS)

Spaulding, R. S.; Darlington, R. C.; Beck, J. C.; DeGrandpre, M. D.

2016-02-01

Understanding the ecological impacts of oceanic CO2 uptake in the post-industrial world requires high spatial and temporal resolution measurements of inorganic carbon. Most researchers aim for measuring two of the four inorganic carbon parameters (partial pressure of CO2, total alkalinity, total dissolve inorganic carbon, and pH), in order to fully characterize the carbonate system. While this is desirable in many circumstances, in some cases it may be possible to fully characterize the system using pH and salinity, or even to use pH alone as a proxy to the health of calcifying marine organisms. The development of relatively inexpensive spectrophotometric pH sensors compatible with Lagrangian drifters would greatly improve the ability of researchers to characterize the changing oceanic carbonate system. We have designed and tested a novel, miniaturized, submersible, autonomous opto-fluidic device that can be manufactured at a relatively low cost. The flexible design can be deployed independent of or in tandem with GDP style drifters and will enable spectrophotometric pH technology on a host of drifting platforms and buoys. This device uses a dual wavelength light emitting diode (LED) light source, low volume mixer, and an optical flow-cell mounted to the electronic controller board. Laboratory testing shows that this device measures pH with similar accuracy and precision to other spectrophotometric methods such as the SAMI-pH.

Sensitive determination of 2-methoxyestradiol in pharmaceutical preparations and serum samples using flow injection chemiluminescence.

PubMed

Yao, Hanchun; Zhang, Min; Zeng, Wenyuan; Zeng, Xiaoying; Zhang, Zhenzhong

2014-05-01

A rapid and sensitive flow injection chemiluminescence (FI-CL) method is described for the determination of 2-methoxyestradiol (2ME) based on enhancement of the CL intensity from a potassium ferricyanide-calcein system in sodium hydroxide medium. The optimum conditions for the CL emission were investigated. Under optimized conditions, a linear calibration graph was obtained over the range 1.0 × 10(-8) to 1.0 × 10(-6) mol/L (r = 0.998) 2ME with a detection limit (3σ) of 5.4 × 10(-9) mol/L. The relative standard deviation (RSD) for 5.0 × 10(-7) mol/L 2ME was 1.7%. As a preliminary application, the proposed method was successfully applied to the determination of 2ME in injection solutions and serum samples. The possible CL mechanism was also proposed. Copyright © 2013 John Wiley & Sons, Ltd.

VizieR Online Data Catalog: Spectrophotometric Standards near the Pole (Tereshchenko, 1994)

NASA Astrophysics Data System (ADS)

Tereshchenko, V. M.

1997-01-01

Absolute energy distributions for 13 circumpolar (δ>+85deg) stars forming a spectrophotometric version of the North Polar Spectrophotometric Sequence (NPSS) are presented. A-type stars of 5-9mag brightness were studied in the range 3100 to 7750A with resolution of 50A. Observations were made with 0.5-m and 1-m telescopes using Seya-Namioka spectrometers. The relative rms error of results in the region 4000-7000A is 2 to 3%, while at the ends of the studied range it is 3-5%. The primary standard was the circumpolar star HD 221525 (V=5.58, A7IV), and its spectral energy distribution had been determined earlier. (1 data file).

Monitoring glucose, calcium, and magnesium levels in saliva as a non-invasive analysis by sequential injection multi-parametric determination.

PubMed

Machado, Ana; Maneiras, Rui; Bordalo, Adriano A; Mesquita, Raquel B R

2018-08-15

The use of saliva for diagnose and surveillance of systemic illnesses, and general health has been arousing great interest worldwide, emerging as a highly desirable goal in healthcare. The collection is non-invasive, stress-free, inexpensive, and simple representing a major asset. Glucose, calcium, and magnesium concentration are three major parameters evaluated in clinical context due to their essential role in a wide range of biochemical reactions, and consequently many health disorders. In this work, a spectrophotometric sequential injection method is described for the fast screening of glucose, calcium, and magnesium in saliva samples. The glucose determination reaction involves the oxidation of the aldehyde functional group present in glucose with simultaneous reduction of 3,5-dinitrosalicylic acid (DNS) to 3-amino, 5-nitrosalicylic acid under alkaline conditions, followed by the development of colour. The determination of both metals is based on their reaction with cresolphtalein complexone (CPC), and the interference of calcium in the magnesium determination minimized by ethylene glycol-bis[β-aminoethyl ether]-N,N,N',N'-tetraacetic acid (EGTA). The developed multi-parametric method enabled dynamic ranges of 50 - 300 mg/dL for glucose, 0.1 - 2 mg/dL for calcium, and 0.1 - 0.5 mg/dL for magnesium. Determination rates of 28, 60, 52 h -1 were achieved for glucose, calcium, and magnesium, respectively. Less than 300 µL of saliva is required for the multi-parametric determination due to saliva viscosity and inherent necessity of dilution prior to analysis. RSDs lower than 5% were obtained, and the results agreed with those obtained by reference methods, while recovery tests confirmed its accuracy. Copyright © 2018 Elsevier B.V. All rights reserved.

Determination of gallic acid with rhodanine by reverse flow injection analysis using simplex optimization.

PubMed

Phakthong, Wilaiwan; Liawruangrath, Boonsom; Liawruangrath, Saisunee

2014-12-01

A reversed flow injection (rFI) system was designed and constructed for gallic acid determination. Gallic acid was determined based on the formation of chromogen between gallic acid and rhodanine, resulting in a colored product with a λmax at 520 nm. The optimum conditions for determining gallic acid were also investigated. Optimizations of the experimental conditions were carried out based on the so-call univariate method. The conditions obtained were 0.6% (w/v) rhodanine, 70% (v/v) ethanol, 0.9 mol L(-1) NaOH, 2.0 mL min(-1) flow rate, 75 μL injection loop and 600 cm mixing tubing length, respectively. Comparative optimizations of the experimental conditions were also carried out by multivariate or simplex optimization method. The conditions obtained were 1.2% (w/v) rhodanine, 70% (v/v) ethanol, 1.2 mol L(-1) NaOH, flow rate 2.5 mL min(-1), 75 μL injection loop and 600 cm mixing tubing length, respectively. It was found that the optimum conditions obtained by the former optimization method were mostly similar to those obtained by the latter method. The linear relationship between peak height and the concentration of gallic acid was obtained over the range of 0.1-35.0 mg L(-1) with the detection limit 0.081 mg L(-1). The relative standard deviations were found to be in the ranges 0.46-1.96% for 1, 10, 30 mg L(-1) of gallic acid (n=11). The method has the advantages of simplicity extremely high selectivity and high precision. The proposed method was successfully applied to the determination of gallic acid in longan samples without interferent effects from other common phenolic compounds that might be present in the longan samples collected in northern Thailand. Copyright © 2014 Elsevier B.V. All rights reserved.

Development and Validation of Chemometric Spectrophotometric Methods for Simultaneous Determination of Simvastatin and Nicotinic Acid in Binary Combinations.

PubMed

Alahmad, Shoeb; Elfatatry, Hamed M; Mabrouk, Mokhtar M; Hammad, Sherin F; Mansour, Fotouh R

2018-01-01

The development and introduction of combined therapy represent a challenge for analysis due to severe overlapping of their UV spectra in case of spectroscopy or the requirement of a long tedious and high cost separation technique in case of chromatography. Quality control laboratories have to develop and validate suitable analytical procedures in order to assay such multi component preparations. New spectrophotometric methods for the simultaneous determination of simvastatin (SIM) and nicotinic acid (NIA) in binary combinations were developed. These methods are based on chemometric treatment of data, the applied chemometric techniques are multivariate methods including classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). In these techniques, the concentration data matrix were prepared by using the synthetic mixtures containing SIM and NIA dissolved in ethanol. The absorbance data matrix corresponding to the concentration data matrix was obtained by measuring the absorbance at 12 wavelengths in the range 216 - 240 nm at 2 nm intervals in the zero-order. The spectrophotometric procedures do not require any separation step. The accuracy, precision and the linearity ranges of the methods have been determined and validated by analyzing synthetic mixtures containing the studied drugs. Chemometric spectrophotometric methods have been developed in the present study for the simultaneous determination of simvastatin and nicotinic acid in their synthetic binary mixtures and in their mixtures with possible excipients present in tablet dosage form. The validation was performed successfully. The developed methods have been shown to be accurate, linear, precise, and so simple. The developed methods can be used routinely for the determination dosage form. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Development of a split-flow system for high precision variable sample introduction in supercritical fluid chromatography.

PubMed

Sakai, Miho; Hayakawa, Yoshihiro; Funada, Yasuhiro; Ando, Takashi; Fukusaki, Eiichiro; Bamba, Takeshi

2017-09-15

In this study, we propose a novel variable sample injection system based on full-loop injection, named the split-flow sample introduction system, for application in supercritical fluid chromatography (SFC). In this system, the mobile phase is split by the differential pressure between two back pressure regulators (BPRs) after full-loop injection suitable for SFC, and this differential pressure determines the introduction rate. Nine compounds with a wide range of characteristics were introduced with high reproducibility and universality, confirming that a robust variable sample injection system was achieved. We also investigated the control factors of our proposed system. Sample introduction was controlled by the ratio between the column-side pressure drops in splitless and split flow, ΔP columnsideinsplitless and ΔP columnsideinsplit , respectively, where ΔP columnsideinsplitless is related to the mobile phase flow rate and composition and the column resistance. When all other conditions are kept constant, increasing the make-up flow induces an additional pressure drop on the column side of the system, which leads to a reduced column-side flow rate, and hence decreased the amount of sample injected, even when the net pressure drop on the column side remains the same. Thus, sample introduction could be highly controlled at low sample introduction rate, regardless of the introduction conditions. This feature is advantageous because, as a control factor, the solvent in the make-up pump is independent of the column-side pressure drop. Copyright © 2017. Published by Elsevier B.V.

Determination of As, Sb, Bi and Hg in water samples by flow-injection inductively coupled plasma mass spectrometry with an in-situ nebulizer/hydride generator

NASA Astrophysics Data System (ADS)

Chen, Chih-Shyue; Jiang, Shiuh-Jen

1996-12-01

A simple and very inexpensive in-situ nebulizer/hydride generator was used with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of As, Sb, Bi and Hg in water samples. The application of hydride generation ICP-MS alleviated the sensitivity problem of As, Sb, Bi and Hg determinations encountered when the conventional pneumatic nebulizer was used for sample introduction. The sample was introduced by flow injection to minimize the deposition of solids on the sampling orifice. The elements in the sample were reduced to the lower oxidation states with L-cysteine before being injected into the hydride generation system. This method has a detection limit of 0.003, 0.003, 0.017 and 0.17 ng ml -1 for As, Bi, Sb and Hg, respectively. This method was applied to determine As, Sb, Bi and Hg in a CASS-3 nearshore seawater reference sample, a SLRS-2 riverine water reference sample and a tap water collected from National Sun Yat-Sen University. The concentrations of the elements were determined by standard addition method. The precision was better than 20% for most of the determinations.

Effect on Gaseous Film Cooling of Coolant Injection Through Angled Slots and Normal Holes

NASA Technical Reports Server (NTRS)

Papell, S. Stephen

1960-01-01

A study was made to determine the effect of coolant injection angularity on gaseous film-cooling effectiveness. In the correlation of experimental data an effective injection angle was defined by a vector summation of the coolant and mainstream gas flows. The cosine of this angle was used as a parameter to empirically develop a corrective term to qualify a correlating equation presented in Technical Note D-130 that was limited to tangential injection of the coolant. Data were also obtained for coolant injection through rows of holes normal to the test plate. The slot correlating equation was adapted to fit these data by the definition of an effective slot height. An additional corrective term was then determined to correlate these data.

Evolution and transition mechanisms of internal swirling flows with tangential entry

NASA Astrophysics Data System (ADS)

Wang, Yanxing; Wang, Xingjian; Yang, Vigor

2018-01-01

The characteristics and transition mechanisms of different states of swirling flow in a cylindrical chamber have been numerically investigated using the Galerkin finite element method. The effects of the Reynolds number and swirl level were examined, and a unified theory connecting different flow states was established. The development of each flow state is considered as a result of the interaction and competition between basic mechanisms: (1) the centrifugal effect, which drives an axisymmetric central recirculation zone (CRZ); (2) flow instabilities, which develop at the free shear layer and the central solid-body rotating flow; (3) the bouncing and restoring effects of the injected flow, which facilitate the convergence of flow on the centerline and the formation of bubble-type vortex breakdown; and (4) the damping effect of the end-induced flow, which suppresses the development of the instability waves. The results show that the CRZ, together with the free shear layer on its surface, composes the basic structure of swirling flow. The development of instability waves produces a number of discrete vortex cores enclosing the CRZ. The azimuthal wave number is primarily determined by the injection angle. Generally, the wave number is smaller at a higher injection angle, due to the reduction of the perimeter of the free shear layer. At the same time, the increase in the Reynolds number facilitates the growth of the wave number. The end-induced flow tends to reduce the wave number near the head end and causes a change in wave number from the head end to the downstream region. Spiral-type vortex breakdown can be considered as a limiting case at a high injection angle, with a wave number equal to 0 near the head end and equal to 1 downstream. At lower Reynolds numbers, the bouncing and restoring effect of the injected flow generates bubble-type vortex breakdown.

Estimating the gas and dye quantities for modified tracer technique measurements of stream reaeration coefficients

USGS Publications Warehouse

Rathbun, R.E.

1979-01-01

Measuring the reaeration coefficient of a stream with a modified tracer technique has been accomplished by injecting either ethylene or ethylene and propane together and a rhodamine-WT dye solution into the stream. The movement of the tracers through the stream reach after injection is described by a one-dimensional diffusion equation. The peak concentrations of the tracers at the downstream end of the reach depend on the concentrations of the tracers in the stream at the injection site, the longitudinal dispersion coefficient, the mean water velocity, the length of the reach, and the duration of the injection period. The downstream gas concentrations also depend on the gas desorption coefficients of the reach. The concentrations of the tracer gases in the stream at the injection site depend on the flow rates of the gases through the injection diffusers, the efficiency of the gas absorption process, and the stream discharge. The concentration of dye in the stream at the injection site depends on the flow rate of the dye solution, the concentration of the dye solution, and the stream discharge. Equations for estimating the gas flow rates, the quantities of the gases, the dye concentration, and the quantity of dye together with procedures for determining the variables in these equations are presented. (Woodard-USGS)

Analysis of total polyphenols in wines by FIA with highly stable amperometric detection using carbon nanotube-modified electrodes.

PubMed

Arribas, Alberto Sánchez; Martínez-Fernández, Marta; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

2013-02-15

The use of glassy carbon electrodes (GCEs) modified with multi-walled carbon nanotube (CNT) films for the continuous monitoring of polyphenols in flow systems has been examined. The performance of these modified electrodes was evaluated and compared to bare GCE by cyclic voltammetry experiments and by flow injection analysis (FIA) with amperometric detection monitoring the response of gallic, caffeic, ferulic and p-coumaric acids in 0.050 M acetate buffer pH 4.5 containing 100 mM NaCl. The GCE modified with CNT dispersions in polyethyleneimine (PEI) provided lower overpotentials, higher sensitivity and much higher signal stability under a dynamic regime than bare GCEs. These properties allowed the estimation of the total polyphenol content in red and white wines with a remarkable long-term stability in the measurements despite the presence of potential fouling substances in the wine matrix. In addition, the versatility of the electrochemical methodology allowed the selective estimation of the easily oxidisable polyphenol fraction as well as the total polyphenol content just by tuning the detection potential at +0.30 or 0.70 V, respectively. The significance of the electrochemical results was demonstrated through correlation studies with the results obtained with conventional spectrophotometric assays for polyphenols (Folin-Ciocalteu, absorbance at 280 nm index and colour intensity index). Copyright © 2012 Elsevier Ltd. All rights reserved.

Determination of As, Hg and Pb in herbs using slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry.

PubMed

Tai, Chia-Yi; Jiang, Shiuh-Jen; Sahayam, A C

2016-02-01

Analysis of herbs for As, Hg and Pb has been carried out using slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) with flow injection vapor generation. Slurry containing 0.5% m/v herbal powder, 0.1% m/v citric acid and 2% v/v HCl was injected into the VG-ICP-MS system for the determination of As, Hg and Pb that obviate dissolution and mineralization. Standard addition and isotope dilution methods were used for quantifications in selected herbal powders. This method has been validated by the determination of As, Hg and Pb in NIST standard reference materials SRM 1547 Peach Leaves and SRM 1573a Tomato Leaves. The As, Hg and Pb analysis results of the reference materials agreed with the certified values. The precision obtained by the reported procedure was better than 7% for all determinations. The detection limit estimated from standard addition curve was 0.008, 0.003, and 0.007 ng mL(-1) for As, Hg and Pb, respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

HPLC and chemometrics-assisted UV-spectroscopy methods for the simultaneous determination of ambroxol and doxycycline in capsule

NASA Astrophysics Data System (ADS)

Hadad, Ghada M.; El-Gindy, Alaa; Mahmoud, Waleed M. M.

2008-08-01

High-performance liquid chromatography (HPLC) and multivariate spectrophotometric methods are described for the simultaneous determination of ambroxol hydrochloride (AM) and doxycycline (DX) in combined pharmaceutical capsules. The chromatographic separation was achieved on reversed-phase C 18 analytical column with a mobile phase consisting of a mixture of 20 mM potassium dihydrogen phosphate, pH 6-acetonitrile in ratio of (1:1, v/v) and UV detection at 245 nm. Also, the resolution has been accomplished by using numerical spectrophotometric methods as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS-1) applied to the UV spectra of the mixture and graphical spectrophotometric method as first derivative of the ratio spectra ( 1DD) method. Analytical figures of merit (FOM), such as sensitivity, selectivity, analytical sensitivity, limit of quantitation and limit of detection were determined for CLS, PLS-1 and PCR methods. The proposed methods were validated and successfully applied for the analysis of pharmaceutical formulation and laboratory-prepared mixtures containing the two component combination.

Application of Certain π-Acceptors for the Spectrophotometric Determination of Alendronate Sodium in Pharmaceutical Bulk and Dosage Forms.

PubMed

Raza, Asad; Zia-Ul-Haq, Muhammad

2011-01-01

Two simple, fast, and accurate spectrophotometric methods for the determination of alendronate sodium are described. The methods are based on charge-transfer complex formation of the drug with two π-electron acceptors 7,7,7,8-tetracyanoquinodimethane (TCNQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetonitrile and methanol medium. The methods are followed spectrophotometrically by measuring the maximum absorbance at 840 nm and 465 nm, respectively. Under the optimized experimental conditions, the calibration curves showed a linear relationship over the concentration ranges of 2-10 μg mL(-1) and 2-12 μg mL(-1), respectively. The optimal reactions conditions values such as the reagent concentration, heating time, and stability of reaction product were determined. No significant difference was obtained between the results of newly proposed methods and the B.P. Titrimetric procedures. The charge transfer approach using TCNQ and DDQ procedures described in this paper is simple, fast, accurate, precise, and extraction-free.

HPLC and chemometrics-assisted UV-spectroscopy methods for the simultaneous determination of ambroxol and doxycycline in capsule.

PubMed

Hadad, Ghada M; El-Gindy, Alaa; Mahmoud, Waleed M M

2008-08-01

High-performance liquid chromatography (HPLC) and multivariate spectrophotometric methods are described for the simultaneous determination of ambroxol hydrochloride (AM) and doxycycline (DX) in combined pharmaceutical capsules. The chromatographic separation was achieved on reversed-phase C(18) analytical column with a mobile phase consisting of a mixture of 20mM potassium dihydrogen phosphate, pH 6-acetonitrile in ratio of (1:1, v/v) and UV detection at 245 nm. Also, the resolution has been accomplished by using numerical spectrophotometric methods as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS-1) applied to the UV spectra of the mixture and graphical spectrophotometric method as first derivative of the ratio spectra ((1)DD) method. Analytical figures of merit (FOM), such as sensitivity, selectivity, analytical sensitivity, limit of quantitation and limit of detection were determined for CLS, PLS-1 and PCR methods. The proposed methods were validated and successfully applied for the analysis of pharmaceutical formulation and laboratory-prepared mixtures containing the two component combination.

Spectrophotometric study of the charge-transfer and ion-pair complexation of methamphetamine with some acceptors

NASA Astrophysics Data System (ADS)

Shahdousti, Parvin; Aghamohammadi, Mohammad; Alizadeh, Naader

2008-04-01

The charge-transfer (CT) complexes of methamphetamine (MPA) as a n-donor with several acceptors including bromocresolgreen (BCG), bromocresolpurple (BCP), chlorophenolred (CPR), picric acid (PIC), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been studied spectrophotometrically in chloroform solutions in order to obtain some information about their stoichiometry and stability of complexation. The oscillator strengths, transition dipole moments and resonance energy of the complex in the ground state for all complexes have been calculated. Vertical ionization potential of MPA and electron affinity of acceptors were determined by ab initio calculation. The acceptors were also used to utilize a simple and sensitive extraction-spectrophotometric method for the determination of MPA. The method is based on the formation of 1:1 ion-pair association complexes of MPA with BCG, BCP and PIC in chloroform medium. Beer's plots were obeyed in a general concentration range of 0.24-22 μg ml -1 for the investigated drug with different acceptors. The proposed methods were applied successfully for the determination of MAP in pure and abuse drug with good accuracy and precision.

Utility of N-Bromosuccinimide for the Titrimetric and Spectrophotometric Determination of Famotidine in Pharmaceutical Formulations

PubMed Central

Zenita, O.; Basavaiah, K.

2011-01-01

Two titrimetric and two spectrophotometric methods are described for the assay of famotidine (FMT) in tablets using N-bromosuccinimide (NBS). The first titrimetric method is direct in which FMT is titrated directly with NBS in HCl medium using methyl orange as indicator (method A). The remaining three methods are indirect in which the unreacted NBS is determined after the complete reaction between FMT and NBS by iodometric back titration (method B) or by reacting with a fixed amount of either indigo carmine (method C) or neutral red (method D). The method A and method B are applicable over the range of 2–9 mg and 1–7 mg, respectively. In spectrophotometric methods, Beer's law is obeyed over the concentration ranges of 0.75–6.0 μg mL−1 (method C) and 0.3–3.0 μg mL−1 (method D). The applicability of the developed methods was demonstrated by the determination of FMT in pure drug as well as in tablets. PMID:21760785

Spectrophotometric methods for simultaneous determination of betamethasone valerate and fusidic acid in their binary mixture.

PubMed

Lotfy, Hayam Mahmoud; Salem, Hesham; Abdelkawy, Mohammad; Samir, Ahmed

2015-04-05

Five spectrophotometric methods were successfully developed and validated for the determination of betamethasone valerate and fusidic acid in their binary mixture. Those methods are isoabsorptive point method combined with the first derivative (ISO Point--D1) and the recently developed and well established methods namely ratio difference (RD) and constant center coupled with spectrum subtraction (CC) methods, in addition to derivative ratio (1DD) and mean centering of ratio spectra (MCR). New enrichment technique called spectrum addition technique was used instead of traditional spiking technique. The proposed spectrophotometric procedures do not require any separation steps. Accuracy, precision and linearity ranges of the proposed methods were determined and the specificity was assessed by analyzing synthetic mixtures of both drugs. They were applied to their pharmaceutical formulation and the results obtained were statistically compared to that of official methods. The statistical comparison showed that there is no significant difference between the proposed methods and the official ones regarding both accuracy and precision. Copyright © 2015 Elsevier B.V. All rights reserved.

Optimized and Validated Spectrophotometric Methods for the Determination of Enalapril Maleate in Commercial Dosage Forms

PubMed Central

Rahman, Nafisur; Haque, Sk Manirul

2008-01-01

Four simple, rapid and sensitive spectrophotometric methods have been proposed for the determination of enalapril maleate in pharmaceutical formulations. The first method is based on the reaction of carboxylic acid group of enalapril maleate with a mixture of potassium iodate (KIO3) and iodide (KI) to form yellow colored product in aqueous medium at 25 ± 1°C. The reaction is followed spectrophotometrically by measuring the absorbance at 352 nm. The second, third and fourth methods are based on the charge transfer complexation reaction of the drug with p-chloranilic acid (pCA) in 1, 4-dioxan-methanol medium, 2, 3-dichloro 5, 6-dicyano 1, 4-benzoquinone (DDQ) in acetonitrile-1,4 dioxane medium and iodine in acetonitrile-dichloromethane medium. Under optimized experimental conditions, Beer’s law is obeyed in the concentration ranges of 2.5–50, 20–560, 5–75 and 10–200 μg mL−1, respectively. All the methods have been applied to the determination of enalapril maleate in pharmaceutical dosage forms. Results of analysis are validated statistically. PMID:19609388

Application of Certain π-Acceptors for the Spectrophotometric Determination of Alendronate Sodium in Pharmaceutical Bulk and Dosage Forms

PubMed Central

Raza, Asad; Zia-ul-Haq, Muhammad

2011-01-01

Two simple, fast, and accurate spectrophotometric methods for the determination of alendronate sodium are described. The methods are based on charge-transfer complex formation of the drug with two π-electron acceptors 7,7,7,8-tetracyanoquinodimethane (TCNQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetonitrile and methanol medium. The methods are followed spectrophotometrically by measuring the maximum absorbance at 840 nm and 465 nm, respectively. Under the optimized experimental conditions, the calibration curves showed a linear relationship over the concentration ranges of 2–10 μg mL−1 and 2–12 μg mL−1, respectively. The optimal reactions conditions values such as the reagent concentration, heating time, and stability of reaction product were determined. No significant difference was obtained between the results of newly proposed methods and the B.P. Titrimetric procedures. The charge transfer approach using TCNQ and DDQ procedures described in this paper is simple, fast, accurate, precise, and extraction-free. PMID:21760789

Spectrophotometric determination of isopropamide iodide and trifluoperazine hydrochloride in presence of trifluoperazine oxidative degradate.

PubMed

Abbas, Samah S; Zaazaa, Hala E; Abdelkawy, M; Abdelrahman, Maha M

2010-04-01

Four sensitive, selective and precise stability indicating methods for the determination of isopropamide iodide (ISO) and trifluoperazine hydrochloride (TPZ) in their binary mixture and in presence of trifluoperazine oxidative degradate (OXD). Method A is a derivative spectrophotometric one, where ISO was determined by first derivative (D(1)) at 226.4 nm while TPZ was determined by second derivative (D(2)) at 270.2 nm. Method B is the first derivative of the ratio spectra (DD(1)) spectrophotometric method, ISO can be determined by measuring the peak amplitude at 227.4 nm using 5 microg mL(-1) of OXD as a divisor, while TPZ can be determined by measuring the peak amplitude at 249.2 and 261.4 nm using 15 microg mL(-1) of ISO as a divisor. Method C is the isoabsorptive spectrophotometric method. This method allows determination of ISO and TPZ in their binary mixture by measuring total concentration of ISO and TPZ at their isoabsorptive point at lambda(229.8) nm (Aiso1) while TPZ concentration alone can be determined at lambda(max) 311.2 nm, then ISO concentration can be determined by subtraction. On the same basis TPZ can be determined in presence of ISO and OXD, where OXD concentration alone was determined by measuring the peak amplitude at lambda(281.6) and lambda(309.4) nm while total concentration of TPZ and OXD was determined at their isoabsorptive points at (Aiso2 = 270.2 nm), (Aiso3 = 310.6 nm) and (Aiso4 = 331.8 nm) then TPZ concentration was determined by subtraction. Method D is the multivariate calibration techniques [the classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS)], using the information contained in the absorption spectra of ISO, TPZ and OXD mixtures. The selectivity of the proposed methods was checked using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of ISO and TPZ in pharmaceutical dosage form without interference from other dosage form additives and the results were statistically compared with the reported method.

Flow-injection chemiluminescence method for the determination of chloramphenicol based on luminol-sodium periodate order-transform second-chemiluminescence reaction.

PubMed

Zhuang, Ya-Feng; Zhu, Sheng-Nan; Wei, Wei; Li, Jie-Li

2011-01-01

A new chemiluminescence (CL) reaction was observed when chloramphenicol solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate was injected into the reaction mixture of chloramphenicol and alkaline luminol. This reaction is described as an order-transform second-chemiluminescence (OTSCL) reaction. The OTSCL method combined with a flow-injection technique was applied to the determination of chloramphenicol. The optimum conditions for the order-transform second-chemiluminescence emission were investigated. A mechanism for OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristics, the UV-visible spectra and the chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of chloramphenicol over the range 5.0 × 10(-7)-5.0 × 10(-5) mol/L with a correlation coefficient of 0.9969 and a detection limit of 6.0 × 10(-8) mol/L (3σ). The relative standard deviation (RSD) for 11 repeated determinations of 5.0 × 10(-6) mol/L chloramphenicol is 1.7%. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

A comparative study of progressive versus successive spectrophotometric resolution techniques applied for pharmaceutical ternary mixtures.

PubMed

Saleh, Sarah S; Lotfy, Hayam M; Hassan, Nagiba Y; Salem, Hesham

2014-11-11

This work represents a comparative study of a novel progressive spectrophotometric resolution technique namely, amplitude center method (ACM), versus the well-established successive spectrophotometric resolution techniques namely; successive derivative subtraction (SDS); successive derivative of ratio spectra (SDR) and mean centering of ratio spectra (MCR). All the proposed spectrophotometric techniques consist of several consecutive steps utilizing ratio and/or derivative spectra. The novel amplitude center method (ACM) can be used for the determination of ternary mixtures using single divisor where the concentrations of the components are determined through progressive manipulation performed on the same ratio spectrum. Those methods were applied for the analysis of the ternary mixture of chloramphenicol (CHL), dexamethasone sodium phosphate (DXM) and tetryzoline hydrochloride (TZH) in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the official BP methods, showing no significant difference with respect to accuracy and precision. Copyright © 2014 Elsevier B.V. All rights reserved.

Parametric Studies of Flow Separation using Air Injection

NASA Technical Reports Server (NTRS)

Zhang, Wei

2004-01-01

Boundary Layer separation causes the airfoil to stall and therefore imposes dramatic performance degradation on the airfoil. In recent years, flow separation control has been one of the active research areas in the field of aerodynamics due to its promising performance improvements on the lifting device. These active flow separation control techniques include steady and unsteady air injection as well as suction on the airfoil surface etc. This paper will be focusing on the steady and unsteady air injection on the airfoil. Although wind tunnel experiments revealed that the performance improvements on the airfoil using injection techniques, the details of how the key variables such as air injection slot geometry and air injection angle etc impact the effectiveness of flow separation control via air injection has not been studied. A parametric study of both steady and unsteady air injection active flow control will be the main objective for this summer. For steady injection, the key variables include the slot geometry, orientation, spacing, air injection velocity as well as the injection angle. For unsteady injection, the injection frequency will also be investigated. Key metrics such as lift coefficient, drag coefficient, total pressure loss and total injection mass will be used to measure the effectiveness of the control technique. A design of experiments using the Box-Behnken Design is set up in order to determine how each of the variables affects each of the key metrics. Design of experiment is used so that the number of experimental runs will be at minimum and still be able to predict which variables are the key contributors to the responses. The experiments will then be conducted in the 1ft by 1ft wind tunnel according to the design of experiment settings. The data obtained from the experiments will be imported into JMP, statistical software, to generate sets of response surface equations which represent the statistical empirical model for each of the metrics as a function of the key variables. Next, the variables such as the slot geometry can be optimized using the build-in optimizer within JMP. Finally, a wind tunnel testing will be conducted using the optimized slot geometry and other key variables to verify the empirical statistical model. The long term goal for this effort is to assess the impacts of active flow control using air injection at system level as one of the task plan included in the NASAs URETI program with Georgia Institute of Technology.

[Flow injection biamperometric analysis of isoniazid].

PubMed

Zhang, J C; Zhao, C; Song, J F

2001-09-01

To establish a simple, rapid, and accurate electrochemical method for on-line determination of isoniazid. Based on the flow injection biamperometry for irreversible couple system, and using two preanodized platinum electrodes with the applied potential difference of 0 V, the biamperometric method for the determination of isoniazid has been proposed by coupling the catalytic oxidation of isoniazid and the reduction of platinum oxide. Common excipients, inorganic ions, amino acids, vitamins and proteins do not interfere with the determination. Linear relationship between current and the concentration of isoniazid is obtained in the range of 1.0 x 10(-6)-1.0 x 10(-4) mol.L-1 (gamma = 0.998, n = 11). The RSD of 1.8% was obtained for 8 successive determinations of 1.0 x 10(-5) mol.L-1 isoniazid. The proposed method has been shown to be sensitive, selective, rapid (120 samples.h-1), and suitable for the on-line direct determination of isoniazid.

Study optimizes gas lift in Gulf of Suez field

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

Abdel-Waly, A.A.; Darwish, T.A.; Osman Salama, A.

1996-06-24

A study using PVT data combined with fluid and multiphase flow correlations optimized gas lift in the Ramadan field, Nubia C, oil wells, in the Gulf of Suez. Selection of appropriate correlations followed by multiphase flow calculations at various points of injection (POI) were the first steps in the study. After determining the POI for each well from actual pressure and temperature surveys, the study constructed lift gas performance curves for each well. Actual and optimum operating conditions were compared to determine the optimal gas lift. The study indicated a net 2,115 bo/d could be gained from implementing its recommendations.more » The actual net oil gained as a result of this optimization and injected gas reallocation was 2,024 bo/d. The paper discusses the Ramadan field, fluid properties, multiphase flow, production optimization, and results.« less

Determination of thiopental in urine sample with high-performance liquid chromatography using iodine-azide reaction as a postcolumn detection system.

PubMed

Zakrzewski, Robert; Ciesielski, Witold

2005-09-25

The reaction between iodine and azide ions induced by thiopental was utilized as a postcolumn reaction for chromatographic determination of thiopental. The method is based on the separation of thiopental on an Nova-Pak CN HP column with an acetonitrile-aqueous solution of sodium azide as a mobile phase, followed by spectrophotometric measurement of the residual iodine (lambda=350 nm) from the postcolumn iodine-azide reaction induced by thiopental after mixing an iodine solution containing iodide ions with the column effluent containing azide ions and thiopental. Chromatograms obtained for thiopental showed negative peaks as a result of the decrease in background absorbance. The detection limit (defined as S/N=3) was 20 nM (0.4 pmol injected amount) for thiopental. Calibration graphs, plotted as peak area versus concentrations, were linear from 40 nM. The elaborated method was applied to determine thiopental in urine samples. The detection limit (defined as S/N=3) was 0.025 nmol/ml urine. Calibration graphs, plotted as peak area versus concentrations, were linear from 0.05 nmol/ml urine. Authentic urine samples were analyzed, thiopental was determined at nmol/ml urine level.

Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis

PubMed Central

Ojeda, Catalina Bosch; Rojas, Fuensanta Sánchez

2006-01-01

Optical techniques for chemical analysis are well established and sensors based on these techniques are now attracting considerable attention because of their importance in applications such as environmental monitoring, biomedical sensing, and industrial process control. On the other hand, flow injection analysis (FIA) is advisable for the rapid analysis of microliter volume samples and can be interfaced directly to the chemical process. The FIA has become a widespread automatic analytical method for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, and ease of assembling. In this paper, an overview of flow injection determinations by using optical chemical sensors is provided, and instrumentation, sensor design, and applications are discussed. This work summarizes the most relevant manuscripts from 1980 to date referred to analysis using optical chemical sensors in FIA.

Repeatability of in vitro measurements of the ultraviolet protection factor (UPF) by spectrophotometry with automatic sampling.

PubMed

Hoffmann, K; Kesners, P; Bader, A; Avermaete, A; Altmeyer, P; Gambichler, T

2001-11-01

Spectrophotometric assessment (in vitro) is the most established method for determining the ultraviolet protection factor (UPF) of textiles. Apart from stringent requirements for measurement precision, practical methods are required for the routine determination of the UPF. We report here spectrophotometric measurements of textiles using a newly developed autosampler. Measurement precision was evaluated under repeatable conditions. Fifteen different textiles were spectrophotometrically assessed for the determination of the UPF. Sample handling inside the spectrophotometer was performed with a computer-controlled sampling device, capable of loading and unloading a textile sample from a magazine as well as rotating the sample perpendicular to the spectrometer beam. In order to evaluate the repeatability of measurements, one sample of each textile was assessed eight times under the same conditions in the same laboratory. A mean percentage of the standard error of 1% [E(UPF)] was calculated for the UPF measurements. For UPFs >30, a significantly higher E(UPF) was found (r=0.78; P<0.001). E(UV) (3.9%) of ultraviolet A (UVA) transmission differed significantly from E(UV) (1.1 %) of ultraviolet B (UVB) transmission (P<0.05). Though a slight decrease of repeatability was observed for UVA transmission measurements and UPFs higher than 30, our data indicate a high measurement precision under repeatable conditions. In conclusion, spectrophotometric measurements of textiles with the aid of the autosampler presented have been shown to be highly practical, time saving and precise.

Central venous catheter integrity during mechanical power injection of iodinated contrast medium.

PubMed

Macha, Douglas B; Nelson, Rendon C; Howle, Laurens E; Hollingsworth, John W; Schindera, Sebastian T

2009-12-01

To evaluate a widely used nontunneled triple-lumen central venous catheter in order to determine whether the largest of the three lumina (16 gauge) can tolerate high flow rates, such as those required for computed tomographic angiography. Forty-two catheters were tested in vitro, including 10 new and 32 used catheters (median indwelling time, 5 days). Injection pressures were continuously monitored at the site of the 16-gauge central venous catheter hub. Catheters were injected with 300 and 370 mg of iodine per milliliter of iopamidol by using a mechanical injector at increasing flow rates until the catheter failed. The infusion rate, hub pressure, and location were documented for each failure event. The catheter pressures generated during hand injection by five operators were also analyzed. Mean flow rates and pressures at failure were compared by means of two-tailed Student t test, with differences considered significant at P < .05. Injections of iopamidol with 370 mg of iodine per milliliter generate more pressure than injections of iopamidol with 300 mg of iodine per milliliter at the same injection rate. All catheters failed in the tubing external to the patient. The lowest flow rate at which catheter failure occurred was 9 mL/sec. The lowest hub pressure at failure was 262 pounds per square inch gauge (psig) for new and 213 psig for used catheters. Hand injection of iopamidol with 300 mg of iodine per milliliter generated peak hub pressures ranging from 35 to 72 psig, corresponding to flow rates ranging from 2.5 to 5.0 mL/sec. Indwelling use has an effect on catheter material property, but even for used catheters there is a substantial safety margin for power injection with the particular triple-lumen central venous catheter tested in this study, as the manufacturer's recommendation for maximum pressure is 15 psig.

Resolution of overlapped spectra for the determination of ternary mixture using different and modified spectrophotometric methods

NASA Astrophysics Data System (ADS)

Moussa, Bahia Abbas; El-Zaher, Asmaa Ahmed; Mahrouse, Marianne Alphonse; Ahmed, Maha Said

2016-08-01

Four new spectrophotometric methods were developed, applied to resolve the overlapped spectra of a ternary mixture of [aliskiren hemifumarate (ALS)-amlodipine besylate (AM)-hydrochlorothiazide (HCT)] and to determine the three drugs in pure form and in combined dosage form. Method A depends on simultaneous determination of ALS, AM and HCT using principal component regression and partial least squares chemometric methods. In Method B, a modified isosbestic spectrophotometric method was applied for the determination of the total concentration of ALS and HCT by measuring the absorbance at 274.5 nm (isosbestic point, Aiso). On the other hand, the concentration of HCT in ternary mixture with ALS and AM could be calculated without interference using first derivative spectrophotometric method by measuring the amplitude at 279 nm (zero crossing of ALS and zero value of AM). Thus, the content of ALS was calculated by subtraction. Method C, double divisor first derivative ratio spectrophotometry (double divisor 1DD method), was based on that for the determination of one drug, the ratio spectra were obtained by dividing the absorption spectra of its different concentrations by the sum of the absorption spectra of the other two drugs as a double divisor. The first derivative of the obtained ratio spectra were then recorded using the appropriate smoothing factor. The amplitudes at 291 nm, 380 nm and 274.5 nm were selected for the determination of ALS, AM and HCT in their ternary mixture, respectively. Method D was based on mean centering of ratio spectra. The mean centered values at 287, 295.5 and 269 nm were recorded and used for the determination of ALS, AM and HCT, respectively. The developed methods were validated according to ICH guidelines and proved to be accurate, precise and selective. Satisfactory results were obtained by applying the proposed methods to the analysis of pharmaceutical dosage form.

Resolution of overlapped spectra for the determination of ternary mixture using different and modified spectrophotometric methods.

PubMed

Moussa, Bahia Abbas; El-Zaher, Asmaa Ahmed; Mahrouse, Marianne Alphonse; Ahmed, Maha Said

2016-08-05

Four new spectrophotometric methods were developed, applied to resolve the overlapped spectra of a ternary mixture of [aliskiren hemifumarate (ALS)-amlodipine besylate (AM)-hydrochlorothiazide (HCT)] and to determine the three drugs in pure form and in combined dosage form. Method A depends on simultaneous determination of ALS, AM and HCT using principal component regression and partial least squares chemometric methods. In Method B, a modified isosbestic spectrophotometric method was applied for the determination of the total concentration of ALS and HCT by measuring the absorbance at 274.5nm (isosbestic point, Aiso). On the other hand, the concentration of HCT in ternary mixture with ALS and AM could be calculated without interference using first derivative spectrophotometric method by measuring the amplitude at 279nm (zero crossing of ALS and zero value of AM). Thus, the content of ALS was calculated by subtraction. Method C, double divisor first derivative ratio spectrophotometry (double divisor (1)DD method), was based on that for the determination of one drug, the ratio spectra were obtained by dividing the absorption spectra of its different concentrations by the sum of the absorption spectra of the other two drugs as a double divisor. The first derivative of the obtained ratio spectra were then recorded using the appropriate smoothing factor. The amplitudes at 291nm, 380nm and 274.5nm were selected for the determination of ALS, AM and HCT in their ternary mixture, respectively. Method D was based on mean centering of ratio spectra. The mean centered values at 287, 295.5 and 269nm were recorded and used for the determination of ALS, AM and HCT, respectively. The developed methods were validated according to ICH guidelines and proved to be accurate, precise and selective. Satisfactory results were obtained by applying the proposed methods to the analysis of pharmaceutical dosage form. Copyright © 2016. Published by Elsevier B.V.

Highly sensitive catalytic spectrophotometric determination of ruthenium

NASA Astrophysics Data System (ADS)

Naik, Radhey M.; Srivastava, Abhishek; Prasad, Surendra

2008-01-01

A new and highly sensitive catalytic kinetic method (CKM) for the determination of ruthenium(III) has been established based on its catalytic effect on the oxidation of L-phenylalanine ( L-Pheala) by KMnO 4 in highly alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance at 526 nm. The proposed CKM is based on the fixed time procedure under optimum reaction conditions. It relies on the linear relationship where the change in the absorbance (Δ At) versus added Ru(III) amounts in the range of 0.101-2.526 ng ml -1 is plotted. Under the optimum conditions, the sensitivity of the proposed method, i.e. the limit of detection corresponding to 5 min is 0.08 ng ml -1, and decreases with increased time of analysis. The method is featured with good accuracy and reproducibility for ruthenium(III) determination. The ruthenium(III) has also been determined in presence of several interfering and non-interfering cations, anions and polyaminocarboxylates. No foreign ions interfered in the determination ruthenium(III) up to 20-fold higher concentration of foreign ions. In addition to standard solutions analysis, this method was successfully applied for the quantitative determination of ruthenium(III) in drinking water samples. The method is highly sensitive, selective and very stable. A review of recently published catalytic spectrophotometric methods for the determination of ruthenium(III) has also been presented for comparison.

Tentative test method for nitrogen oxides (combined) content in the atmosphere by the Griess--Saltzman reaction

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

Not Available

1977-01-01

A spectrophotometric method is described for the determination of the combined NO/sub 2/ and NO in the atmosphere. The NO is quantitatively converted to NO/sub 2/ by a chromic acid oxidizer, and this resulting NO/sub 2/ plus the NO/sub 2/ already present in the air sample are absorbed in an azo-dye forming reagent. Within 15 min a red-violet color is produced which is measured spectrophotometrically at 550 nm. The method is applicable to the determination of 0.002 to 5 ppM.

Development of normalized spectra manipulating spectrophotometric methods for simultaneous determination of Dimenhydrinate and Cinnarizine binary mixture.

PubMed

Lamie, Nesrine T; Yehia, Ali M

2015-01-01

Simultaneous determination of Dimenhydrinate (DIM) and Cinnarizine (CIN) binary mixture with simple procedures were applied. Three ratio manipulating spectrophotometric methods were proposed. Normalized spectrum was utilized as a divisor for simultaneous determination of both drugs with minimum manipulation steps. The proposed methods were simultaneous constant center (SCC), simultaneous derivative ratio spectrophotometry (S(1)DD) and ratio H-point standard addition method (RHPSAM). Peak amplitudes at isoabsorptive point in ratio spectra were measured for determination of total concentrations of DIM and CIN. For subsequent determination of DIM concentration, difference between peak amplitudes at 250 nm and 267 nm were used in SCC. While the peak amplitude at 275 nm of the first derivative ratio spectra were used in S(1)DD; then subtraction of DIM concentration from the total one provided the CIN concentration. The last RHPSAM was a dual wavelength method in which two calibrations were plotted at 220 nm and 230 nm. The coordinates of intersection point between the two calibration lines were corresponding to DIM and CIN concentrations. The proposed methods were successfully applied for combined dosage form analysis, Moreover statistical comparison between the proposed and reported spectrophotometric methods was applied. Copyright © 2015 Elsevier B.V. All rights reserved.

Coefficients of discharge of fuel-injection nozzles for compression-ignition engines

NASA Technical Reports Server (NTRS)

Gelalles, A G

1932-01-01

This report presents the results of an investigation to determine the coefficients of discharge of nozzles with small, round orifices of the size used with high-speed compression-ignition engines. The injection pressures and chamber back pressures employed were comparable to those existing in compression-ignition engines during injection. The construction of the nozzles was varied to determine the effect of the nozzle design on the coefficient. Tests were also made with nozzles assembled in an automatic injection valve, both with a plain and with a helically grooved stem. It was found that a smooth passage before the orifice is requisite for high flow efficiency. A beveled leading edge before the orifice gave a higher coefficient of discharge than a rounded edge. The results with the nozzles assembled in an automatic injection valve having a plain stem duplicated those with the nozzles assembled at the end of a straight tube of constant diameter. Lower coefficients were obtained with the nozzles assembled in an injection valve having a helically grooved stem. When the coefficients of nozzles of any one geometrical shape were plotted against values of corresponding Reynold's numbers for the orifice diameters and rates of flow tested, it was found that experimental points were distributed along a single curve.

Rapid food decomposition by H2O2-H2SO4 for determination of total mercury by flow injection cold vapor atomic absorption spectrometry.

PubMed

Zenebon, Odair; Sakuma, Alice M; Dovidauskas, Sergio; Okada, Isaura A; de, MaioFrancaD; Lichtig, Jaim

2002-01-01

A mixture of 50% H2O2-H2SO4 (3 + 1, v/v) was used for decomposition of food in open vessels at 80 degrees C. The treatment allowed rapid total mercury determination by flow injection cold vapor atomic absorption spectrometry. Cabbage, potatoes, peanuts paste, hazelnuts paste, oats, tomatoes and their derivatives, oysters, shrimps, prawns, shellfish, marine algae, and many kinds of fish were analyzed by the proposed methodology with a limit of quantitation of 0.86 +/- 0.08 microg/L mercury in the final solution. Reference materials tested also gave excellent recovery.

Determination of total mercury in environmental and biological samples by flow injection cold vapour atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Murphy, James; Jones, Phil; Hill, Steve J.

1996-12-01

A simple and accurate method has been developed for the determination of total mercury in environmental and biological samples. The method utilises an off-line microwave digestion stage followed by analysis using a flow injection system with detection by cold vapour atomic absorption spectrometry. The method has been validated using two certified reference materials (DORM-1 dogfish and MESS-2 estuarine sediment) and the results agreed well with the certified values. A detection limit of 0.2 ng g -1 Hg was obtained and no significant interference was observed. The method was finally applied to the determination of mercury in river sediments and canned tuna fish, and gave results in the range 0.1-3.0 mg kg -1.

Simple flow injection colorimetric system for determination of paraquat in natural water.

PubMed

Chuntib, Prakit; Jakmunee, Jaroon

2015-11-01

A simple and low cost flow injection colorimetric system has been developed for determination of paraquat in natural water. The developed method is based on the reduction of paraquat by using sodium dithionite as a reducing agent in an alkaline medium to produce a blue free radical ion that can be detected by a simple light emitting diode-light dependent resistor (LED-LDR) colorimeter. The standard or sample solution was injected via a set of 3-way solenoid valves into a water carrier stream and flowed to merge with reagent to generate a colored product which is proportional to the concentration of paraquat ion in the solution. Under the optimum condition of the system, i.e., mixing coil length 30 cm, flow rate 2.0 mL min(-1), sample volume 100 μL, concentrations of dithionite 0.1% (w/v) and sodium hydroxide 0.06 mol L(-1), a linear calibration graph in the range of 0.2-10.0 mg L(-1) with a correlation coefficient of 0.9996, and a limit of detection of 0.15 mg L(-1) were achieved. Relative standard deviation for 9 replicate injections of 1 mg L(-1) paraquat is 3.7%. A sample throughput of 40 injections h(-1) was achieved. The limit of detection can be improved by off-line preconcentration of paraquat employing a column packed with Dowex 50WX8-100 (H) cation exchange resin and eluted with 10% (w/v) ammonium chloride in ammonium buffer solution pH 10. The eluting solution was then injected into the FI system for paraquat determination. The proposed system did not suffer from interferences of some possible ions in natural water and other herbicides. Recoveries obtained by spiking 0.5 and 5.0 mg L(-1) paraquat standard into water samples were in the range of 104-110% and 101-105%, respectively. The developed system can be conveniently applied for screening of paraquat contaminated in natural water. Copyright © 2015 Elsevier B.V. All rights reserved.

Spectrophotometric Method for the Determination of Two Coformulated Drugs with Highly Different Concentrations. Application on Vildagliptin and Metformin Hydrochloride

NASA Astrophysics Data System (ADS)

Zaazaa, H. E.; Elzanfaly, E. S.; Soudi, A. T.; Salem, M. Y.

2016-03-01

A new smart simple validated spectrophotometric method was developed for the determination of two drugs one of which is in a very low concentration compared to the other. The method is based on spiking and dilution then simple mathematical manipulation of the absorbance spectra. This method was applied for the determination of a binary mixture of vildagliptin and metformin hydrochloride in the ratio 50:850 in laboratory prepared mixtures containing both drugs in this ratio and in pharmaceutical dosage form with good recoveries. The developed method was validated according to ICH guidelines and can be used for routine quality control testing.

Indirect spectrophotometric determination of traces of bromide in water

USGS Publications Warehouse

Fishman, M. J.; Skougstad, M.W.

1963-01-01

A rapid, accurate, and sensitive indirect spectrophotometric method for the determination of bromide in natural waters is based on the catalytic effect of bromide on the oxidation of iodine to iodate by potassium permanganate in sulfuric acid solution. The method is applicable to concentrations ranging from 1 to 100 ??g. of bromide per liter, but may be modified to extend the concentration range. Most ions commonly occurring in water do not interfere. The standard deviation is 2.9 at bromide concentrations of 100 ??g. per liter and less at lower concentrations. The determination of bromide in samples containing known added amounts gave values ranging from 99 to 105% of the concentration calculated to be present.

Characteristics of trapping various organophosphorus pesticides with a ferritin reactor of shark liver (Sphyrna zygaena).

PubMed

Huang, He-Qing; Xiao, Zhi-Qun; Lin, Qing-Mei; Chen, Ping

2005-03-15

A reactor is composed of liver ferritin of Sphyrna zygaena (SZLF) and an oscillating bag. A reactive procedure for trapping various organphosphorus pesticides (OPs) with the SZLF reactor in the flowing water is described in detail, showing the maximal trapping numbers of 28 +/-1.0 dichlorovos/SZLF, 42 +/- 1.0 dimethoate/SZLF, and 55 +/- 1.0 methamido-phos/SZLF determined by a improved spectrophotometric method in 12 h. In addition, it is found that the OP numbers trapped by the reactor increase along with the incubation time and its concentration increment in the flowing water (or seawater), respectively. This trapping capacity is considered to depend on the composition of amino acids on the surface of the ferritin shell interior rather than the available volume within the shell. A novel pathway for trapping various OPs with the ferritin is suggested in reference to unstable characteristics of the protein subunits. We claim that the ferritin reactor will be employed to monitor the contamination level of various OPs in the flowing water continuously.

Programmable electrochemical flow system for high throughput determination of total antioxidant capacity.

PubMed

Veenuttranon, Kornautchaya; Nguyen, Loc Thai

2018-08-15

The aim of this work was to develop a programmable flow system for rapid assessment of total antioxidant capacity (TAC). Novel features of the prototype include a single pressure-driven source, versatile manipulation of fluid flows, ability to adapt to different TAC assays, and compatibility with microfluidic design. Antioxidant activity was determined by electrochemical measurement of residual 2,2-diphenyl-2-picrylhydrayl hydrate (DPPH•) free radicals in the solution. The overall performance of the device was validated by the spectrophotometric method. The results indicated that dosing of reagents and samples could be controlled by pressure (R 2 = 0.992) and time (R 2 = 0.999) with high accuracy, and the mixing uniformity of the device was equivalent to that of the batch mixing (R 2 = 0.994). TAC assays of a standard antioxidant, ascorbic acid, as well as selected samples such as orange and pomegranate juices, white wine, and green tea by the device were comparable to traditional measurement techniques. Due to the short incubation time, the approach may be more suitable for fast, rather than slow reacting antioxidant compounds. The developed system could be used for rapid TAC screening of food and biological samples. Copyright © 2018 Elsevier B.V. All rights reserved.

A novel approach for determination of free fatty acids in vegetable oils by a flow injection system with manual injection.

PubMed

Ayyildiz, H Filiz; Kara, Huseyin; Sherazi, S T H

2011-12-01

A non-aqueous flow injection method for determining free fatty acid (FFA) content in corn and sunflower oil samples was developed. A single-line manifold system was built by modification of an HPLC for flow injection analysis (FIA). Without pre-treatment, oil samples were injected into a n-propanol solution containing KOH and phenolphthalein (PHP). The main parameters, such as flow rate of carrier phase, length, geometry, inner diameters of the coils and reagent concentration were all optimized. The proposed FIA method was validated for precision, accuracy, linear region, limit of detection (LOD) and limit of quantification (LOQ). The intra- and inter-day measurements of the precision of the method were found to be within the limits of acceptance criteria (RSD < 1%), and were rugged when the method was performed by a different analyst. The linear concentration range was calculated as 0.09-1.50 and 0.07-1.40 FFA% for corn and sunflower oils, correspondingly. The LOD and LOQ were found to be 7.53 × 10(-4)-2.28 × 10(-3) oleic acid % and 7.11 × 10(-4)-2.23 × 10(-3) oleic acid % for corn and sunflower oils, respectively. The results were compared with those obtained by the AOCS (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at a 95% confidence level. The proposed method is suitable for quality control of routine applications due to its simplicity, high sample throughput, and economy of solvents and sample, offering considerable promise as a low cost analytical system that needs minimum human intervention over long periods of time.

Comparison of methods for measuring cholinesterase inhibition by carbamates

PubMed Central

Wilhelm, K.; Vandekar, M.; Reiner, E.

1973-01-01

The Acholest and tintometric methods are used widely for measuring blood cholinesterase activity after exposure to organophosphorus compounds. However, if applied for measuring blood cholinesterase activity in persons exposed to carbamates, the accuracy of the methods requires verification since carbamylated cholinesterases are unstable. The spectrophotometric method was used as a reference method and the two field methods were employed under controlled conditions. Human blood cholinesterases were inhibited in vitro by four methylcarbamates that are used as insecticides. When plasma cholinesterase activity was measured by the Acholest and spectrophotometric methods, no difference was found. The enzyme activity in whole blood determined by the tintometric method was ≤ 11% higher than when the same sample was measured by the spectrophotometric method. PMID:4541147

Micellar modified spectrophotometric determination of nitrobenzenes based upon reduction with tin(II), diazotisation and coupling with the Bratton-Marshall reagent.

PubMed

Escrig-Tena, I; Alvarez Rodríguez, L; Esteve-Romero, J; García-Alvarez-Coque, M C

1998-09-01

Nitrobenzenes, such as the antibiotic chloramphenicol, the vasodilator nicardipine, and the herbicides dinitramin, dinobuton, fenitrothion, methylparathion, oxyfluorfen, parathion, pendimethalin, quintozene, and trifluralin, were determined by using a spectrophotometric method in the visible region (540 nm). The method was based on the reduction of the nitrobenzenes to arylamines with tin(II) chloride, diazotisation of the arylamines and coupling of the diazonium ions with the Bratton-Marshall reagent. The two latter reactions were performed in a micellar medium of sodium dodecyl sulphate. The linear calibration range was 2x10(-6) to 7x10(-5) M (r>0.999), with limits of detection in the 10(-7) M level, which is 2-6 fold lower with respect to the corresponding spectrophotometric procedure in non-micellar medium. The procedure was applied to the analysis of the compounds in commercial preparations (pharmaceuticals and herbicide formulations) and in water samples, with good recoveries.

Liquid chromatographic and ultraviolet spectrophotometric determination of bevantolol and hydrochlorothiazide in feeds.

PubMed

Spurlock, C H; Schneider, H G

1984-01-01

Separate assay methods have been developed for the 2 components of an 80 + 20 drug blend of bevantolol and hydrochlorothiazide (HCT) in admixtures with animal feed. Drug/diet admixtures are extracted with methanol for reverse phase ion-pair liquid chromatographic (LC) assay of bevantolol, and with acetonitrile for ultraviolet spectrophotometric assay of HCT. Bevantolol, a cardioselective beta blocker, is separated from soluble feed components with an RP-18 column, using methanol-water-acetic acid (60 + 40 + 1) containing 0. 005M octane-sulfonic acid, sodium salt, as ion-pairing reagent. HCT is determined spectrophotometrically in acetonitrile extracts, using a suitable blank extract as reference. Average recovery of HCT from an admixture of 0.5 mg blend/g diet is 94.5% +/- 4.3 RSD and at 2.0 mg/g, 101.5% +/- 3.5 RSD. Bevantolol recovery from the same admixtures is 101.8% +/- 2.7 RSD and 99.0% +/- 3.5 RSD, respectively, using the method as described.

Flow injection chemiluminescence determination of naphazoline hydrochloride in pharmaceuticals.

PubMed

Iranifam, Mortaza; Sorouraddin, Mohammad H

2014-02-01

A simple and sensitive flow injection chemiluminescence (FI-CL) method was developed for the determination of naphazoline hydrochloride (NPZ). The method is based on the enhancing effect of NPZ on the weak CL signal from the reaction of KIO4 with H2 O2 . Experimental parameters that affected the CL signal, including the pH of the KIO4 solution, concentrations of KIO4 , H2 O2 and disodium-EDTA and flow rate were optimized. Under the optimum conditions, the increment of CL intensity was linearly proportional to the concentration of NPZ in the range 5.0 × 10(-6) to 70 × 10(-6) mol/L. The detection limit was 1.0 × 10(-6) mol/L and the relative standard deviation for 50 × 10(-6) mol/L NPZ solution was 2.8% (n = 11). In addition, a high throughput of 120 samples/h was achieved. The utility of this method was demonstrated by determining NPZ in pharmaceuticals. Copyright © 2013 John Wiley & Sons, Ltd.

A novel flow injection chemiluminescence method for automated and miniaturized determination of phenols in smoked food samples.

PubMed

Vakh, Christina; Evdokimova, Ekaterina; Pochivalov, Aleksei; Moskvin, Leonid; Bulatov, Andrey

2017-12-15

An easily performed fully automated and miniaturized flow injection chemiluminescence (CL) method for determination of phenols in smoked food samples has been proposed. This method includes the ultrasound assisted solid-liquid extraction coupled with gas-diffusion separation of phenols from smoked food sample and analytes absorption into a NaOH solution in a specially designed gas-diffusion cell. The flow system was designed to focus on automation and miniaturization with minimal sample and reagent consumption by inexpensive instrumentation. The luminol - N-bromosuccinimide system in an alkaline medium was used for the CL determination of phenols. The limit of detection of the proposed procedure was 3·10 -8 ·molL -1 (0.01mgkg -1 ) in terms of phenol. The presented method demonstrated to be a good tool for easy, rapid and cost-effective point-of-need screening phenols in smoked food samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of L-phenylalanine on-line based on molecularly imprinted polymeric microspheres and flow injection chemiluminescence

NASA Astrophysics Data System (ADS)

Qiu, Huamin; Xi, Yulei; Lu, Fuguang; Fan, Lulu; Luo, Chuannan

2012-02-01

A novel molecular imprinting-chemiluminescence (MIP-CL) sensor for the determination of L-phenylalanine (Phe) using molecularly imprinted polymer (MIP) as recognition element is reported. The Phe-MIP was synthesized using acrylamide (AM) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker, 2,2-azobisisobutyronitrile (AIBN) as initiator and the polymers' properties were characterized. Then the synthesized MIP was employed as recognition element by packing into flow cell to establish a novel flow injection CL sensor. The CL intensity responded linearly to the concentration of Phe in the range 1.3 × 10 -6 to 5.44 × 10 -4 mol/L with a detection limit of 6.23 × 10 -7 mol/L (3 σ), which is lower than that of conventional methods. The sensor is reusable and has a great improvement in sensitivity and selectivity for CL analysis. As a result, the new MIP-CL sensor had been successfully applied to the determination of Phe in samples.

A microchip-based flow injection-amperometry system with mercaptopropionic acid modified electroless gold microelectrode for the selective determination of dopamine.

PubMed

Wang, Yi; Luo, Jie; Chen, Hengwu; He, Qiaohong; Gan, Nin; Li, Tianhua

2008-09-12

A novel chip-based flow injection analysis (FIA) system has been developed for automatic, rapid and selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The system is composed of a polycarbonate (PC) microfluidic chip with an electrochemical detector (ED), a gravity pump, and an automatic sample loading and injection unit. The selectivity of the ED was improved by modification of the gold working microelectrode, which was fabricated on the PC chip by UV-directed electroless gold plating, with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA). Postplating treatment methods for cleaning the surface of electroless gold microelectrodes were investigated to ensure the formation of high quality SAMs. The effects of detection potential, flow rate, and sampling volume on the performance of the chip-based FIA system were studied. Under optimum conditions, a detection limit of 74 nmol L(-1) for DA was achieved at the sample throughput rate of 180 h(-1). A RSD of 0.9% for peak heights was observed for 19 runs of a 100 micromol L(-1) DA solution. Interference-free determination of DA could be conducted if the concentration ratio of AA-DA was no more than 10.

A novel stopped flow injection-amperometric procedure for the determination of chlorate.

PubMed

Tue-Ngeun, Orawan; Jakmunee, Jaroon; Grudpan, Kate

2005-12-15

A novel stopped flow injection-amperometric (sFI-Amp) procedure for determination of chlorate has been developed. The reaction of chlorate with excess potassium iodide and hydrochloric acid, forming iodine/triiodide that is further electrochemically reduced at a glassy carbon electrode at +200mV versus Ag/AgCl electrode is employed. In order to increase sensitivity without using of too high acid concentration, promoting of the reaction by increasing reaction time and temperature can be carried out. This can be done without increase of dispersion of the product zone by stopping the flow while the injected zone is being in a mixing coil which is immersed in a water bath of 55+/-0.5 degrees C. In a closed system of FIA, a side reaction of oxygen with iodide is also minimized. Under a set of conditions, linear calibration graphs were in the ranges of 1.2x10(-6)-6.0x10(-5)moll(-1)and 6.0x10(-5)-6.0x10(-4)moll(-1). A sample throughput of 25h(-1) was accomplished. Relative standard deviation was 2% (n=21, 1.2x10(-4)moll(-1) chlorate). The proposed sFI-Amp procedure was successfully applied to the determination of chlorate in soil samples from longan plantation area.

Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection

NASA Astrophysics Data System (ADS)

Zmijanovic, V.; Lago, V.; Sellam, M.; Chpoun, A.

2014-01-01

Transverse secondary gas injection into the supersonic flow of an axisymmetric convergent-divergent nozzle is investigated to describe the effects of the fluidic thrust vectoring within the framework of a small satellite launcher. Cold-flow dry-air experiments are performed in a supersonic wind tunnel using two identical supersonic conical nozzles with the different transverse injection port positions. The complex three-dimensional flow field generated by the supersonic cross-flows in these test nozzles was examined. Valuable experimental data were confronted and compared with the results obtained from the numerical simulations. Different nozzle models are numerically simulated under experimental conditions and then further investigated to determine which parameters significantly affect thrust vectoring. Effects which characterize the nozzle and thrust vectoring performances are established. The results indicate that with moderate secondary to primary mass flow rate ratios, ranging around 5 %, it is possible to achieve pertinent vector side forces. It is also revealed that injector positioning and geometry have a strong effect on the shock vector control system and nozzle performances.

A line source tracer test - a better method for assessing high groundwater velocity

NASA Astrophysics Data System (ADS)

Magal, E.; Weisbrod, N.; Yakirevich, A.; Kurtzman, D.; Yechieli, Y.

2009-12-01

A line source injection is suggested as an effective method for assessing groundwater velocities and flow directions in subsurface characterized by high water fluxes. Modifying the common techniques of injecting a tracer into a well was necessary after frequently-used methods of natural and forced gradient tracer tests ended with no reliable information on the local groundwater flow. In a field experiment, tracers were injected into 8-m long line injection system constructed below the water table almost perpendicular to the assumed flow direction. The injection system was divided to four separate segments (each 2 m long) enabling the injection of four different tracers along the line source. An array of five boreholes located in an area of 10x10 m downstream was used for monitoring the tracers' transport. Two dye tracers (Uranine and Na Naphthionate) were injected in a long pulse of several hours into two of the injection pipe segments and two tracers (Rhenium oxide and Gd-DTPA) were instantaneously injected to the other two segments. The tracers were detected 0.7 to 2.3 hours after injection in four of the five observation wells, located 2.3 to 10 m from the injection system, respectively. Groundwater velocities were calculated directly from the tracers' arrival times and by fitting the observed breakthrough curves to simulations with one and two dimensions analytical solutions for conservative tracer transport. The groundwater velocity was determined to be ~100 m/d. The longitudinal dispersivity value, generated from fitting the tracer breakthrough curves, was in a range of 0.2-3m. The groundwater flow direction was derived based on the arrival of the tracers and was found to be consistent with the apparent direction of the hydraulic gradient. The hydraulic conductivity derived from the groundwater velocity was ~1200 m/d, which is in the upper range of gravel sediment.

Online assay of bone specific alkaline phosphatase with a flow injection-bead injection system.

PubMed

Hartwell, Supaporn Kradtap; Somprayoon, Duangporn; Kongtawelert, Prachya; Ongchai, Siriwan; Arppornchayanon, Olarn; Ganranoo, Lucksagoon; Lapanantnoppakhun, Somchai; Grudpan, Kate

2007-09-26

Alkaline phosphatase (ALP) has been used as one of the biomarkers for bone resorption and liver diseases. Normally, total alkaline phosphatase is quantified along with other symptoms to determine the releasing source of the alkaline phosphatase. A semi-automated flow injection-bead injection system was proposed to conveniently and selectively assay bone alkaline phosphatase (BALP) based on its specific binding to wheat germ coated beads. Amount of BALP in serum was determined from the intensity of the yellow product produced from bound BALP on the retained beads and its substrate pNPP. The used beads were discarded and the fresh ones were introduced for the next analysis. The reaction cell was designed to be opened and closed using a computer controlled solenoid valve for a precise incubation time. The performance of the proposed system was evaluated by using it to assay BALP in human serum. The results were compared to those obtained by using a commercial ELISA kit. The system is proposed to be an easy and cost effective system for quantification of BALP as an alternative to batch wise wheat germ specific binding technique.

Spectrophotometric and spectrofluorimetric methods for determination of certain biologically active phenolic drugs in their bulk powders and different pharmaceutical formulations.

PubMed

Omar, Mahmoud A; Badr El-Din, Kalid M; Salem, Hesham; Abdelmageed, Osama H

2018-03-05

Two simple and sensitive spectrophotometric and spectrofluorimetric methods for the determination of terbutaline sulfate, fenoterol hydrobromide, etilefrine hydrochloride, isoxsuprine hydrochloride, ethamsylate, doxycycline hyclate have been developed. Both methods were based on the oxidation of the cited drugs with cerium (IV) in acid medium. The spectrophotometric method was based on measurement of the absorbance difference (ΔA), which represents the excess cerium (IV), at 317nm for each drug. On the other hand, the spectrofluorimetric method was based on measurement of the fluorescent of the produced cerium (III) at emission wavelength 354nm (λ excitation =255nm) for the concentrations studied for each drug. For both methods, the variables affecting the reactions were carefully investigated and the conditions were optimized. Linear relationships were found between either ΔA or the fluorescent of the produced cerium (III) values and the concentration of the studied drugs in a general concentration range of 2.0-24.0μgmL -1 , 20.0-24.0ngmL -1 with good correlation coefficients in the following range 0.9990-0.9999, 0.9990-0.9993 for spectrophotometric and spectrofluorimetric methods respectively. The limits of detection and quantitation of spectrophotometric method were found in general concentration range 0.190-0.787 and 0.634-2.624μgmL -1 respectively. For spectrofluorimetric method, the limits of detection and quantitation were found in general concentration range 4.77-9.52 and 15.91-31.74ngmL -1 respectively. The stoichiometry of the reaction was determined, and the reactions pathways were postulated. The analytical performance of the methods, in terms of accuracy and precision, were statistically validated and the results obtained were satisfactory. The methods have been successfully applied to the determination of the cited drugs in their commercial pharmaceutical formulations. Statistical comparison of the results with the reference methods showed excellent agreement and proved that no significant difference in the accuracy and precision. Copyright © 2017 Elsevier B.V. All rights reserved.

Integration of a Capacitive EIS Sensor into a FIA System for pH and Penicillin Determination

PubMed Central

Rolka, David; Poghossian, Arshak; Schöning, Michael J.

2004-01-01

A field-effect based capacitive EIS (electrolyte-insulator-semiconductor) sensor with a p-Si-SiO2-Ta2O5 structure has been successfully integrated into a commercial FIA (flow-injection analysis) system and system performances have been proven and optimised for pH and penicillin detection. A flow-through cell was designed taking into account the requirement of a variable internal volume (from 12 μl up to 48 μl) as well as an easy replacement of the EIS sensor. FIA parameters (sample volume, flow rate, distance between the injection valve and the EIS sensor) have been optimised in terms of high sensitivity and reproducibility as well as a minimum dispersion of the injected sample zone. An acceptable compromise between different FIA parameters has been found. For the cell design used in this study, best results have been achieved with a flow rate of 1.4 ml/min, distance between the injection valve and the EIS sensor of 6.5 cm, probe volume of 0.75 ml, cell internal volume of 12 μl. A sample throughput of at least 15 samples/h was typically obtained.

Validated stability-indicating spectrophotometric methods for the determination of cefixime trihydrate in the presence of its acid and alkali degradation products.

PubMed

Mostafa, Nadia M; Abdel-Fattah, Laila; Weshahy, Soheir A; Hassan, Nagiba Y; Boltia, Shereen A

2015-01-01

Five simple, accurate, precise, and economical spectrophotometric methods have been developed for the determination of cefixime trihydrate (CFX) in the presence of its acid and alkali degradation products without prior separation. In the first method, second derivative (2D) and first derivative (1D) spectrophotometry was applied to the absorption spectra of CFX and its acid (2D) or alkali (1D) degradation products by measuring the amplitude at 289 and 308 nm, respectively. The second method was a first derivative (1DD) ratio spectrophotometric method where the peak amplitudes were measured at 311 nm in presence of the acid degradation product, and 273 and 306 nm in presence of its alkali degradation product. The third method was ratio subtraction spectrophotometry where the drug is determined at 286 nm in laboratory-prepared mixtures of CFX and its acid or alkali degradation product. The fourth method was based on dual wavelength analysis; two wavelengths were selected at which the absorbances of one component were the same, so wavelengths 209 and 252 nm were used to determine CFX in presence of its acid degradation product and 310 and 321 nm in presence of its alkali degradation product. The fifth method was bivariate spectrophotometric calibration based on four linear regression equations obtained at the wavelengths 231 and 290 nm, and 231 and 285 nm for the binary mixture of CFX with either its acid or alkali degradation product, respectively. The developed methods were successfully applied to the analysis of CFX in laboratory-prepared mixtures and pharmaceutical formulations with good recoveries, and their validation was carried out following the International Conference on Harmonization guidelines. The results obtained were statistically compared with each other and showed no significant difference with respect to accuracy and precision.

Deposition and fine particle production during dynamic flow in a dry powder inhaler: a CFD approach.

PubMed

Milenkovic, J; Alexopoulos, A H; Kiparissides, C

2014-01-30

In this work the dynamic flow as well as the particle motion and deposition in a commercial dry powder inhaler, DPI (i.e., Turbuhaler) is described using computational fluid dynamics, CFD. The dynamic flow model presented here is an extension of a steady flow model previously described in Milenkovic et al. (2013). The model integrates CFD simulations for dynamic flow, an Eulerian-fluid/Lagrangian-particle description of particle motion as well as a particle/wall interaction model providing the sticking efficiency of particles colliding with the DPI walls. The dynamic flow is imposed by a time varying outlet pressure and the particle injections into the DPI are assumed to occur instantaneously and follow a prescribed particle size distribution, PSD. The total particle deposition and the production of fine particles in the DPI are determined for different peak inspiratory flow rates, PIFR, flow increase rates, FIR, and particle injection times. The simulation results for particle deposition are found to agree well with available experimental data for different values of PIFR and FIR. The predicted values of fine particle fraction are in agreement with available experimental results when the mean size of the injected PSD is taken to depend on the PIFR. Copyright © 2013 Elsevier B.V. All rights reserved.

Validated spectrophotometric methods for determination of Alendronate sodium in tablets through nucleophilic aromatic substitution reactions

PubMed Central

2012-01-01

Background Alendronate (ALD) is a member of the bisphosphonate family which is used for the treatment of osteoporosis, bone metastasis, Paget's disease, hypocalcaemia associated with malignancy and other conditions that feature bone fragility. ALD is a non-chromophoric compound so its determination by conventional spectrophotometric methods is not possible. So two derivatization reactions were proposed for determination of ALD through the reaction with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) and 2,4-dinitrofluorobenzene (DNFB) as chromogenic derivatizing reagents. Results Three simple and sensitive spectrophotometric methods are described for the determination of ALD. Method I is based on the reaction of ALD with NBD-Cl. Method II involved heat-catalyzed derivatization of ALD with DNFB, while, Method III is based on micellar-catalyzed reaction of the studied drug with DNFB at room temperature. The reactions products were measured at 472, 378 and 374 nm, for methods I, II and III, respectively. Beer's law was obeyed over the concentration ranges of 1.0-20.0, 4.0-40.0 and 1.5-30.0 μg/mL with lower limits of detection of 0.09, 1.06 and 0.06 μg/mL for Methods I, II and III, respectively. The proposed methods were applied for quantitation of the studied drug in its pure form with mean percentage recoveries of 100.47 ± 1.12, 100.17 ± 1.21 and 99.23 ± 1.26 for Methods I, II and III, respectively. Moreover the proposed methods were successfully applied for determination of ALD in different tablets. Proposals of the reactions pathways have been postulated. Conclusion The proposed spectrophotometric methods provided sensitive, specific and inexpensive analytical procedures for determination of the non-chromophoric drug alendronate either per se or in its tablet dosage forms without interference from common excipients. Graphical abstract PMID:22472190

Validated spectrophotometric methods for determination of Alendronate sodium in tablets through nucleophilic aromatic substitution reactions.

PubMed

Walash, Mohamed I; Metwally, Mohamed E-S; Eid, Manal; El-Shaheny, Rania N

2012-04-02

Alendronate (ALD) is a member of the bisphosphonate family which is used for the treatment of osteoporosis, bone metastasis, Paget's disease, hypocalcaemia associated with malignancy and other conditions that feature bone fragility. ALD is a non-chromophoric compound so its determination by conventional spectrophotometric methods is not possible. So two derivatization reactions were proposed for determination of ALD through the reaction with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) and 2,4-dinitrofluorobenzene (DNFB) as chromogenic derivatizing reagents. Three simple and sensitive spectrophotometric methods are described for the determination of ALD. Method I is based on the reaction of ALD with NBD-Cl. Method II involved heat-catalyzed derivatization of ALD with DNFB, while, Method III is based on micellar-catalyzed reaction of the studied drug with DNFB at room temperature. The reactions products were measured at 472, 378 and 374 nm, for methods I, II and III, respectively. Beer's law was obeyed over the concentration ranges of 1.0-20.0, 4.0-40.0 and 1.5-30.0 μg/mL with lower limits of detection of 0.09, 1.06 and 0.06 μg/mL for Methods I, II and III, respectively. The proposed methods were applied for quantitation of the studied drug in its pure form with mean percentage recoveries of 100.47 ± 1.12, 100.17 ± 1.21 and 99.23 ± 1.26 for Methods I, II and III, respectively. Moreover the proposed methods were successfully applied for determination of ALD in different tablets. Proposals of the reactions pathways have been postulated. The proposed spectrophotometric methods provided sensitive, specific and inexpensive analytical procedures for determination of the non-chromophoric drug alendronate either per se or in its tablet dosage forms without interference from common excipients. GRAPHICAL

Micro-flow injection system for the urinary protein assay.

PubMed

Nishihama, Syouhei; Imabayashi, Hisano; Matoba, Tomoko; Toya, Chika; Watanabe, Kosuke; Yoshizuka, Kazuharu

2008-02-15

A urinary protein assay has been investigated, employing a micro-flow injection analysis (muFIA) combined with an adsorptive separation of protein from analyte. The adsorptive separation part of protein in the artificial urine with ceramic hydroxyapatite is integrated on the muFIA chip, since the interference of other components coexisting in urine occurs in the conventional FIA system. The typical FI peak can be obtained following the adsorption-elution process of the protein prior to the detection, and the protein concentration in artificial urine can be quantitatively determined.

Flow-injection system for automated dissolution testing of isoniazid tablets with chemiluminescence detection.

PubMed

Li, B; Zhang, Z; Liu, W

2001-05-30

A simple and sensitive flow-injection chemiluminescence (CL) system for automated dissolution testing is described and evaluated for monitoring of dissolution profiles of isoniazid tablets. The undissolved suspended particles in the dissolved solution were eliminated via on-line filter. The novel CL system of KIO(4)-isoniazid was also investigated. The sampling frequency of the system was 120 h(-1). The dissolution profiles of isoniazid fast-release tablets from three sources were determined, which demonstrates the stability, great sensitivity, large dynamic measuring range and robustness of the system.

Rapid determination of isoamyl nitrite in pharmaceutical preparations by flow injection analysis with on-line UV irradiation and luminol chemiluminescence detection.

PubMed

Kishikawa, Naoya; Kondo, Naoko; Amponsaa-Karikari, Abena; Kodamatani, Hitoshi; Ohyama, Kaname; Nakashima, Kenichiro; Yamazaki, Shigeo; Kuroda, Naotaka

2014-02-01

Isoamyl nitrite is used as a therapeutic reagent for cardiac angina and as an antidote for cyanide poisoning, but it is abused because of its euphoric properties. Therefore, a method to determine isoamyl nitrite is required in many fields, including pharmaceutical and forensic studies. In this study, a simple, rapid and sensitive method for the determination of isoamyl nitrite was developed using a flow injection analysis system equipped with a chemiluminescence detector and on-line photoreactor. This method is based on on-line ultraviolet irradiation of isoamyl nitrite and subsequent luminol chemiluminescence detection without the addition of an oxidant. A linear standard curve was obtained up to 1.0 μM of isoamyl nitrite with a detection limit (blank + 3SD) of 0.03 μM. The method was successfully applied to determine isoamyl nitrite content in pharmaceutical preparations. Copyright © 2013 John Wiley & Sons, Ltd.

Injection and swirl driven flowfields in solid and liquid rocket motors

NASA Astrophysics Data System (ADS)

Vyas, Anand B.

In this work, we seek approximate analytical solutions to describe the bulk flow motion in certain types of solid and liquid rocket motors. In the case of an idealized solid rocket motor, a cylindrical double base propellant grain with steady regression rate is considered. The well known inviscid profile determined by Culick is extended here to include the effects of viscosity and steady grain regression. The approximate analytical solution for the cold flow is obtained from similarity principles, perturbation methods and the method of variation of parameters. The velocity, vorticity, pressure gradient and the shear stress distributions are determined and interpreted for different rates of wall regression and injection Reynolds number. The liquid propellant rocket engine considered here is based on a novel design that gives rise to a cyclonic flow. The resulting bidirectional motion is triggered by the tangential injection of an oxidizer just upstream of the chamber nozzle. Velocity, vorticity and pressure gradient distributions are determined for the bulk gas dynamics using a non-reactive inviscid model. Viscous corrections are then incorporated to explain the formation of a forced vortex near the core. Our results compare favorably with numerical simulations and experimental measurements obtained by other researchers. They also indicate that the bidirectional vortex in a cylindrical chamber is a physical solution of the Euler equations. In closing, we investigate the possibility of multi-directional flow behavior as predicted by Euler's equation and as reported recently in laboratory experiments.

Application of direct-injection detector integrated with the multi-pumping flow system to chemiluminescence determination of the total polyphenol index.

PubMed

Nalewajko-Sieliwoniuk, Edyta; Iwanowicz, Magdalena; Kalinowski, Sławomir; Kojło, Anatol

2016-03-10

In this work, we present a novel chemiluminescence (CL) method based on direct-injection detector (DID) integrated with the multi-pumping flow system (MPFS) to chemiluminescence determination of the total polyphenol index. In this flow system, the sample and the reagents are injected directly into the cone-shaped detection cell placed in front of the photomultiplier window. Such construction of the detection chamber allows for fast measurement of the CL signal in stopped-flow conditions immediately after mixing the reagents. The proposed DID-CL-MPFS method is based on the chemiluminescence of nanocolloidal manganese(IV)-hexametaphosphate-ethanol system. The application of ethanol as a sensitizer, eliminated the use of carcinogenic formaldehyde. Under the optimized experimental conditions, the chemiluminescence intensities are proportional to the concentration of gallic acid in the range from 5 to 350 ng mL(-1). The DID-CL-MPFS method offers a number of advantages, including low limit of detection (0.80 ng mL(-1)), high precision (RSD = 3.3%) and high sample throughput (144 samples h(-1)) as well as low consumption of reagents, energy and low waste generation. The proposed method has been successfully applied to determine the total polyphenol index (expressed as gallic acid equivalent) in a variety of plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices). Copyright © 2016 Elsevier B.V. All rights reserved.

Development of a Flow Injection System for Differential Pulse Amperometry and Its Application for Diazepam Determination

PubMed Central

Antunović, Vesna; Tešanović, Slavna; Perušković, Danica; Stevanović, Nikola; Baošić, Rada; Mandić, Snežana

2018-01-01

This work presents the development of a flow injection system for differential pulse amperometry (DPA) for diazepam determination in the presence of oxygen. The thin flow cell consisted of the bare glassy carbon electrode, reference silver/silver chloride, and stainless steel as the auxiliary electrode. Electrochemical reduction of diazepam (DZP) was characterised by cyclic voltammetry. Azomethine reduction peak was used for DZP quantification. The detector response was linear in the range 20–250 µmol/dm3 of diazepam, with a calculated detection limit of 3.83 µg/cm3. Intraday and interday precision were 1.53 and 10.8%, respectively. The method was applied on three beverage samples, energetic drink, and two different beer samples, and obtained recoveries were from 93.65 up to 104.96%. The throughoutput of the method was up to 90 analyses per hour. PMID:29744233

Flow regimes for fluid injection into a confined porous medium

DOE PAGES

Zheng, Zhong; Guo, Bo; Christov, Ivan C.; ...

2015-02-24

We report theoretical and numerical studies of the flow behaviour when a fluid is injected into a confined porous medium saturated with another fluid of different density and viscosity. For a two-dimensional configuration with point source injection, a nonlinear convection–diffusion equation is derived to describe the time evolution of the fluid–fluid interface. In the early time period, the fluid motion is mainly driven by the buoyancy force and the governing equation is reduced to a nonlinear diffusion equation with a well-known self-similar solution. In the late time period, the fluid flow is mainly driven by the injection, and the governingmore » equation is approximated by a nonlinear hyperbolic equation that determines the global spreading rate; a shock solution is obtained when the injected fluid is more viscous than the displaced fluid, whereas a rarefaction wave solution is found when the injected fluid is less viscous. In the late time period, we also obtain analytical solutions including the diffusive term associated with the buoyancy effects (for an injected fluid with a viscosity higher than or equal to that of the displaced fluid), which provide the structure of the moving front. Numerical simulations of the convection–diffusion equation are performed; the various analytical solutions are verified as appropriate asymptotic limits, and the transition processes between the individual limits are demonstrated.« less

Spectrophotometric procedure using rhodamine B for determination of submicrogram quantities of antimony in rocks

USGS Publications Warehouse

Schnepfe, M.M.

1973-01-01

A spectrophotometric procedure using Rhodamine B is given for the determination of antimony in mineralized rocks after its separation as stibine. A study of the Rhodamine B reaction points to the importance of the order of addition of reagents in enhancing sensitivity and increasing the stability of the system. The tolerance of some 26 elements is established for the overall procedure. Although the limit of determination is approximately 0??5 ppm Sb in a 0??2-g sample, the procedure is intended primarily for screening samples containing more than 1 ppm Sb. In pure solutions 0??1 ??g of antimony can be determined with a relative standard deviation of 25%. For >0??2 ??g of antimony a relative standard deviation of 15% or less can be expected. ?? 1973.

Preconcentration of Sn (II) using the methylene blue on the activated carbon and its determination by spectrophotometry method.

PubMed

Khodadoust, Saeid; Cham Kouri, Narges

2014-04-05

A simple and accurate spectrophotometric method for determination of trace amounts of Sn (II) ion in soil sample was developed by using the methylene blue (MB) in the presence of activated carbon (AC) as the adsorbent Solid Phase Extraction (SPE) of Sn (II) and then determined by UV-Vis. The Beer's law is obeyed over the concentration range of 1-80ngmL(-1) of Sn (II) with the detection limits of 0.34ngmL(-1). The influence of type and volume of eluent, concentration of MB, pH, and amount of AC on sensitivity of spectrophotometric method were optimized. The method has been successfully applied for Sn (II) ion determination in soil sample. Copyright © 2013 Elsevier B.V. All rights reserved.

Comparison of HPLC, UV spectrophotometry and potentiometric titration methods for the determination of lumefantrine in pharmaceutical products.

PubMed

da Costa César, Isabela; Nogueira, Fernando Henrique Andrade; Pianetti, Gérson Antônio

2008-09-10

This paper describes the development and evaluation of a HPLC, UV spectrophotometry and potentiometric titration methods to quantify lumefantrine in raw materials and tablets. HPLC analyses were carried out using a Symmetry C(18) column and a mobile phase composed of methanol and 0.05% trifluoroacetic acid (80:20), with a flow rate of 1.0ml/min and UV detection at 335nm. For the spectrophotometric analyses, methanol was used as solvent and the wavelength of 335nm was selected for the detection. Non-aqueous titration of lumefantrine was carried out using perchloric acid as titrant and glacial acetic acid/acetic anhydride as solvent. The end point was potentiometrically determined. The three evaluated methods showed to be adequate to quantify lumefantrine in raw materials, while HPLC and UV methods presented the most reliable results for the analyses of tablets.

A computational investigation of fuel mixing in a hypersonic scramjet

NASA Technical Reports Server (NTRS)

Fathauer, Brett W.; Rogers, R. C.

1993-01-01

A parabolized, Navier-Stokes code, SHIP3D, is used to numerically investigate the mixing between air injection and hydrogen injection from a swept ramp injector configuration into either a mainstream low-enthalpy flow or a hypervelocity test flow. The mixing comparisons between air and hydrogen injection reveal the importance of matching injectant-to-mainstream mass flow ratios. In flows with the same injectant-to-mainstream dynamic pressure ratio, the mixing definition was altered for the air injection cases. Comparisons of the computed results indicate that the air injection cases overestimate the mixing performance associated with hydrogen injection simulation. A lifting length parameter, to account for the time a fluid particle transverses through the mixing region, is defined and used to establish a connection of injectant mixing in hypervelocity flows, based on nonreactive, low-enthalpy flows.

Down scaled Kjeldahl digestion and flow injection conductometric system for determination of protein content in some traditional northern Thai foods.

PubMed

Yanu, Pattama; Jakmunee, Jaroon

2017-09-01

A flow injection conductometric (FIC) system for determination of total Kjeldahl nitrogen (TKN) was developed for estimating total protein content in food. A small scale Kjeldahl digestion was performed with a short digestion time of only 20min. The digested solution was injected into the FIC system, and TKN was converted to ammonia gas in an alkaline donor stream of the system. The gas diffused through a membrane and dissolved into an acceptor stream causing an increase in conductivity as detected by a detector and recorded as a peak. Under the optimum condition, a linear calibration graph in the range of 4.00-100.00mgL -1 was obtained with LOD of 0.05mgL -1 . A good precision (0.04% RSD, n=11, 30.00mgNL -1 ) and high sample throughput of 72h -1 was achieved. The method was applied for determination of protein in some traditional northern Thai foods, revealing that they are good sources of proteins. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spectrophotometric and theoretical studies of the protonation of Allura Red AC and Ponceau 4R

NASA Astrophysics Data System (ADS)

Bevziuk, Kateryna; Chebotarev, Alexander; Snigur, Denys; Bazel, Yaroslav; Fizer, Maksym; Sidey, Vasyl

2017-09-01

The acid-base properties of Allura Red AC and Ponceau 4R azo dyes were investigated by spectrophotometric, potentiometric and tristimulus colourimetry methods. Ionization constants of the functional groups were also found in aqueous solutions of the dyes. It was discovered that the wavelength of the maximum light absorption of Allura Red AC and Ponceau 4R solutions does not change significantly over a wide pH range. As a result, spectrophotometric methods yield little information for assessing the acid-base properties of the dyes. It was shown with a help of the tristimulus colourimetry method that it is possible to determine the ionization constants of the functional groups of the dyes even when there is significant overlap of the absorption bands of the acid-base forms. The basic spectrophotometric characteristics of the main forms of Allura Red AC and Ponceau 4R in water and organic solvents were calculated. The molar absorbance coefficients of azo forms were shown to increase as the dielectric permittivity of the solvent increases. It was determined that in aqueous solution the dyes exist in the azo form over a wide range of acidity - pH 2-12 for Allura Red AC (λmax = 505 nm; ελ = 3.1·104 dm3 mol-1 cm-1) and 1-13 for Ponceau 4R (λmax = 510 nm; ελ = 1.7·10-4 dm3 mol-1 cm-1). The most probable protonation/deprotonation schemes were theoretically determined for Allura Red AC and Ponceau 4R using DFT calculations.

[Research on the Spectrophotometry for Determination of Flavonoids in Waste Residue of Stevia Rebaudiana].

PubMed

Luo, Xu-yan; Fang, Hao-bin; Huang, Rui-yu; Zhao, Dong-fang; Zhu, Ting; Guo, Yang-yang; Zeng Yi-ping; Liu, Ren-yue; Zhu, Dong

2015-10-01

A spectrophotometric method for the determination of flavonoids content in Waste Residue of Stevia Rebaudiana was established by comparing the UV-Vis spectra with three spectrophotometric methods: Direct, AlCl3 and NaNO2-Al (NO3)3-NaOH method. The effects of spectrophotometric reaction were studied by analyzing the wavelength, the dosage of color development reagent, reaction time, temperature and pH. The further research was studied by analyzing linearity between the absorbance and the concentration, the stability of this color system, the recovery rate and so on. The results showed that NaNO2-Al(NO3)3-NaOH method was best. The wavelength was 500 nm. The standard sample was rutin. There was a good linear relationship in the ranges of 2 - 24 μg x mL(-1), correlation coefficient R2 = 0.999 5. The recovery of the additional sample was 96.0%-104.3%. The relative standard deviation(RSD) is respectively 3.75%. The dosages of NaNO2 and Al(NO3)3 both were 1.0 mL, both of their reaction time was 6 min. The dosage of NaOH was 15.0 mL and the reaction time was 15 min. The temperature in the whole process of the reaction must be maintained at 40 degrees C and pH is 5. The spectrophotometric condition was further improved on the determination of flavonoids content. This method, which is simple, rapid and accuracy, can be used in practical application.

Flow visualization study of close-coupled canard wing and strake wing configuration

NASA Technical Reports Server (NTRS)

Miner, D. D.; Gloss, B. B.

1975-01-01

The Langley 1/8-scale V/STOL model tunnel was used to qualitatively determine the flow fields associated with semi-span close coupled canard wing and strake wing models. Small helium filled bubbles were injected upstream of the models to make the flow visible. Photographs were taken over the angle-of-attack ranges of -10 deg to 40 deg.

Efficient Generation of Chemiluminescence during the reduction of manganese(IV) ions with lactic acid

NASA Astrophysics Data System (ADS)

Tsaplev, Yu. B.

2016-12-01

The kinetics and mechanism of chemiluminescence during the reduction of manganese(IV) ions with lactic acid in an H2SO4-AcOH medium are studied. Kinetic spectrophotometric measurements are used to determine the profiles of change in the concentrations of Mn(IV) and Mn(III) ions during the reaction. The results from kinetic spectrophotometric measurements are compared to the light yield kinetics. The quantum chemiluminescence and chemiexcitation yields reach record values.

Spectrophotometric and HPLC Methods for Simultaneous Estimation of Amlodipine Besilate, Losartan Potassium and Hydrochlorothiazide in Tablets

PubMed Central

Wankhede, S. B.; Raka, K. C.; Wadkar, S. B.; Chitlange, S. S.

2010-01-01

Two UV-spectrophotometric and one reverse phase high performance liquid chromatography methods have been developed for the simultaneous estimation of amlodipine besilate, losartan potassium and hydrochlorothiazide in tablet dosage form. The first UV spectrophotometric method was a determination using the simultaneous equation method at 236.5, 254 and 271 nm over the concentration range 5-25, 10-50 and 5-25 μg/ml for amlodipine besilate, losartan potassium and hydrochlorothiazide, respectively. The second UV method was a determination using the area under curve method at 231.5-241.5, 249-259 and 266-276 nm over the concentration range of 5-25, 5-25 and 10-50 μg/ml for amlodipine besilate, hydrochlorothiazide and losartan potassium, respectively. In reverse phase high performance liquid chromatography analysis is carried out using 0.025 M phosphate buffer (pH 3.7):acetonitrile (57:43 v/v) as the mobile phase and Kromasil C18 (4.6 mm i.d×250 mm) column as stationery phase with detection wavelength of 232 nm linearity was obtained in the concentration range of 2-14, 20-140 and 5-40 μg/ml for amlodipine besilate, losartan potassium and hydrochlorothiazide, respectively. Both UV-spectrophotometric and reverse phase high performance liquid chromatography methods were statistically validated and can be used for analysis of combined dose tablet formulation containing amlodipine besilate, losartan potassium and hydrochlorothiazide. PMID:20582208

Validated chromatographic and spectrophotometric methods for analysis of some amoebicide drugs in their combined pharmaceutical preparation.

PubMed

Abdelaleem, Eglal Adelhamid; Abdelwahab, Nada Sayed

2013-01-01

This work is concerned with development and validation of chromatographic and spectrophotometric methods for analysis of mebeverine HCl (MEH), diloxanide furoate (DF) and metronidazole (MET) in Dimetrol® tablets - spectrophotometric and RP-HPLC methods using UV detection. The developed spectrophotometric methods depend on determination of MEH and DF in the combined dosage form using the successive derivative ratio spectra method which depends on derivatization of the obtained ratio spectra in two steps using methanol as a solvent and measuring MEH at 226.4-232.2 nm (peak to peak) and DF at 260.6-264.8 nm (peak to peak). While MET concentrations were determined using first derivative (1D) at λ = 327 nm using the same solvent. The chromatographic method depends on HPLC separation on ODS column and elution with a mobile phase consisting water: methanol: triethylamine (25: 75: 0.5, by volume, orthophosphoric acid to pH =4). Pumping the mobile phase at 0.7 ml min-1 with UV at 230 nm. Factors affecting the developed methods were studied and optimized, moreover, they have been validated as per ICH guideline and the results demonstrated that the suggested methods are reproducible, reliable and can be applied for routine use with short time of analysis. Statistical analysis of the two developed methods with each other using F and student's-t tests showed no significant difference.

Spectrophotometric estimation of bromide ion in excess chloride media.

PubMed

Adimurthy, S; Susarla, V R K S; Reddy, M P; Ramachandraiah, G

2005-10-31

The redox reaction between bromate and chloride ions in the presence and the absence of two or less equivalents of bromide ion ascertaining the formation of bromine chloride species of type BrCl and BrCl(2)(-) in subsequent reactions in 4% H(2)SO(4), has been studied by spectrophotometry. Calibration graphs for the bromide ion estimation in 0.1% KBrO(3)-4% H(2)SO(4) medium are determined separately in the presence of known amounts of NaCl. The effect of Cl(-) ion percentage on the determination of Br(-) ion is studied and reported herewith a suitable equation for a precise, reliable and quick spectrophotometric estimation.

Direct spectrophotometric method for analysis of food supplements containing synthetic polyhydroquinones

NASA Astrophysics Data System (ADS)

Vasilevsky, A. M.; Konoplev, G. A.; Stepanova, O. S.; Toropov, D. K.; Zagorsky, A. L.

2016-04-01

A novel direct spectrophotometric method for quantitative determination of Oxiphore® drug substance (synthetic polyhydroquinone complex) in food supplements is developed. Absorption spectra of Oxiphore® water solutions in the ultraviolet region are presented. Samples preparation procedures and mathematical methods of spectra post-analytical procession are discussed. Basic characteristics of the automatic CCD-based UV spectrophotometer and special software implementing the developed method are described. The results of the trials of the developed method and software are analyzed: the error of determination for Oxiphore® concentration in water solutions of the isolated substance and singlecomponent food supplements did not exceed 15% (average error was 7…10%).

Novel spectrophotometric determination of chloramphenicol and dexamethasone in the presence of non labeled interfering substances using univariate methods and multivariate regression model updating

NASA Astrophysics Data System (ADS)

Hegazy, Maha A.; Lotfy, Hayam M.; Rezk, Mamdouh R.; Omran, Yasmin Rostom

2015-04-01

Smart and novel spectrophotometric and chemometric methods have been developed and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and dexamethasone sodium phosphate (DSP) in presence of interfering substances without prior separation. The first method depends upon derivative subtraction coupled with constant multiplication. The second one is ratio difference method at optimum wavelengths which were selected after applying derivative transformation method via multiplying by a decoding spectrum in order to cancel the contribution of non labeled interfering substances. The third method relies on partial least squares with regression model updating. They are so simple that they do not require any preliminary separation steps. Accuracy, precision and linearity ranges of these methods were determined. Moreover, specificity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied for analysis of both drugs in their pharmaceutical formulation. The obtained results have been statistically compared to that of an official spectrophotometric method to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision.

Fourth-order derivative spectrophotometric method for simultaneous determination of pseudoephedrine and naproxen in pharmaceutical dosage forms

PubMed Central

Souri, Effat; Mosafer, Amir; Tehrani, Maliheh Barazandeh

2016-01-01

Combination dosage forms of naproxen sodium and pseudoephedrine hydrochloride are used for symptomatic treatment of cold and sinus disorders. In this study, fourth-order derivative spectrophotometric method was used for simultaneous determination of naproxen sodium and pseudoephedrine hydrochloride. The method was linear over the range of 2-28 μg/ml for pseudoephedrine hydrochloride and 4-200 μg/ml for naproxen sodium. The within-day and between-day coefficient of variation values were less than 5.8% and 2.5% for pseudoephedrine hydrochloride and naproxen sodium, respectively. The application of the proposed method for simultaneous determination of naproxen and pseudoephedrine in dosage forms was demonstrated without any special pretreatment. PMID:27168748

Selective Precipitation of Thorium lodate from a Tartaric Acid-Hydrogen Peroxide Medium Application to Rapid Spectrophotometric Determination of Thorium in Silicate Rocks and in Ores

USGS Publications Warehouse

Grimaldi, F.S.

1957-01-01

This paper presents a selective iodate separation of thorium from nitric acid medium containing d-tartaric acid and hydrogen peroxide. The catalytic decomposition of hydrogen peroxide is prevented by the use of 8quinolinol. A few micrograms of thorium are separated sufficiently clean from 30 mg. of such oxides as cerium, zirconium, titanium, niobium, tantalum, scandium, or iron with one iodate precipitation to allow an accurate determination of thorium with the thoronmesotartaric acid spectrophotometric method. The method is successful for the determination of 0.001% or more of thorium dioxide in silicate rocks and for 0.01% or more in black sand, monazite, thorite, thorianite, eschynite, euxenite, and zircon.

Electrokinetic injection techniques in microfluidic chips.

PubMed

Fu, L M; Yang, R J; Lee, G B; Liu, H H

2002-10-01

The separation efficiency of a microfluidic chip is influenced to a significant degree by the flow field conditions within the injection microchannel. Therefore, an understanding of the physics of the flow within this channel is beneficial in the design and operation of such a system. The configuration of an injection system is determined by the volume of the sample plug that is to be delivered to the separation process. Accordingly, this paper addresses the design and testing of injection systems with a variety of configurations, including a simple cross, a double-T, and a triple-T configuration. This paper also presents the design of a unique multi-T injection configuration. Each injection system cycles through a predetermined series of steps, in which the electric field magnitude and distribution within the various channels is strictly manipulated, to effectuate a virtual valve. The uniquemulti-T configuration injection system presented within this paper has the ability to simulate the functions of the cross, double-T, and triple-T systems through appropriate manipulations of the electric field within its various channels. In other words, the proposed design successfully combines several conventional injection systems within a single microfluidic chip.

Spectrophotometric Determination of Iron(II) and Cobalt(II) by Direct, Derivative, and Simultaneous Methods Using 2-Hydroxy-1-Naphthaldehyde-p-Hydroxybenzoichydrazone

PubMed Central

Devi, V. S. Anusuya; Reddy, V. Krishna

2012-01-01

Optimized and validated spectrophotometric methods have been proposed for the determination of iron and cobalt individually and simultaneously. 2-hydroxy-1-naphthaldehyde-p-hydroxybenzoichydrazone (HNAHBH) reacts with iron(II) and cobalt(II) to form reddish-brown and yellow-coloured [Fe(II)-HNAHBH] and [Co(II)-HNAHBH] complexes, respectively. The maximum absorbance of these complexes was found at 405 nm and 425 nm, respectively. For [Fe(II)-HNAHBH], Beer's law is obeyed over the concentration range of 0.055–1.373 μg mL−1 with a detection limit of 0.095 μg mL−1 and molar absorptivity ɛ, 5.6 × 104 L mol−1 cm−1. [Co(II)-HNAHBH] complex obeys Beer's law in 0.118–3.534 μg mL−1 range with a detection limit of 0.04 μg mL−1 and molar absorptivity, ɛ of 2.3 × 104 L mol−1 cm−1. Highly sensitive and selective first-, second- and third-order derivative methods are described for the determination of iron and cobalt. A simultaneous second-order derivative spectrophotometric method is proposed for the determination of these metals. All the proposed methods are successfully employed in the analysis of various biological, water, and alloy samples for the determination of iron and cobalt content. PMID:22505925

Four Derivative Spectrophotometric Methods for the Simultaneous Determination of Carmoisine and Ponceau 4R in Drinks and Comparison with High Performance Liquid Chromatography

PubMed Central

Turak, Fatma; Dinç, Mithat; Dülger, Öznur; Özgür, Mahmure Ustun

2014-01-01

Four simple, rapid, and accurate spectrophotometric methods were developed for the simultaneous determination of two food colorants, Carmoisine (E122) and Ponceau 4R (E124), in their binary mixtures and soft drinks. The first method is based on recording the first derivative curves and determining each component using the zero-crossing technique. The second method uses the first derivative of ratio spectra. The ratio spectra are obtained by dividing the absorption spectra of the binary mixture by that of one of the components. The third method, derivative differential procedure, is based on the measurement of difference absorptivities derivatized in first order of solution of drink samples in 0,1 N NaOH relative to that of an equimolar solution in 0,1 N HCl at wavelengths of 366 and 451 nm for Carmoisine and Ponceau 4R, respectively. The last method, based on the compensation method is presented for derivative spectrophotometric determination of E122 and E124 mixtures with overlapping spectra. By using ratios of the derivative maxima, the exact compensation of either component in the mixture can be achieved, followed by its determination. These proposed methods have been successfully applied to the binary mixtures and soft drinks and the results were statistically compared with the reference HPLC method (NMKL 130). PMID:24672549

Development and validation of spectrophotometric, atomic absorption and kinetic methods for determination of moxifloxacin hydrochloride.

PubMed

Abdellaziz, Lobna M; Hosny, Mervat M

2011-01-01

Three simple spectrophotometric and atomic absorption spectrometric methods are developed and validated for the determination of moxifloxacin HCl in pure form and in pharmaceutical formulations. Method (A) is a kinetic method based on the oxidation of moxifloxacin HCl by Fe(3+) ion in the presence of 1,10 o-phenanthroline (o-phen). Method (B) describes spectrophotometric procedures for determination of moxifloxacin HCl based on its ability to reduce Fe (III) to Fe (II), which was rapidly converted to the corresponding stable coloured complex after reacting with 2,2' bipyridyl (bipy). The formation of the tris-complex formed in both methods (A) and (B) were carefully studied and their absorbance were measured at 510 and 520 nm respectively. Method (C) is based on the formation of ion- pair associated between the drug and bismuth (III) tetraiodide in acidic medium to form orange-red ion-pair associates. This associate can be quantitatively determined by three different procedures. The formed precipitate is either filtered off, dissolved in acetone and quantified spectrophotometrically at 462 nm (Procedure 1), or decomposed by hydrochloric acid, and the bismuth content is determined by direct atomic absorption spectrometric (Procedure 2). Also the residual unreacted metal complex in the filtrate is determined through its metal content using indirect atomic absorption spectrometric technique (procedure 3). All the proposed methods were validated according to the International Conference on Harmonization (ICH) guidelines, the three proposed methods permit the determination of moxifloxacin HCl in the range of (0.8-6, 0.8-4) for methods A and B, (16-96, 16-96 and 16-72) for procedures 1-3 in method C. The limits of detection and quantitation were calculated, the precision of the methods were satisfactory; the values of relative standard deviations did not exceed 2%. The proposed methods were successfully applied to determine the drug in its pharmaceutical formulations without interference from the common excipients. The results obtained by the proposed methods were comparable with those obtained by the reference method.

Development and Validation of Spectrophotometric, Atomic Absorption and Kinetic Methods for Determination of Moxifloxacin Hydrochloride

PubMed Central

Abdellaziz, Lobna M.; Hosny, Mervat M.

2011-01-01

Three simple spectrophotometric and atomic absorption spectrometric methods are developed and validated for the determination of moxifloxacin HCl in pure form and in pharmaceutical formulations. Method (A) is a kinetic method based on the oxidation of moxifloxacin HCl by Fe3+ ion in the presence of 1,10 o-phenanthroline (o-phen). Method (B) describes spectrophotometric procedures for determination of moxifloxacin HCl based on its ability to reduce Fe (III) to Fe (II), which was rapidly converted to the corresponding stable coloured complex after reacting with 2,2′ bipyridyl (bipy). The formation of the tris-complex formed in both methods (A) and (B) were carefully studied and their absorbance were measured at 510 and 520 nm respectively. Method (C) is based on the formation of ion- pair associated between the drug and bismuth (III) tetraiodide in acidic medium to form orange—red ion-pair associates. This associate can be quantitatively determined by three different procedures. The formed precipitate is either filtered off, dissolved in acetone and quantified spectrophotometrically at 462 nm (Procedure 1), or decomposed by hydrochloric acid, and the bismuth content is determined by direct atomic absorption spectrometric (Procedure 2). Also the residual unreacted metal complex in the filtrate is determined through its metal content using indirect atomic absorption spectrometric technique (procedure 3). All the proposed methods were validated according to the International Conference on Harmonization (ICH) guidelines, the three proposed methods permit the determination of moxifloxacin HCl in the range of (0.8–6, 0.8–4) for methods A and B, (16–96, 16–96 and 16–72) for procedures 1–3 in method C. The limits of detection and quantitation were calculated, the precision of the methods were satisfactory; the values of relative standard deviations did not exceed 2%. The proposed methods were successfully applied to determine the drug in its pharmaceutical formulations without interference from the common excipients. The results obtained by the proposed methods were comparable with those obtained by the reference method. PMID:22219661

Examination of the effect of blowing on the near-surface flow structure over a dimpled surface

NASA Astrophysics Data System (ADS)

Borchetta, C. G.; Martin, A.; Bailey, S. C. C.

2018-03-01

The near surface flow over a dimpled surface with flow injection through it was documented using time-resolved particle image velocimetry. The instantaneous flow structure, time-averaged statistics, and results from snapshot proper orthogonal decomposition were used to examine the coherent structures forming near the dimpled surface. In particular, the modifications made to the flow structures by the addition of flow injection through the surface were studied. It was observed that without flow injection, inclined flow structures with alternating vorticity from neighboring dimples are generated by the dimples and advect downstream. This behavior is coupled with fluid becoming entrained inside the dimples, recirculating and ejecting away from the surface. When flow injection was introduced through the surface, the flow structures became more disorganized, but some of the features of the semi-periodic structures observed without flow injection were preserved. The structures with flow injection appear in multiple wall-normal layers, formed from vortical structures shed from upstream dimples, with a corresponding increase in the size of the advecting structures. As a result of the more complex flow field observed with flow injection, there was an increase in turbulent kinetic energy and Reynolds shear stress, with the Reynolds shear stress representing an increase in vertical transport of momentum by sweeping and ejecting motions that were not present without flow injection.

Experimental research on the behavior of the pneumatic transport of fine-grained iron

NASA Astrophysics Data System (ADS)

Andrei, V.; Hritac, M.; Constantin, N.; Dobrescu, C.

2017-01-01

Mixed injection of fine-grained iron ore and pulverized coal in the furnace, involves determining the behavior of these materials during pneumatic transport in a dense state through the pipe and setting possibilities for adjusting the flow rate of material transported with the corresponding values of the process. Parameters of the pneumatic transport were determined for the main types of iron ore and chalk used in Arcelor Mittal Galati. Outside the intended purpose of injecting iron ore and flux, it was considered also the experimental check of the possibility for injecting ilmenite in the furnace for crucible protection purpose. The possibility of injecting cinder mill into the furnace was also considered. Injecting cinder could be taken into account for the recycling of ferrous waste in the furnace, also as additive for intensifying the combustion process around the tuyeres.

Effect of injection screen slot geometry on hydraulic conductivity tests

NASA Astrophysics Data System (ADS)

Klammler, Harald; Nemer, Bassel; Hatfield, Kirk

2014-04-01

Hydraulic conductivity and its spatial variability are important hydrogeological parameters and are typically determined through injection tests at different scales. For injection test interpretation, shape factors are required to account for injection screen geometry. Shape factors act as proportionality constants between hydraulic conductivity and observed ratios of injection flow rate and injection head at steady-state. Existing results for such shape factors assume either an ideal screen (i.e., ignoring effects of screen slot geometry) or infinite screen length (i.e., ignoring effects of screen extremes). In the present work, we investigate the combined effects of circumferential screen slot geometry and finite screen length on injection shape factors. This is done in terms of a screen entrance resistance by solving a steady-state potential flow mixed type boundary value problem in a homogeneous axi-symmetric flow domain using a semi-analytical solution approach. Results are compared to existing analytical solutions for circumferential and longitudinal slots on infinite screens, which are found to be identical. Based on an existing approximation, an expression is developed for a dimensionless screen entrance resistance of infinite screens, which is a function of the relative slot area only. For anisotropic conditions, e.g., when conductivity is smaller in the vertical direction than in the horizontal, screen entrance losses for circumferential slots increase, while they remain unaffected for longitudinal slots. This work is not concerned with investigating the effects of (possibly turbulent) head losses inside the injection device including the passage through the injection slots prior to entering the porous aquifer.

Reductions in Multi-Component Jet Noise by Water Injection

NASA Technical Reports Server (NTRS)

Norum, Thomas D.

2004-01-01

An experimental investigation was performed in the NASA Langley Low Speed Aeroacoustics Wind Tunnel to determine the extent of jet exhaust noise reduction that can be obtained using water injection in a hot jet environment. The effects of water parameters such as mass flow rate, injection location, and spray patterns on suppression of dominant noise sources in both subsonic and supersonic jets were determined, and extrapolations to full-scale engine noise reduction were made. Water jets and sprays were injected in to the shear layers of cold and hot circular jets operating at both subsonic and supersonic exhaust conditions. Use of convergent-divergent and convergent nozzles (2.7in. D) allowed for simulations of all major jet noise sources. The experimental results show that water injection clearly disrupts shock noise sources within the jet plume, with large reductions in radiated shock noise. There are smaller reductions in jet mixing noise, resulting in only a small decrease in effective perceived noise level when projections are made to full scale. The fact that the measured noise reduction in the direction upstream of the nozzle was consistently larger than in the noisier downstream direction contributed to keeping effective perceived noise reductions small. Variations in the operation of the water injection system clearly show that injection at the nozzle exit rather than further downstream is required for the largest noise reduction. Noise reduction increased with water pressure as well as with its mass flow, although the type of injector had little effect.

Simultaneous determination of phenylephrine hydrochloride, guaifenesin, and chlorpheniramine maleate in cough syrup by gradient liquid chromatography.

PubMed

Amer, Sawsan M; Abbas, Samah S; Shehata, Mostafa A; Ali, Nahed M

2008-01-01

A simple and reliable high-performance liquid chromatographic method was developed for the simultaneous determination of mixture of phenylephrine hydrochloride (PHENYL), guaifenesin (GUAIF), and chlorpheniramine maleate (CHLO) either in pure form or in the presence of methylparaben and propylparaben in a commercial cough syrup dosage form. Separation was achieved on a C8 column using 0.005 M heptane sulfonic acid sodium salt (pH 3.4 +/- 0.1) and acetonitrile as a mobile phase by gradient elution at different flow rates, and detection was done spectrophotometrically at 210 nm. A linear relationship in the range of 30-180, 120-1800, and 10-60 microg/mL was obtained for PHENYL, GUAIF, and CHLO, respectively. The results were statistically analyzed and compared with those obtained by applying the British Pharmacopoeia (2002) method and showed that the proposed method is precise, accurate, and can be easily applied for the determination of the drugs under investigation in pure form and in cough syrup formulations.

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

PubMed

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

2015-08-01

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

Spectrophotometric study for the reaction between fluvoxamine and 1,2-naphthoquinone-4-sulphonate: Kinetic, mechanism and use for determination of fluvoxamine in its dosage forms

NASA Astrophysics Data System (ADS)

Darwish, Ibrahim A.; Abdine, Heba H.; Amer, Sawsan M.; Al-Rayes, Lama I.

2009-05-01

Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antidepressant fluvoxamine (FXM) and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 9), an orange-colored product exhibiting maximum absorption peak ( λmax) at 470 nm was produced. The kinetics of the reaction was investigated and its activation energy was found to be 2.65 kcal mol -1. Because of this low activation energy, the reaction proceeded easily. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This color-developing reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of FXM in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beer's law correlating the absorbance ( A) with FXM concentration ( C) was obeyed in the range of 0.6-8 μg ml -1. The regression equation for the calibration data was A = 0.0086 + 0.1348 C, with good correlation coefficient (0.9996). The molar absorptivity ( ɛ) was 5.9 × 10 4 l mol -1 cm -1. The limits of detection and quantification were 0.2 and 0.6 μg ml -1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47 ± 0.96%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to all the previously reported spectrophotometric methods for determination of FXM in terms of its simplicity and sensitivity. The method is practical and valuable for its routine application in quality control laboratories for analysis of FXM.

A multitracer system for multizone ventilation measurement

NASA Astrophysics Data System (ADS)

Sherman, Max

1990-09-01

Mass transfer due to pressure-driven air flow is one of the most important processes for determining both environmental quality and energy requirements in buildings. Heat, moisture, and contaminants are all transported by air movement between indoors and outdoors as well as between different zones within a building. Measurement of these air flows is critical to understanding the performance of buildings. Virtually all measurements of ventilation are made using the dilution of a tracer gas. The vast majority of such measurements have been made in a single zone, using a single tracer gas. For the past several years LBL has been developing the MultiTracer Measurement System (MTMS) to provide full multizone air flow information in an accurate, real-time manner. MTMS is based on a quadrupole mass spectrometer to provide high-speed concentration analysis of multiple tracer gases in the (low) ppm level that are injected into multiple zones using mass-flow controllers. The measurement and injection system is controlled by a PC and can measure all concentrations in all zones (and adjust the injected tracer flows) within 2 min and can operate unattended for weeks. The resulting injection rate and concentration data can be analyzed to infer the bulk air movement between zones. The system also measures related quantities such as weather and zonal temperature to assist in the data interpretation. Using MTMS, field measurements have been made for the past two years.

Interaction of diazepam with surfactants. Spectrophotometric and spectrofluorometric study

NASA Astrophysics Data System (ADS)

De La Guardia, M.; Rodilla, F.

1986-03-01

The interaction of diazepam with non-ionic, anionic and cationic surfactants has been studied spectrophotometrically and fluorometrically. It has been verified that the absorption spectrum of diazepam is not modified in micellar medium. However, a dramatic five-fold increase in fluorescence sensitivity is observed in the presence of sodium lauryl sulphate (SDS). The experimental conditions, temperature, pH and surfactant concentration have been optimized to improve the fluorometric determination of diazepam and a detection limit of 0,04 ppmhas been obtained.

Miniaturized flow system based on enzyme modified PMMA microreactor for amperometric determination of glucose.

PubMed

Cerdeira Ferreira, Luís Marcos; da Costa, Eric Tavares; do Lago, Claudimir Lucio; Angnes, Lúcio

2013-09-15

This paper describes the development of a microfluidic system having as main component an enzymatic reactor constituted by a microchannel assembled in poly(methyl methacrylate) (PMMA) substrate connected to an amperometric detector. A CO2 laser engraving machine was used to make the channels, which in sequence were thermally sealed. The internal surfaces of the microchannels were chemically modified with polyethyleneimine (PEI), which showed good effectiveness for the immobilization of the glucose oxidase enzyme using glutaraldehyde as crosslinking agent, producing a very effective microreactor for the detection of glucose. The hydrogen peroxide generated by the enzymatic reaction was detected in an electrochemical flow cell localized outside of the reactor using a platinum disk as the working electrode. The proposed system was applied to the differential amperometric determination of glucose content in soft drinks showing good repeatability (DPR=1.72%, n=50), low detection limit (1.40×10(-6)molL(-1)), high sampling frequency (calculated as 345 samples h(-1)), and relatively good stability for long-term use. The results were in close agreement with those obtained by the classical spectrophotometric method utilized to quantify glucose in biological fluids. Copyright © 2013 Elsevier B.V. All rights reserved.

Comparison of Descemet stripping under continuous air flow, manual air injection and balanced salt solution for DMEK: a pilot study.

PubMed

Gabbay, I E; Bahar, I; Nahum, Y; Livny, E

2017-08-01

Descemet's membrane endothelial keratoplasty (DMEK) involves removal of the recipient's Descemet membrane (DM) prior to transplanting the donor's DM. When using balanced salt solution (BSS) or ophthalmic viscosurgical devices (OVDs), visualization of the host's DM during its stripping may be inadequate and may result in Descemet remnants and could lead to sub-optimal surgical results. Previous articles described excellent visualization when utilizing air injection but this requires repeated air injection into the anterior chamber (AC). We present a pilot study that compares different techniques under which DM stripping can be performed: with continuous automated air infusion, with manual air infusion, and with BSS. We retrospectively compared video footage of DM stripping with BSS, with continuous air and with manual injection of air into the AC to determine DM stripping duration and the number of times the surgeon had to insert and retrieve a surgical instrument from the AC. Thirty videos of 10 consecutive cases of the three DM stripping techniques were evaluated. DM stripping duration was 3.26 (±1.32), 3.92 (±1.2) and 12.9 (±3.98) minutes for BSS, continuous air flow, and manual air injection, respectively. Frequency of instrument retrieval (FIR) was 3.6 (±1.71), 1.5 (±0.71) and 15.1 (±3.28) for BSS, continuous air flow, and manual air injection, respectively. Continuous air flow and BSS were both statistically different than manual air injection into the AC (p < 0.05), but did not differ from one another statistically. DM stripping during posterior lamellar surgery is imperative for favorable post-operative results and prevention of complications. Performing this step under air in the AC contributes to better visualization and an efficient surgery.

In Situ NAPL Modification for Contaminant Source-Zone Passivation, Mass Flux Reduction, and Remediation

NASA Astrophysics Data System (ADS)

Mateas, D. J.; Tick, G.; Carroll, K. C.

2016-12-01

A remediation method was developed to reduce the aqueous solubility and mass-flux of target NAPL contaminants through the in-situ creation of a NAPL mixture source-zone. This method was tested in the laboratory using equilibrium batch tests and two-dimensional flow-cell experiments. The creation of two different NAPL mixture source zones were tested in which 1) volumes of relatively insoluble n-hexadecane (HEX) or vegetable oil (VO) were injected into a trichloroethene (TCE) contaminant source-zone; and 2) pre-determined HEX-TCE and VO-TCE mixture ratio source zones were emplaced into the flow cell prior to water flushing. NAPL-aqueous phase batch tests were conducted prior to the flow-cell experiments to evaluate the effects of various NAPL mixture ratios on equilibrium aqueous-phase concentrations of TCE and toluene (TOL) and to design optimal NAPL (HEX or VO) injection volumes for the flow-cell experiments. Uniform NAPL mixture source-zones were able to quickly decrease contaminant mass-flux, as demonstrated by the emplaced source-zone experiments. The success of the HEX and VO injections to also decrease mass flux was dependent on the ability of these injectants to homogeneously mix with TCE source-zone. Upon injection, both HEX and VO migrated away from the source-zone, to some extent. However, the lack of a steady-state dissolution phase and the inefficient mass-flux-reduction/mass-removal behavior produced after VO injection suggest that VO was more effective than HEX for mixing and partitioning within the source-zone region to form a more homogeneous NAPL mixture with TCE. VO appears to be a promising source-zone injectant-NAPL due to its negligible long-term toxicity and lower mobilization potential.

Comparison of two methods for selegiline determination: A flow-injection chemiluminescence method using cadmium sulfide quantum dots and corona discharge ion mobility spectrometry.

PubMed

Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Zarei, Mahmoud; Joo, Sang Woo

2016-01-15

Two analytical approaches including chemiluminescence (CL) and corona discharge ionization ion mobility spectrometry (CD-IMS) were developed for sensitive determination of selegiline (SG). We found that the CL intensity of the KMnO4-Na2S2O3 CL system was significantly enhanced in the presence of L-cysteine capped CdS quantum dots (QDs). A possible CL mechanism for this CL reaction is proposed. In the presence of SG, the enhanced CL system was inhibited. Based on this inhibition, a simple and sensitive flow-injection CL method was proposed for the determination of SG. Under optimum experimental conditions, the decreased CL intensity was proportional to SG concentration in the range of 0.01 to 30.0 mg L(-1). The detection limit (3σ) was 0.004 mg L(-1). Also, SG was determined using CD-IMS, and under optimum conditions of CD-IMS, calibration curves were linear in the range of 0.15 to 42.0 mg L(-1), with a detection limit (3σ) of 0.03 mg L(-1). The precision of the two methods was calculated by analyzing samples containing 5.0 mg L(-1) of SG (n=11). The relative standard deviations (RSDs%) of the flow-injection CL and CD-IMS methods are 2.17% and 3.83%, respectively. The proposed CL system exhibits a higher sensitivity and precision than the CD-IMS method for the determination of SG. Copyright © 2015. Published by Elsevier B.V.

A simple and sensitive flow injection method based on the catalytic activity of CdS quantum dots in an acidic permanganate chemiluminescence system for determination of formaldehyde in water and wastewater.

PubMed

Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza

2016-04-01

A simple and sensitive flow injection chemiluminescence (CL) method in which CdS quantum dots (QDs) enhanced the CL intensity of a KMnO4-formaldehyde (HCHO) reaction was offered for the determination of HCHO. This CL system was based on the catalytic activity of CdS QDs and their participation in the CL resonance energy transfer (CRET) phenomenon. A possible mechanism for the supplied CL system was proposed using the kinetic curves of the CL systems and the spectra of CL, photoluminescence (PL) and ultraviolet-visible (UV-Vis). The emanated CL intensity of the KMnO4-CdS QDs system was amplified in the presence of a trace level of HCHO. Based on this enhancement effect, a simple and sensitive flow injection CL method was suggested for the determination of HCHO concentration in environmental water and wastewater samples. Under selected optimized experimental conditions, the increased CL intensity was proportional to the HCHO concentration in the range of 0.03-4.5 μg L(-1) and 4.5-10.0 μg L(-1). The detection limits (3σ) were 0.0003 μg L(-1) and 1.2 μg L(-1). The relative standard deviations (RSD%) for eleven replicate determinations of 4.0 μg L(-1) HCHO were 2.2%. Furthermore, the feasibility of the developed method was investigated via the determination of HCHO concentration in environmental water and wastewater samples.

Multi-reverse flow injection analysis integrated with multi-optical sensor for simultaneous determination of Mn(II), Fe(II), Cu(II) and Fe(III) in natural waters.

PubMed

Youngvises, Napaporn; Suwannasaroj, Kittigan; Jakmunee, Jaroon; AlSuhaimi, Awadh

2017-05-01

Multi-reverse flow injection analysis (Mr-FIA) integrated with multi-optical sensor was developed and optimized for the simultaneous determination of multi ions; Mn(II), Fe(II), Cu(II) and Fe(III) in water samples. The sample/standard solutions were propelled making use of a four channels peristaltic pump whereas 4 colorimetric reagents specific for the metal ions were separately injected in sample streams using multi-syringe pump. The color zones that formed in the individual mixing coils were then streamed into multi-channels spectrometer, which comprised of four flows through cell and four pairs of light emitting diode and photodiode, whereby signals were measured concurrently. The linearity range (along with detection limit, µgL -1 ) was 0.050-3.0(16), 0.30-2.0 (11), 0.050-1.0(12) and 0.10-1.0(50)mgL -1 , for Mn(II), Fe(II), Cu(II) and Fe(III), respectively. In the interim, the correlation coefficients were 0.9924-0.9942. The percentages relative standard deviation was less than 3. The proposed system was applied successfully to determine targeted metal ions simultaneously in natural water with high sample throughput and low reagent consumption, thus it satisfies the criteria of Green Analytical Chemistry (GAC) and its goals. Copyright © 2016 Elsevier B.V. All rights reserved.

Investigation of different spectrophotometric and chemometric methods for determination of entacapone, levodopa and carbidopa in ternary mixture

NASA Astrophysics Data System (ADS)

Abdel-Ghany, Maha F.; Hussein, Lobna A.; Ayad, Miriam F.; Youssef, Menatallah M.

2017-01-01

New, simple, accurate and sensitive UV spectrophotometric and chemometric methods have been developed and validated for determination of Entacapone (ENT), Levodopa (LD) and Carbidopa (CD) in ternary mixture. Method A is a derivative ratio spectra zero-crossing spectrophotometric method which allows the determination of ENT in the presence of both LD and CD by measuring the peak amplitude at 249.9 nm in the range of 1-20 μg mL- 1. Method B is a double divisor-first derivative of ratio spectra method, used for determination of ENT, LD and CD at 245, 239 and 293 nm, respectively. Method C is a mean centering of ratio spectra which allows their determination at 241, 241.6 and 257.1 nm, respectively. Methods B and C could successfully determine the studied drugs in concentration ranges of 1-20 μg mL- 1 for ENT and 10-90 μg mL- 1 for both LD and CD. Methods D and E are principal component regression and partial least-squares, respectively, used for the simultaneous determination of the studied drugs by using seventeen mixtures as calibration set and eight mixtures as validation set. The developed methods have the advantage of simultaneous determination of the cited components without any pre-treatment. All the results were statistically compared with the reported methods, where no significant difference was observed. The developed methods were satisfactorily applied to the analysis of the investigated drugs in their pure form and in pharmaceutical dosage forms.

A study of selective spectrophotometric methods for simultaneous determination of Itopride hydrochloride and Rabeprazole sodium binary mixture: Resolving sever overlapping spectra

NASA Astrophysics Data System (ADS)

Mohamed, Heba M.

2015-02-01

Itopride hydrochloride (IT) and Rabeprazole sodium (RB) are co-formulated together for the treatment of gastro-esophageal reflux disease. Three simple, specific and accurate spectrophotometric methods were applied and validated for simultaneous determination of Itopride hydrochloride (IT) and Rabeprazole sodium (RB) namely; constant center (CC), ratio difference (RD) and mean centering of ratio spectra (MCR) spectrophotometric methods. Linear correlations were obtained in range of 10-110 μg/μL for Itopride hydrochloride and 4-44 μg/mL for Rabeprazole sodium. No preliminary separation steps were required prior the analysis of the two drugs using the proposed methods. Specificity was investigated by analyzing the synthetic mixtures containing the two cited drugs and their capsules dosage form. The obtained results were statistically compared with those obtained by the reported method, no significant difference was obtained with respect to accuracy and precision. The three methods were validated in accordance with ICH guidelines and can be used for quality control laboratories for IT and RB.

A study of selective spectrophotometric methods for simultaneous determination of Itopride hydrochloride and Rabeprazole sodium binary mixture: Resolving sever overlapping spectra.

PubMed

Mohamed, Heba M

2015-02-05

Itopride hydrochloride (IT) and Rabeprazole sodium (RB) are co-formulated together for the treatment of gastro-esophageal reflux disease. Three simple, specific and accurate spectrophotometric methods were applied and validated for simultaneous determination of Itopride hydrochloride (IT) and Rabeprazole sodium (RB) namely; constant center (CC), ratio difference (RD) and mean centering of ratio spectra (MCR) spectrophotometric methods. Linear correlations were obtained in range of 10-110μg/μL for Itopride hydrochloride and 4-44μg/mL for Rabeprazole sodium. No preliminary separation steps were required prior the analysis of the two drugs using the proposed methods. Specificity was investigated by analyzing the synthetic mixtures containing the two cited drugs and their capsules dosage form. The obtained results were statistically compared with those obtained by the reported method, no significant difference was obtained with respect to accuracy and precision. The three methods were validated in accordance with ICH guidelines and can be used for quality control laboratories for IT and RB. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparative study of novel versus conventional two-wavelength spectrophotometric methods for analysis of spectrally overlapping binary mixture.

PubMed

Lotfy, Hayam M; Hegazy, Maha A; Rezk, Mamdouh R; Omran, Yasmin Rostom

2015-09-05

Smart spectrophotometric methods have been applied and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and prednisolone acetate (PA) without preliminary separation. Two novel methods have been developed; the first method depends upon advanced absorbance subtraction (AAS), while the other method relies on advanced amplitude modulation (AAM); in addition to the well established dual wavelength (DW), ratio difference (RD) and constant center coupled with spectrum subtraction (CC-SS) methods. Accuracy, precision and linearity ranges of these methods were determined. Moreover, selectivity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied to the assay of drugs in their pharmaceutical formulations. No interference was observed from common additives and the validity of the methods was tested. The obtained results have been statistically compared to that of official spectrophotometric methods to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision. Copyright © 2015 Elsevier B.V. All rights reserved.

Spectrophotometric determination of [2-(2,6-dichloro-phenylamino)-phenyl]-acetic acid in pure form and in pharmaceuticals

NASA Astrophysics Data System (ADS)

Bazel, Yaroslav; Hunka, Iryna; Kormosh, Zholt; Andruch, Vasil

2009-12-01

A new sensitive and selective spectrophotometric method has been developed for the determination of [2-(2,6-dichloro-phenylamino)-phenyl]-acetic acid in pharmaceuticals in the presence of nicotinic acid. The method is based on the reaction of [2-(2,6-dichloro-phenylamino)-phenyl]-acetic acid with 1,3,3-trimethyl-5-phenyl-2-[3-(1,3,3-trimethyl-1,3-dihydro-indol-2-ylidene)-propenyl]-3 H-indolium chloride (PIC) followed by the extraction of the formed ion associate into toluene and spectrophotometric detection at 581 nm. Appropriate experimental conditions were found to be pH 7.8-9.8 and 3.6 × 10 -4 mol L -1 of PIC. The molar absorptivity is 5.0 × 10 -4 L mol -1 cm -1. The absorbance obeys Beer's law in the range 0.61-12.60 μg mL -1 of [2-(2,6-dichloro-phenylamino)-phenyl]-acetic acid, and the detection limit calculated from a blank test was 0.20 μg mL -1.

Particle Image Velocimetry During Injection Molding

NASA Astrophysics Data System (ADS)

Bress, Thomas; Dowling, David

2012-11-01

Injection molding involves the unsteady non-isothermal flow of a non-Newtonian polymer melt. An optical-access mold has been used to perform particle image velocimetry (PIV) on molten polystyrene during injection molding. Velocimetry data of the mold-filling flow will be presented. Statistical assessments of the velocimetry data and scaled residuals of the continuity equation suggest that PIV can be conducted in molten plastics with an uncertainty of +/-2 percent. Simulations are often used to model polymer flow during injection molding to design molds and select processing parameters but it is difficult to determine the accuracy of these simulations due to a lack of in-mold velocimetry and melt-front progression data. Moldflow was used to simulate the filling of the optical-access mold, and these simulated results are compared to the appropriately-averaged time-varying velocity field measurements. Simulated results for melt-front progression are also compared with the experimentally observed flow fronts. The ratio of the experimentally measured average velocity magnitudes to the simulation magnitudes was found on average to be 0.99 with a standard deviation of 0.25, and the difference in velocity orientations was found to be 0.9 degree with a standard deviation of 3.2 degrees. formerly at the University of Michigan.

Electrochemical biotin detection based on magnetic beads and a new magnetic flow cell for screen printed electrode.

PubMed

Biscay, Julien; González García, María Begoña; Costa García, Agustín

2015-01-01

The use of the first flow-cell for magnetic assays with an integrated magnet is reported here. The flow injection analysis system (FIA) is used for biotin determination. The reaction scheme is based on a one step competitive assay between free biotin and biotin labeled with horseradish peroxidase (B-HRP). The mixture of magnetic beads modified with streptavidin (Strep-MB), biotin and B-HRP is left 15 min under stirring and then a washing step is performed. After that, 100 μL of the mixture is injected and after 30s 100 μL of 3,3',5,5'-Tetramethylbenzidine (TMB) is injected and the FIAgram is recorded applying a potential of -0.2V. The linear range obtained is from 0.01 to 1 nM of biotin and the sensitivity is 758 nA/nM. The modification and cleaning of the electrode are performed in an easy way due to the internal magnet of the flow cell. Copyright © 2014 Elsevier B.V. All rights reserved.

Performance of a Compression-ignition Engine with a Precombustion Chamber Having High-Velocity Air Flow

NASA Technical Reports Server (NTRS)

Spanogle, J A; Moore, C S

1931-01-01

Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.

Flow-injection chemiluminescence determination of melamine in urine and plasma.

PubMed

Tang, Xiaoshuang; Shi, Xiyan; Tang, Yuhai; Yue, Zhongjin; He, Qiqi

2012-01-01

A novel flow-injection chemiluminescence method for the determination of melamine in urine and plasma was developed. It was found that melamine can remarkably enhance chemiluminescence emission from the luminol-K(3) Fe(CN)(6) system in an alkaline medium. Under the optimum conditions, chemiluminescence intensity had a good linear relationship with the concentration of melamine in the range 9.0 × 10(-9) -7.0 × 10(-6) g/mL, with a correlation coefficient of 0.9992. The detection limit (3σ) was 3.5 ng/mL. The method has been applied to determine the concentration of melamine in samples using liquid-liquid extraction. Average recoveries of melamine were 102.6% in urine samples and 95.1% in plasma samples. The method provided a reproducible and stable approach for the sensitive detection of melamine in urine and plasma samples. Copyright © 2011 John Wiley & Sons, Ltd.

Sibutramine selective electrodes for batch and flow injection determinations in pharmaceutical preparations.

PubMed

Zayed, S I M; Issa, Y M

2010-01-01

The construction and electrochemical response characteristics of two new polyvinyl chloride (PVC) membrane sensors for the determination of sibutramine hydrochloride were described. The sensors are based on the ion association complexes of sibutramine with sodium tetraphenylborate (NaTPB) or phosphotungstic acid (PTA) using dibutyl phthalate as plasticizing solvent. The sensors display a fast, stable response over the concentration range 3.84 x 10(-5)-1.00 x 10(-2) M sibutramine hydrochloride monohydrate (SibuCl), with cationic slopes of 57.7 +/- 0.57 and 59.7 +/- 1.79 mV concentration decade(-1) and detection limits of 8.91 x 10(-6) and 1.47 x 10(-5) M in case of sibutramine-tetraphenylborate (Sibu-TPB) and sibutramine-phosphotungstate ((Sibu)(3)-PT), respectively. The proposed sensors have been successfully applied for the determination of sibutramine hydrochloride in Regitrim capsules in batch and flow injection (FI) conditions.

Subnanogram determination of aniracetam in pharmaceutical preparations and biofluids by flow injection analysis with chemiluminescence detection based on its enhancement of the myoglobin-luminol reaction.

PubMed

Shao, Xiaodong; Li, Ying; Li, Fagen; Liu, Yangqin; Song, Zhenghua

2011-01-01

A novel flow injection chemiluminescence method with a myoglobin-luminol system is described for determining aniracetam. Myoglobin-bound aniracetam produced a complex that catalyzed the chemiluminescence reaction between luminol and myoglobin, leading to fast chemiluminescence. The chemiluminescence intensity in the presence of aniracetam was remarkably enhanced compared with that in the absence of aniracetam. Under the optimum reaction conditions the chemiluminescence increment produced was proportional to the concentration of aniracetam in the range of 0.1-1000.0 ng/mL (R2 = 0.9992), with a detection limit of 0.03 ng/mL (3delta). At a flow rate of 2.0 mL/min, the whole process, including sampling and washing, could be completed in 0.5 min, offering a sampling efficiency of 120/h; the RSD was less than 3.0% (n = 5). The method was satisfactory for determination of aniracetam in pharmaceutical preparations and human urine and serum samples. A possible mechanism of the reaction is also discussed.

Multi-Phase Modeling of Rainbird Water Injection

NASA Technical Reports Server (NTRS)

Vu, Bruce T.; Moss, Nicholas; Sampson, Zoe

2014-01-01

This paper describes the use of a Volume of Fluid (VOF) multiphase model to simulate the water injected from a rainbird nozzle used in the sound suppression system during launch. The simulations help determine the projectile motion for different water flow rates employed at the pad, as it is critical to know if water will splash on the first-stage rocket engine during liftoff.

Simultaneous Spectrophotometric Estimation of Nitazoxanide and Ofloxacin in Tablets

PubMed Central

Game, Madhuri D.; Sakarkar, D. M.

2011-01-01

Two simple, accurate and precise spectrophotometric methods have been developed for simultaneous determination of nitazoxanide and ofloxacin in tablets. Method I is Q-absorbance ratio method which involves Q-absorbance at isobestic point (306.25 nm) and max (347.5 nm) of nitazoxanide, while method II is two wavelength method, where 244.6 nm and 273.0 nm were selected as 1 and 2 for determination of nitazoxanide and 294.3 nm and 388.1 nm were selected as 3 and 4 for determination of ofloxacin. Both drugs obeyed the Beer's law in the concentration range 2-30 μg/ml,correlation coefficient (r2<1). Both methods were validated statistically and recovery studies were carried out to confirm the accuracy. Commercial tablet formulation was successfully analyzed using the developed methods. PMID:22131624

Sensitive flotation-spectrophotometric determination of gold, based on the gold(I)-iodide-methylene blue system.

PubMed

Marczenko, Z; Jankowski, K

1985-04-01

The gold(I)-iodide-Methylene Blue (MB) system is suitable for flotation separation and spectrophotometric determination of gold. Under the optimum conditions [(MB(+))(AuI(2)(-))].3[(MB(+))(I(3)(-))] is formed, and floated with cyclohexane. The product is dissolved in methanol and its absorbance measured. The molar absorptivity is 3.4 x 10(5)1.mole(-1).cm(-1) at 655 nm. The proposed method is more than three times as sensitive as the Rhodamine B method. Pt, Pd, Ag and Hg interfere seriously, and Ir, Rh, Bi and Cd to a smaller extent. Preliminary separation of gold by precipitation with tellurium as a collector is recommended. The method has been applied to determination of gold traces (about 1 x 10(-4)%) in a copper sample.

Individual and simultaneous spectrophotometric determination of dapsone and metoclopramide HCl in pharmaceutical dosage forms and synthetic binary mixtures.

PubMed

Omran, Ahmed Ahmed

2005-11-01

A rapid, sensitive and selective spectrophotometric method has been developed for the quantitative determination of dapsone (DAP) and metoclopramide hydrochloride (MCP) in both pure and dosage forms. Individual and simultaneous methods are based on the diazo coupling reaction of these drugs with benzoylacetone (BAC) in alkaline medium. The resulting azo dyes exhibit maximum absorption at 437 and 411 nm with a molar absorptivity of 4.14x10(4) and 2.97x10(4) l mol-1 cm-1 for DAP and MCP, respectively. Simultaneous determination of DAP and MCP was developed utilizing first-order digital derivative spectrophotometry. All variables have been optimized. No interferences were observed from drug excipients and the validity of the methods was tested against reference methods.

Design and development of an automated flow injection instrument for the determination of arsenic species in natural waters.

PubMed

Hanrahan, Grady; Fan, Tina K; Kantor, Melanie; Clark, Keith; Cardenas, Steven; Guillaume, Darrell W; Khachikian, Crist S

2009-10-01

The design and development of an automated flow injection instrument for the determination of arsenite [As(III)] and arsenate [As(V)] in natural waters is described. The instrument incorporates solenoid activated self-priming micropumps and electronic switching valves for controlling the fluidics of the system and a miniature charge-coupled device spectrometer operating in a graphical programming environment. The limits of detection were found to be 0.79 and 0.98 microM for As(III) and As(V), respectively, with linear range of 1-50 microM. Spiked ultrapure water samples were analyzed and recoveries were found to be 97%-101% for As(III) and 95%-99% for As(V), respectively. Future directions in terms of automation, optimization, and field deployment are discussed.

Nonenzymic spectrophotometric determination of potential poison ivy cross-reactors.

PubMed

Quattrone, A J

1977-03-01

I describe an inexpensive, nonenzymic analytical system for prescreening substances that might cross-react as Rhus toxing (e.g., poison ivy, poison oak, and sumac allergens) on human skin. By spectrophotometric assay after incubation with an oxidizing mixture of Cu(II)ammine complex and ammonium persulfate, I could accurately and reproducibly determine o-quinoidal products of several potential synthetic cross-reactors and native poison ivy allergen, and could distinguish these from catecholamines, resorcinol, p-hydroquinone, and a closely related phenol. A good correlation was obtained between this nonenzymic technique and an enzymic assay. This Cu(II)ammine/persulfate oxidative assay, however, is inexpensive and obviates any spectral interference from enzymic proteins.

[A comparative evaluation of the methods for determining nitrogen dioxide in an industrial environment].

PubMed

Panev, T

1991-01-01

The present work has the purpose to make a comparative evaluation of the different types detector tubes--for analysis, long-term and passive for determination of NO2 and the results to be compared, with those received by the spectrophotometric method and the reagent of Zaltsman. Studies were performed in the hall of the garage for repair of diesel buses during one working shift. The results point out that the analysing tubes for NO2 give good results with the spectrophotometric method. The measured average-shift concentrations of NO2 by long-term and passive tubes are juxtaposed with the average-received values with the analytical tubes and with the analytical method.

A convenient spectrophotometric assay for the determination of l-ergothioneine in blood

PubMed Central

Carlsson, Jan; Kierstan, Marek P. J.; Brocklehurst, Keith

1974-01-01

1. A convenient spectrophotometric assay for the determination of l-ergothioneine in solution including deproteinized blood haemolysate was developed. 2. The method consists of deproteinization by heat precipitation and Cu2+-catalysed oxidation of thiols such as glutathione and of l-ascorbic acid, both in alkaline media, and titration of l-ergothioneine (which is not oxidized under these conditions) by its virtually instantaneous reaction with 2,2′-dipyridyl disulphide at pH1. 3. This method and the results obtained with it for the analysis of human, horse, sheep and pig blood are compared with existing methods of l-ergothioneine analysis and the results obtained thereby. PMID:4463946

A Semi-Analytical Method for Rapid Estimation of Near-Well Saturation, Temperature, Pressure and Stress in Non-Isothermal CO2 Injection

NASA Astrophysics Data System (ADS)

LaForce, T.; Ennis-King, J.; Paterson, L.

2015-12-01

Reservoir cooling near the wellbore is expected when fluids are injected into a reservoir or aquifer in CO2 storage, enhanced oil or gas recovery, enhanced geothermal systems, and water injection for disposal. Ignoring thermal effects near the well can lead to under-prediction of changes in reservoir pressure and stress due to competition between increased pressure and contraction of the rock in the cooled near-well region. In this work a previously developed semi-analytical model for immiscible, nonisothermal fluid injection is generalised to include partitioning of components between two phases. Advection-dominated radial flow is assumed so that the coupled two-phase flow and thermal conservation laws can be solved analytically. The temperature and saturation profiles are used to find the increase in reservoir pressure, tangential, and radial stress near the wellbore in a semi-analytical, forward-coupled model. Saturation, temperature, pressure, and stress profiles are found for parameters representative of several CO2 storage demonstration projects around the world. General results on maximum injection rates vs depth for common reservoir parameters are also presented. Prior to drilling an injection well there is often little information about the properties that will determine the injection rate that can be achieved without exceeding fracture pressure, yet injection rate and pressure are key parameters in well design and placement decisions. Analytical solutions to simplified models such as these can quickly provide order of magnitude estimates for flow and stress near the well based on a range of likely parameters.

Simplex optimization of the variables influencing the determination of pefloxacin by time-resolved chemiluminescence

NASA Astrophysics Data System (ADS)

Murillo Pulgarín, José A.; Alañón Molina, Aurelia; Jiménez García, Elisa

2018-03-01

A new chemiluminescence (CL) detection system combined with flow injection analysis (FIA) for the determination of Pefloxacin is proposed. The determination is based on an energy transfer from Pefloxacin to terbium (III). The metal ion enhances the weak CL signal produced by the KMnO4/H2SO3/Pefloxacin system. A modified simplex method was used to optimize chemical and instrumental variables. The influence of the interaction of the permanganate, Tb (III), sodium sulphite and sulphuric acid concentrations, flow rate and injected sample volume was thoroughly investigated by using a modified simplex optimization procedure. The results revealed a strong direct relationship between flow rate and CL intensity throughout the studied range that was confirmed by a gamma test. The response factor for the CL emission intensity was used to assess performance in order to identify the optimum conditions for maximization of the response. Under such conditions, the CL response was proportional to the Pefloxacin concentration over a wide range. The detection limit as calculated according to Clayton's criterion 13.7 μg L- 1. The analyte was successfully determined in milk samples with an average recovery of 100.6 ± 9.8%.

The G6PD flow-cytometric assay is a reliable tool for diagnosis of G6PD deficiency in women and anaemic subjects.

PubMed

Bancone, Germana; Kalnoky, Michael; Chu, Cindy S; Chowwiwat, Nongnud; Kahn, Maria; Malleret, Benoit; Wilaisrisak, Pornpimon; Rénia, Laurent; Domingo, Gonzalo J; Nosten, Francois

2017-08-29

Glucose-6-phosphate dehydrogenase (G6PD) activity is essential for redox equilibrium of red blood cells (RBCs) and, when compromised, the RBCs are more susceptible to haemolysis. 8-aminoquinolines (primaquine and tafenoquine) are used for the radical curative treatment of Plasmodium vivax malaria and can cause haemolysis in G6PD deficient subjects. Haemolytic risk is dependent on treatment dose and patient G6PD status but ultimately it correlates with the number of G6PD deficient RBCs. The G6PD spectrophotometric assay reliably identifies deficient subjects but is less reliable in heterozygous females, especially when other blood conditions are present. In this work we analysed samples with a range of G6PD phenotypes and haematologic conditions from 243 healthy volunteers of Asian or African-American heritage using both the spectrophotomeric assay and the G6PD flow-cytometric assay. Overall 18.5% of subjects (29.3% of Asian females) presented with anaemia, associated with decreased RBCs volume (MCV) and reticulocytosis; the flow-cytometric assay showed good correlation with the spectrophotometric assay (Pearson's r 0.918-0.957) and was less influenced by haemoglobin concentration, number of RBCs and number of reticulocytes. This resulted in more precise quantification of the number of G6PD deficient RBCs and presumably higher predictive power of drug induced haemolytic risk.

Sampling strategies exploiting multi-pumping flow systems.

PubMed

Prior, João A V; Santos, João L M; Lima, José L F C

2003-04-01

In this work new strategies were exploited to implement multi-pumping flow systems relying on the utilisation of multiple devices that act simultaneously as sample-insertion, reagent-introduction, and solution-propelling units. The solenoid micro-pumps that were initially used as the only active elements of multi-pumping systems, and which were able to produce pulses of 3 to 25 microL, were replaced by syringe pumps with the aim of producing pulses between 1 and 4 microL. The performance of the developed flow system was assessed by using distinct sample-insertion strategies like single sample volume, merging zones, and binary sampling in the spectrophotometric determination of isoniazid in pharmaceutical formulations upon reaction with 1,2-naphthoquinone-4-sulfonate, in alkaline medium. The results obtained showed that enhanced sample/reagent mixing could be obtained with binary sampling and by using a 1 microL per step pump, even in limited dispersion conditions. Moreover, syringe pumps produce very reproducible flowing streams and are easily manipulated and controlled by a computer program, which is greatly simplified since they are the only active manifold component. Linear calibration plots up to 18.0 microg mL(-1), with a relative standard deviation of less than 1.48% (n=10) and a throughput of about 20 samples per hour, were obtained.

Spectrophotometric Determination of Phenolic Antioxidants in the Presence of Thiols and Proteins.

PubMed

Avan, Aslı Neslihan; Demirci Çekiç, Sema; Uzunboy, Seda; Apak, Reşat

2016-08-12

Development of easy, practical, and low-cost spectrophotometric methods is required for the selective determination of phenolic antioxidants in the presence of other similar substances. As electron transfer (ET)-based total antioxidant capacity (TAC) assays generally measure the reducing ability of antioxidant compounds, thiols and phenols cannot be differentiated since they are both responsive to the probe reagent. In this study, three of the most common TAC determination methods, namely cupric ion reducing antioxidant capacity (CUPRAC), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt/trolox equivalent antioxidant capacity (ABTS/TEAC), and ferric reducing antioxidant power (FRAP), were tested for the assay of phenolics in the presence of selected thiol and protein compounds. Although the FRAP method is almost non-responsive to thiol compounds individually, surprising overoxidations with large positive deviations from additivity were observed when using this method for (phenols + thiols) mixtures. Among the tested TAC methods, CUPRAC gave the most additive results for all studied (phenol + thiol) and (phenol + protein) mixtures with minimal relative error. As ABTS/TEAC and FRAP methods gave small and large deviations, respectively, from additivity of absorbances arising from these components in mixtures, mercury(II) compounds were added to stabilize the thiol components in the form of Hg(II)-thiol complexes so as to enable selective spectrophotometric determination of phenolic components. This error compensation was most efficient for the FRAP method in testing (thiols + phenols) mixtures.

Quantitative determination of zopiclone and its impurity by four different spectrophotometric methods.

PubMed

Abdelrahman, Maha M; Naguib, Ibrahim A; El Ghobashy, Mohamed R; Ali, Nesma A

2015-02-25

Four simple, sensitive and selective spectrophotometric methods are presented for determination of Zopiclone (ZPC) and its impurity, one of its degradation products, namely; 2-amino-5-chloropyridine (ACP). Method A is a dual wavelength spectrophotometry; where two wavelengths (252 and 301 nm for ZPC, and 238 and 261 nm for ACP) were selected for each component in such a way that difference in absorbance is zero for the second one. Method B is isoabsorptive ratio method by combining the isoabsorptive point (259.8 nm) in the ratio spectrum using ACP as a divisor and the ratio difference for a single step determination of both components. Method C is third derivative (D(3)) spectrophotometric method which allows determination of both ZPC at 283.6 nm and ACP at 251.6 nm without interference of each other. Method D is based on measuring the peak amplitude of the first derivative of the ratio spectra (DD(1)) at 263.2 nm for ZPC and 252 nm for ACP. The suggested methods were validated according to ICH guidelines and can be applied for routine analysis in quality control laboratories. Statistical analysis of the results obtained from the proposed methods and those obtained from the reported method has been carried out revealing high accuracy and good precision. Copyright © 2014 Elsevier B.V. All rights reserved.

COMPARISON OF THREE TRACER TESTS AT THE RAFT RIVER GEOTHERMAL SITE

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

Earl D Mattson; Mitchell Plummer; Carl Palmer

2011-02-01

Three conservative tracer tests have been conducted through the Bridge Fault fracture zone at the Raft River Geothermal (RRG) site. All three tests were conducted between injection well RRG-5 and production wells RRG-1 (790 m distance) and RRG-4 (740 m distance). The injection well is used during the summer months to provide pressure support to the production wells. The first test was conducted in 2008 using 136 kg of fluorescein tracer. Two additional tracers were injected in 2010. The first 2010 tracer injected was 100 kg fluorescein disodium hydrate salt on June, 21. The second tracer (100 kg 2,6-naphthalene disulfonicmore » acid sodium salt) was injected one month later on July 21. Sampling of the two productions wells is still being performed to obtain the tail end of the second 2010 tracer test. Tracer concentrations were measured using HPLC with a fluorescence detector. Results for the 2008 test, suggest 80% tracer recover at the two production wells. Of the tracer recovered, 85% of tracer mass was recovered in well RRG-4 indicating a greater flow pathway connection between injection well and RRG-4 than RRG-1. Fluorescein tracer results appear to be similar between the 2008 and 2010 tests for well RRG-4 with peak concentrations arriving approximately 20 days after injection despite the differences between the injection rates for the two tests (~950 gpm to 475 gpm) between the 2008 and 2010. The two 2010 tracer tests will be compared to determine if the results support the hypothesis that rock contraction along the flow pathway due to the 55 oC cooler water injection alters the flow through the ~140 oC reservoir.« less

Flow-injection chemiluminescence determination of diazepam by oxidation with N-bromosuccinimide.

PubMed

Han, Suqin; Jia, Shize; Guo, Liang

2013-01-01

A rapid and sensitive flow-injection chemiluminescence (FI-CL) method is described for the determination of diazepam based on its reaction with N-bromosuccinimide (NBS) in alkaline medium in the presence of dichlorofluorescein (DCF) as an effective energy-transfer agent. Under optimum conditions, the proposed method allowed the measurement of diazepam over the range of 2.0 × 10(-6) to 2.0 × 10(-4) mol/L with a detection limit of 5.0 × 10(-7) mol/L. The relative standard deviation for 11 parallel measurements of 2.0 × 10(-5) mol/L diazepam was 2.1%. The method was applied satisfactorily for the determination of diazepam in pharmaceutical preparations, and the results agree well with those obtained by spectrophotometry. The use of the proposed system for the determination of diazepam in urine and plasma samples was also tested. The possible mechanism of the chemiluminescence reaction is discussed briefly. Copyright © 2012 John Wiley & Sons, Ltd.

The determination of trace lead in Chinese medicinal herbs by flow injection analysis in polyethyleneglycol medium

NASA Astrophysics Data System (ADS)

Gong, Aiqin; Zhu, Xiashi; Huang, Xiaoyan; Zhang, Yaqin

2008-01-01

In this work, a new flow injection analysis (FIA) for the determination of Pb 2+ in Chinese medicinal herbs was developed. In the buffer solution of borax-NaOH (pH 10.5), Pb 2+ reacted with 2-[(5-bromo-2-pyridyl)-azo]-5-(diethyl-amino)phenol (5-Br-PADAP) to form a complex. The experimental results showed that the sensitivity was enhanced in the presence of polyethyleneglycol-800 (PG-800). The main factors affecting the determination were investigated in detail. Under the optimum conditions, the linear range and detection limit is 0.0-0.3 μg/mL and 1.5 ng/mL (correlation coefficient r = 0.9996), respectively. The linear regression equation is A = -0.005 + 0.60 c (μg/mL). The sample throughout is 10 h -1. Foreign substrates effects were also investigated. The proposed method has been successfully applied to the determination of lead in reference material, goldthread and lepidium seed.

[Determination of trace amounts of zinc in nickel electrolyte by flow injection on-line enrichment].

PubMed

Zhou, Z; Wang, Y; Dong, Z; Tong, K; Guo, X; Guo, X

1999-10-01

A method for the determination of trace amount of zinc in nickel electrolyte utilizing the flow injection on-line enrichment technique is reported in this paper. Atomic absorption spectrometer was used as detector. Zinc was separated from large amounts of nickel andother components in the electrolyte by absorption its chlorocomplex on a mini-column packed with strongly basic anion exchangers. It was found that sodium chloride containing in the electrolyte offered a sufficient chloride concentration needed for the formation of the zinc chlorocomplex and thus no additional reagent was required for the determination. The throughput of the method is 30 determinations per hour. The detection limit of the method is 0.002 microg x mL(-1) and the precision is 1.9% (RSD). The proposed method is rapid and cost-effective. It has been used for almost three years in the quality control of the electrolyte in the factory with great success.

Determination of thiram in natural waters using flow-injection with cerium(IV)-quinine chemiluminescence system.

PubMed

Waseem, Amir; Yaqoob, Mohammad; Nabi, Abdul

2010-01-01

A simple and rapid flow-injection chemiluminescence method has been developed for the determination of dithiocarbamate fungicide thiram based on the chemiluminescence reaction of thiram with ceric sulfate and quinine in aqueous sulfuric acid. The present method allowed the determination of thiram in the concentration range of 7.5-2500 ng/mL and the detection limit (signal-to-noise ratio = 3) was 7.5 ng/mL with sample throughput of 120/h. The relative standard deviation was 2.5% for 10 replicate analyses of 500 ng/mL thiram. The effects of foreign species including various anions and cations present in water at environmentally relevant concentrations and some pesticides were also investigated. The proposed method was applied to determine thiram in spiked natural waters using octadecyl bonded phase silica (C(18)) cartridges for solid-phase extraction. The recoveries were in the range 99 +/- 1 to 104 +/- 1%. Copyright (c) 2009 John Wiley & Sons, Ltd.

Comparison of Spectrophotometric and Visual Readings of NCCLS Method and Evaluation of a Colorimetric Method Based on Reduction of a Soluble Tetrazolium Salt, 2,3-Bis {2-Methoxy-4-Nitro-5-[(Sulfenylamino) Carbonyl]-2H- Tetrazolium-Hydroxide}, for Antifungal Susceptibility Testing of Aspergillus Species

PubMed Central

Meletiadis, Joseph; Mouton, Johan W.; Meis, Jacques F. G. M.; Bouman, Bianca A.; Donnelly, Peter J.; Verweij, Paul E.

2001-01-01

The susceptibilities of 25 clinical isolates of various Aspergillus species (Aspergillus fumigatus, A. flavus, A. terreus, A. ustus, and A. nidulans) to itraconazole (ITC) and amphotericin B (AMB) were determined using the standard proposed by NCCLS for antifungal susceptibility testing of filamentous fungi, a modification of this method using spectrophotometric readings, and a colorimetric method using the tetrazolium salt 2,3-bis {2-methoxy-4-nitro-5-[(sulfenylamino) carbonyl]-2H-tetrazolium-hydroxide} (XTT). Five MIC end points for ITC (MIC-0, no visible growth or ≤5% the growth control value [GC]; MIC-1, slight growth or 6 to 25% the GC; MIC-2, prominent reduction in growth or 26 to 50% the GC; MIC-3, slight reduction in growth or 51 to 75% the GC; and MIC-4, no reduction in growth or 76 to 100% the GC) and one for AMB (MIC-0) were determined visually by four observers and spectrophotometrically. The intraexperimental (between the observers) and interexperimental (between the experiments) levels of agreement of the NCCLS and XTT methods exceeded 95% for MIC-0 of AMB and MIC-0 and MIC-1 of ITC. The MIC-2 of ITC showed lower reproducibility, although spectrophotometric reading and/or incubation for 48 h increased the interexperimental reproducibility from 85 to >93%. Between visual and spectrophotometric readings, high levels of agreement were found for AMB (≈97%) and MIC-1 (≈92%) and MIC-2 (≈88%) of ITC. Poor agreement was found for MIC-0 of ITC (51% after 24 h), since the spectrophotometric readings resulted in higher MIC-0 values than the visual readings. The agreement was increased to 98% by shifting the threshold level of MIC-0 from 5 to 10% relative optical density and by establishing an optical density of greater than 0.1 for the GC as the validation criterion. No statistically significant differences were found between the NCCLS method and the XTT method, with the levels of agreement exceeding 97% for MIC-0 of AMB and 83% for MIC-0, MIC-1, and MIC-2 of ITC. The XTT method and spectrophotometric readings can increase the sensitivity and the precision, respectively, of in vitro susceptibility testing of Aspergillus species. PMID:11724829

Novel two wavelength spectrophotometric methods for simultaneous determination of binary mixtures with severely overlapping spectra

NASA Astrophysics Data System (ADS)

Lotfy, Hayam M.; Saleh, Sarah S.; Hassan, Nagiba Y.; Salem, Hesham

2015-02-01

This work presents the application of different spectrophotometric techniques based on two wavelengths for the determination of severely overlapped spectral components in a binary mixture without prior separation. Four novel spectrophotometric methods were developed namely: induced dual wavelength method (IDW), dual wavelength resolution technique (DWRT), advanced amplitude modulation method (AAM) and induced amplitude modulation method (IAM). The results of the novel methods were compared to that of three well-established methods which were: dual wavelength method (DW), Vierordt's method (VD) and bivariate method (BV). The developed methods were applied for the analysis of the binary mixture of hydrocortisone acetate (HCA) and fusidic acid (FSA) formulated as topical cream accompanied by the determination of methyl paraben and propyl paraben present as preservatives. The specificity of the novel methods was investigated by analyzing laboratory prepared mixtures and the combined dosage form. The methods were validated as per ICH guidelines where accuracy, repeatability, inter-day precision and robustness were found to be within the acceptable limits. The results obtained from the proposed methods were statistically compared with official ones where no significant difference was observed. No difference was observed between the obtained results when compared to the reported HPLC method, which proved that the developed methods could be alternative to HPLC techniques in quality control laboratories.

Kinetic spectrophotometric method for trace determination of thiocyanate based on its inhibitory effect

NASA Astrophysics Data System (ADS)

Naik, Radhey M.; Kumar, Basant; Asthana, Abhas

2010-03-01

A kinetic spectrophotometric method for the determination of thiocyanate, based on its inhibitory effect on silver(I) catalyzed substitution of cyanide ion, by phenylhydrazine in hexacyanoferrate(II) is described. Thiocyanate ions form strong complexes with silver(I) catalyst which is used as the basis for its determination at trace level. The progress of reaction was monitored, spectrophotometrically, at 488 nm ( λmax of [Fe(CN) 5PhNHNH 2] 3-, complex) under the optimum reaction conditions at: 2.5 × 10 -3 M [Fe(CN) 6] 4-, 1.0 × 10 -3 M [PhNHNH 2], 8.0 × 10 -7 M [Ag +], pH 2.8 ± 0.02, ionic strength ( μ) 0.02 M (KNO 3) and temperature 30 ± 0.1 °C. A linear relationship obtained between absorbance (measured at 488 nm at different times) and inhibitor concentration, under specified conditions, has been used for the determination of [thiocyanate] in the range of 0.8-8.0 × 10 -8 M with a detection limit of 2 × 10 -9 M. The standard deviation and percentage error have been calculated and reported with each datum. A most plausible mechanistic scheme has been proposed for the reaction. The values of equilibrium constants for complex formation between catalyst-inhibitor ( KCI), catalyst-substrate ( Ks) and Michaelis-Menten constant ( Km) have been computed from the kinetic data. The influence of possible interference by major cations and anions on the determination of thiocyanate and their limits has been investigated.

Experimental Investigation of Diffuser Hub Injection to Improve Centrifugal Compressor Stability

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

2004-01-01

Results from a series of experiments to investigate whether centrifugal compressor stability could be improved by injecting air through the diffuser hub surface are reported. The research was conducted in a 4:1 pressure ratio centrifugal compressor configured with a vane-island diffuser. Injector nozzles were located just upstream of the leading edge of the diffuser vanes. Nozzle orientations were set to produce injected streams angled at 8, 0 and +8 degrees relative to the vane mean camber line. Several injection flow rates were tested using both an external air supply and recirculation from the diffuser exit. Compressor flow range did not improve at any injection flow rate that was tested. Compressor flow range did improve slightly at zero injection due to the flow resistance created by injector openings on the hub surface. Leading edge loading and semi-vaneless space diffusion showed trends similar to those reported earlier from shroud surface experiments that did improve compressor flow range. Opposite trends are seen for hub injection cases where compressor flow range decreased. The hub injection data further explain the range improvement provided by shroud-side injection and suggest that different hub-side techniques may produce range improvement in centrifugal compressors.

Automated system for on-line determination of dimethylarsinic and inorganic arsenic by hydride generation-atomic fluorescence spectrometry.

PubMed

Chaparro, L L; Ferrer, L; Cerdà, V; Leal, L O

2012-09-01

A multisyringe flow-injection approach has been coupled to hydride generation-atomic fluorescence spectrometry (HG-AFS) with UV photo-oxidation for dimethylarsinic (DMA), inorganic As and total As determination, depending on the pre-treatment given to the sample (extraction or digestion). The implementation of a UV lamp allows on-line photo-oxidation of DMA and the following arsenic detection, whereas a bypass leads the flow directly to the HG-AFS system, performing inorganic arsenic determination. DMA concentration is calculated by the difference of total inorganic arsenic and measurement of the photo-oxidation step. The detection limits for DMA and inorganic arsenic were 0.09 and 0.47 μg L(-1), respectively. The repeatability values accomplished were of 2.4 and 1.8%, whereas the injection frequencies were 24 and 28 injections per hour for DMA and inorganic arsenic, respectively. This method was validated by means of a solid reference material BCR-627 (muscle of tuna) with good agreement with the certified values. Satisfactory results for DMA and inorganic arsenic determination were obtained in several water matrices. The proposed method offers several advantages, such as increasing the sampling frequency, low detection limits and decreasing reagents and sample consumption, which leads to lower waste generation.

Identification and quantitation of vitamins K1 and K3 in cosmetic products for facial skin protection.

PubMed

De Orsi, D; Giannini, G; Gagliardi, L; Carpani, I; Tonelli, D

2008-01-01

A simple and rapid analytical method was developed for the determination of vitamins K1 and K3 in facial anti-rash creams. The procedure is based on an ultrasonic extraction of the cosmetic sample with dimethylacetamide, in the presence of an internal standard, followed by HPLC separation. HPLC was performed using a C18 column and spectrophotometric detection at 333 nm. A linear gradient elution was carried out starting with 50% acetonitrile-methanol (75:25 v/v) and water up to 100% acetonitrile-methanol for 5 min. Linearity was established over the concentration range from 0.2 to 1.0 mg/ml for vitamin K1 and from 0.02 to 0.1 mg/ml for vitamin K3, with LOD values of 100 ng and 20 ng injected, respectively. The accuracy was verified by spiking experiments on model cosmetic samples. The proposed method has been successfully applied for the analysis of commercial samples of creams.

Visualisation of diesel injector with neutron imaging

NASA Astrophysics Data System (ADS)

Lehmann, E.; Grünzweig, C.; Jollet, S.; Kaiser, M.; Hansen, H.; Dinkelacker, F.

2015-12-01

The injection process of diesel engines influences the pollutant emissions. The spray formation is significantly influenced by the internal flow of the injector. One of the key parameters here is the generation of cavitation caused by the geometry and the needle lift. In modern diesel engines the injection pressure is established up to 3000 bar. The details of the flow and phase change processes inside the injector are of increasing importance for such injectors. With these experimental measurements the validation of multiphase and cavitation models is possible for the high pressure range. Here, for instance, cavitation effects can occur. Cavitation effects in the injection port area destabilize the emergent fuel jet and improve the jet break-up. The design of the injection system in direct-injection diesel engines is an important challenge, as the jet breakup, the atomization and the mixture formation in the combustion chamber are closely linked. These factors have a direct impact on emissions, fuel consumption and performance of an engine. The shape of the spray at the outlet is determined by the internal flow of the nozzle. Here, geometrical parameters, the injection pressure, the injection duration and the cavitation phenomena play a major role. In this work, the flow dependency in the nozzles are analysed with the Neutron-Imaging. The great advantage of this method is the penetrability of the steel structure while a high contrast to the fuel is given due to the interaction of the neutrons with the hydrogen amount. Compared to other methods (optical with glass structures) we can apply real components under highest pressure conditions. During the steady state phase of the injection various cavitation phenomena are visible in the injector, being influenced by the nozzle geometry and the fuel pressure. Different characteristics of cavitation in the sac and spray hole can be detected, and the spray formation in the primary breakup zone is influenced.

Two different spectrophotometric determinations of potential anticancer drug and its toxic metabolite

NASA Astrophysics Data System (ADS)

Farid, Nehal F.; Abdelwahab, Nada S.

2015-06-01

Flutamide is a hormone therapy used for men with advanced prostate cancer. Flutamide is highly susceptible to hydrolysis with the production of 3-(trifluoromethyl)aniline, which is reported to be one of its toxic metabolites, impurities and related substances according to BP and USP. Flutamide was found to be stable when exposed to oxidation by 30% hydrogen peroxide and direct sunlight for up to 4 h. Two accurate and sensitive spectrophotometric methods were used for determination of flutamide in bulk and in pharmaceutical formulations. Method (I) is the area under curve (AUC) spectrophotometric method that depends on measuring the AUC in the wavelength ranges of 275-305 nm and 350-380 nm and using Cramer's rule. The linearity range was found to be 1-35 μg/mL and 0.5-16 μg/mL for the drug and the degradate, respectively. In method (II), combination of the isoabsorptive and dual wavelength spectrophotometric methods was used for resolving the binary mixture. The absorbance at 249.2 nm (λiso) was used for determination of total mixture concentration, while the difference in absorbance between 232 nm and 341.2 nm was used for measuring the drug concentration. By subtraction, the degradate concentration was obtained. Beer's law was obeyed in the range of 2-35 μg/mL and 0.5-20 μg/mL for the drug and its degradate, respectively. The two methods were validated according to USP guidelines and were applied for determination of the drug in its pharmaceutical dosage form. Moreover AUC method was used for the kinetic study of the hydrolytic degradation of flutamide. The kinetic degradation of flutamide was found to follow pseudo-first order kinetics and is pH and temperature dependent. Activation energy, kinetic rate constants and t1/2 at different temperatures and pH values were calculated.

Validated spectrophotometric methods for determination of some oral hypoglycemic drugs.

PubMed

Farouk, M; Abdel-Satar, O; Abdel-Aziz, O; Shaaban, M

2011-02-01

Four accurate, precise, rapid, reproducible, and simple spectrophotometric methods were validated for determination of repaglinide (RPG), pioglitazone hydrochloride (PGL) and rosiglitazone maleate (RGL). The first two methods were based on the formation of a charge-transfer purple-colored complex of chloranilic acid with RPG and RGL with a molar absorptivity 1.23 × 10³ and 8.67 × 10² l•mol^-1•cm^-1 and a Sandell's sensitivity of 0.367 and 0.412 μg•cm^-2, respectively, and an ion-pair yellow-colored complex of bromophenol blue with RPG, PGL and RGL with molar absorptivity 8.86 × 10³, 6.95 × 10³, and 7.06 × 10³ l•mol^-1•cm^-1, respectively, and a Sandell's sensitivity of 0.051 μg•cm^-2 for all ion-pair complexes. The influence of different parameters on color formation was studied to determine optimum conditions for the visible spectrophotometric methods. The other spectrophotometric methods were adopted for demtermination of the studied drugs in the presence of their acid-, alkaline- and oxidative-degradates by computing derivative and pH-induced difference spectrophotometry, as stability-indicating techniques. All the proposed methods were validated according to the International Conference on Harmonization guidelines and successfully applied for determination of the studied drugs in pure form and in pharmaceutical preparations with good extraction recovery ranges between 98.7-101.4%, 98.2-101.3%, and 99.9-101.4% for RPG, PGL, and RGL, respectively. Results of relative standard deviations did not exceed 1.6%, indicating that the proposed methods having good repeatability and reproducibility. All the obtained results were statistically compared to the official method used for RPG analysis and the manufacturers methods used for PGL and RGL analysis, respectively, where no significant differences were found.

Two different spectrophotometric determinations of potential anticancer drug and its toxic metabolite.

PubMed

Farid, Nehal F; Abdelwahab, Nada S

2015-06-15

Flutamide is a hormone therapy used for men with advanced prostate cancer. Flutamide is highly susceptible to hydrolysis with the production of 3-(trifluoromethyl)aniline, which is reported to be one of its toxic metabolites, impurities and related substances according to BP and USP. Flutamide was found to be stable when exposed to oxidation by 30% hydrogen peroxide and direct sunlight for up to 4h. Two accurate and sensitive spectrophotometric methods were used for determination of flutamide in bulk and in pharmaceutical formulations. Method (I) is the area under curve (AUC) spectrophotometric method that depends on measuring the AUC in the wavelength ranges of 275-305 nm and 350-380nm and using Cramer's rule. The linearity range was found to be 1-35 μg/mL and 0.5-16 μg/mL for the drug and the degradate, respectively. In method (II), combination of the isoabsorptive and dual wavelength spectrophotometric methods was used for resolving the binary mixture. The absorbance at 249.2 nm (λiso) was used for determination of total mixture concentration, while the difference in absorbance between 232 nm and 341.2 nm was used for measuring the drug concentration. By subtraction, the degradate concentration was obtained. Beer's law was obeyed in the range of 2-35 μg/mL and 0.5-20 μg/mL for the drug and its degradate, respectively. The two methods were validated according to USP guidelines and were applied for determination of the drug in its pharmaceutical dosage form. Moreover AUC method was used for the kinetic study of the hydrolytic degradation of flutamide. The kinetic degradation of flutamide was found to follow pseudo-first order kinetics and is pH and temperature dependent. Activation energy, kinetic rate constants and t1/2 at different temperatures and pH values were calculated. Copyright © 2015 Elsevier B.V. All rights reserved.

Successive spectrophotometric resolution as a novel technique for the analysis of ternary mixtures of pharmaceuticals

NASA Astrophysics Data System (ADS)

Lotfy, Hayam M.; Tawakkol, Shereen M.; Fahmy, Nesma M.; Shehata, Mostafa A.

2014-03-01

A novel spectrophotometric technique was developed for the simultaneous determination of ternary mixtures, without prior separation steps. This technique was called successive spectrophotometric resolution technique. The technique was based on either the successive ratio subtraction or successive derivative subtraction. The mathematical explanation of the procedure was illustrated. In order to evaluate the applicability of the methods a model data as well as an experimental data were tested. The results from experimental data related to the simultaneous spectrophotometric determination of lidocaine hydrochloride (LH), calcium dobesilate (CD) and dexamethasone acetate (DA); in the presence of hydroquinone (HQ), the degradation product of calcium dobesilate were discussed. The proposed drugs were determined at their maxima 202 nm, 305 nm, 239 nm and 225 nm for LH, CD, DA and HQ respectively; by successive ratio subtraction coupled with constant multiplication method to obtain the zero order absorption spectra, while by applying successive derivative subtraction they were determined at their first derivative spectra at 210 nm for LH, 320 nm or P292-320 for CD, 256 nm or P225-252 for DA and P220-233 for HQ respectively. The calibration curves were linear over the concentration range of 2-20 μg/mL for both LH and DA, 6-50 μg/mL for CD, and 3-40 μg/mL for HQ. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs with no interference from other dosage form additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with those of the official BP methods for LH, DA, and CD, and with the official USP method for HQ; using student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.

Simultaneous spectrophotometric determination of paracetamol and salicylamide in human serum and pharmaceutical formulations by a differential kinetic method.

PubMed

Zarei, Ali Reza; Afkhami, Abbas; Sarlak, Nahid

2005-01-01

A rapid, simple, and sensitive differential kinetic method is presented for the determinations of acetaminophen (also known as paracetamol) and salicylamide. The method is based on their oxidation reaction by Fe3+ ion in the presence of 1, 10-phenanthroline as indicator. The reactions can be monitored spectrophotometrically by measuring the increase in the absorbance of the solution at 510 nm. Two times were selected one in which only paracetamol is oxidized by Fe3+ ion and the other in which both drugs are oxidized by Fe3+ ion. The data were evaluated by the proportional equations method. The method allowed the simultaneous determination of paracetamol and salicylamide at concentrations between 0.5-20 and 1-40 microg/mL with relative standard deviations of 3.47 and 2.58%, respectively. The method was applied to the simultaneous determination of paracetamol and salicylamide in human serum and pharmaceutical formulations.

Spectrophotometric determination of the tannin contents of various Turkish black tea, beer and wine samples.

PubMed

Tinkiliç, N; Uyanik, A

2001-05-01

This study reports tannin contents of various tea (19), beer (6) and wine (6) samples, produced or sold in Turkey under different brand names. Determinations were carried out by employing a previously reported UV-vis spectrophotometric method. The standard addition procedure was also compared to the direct determination procedure and found to be more reliable. The tannin contents of hot water extracts of tea, tea bag and herbal tea samples ranged between 6.20-8.33, 8.03-6.59 and 2.76-6.54 percent (w/w) respectively. Tannin contents of beer and wine samples determined without extraction were found ranging between 66.36-77.26 and 67.18-107.62 micrograms/mL respectively. Iron contents of analysed wine samples were also found ranging between 0.36 and 10.33 ppm by AAS and no relation is found between tannin and iron contents.

Simultaneous determination of binary mixture of amlodipine besylate and atenolol based on dual wavelengths

NASA Astrophysics Data System (ADS)

Lamie, Nesrine T.

2015-10-01

Four, accurate, precise, and sensitive spectrophotometric methods are developed for simultaneous determination of a binary mixture of amlodipine besylate (AM) and atenolol (AT). AM is determined at its λmax 360 nm (0D), while atenolol can be determined by four different methods. Method (A) is absorption factor (AF). Method (B) is the new ratio difference method (RD) which measures the difference in amplitudes between 210 and 226 nm. Method (C) is novel constant center spectrophotometric method (CC). Method (D) is mean centering of the ratio spectra (MCR) at 284 nm. The methods are tested by analyzing synthetic mixtures of the cited drugs and they are applied to their commercial pharmaceutical preparation. The validity of results is assessed by applying standard addition technique. The results obtained are found to agree statistically with those obtained by official methods, showing no significant difference with respect to accuracy and precision.

Extractive-spectrophotometric determination of disopyramide and irbesartan in their pharmaceutical formulation

NASA Astrophysics Data System (ADS)

Abdellatef, Hisham E.

2007-04-01

Picric acid, bromocresol green, bromothymol blue, cobalt thiocyanate and molybdenum(V) thiocyanate have been tested as spectrophotometric reagents for the determination of disopyramide and irbesartan. Reaction conditions have been optimized to obtain coloured comoplexes of higher sensitivity and longer stability. The absorbance of ion-pair complexes formed were found to increases linearity with increases in concentrations of disopyramide and irbesartan which were corroborated by correction coefficient values. The developed methods have been successfully applied for the determination of disopyramide and irbesartan in bulk drugs and pharmaceutical formulations. The common excipients and additives did not interfere in their determination. The results obtained by the proposed methods have been statistically compared by means of student t-test and by the variance ratio F-test. The validity was assessed by applying the standard addition technique. The results were compared statistically with the official or reference methods showing a good agreement with high precision and accuracy.

Simple flow injection for determination of sulfite by amperometric detection using glassy carbon electrode modified with carbon nanotubes-PDDA-gold nanoparticles.

PubMed

Amatatongchai, Maliwan; Sroysee, Wongduan; Chairam, Sanoe; Nacapricha, Duangjai

2015-02-01

A new approach is presented for sensitive and selective measurement of sulfite (SO3(2-)) in beverages based on a simple flow injection system with amperometric detection. In this work, the sulfite sensor was a glassy carbon electrode modified with multiwall carbon nanotubes-poly(diallyldimethylammonium chloride)-gold nanoparticles composites (CNTs-PDDA-AuNPs/GC). Electrochemical oxidation of sulfite with this electrode was first studied in 0.1M phosphate buffer (pH 7.0) using cyclic voltammetry. The results indicated that the CNTs-PDDA-AuNPs/GC electrode possesses electrocatalytic activity for the oxidation of sulfite with high sensitivity and selectivity. Sulfite was quantified using amperometric measurement with the new sensor at +0.4V vs Ag/AgCl in conjunction with flow injection. The linear working range for the quantitation of sulfite was 2-200 mg L(-1) (r(2)=0.998) with a detection limit of 0.03 mg L(-1) (3σ of blank) and an estimated precision of 1.5%.The proposed method was successfully applied to the determination of sulfite in fruit juices and wines with a sample throughput of 23 samples per hour. Copyright © 2014 Elsevier B.V. All rights reserved.

Injectable Solid Peptide Hydrogel as Cell Carrier: Effects of Shear Flow on Hydrogel and Cell Payload

PubMed Central

Yan, Congqi; Mackay, Michael E.; Czymmek, Kirk; Nagarkar, Radhika P.; Schneider, Joel P.; Pochan, Darrin J.

2012-01-01

β-hairpin peptide-based hydrogels are a class of injectable solid hydrogels that can deliver encapsulated cells or molecular therapies to a target site via syringe or catheter injection as a carrier material. These physical hydrogels can shear-thin and consequently flow as a low-viscosity material under a sufficient shear stress but immediately recover back into a solid upon removal of the stress, allowing them to be injected as preformed gel solids. Hydrogel behavior during flow was studied in a cylindrical capillary geometry that mimicked the actual situation of injection through a syringe needle in order to quantify effects of shear-thin injection delivery on hydrogel flow behavior and encapsulated cell payloads. It was observed that all β-hairpin peptide hydrogels investigated displayed a promising flow profile for injectable cell delivery: a central wide plug flow region where gel material and cell payloads experienced little or no shear rate and a narrow shear zone close to the capillary wall where gel and cells were subject to shear deformation. The width of the plug flow region was found to be weakly dependent on hydrogel rigidity and flow rate. Live-dead assays were performed on encapsulated MG63 cells three hours after injection flow and revealed that shear-thin delivery through the capillary had little impact on cell viability and the spatial distribution of encapsulated cell payloads. These observations help us to fundamentally understand how the gels flow during injection through a thin catheter and how they immediately restore mechanically and morphologically relative to pre-flow, static gels. PMID:22390812

Determination of mercury in agroindustrial samples by flow-injection cold vapor atomic absorption spectrometry using ion exchange and reductive elution.

PubMed

Gomes Neto, J A; Zara, L F; Rocha, J C; Santos, A; Dakuzaku, C S; Nóbrega, J A

2000-03-06

A flow-injection system with a Chelite-S(R) cationic resin packed minicolumn is proposed for the determination of trace levels of mercury in agroindustrial samples by cold vapor atomic absorption spectrometry. Improved sensitivity and selectivity are attained since mercuric ions are on-line concentrated whereas other potential interferents are discarded. With on-line reductive elution procedure, concentrated hydrochloric acid could be replaced by 10% w/v SnCl(2), in 6 M HCl as eluent. The reversed-intermittent stream either carries the atomic mercury to the flow cell in the forward direction or removes the residue from reactor/gas-liquid separator to a discarding flask in the opposite direction. Concentration and volume of reagent, acidity, flow rates, commutation times and potential interfering species were investigated. For 120 s preconcentration time, the proposed system handles about 25 samples h(-1) (50.0-500 ng l(-1)), consuming about 10 ml sample and 5 mg SnCl(2) per determination. The detection limit is 0.8 ng l(-1) and the relative standard deviation (RSD) (n=12) of a 76.7 ng l(-1) sample is about 5%. Results are in agreement with certified value of standard materials at 95% confidence level and good recoveries (97-128%) of spiked samples were found.

A flow injection chemiluminescence system for the determination of isoniazid.

PubMed

Huang, Y; Zhang, Z; Zhang, D; Lv, J

2000-10-01

A chemiluminescence (CL) flow system is described for the determination of isoniazid based on its enhancement on the chemiluminescence (CL) emission produced upon mixing a hexacyanoferrate(III) solution with an alkaline luminol solution. The system responds linearly to isoniazid concentration in the range 0-1 mg/L with a detection limit (3sigma) of 0.03 microg/L, relative standard deviation (RSD) of 1.2% for 0.1 mg/L isoniazid (n = 11). The system has been successfully applied to the determination of isoniazid in pharmaceutical preparations.

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

NASA Astrophysics Data System (ADS)

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

2016-05-01

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

Two smart spectrophotometric methods for the simultaneous estimation of Simvastatin and Ezetimibe in combined dosage form

NASA Astrophysics Data System (ADS)

Magdy, Nancy; Ayad, Miriam F.

2015-02-01

Two simple, accurate, precise, sensitive and economic spectrophotometric methods were developed for the simultaneous determination of Simvastatin and Ezetimibe in fixed dose combination products without prior separation. The first method depends on a new chemometrics-assisted ratio spectra derivative method using moving window polynomial least square fitting method (Savitzky-Golay filters). The second method is based on a simple modification for the ratio subtraction method. The suggested methods were validated according to USP guidelines and can be applied for routine quality control testing.

Recent Electrochemical and Optical Sensors in Flow-Based Analysis

PubMed Central

Chailapakul, Orawon; Ngamukot, Passapol; Yoosamran, Alongkorn; Siangproh, Weena; Wangfuengkanagul, Nattakarn

2006-01-01

Some recent analytical sensors based on electrochemical and optical detection coupled with different flow techniques have been chosen in this overview. A brief description of fundamental concepts and applications of each flow technique, such as flow injection analysis (FIA), sequential injection analysis (SIA), all injection analysis (AIA), batch injection analysis (BIA), multicommutated FIA (MCFIA), multisyringe FIA (MSFIA), and multipumped FIA (MPFIA) were reviewed.

Novel Spectrophotometric Method for the Assay of Captopril in Dosage Forms using 2,6-Dichloroquinone-4-Chlorimide

PubMed Central

El-Enany, Nahed; Belal, Fathalla; Rizk, Mohamed

2008-01-01

A simple spectrophotometric method was developed for the determination of captopril (CPL) in pharmaceutical preparations. The method is based on coupling captopril with 2,6-dichloroquinone-4-chlorimide (DCQ) in dimethylsulphoxide. The yellow reaction product was measured at 443 nm. The absorbance–concentration plot was rectilinear over the range of 10-50 μg/mL with minimum detection limit (LOD) of 0.66 μg/mL and a quantification limit (LOQ) of 2.0 μg/mL. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The proposed method was successfully applied to the analysis of commercial tablets and the results were in good agreement with those obtained using official and reference spectrophotometric methods. Hydrochlorothiazide which is frequently co-formulated with CPL did not interfere with the assay. A proposal of the reaction pathway was presented. PMID:23675082

Spectrophotometric analyses of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in water.

PubMed

Shi, Cong; Xu, Zhonghou; Smolinski, Benjamin L; Arienti, Per M; O'Connor, Gregory; Meng, Xiaoguang

2015-07-01

A simple and accurate spectrophotometric method for on-site analysis of royal demolition explosive (RDX) in water samples was developed based on the Berthelot reaction. The sensitivity and accuracy of an existing spectrophotometric method was improved by: replacing toxic chemicals with more stable and safer reagents; optimizing the reagent dose and reaction time; improving color stability; and eliminating the interference from inorganic nitrogen compounds in water samples. Cation and anion exchange resin cartridges were developed and used for sample pretreatment to eliminate the effect of ammonia and nitrate on RDX analyses. The detection limit of the method was determined to be 100 μg/L. The method was used successfully for analysis of RDX in untreated industrial wastewater samples. It can be used for on-site monitoring of RDX in wastewater for early detection of chemical spills and failure of wastewater treatment systems. Copyright © 2015. Published by Elsevier B.V.

New spectrophotometric estimation of indomethacin capsules with niacinamide as hydrotropic solubilizing agent.

PubMed

Maheshwari, R K; Rathore, Amit; Agrawal, Archana; Gupta, Megha A

2011-07-01

Hydrotropic solubilization process involves cooperative intermolecular interaction with several balancing molecular forces, rather than either a specific complexation event or a process dominated by a medium effect, such as co-solvency or salting-in. In the present investigation, hydrotropic solution of 2 M niacinamide was employed as the solubilizing agent to solubilize the poorly water-soluble drug, indomethacin, from the capsule dosage form for spectrophotometric determination in ultraviolet region. Hydrotropic agent used did not interfere in the spectrophotometric analysis. In preliminary solubility studies, it was found that there was more than fivefold enhancement in the aqueous solubility of indomethacin (poorly water-soluble drug) in 2 M niacinamide solution as compared to its aqueous solubility at 28 ± 1°C. The proposed method is new, simple, safe, environmentally friendly, economic, accurate and cost-effective and can be successfully employed in routine analysis.

Skin colour changes during experimentally-induced sickness.

PubMed

Henderson, Audrey J; Lasselin, Julie; Lekander, Mats; Olsson, Mats J; Powis, Simon J; Axelsson, John; Perrett, David I

2017-02-01

Skin colour may be an important cue to detect sickness in humans but how skin colour changes with acute sickness is currently unknown. To determine possible colour changes, 22 healthy Caucasian participants were injected twice, once with lipopolysaccharide (LPS, at a dose of 2ng/kg body weight) and once with placebo (saline), in a randomised cross-over design study. Skin colour across 3 arm and 3 face locations was recorded spectrophotometrically over a period of 8h in terms of lightness (L ∗ ), redness (a ∗ ) and yellowness (b ∗ ) in a manner that is consistent with human colour perception. In addition, carotenoid status was assessed as we predicted that a decrease it skin yellowness would reflect a drop in skin carotenoids. We found an early change in skin colouration 1-3h post LPS injection with facial skin becoming lighter and less red whilst arm skin become darker but also less red and less yellow. The LPS injection also caused a drop in plasma carotenoids from 3h onwards. However, the timing of the carotenoid changes was not consistent with the skin colour changes suggesting that other mechanisms, such as a reduction of blood perfusion, oxygenation or composition. This is the first experimental study characterising skin colour associated with acute illness, and shows that changes occur early in the development of the sickness response. Colour changes may serve as a cue to health, prompting actions from others in terms of care-giving or disease avoidance. Specific mechanisms underlying these colour changes require further investigation. Copyright © 2016 Elsevier Inc. All rights reserved.

Wicket gate trailing-edge blowing: A method for improving off-design hydroturbine performance by adjusting the runner inlet swirl angle

NASA Astrophysics Data System (ADS)

Lewis, B. J.; Cimbala, J. M.; Wouden, A. M.

2014-03-01

At their best efficiency point (BEP), hydroturbines operate at very high efficiency. However, with the ever-increasing penetration of alternative electricity generation, it has become common to operate hydroturbines at off-design conditions in order to maintain stability in the electric power grid. This paper demonstrates a method for improving hydroturbine performance during off-design operation by injecting water through slots at the trailing edges of the wicket gates. The injected water causes a change in bulk flow direction at the inlet of the runner. This change in flow angle from the wicket gate trailing-edge jets provides the capability of independently varying the flow rate and swirl angle through the runner, which in current designs are both determined by the wicket gate opening angle. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation.

Injection characteristics study of high-pressure direct injector for Compressed Natural Gas (CNG) using experimental and analytical method

NASA Astrophysics Data System (ADS)

Taha, Z.; Rahim, MF Abdul; Mamat, R.

2017-10-01

The injection characteristics of direct injector affect the mixture formation and combustion processes. In addition, the injector is converted from gasoline operation for CNG application. Thus measurement of CNG direct injector mass flow rate was done by independently tested a single injector on a test bench. The first case investigated the effect of CNG injection pressure and the second case evaluate the effect of pulse-width of injection duration. An analytical model was also developed to predict the mass flow rate of the injector. The injector was operated in a choked condition in both the experiments and simulation studies. In case 1, it was shown that mass flow rate through the injector is affected by injection pressure linearly. Based on the tested injection pressure of 20 bar to 60 bar, the resultant mass flow rate are in the range of 0.4 g/s to 1.2 g/s which are met with theoretical flow rate required by the engine. However, in Case 2, it was demonstrated that the average mass flow rate at short injection durations is lower than recorded in Case 1. At injection pressure of 50 bar, the average mass flow rate for Case 2 and Case 1 are 0.7 g/s and 1.1 g/s respectively. Also, the measured mass flow rate at short injection duration showing a fluctuating data in the range of 0.2 g/s - 1.3 g/s without any noticeable trends. The injector model able to predict the trend of the mass flow rate at different injection pressure but unable to track the fluctuating trend at short injection duration.

Three-dimensional numerical simulation for plastic injection-compression molding

NASA Astrophysics Data System (ADS)

Zhang, Yun; Yu, Wenjie; Liang, Junjie; Lang, Jianlin; Li, Dequn

2018-03-01

Compared with conventional injection molding, injection-compression molding can mold optical parts with higher precision and lower flow residual stress. However, the melt flow process in a closed cavity becomes more complex because of the moving cavity boundary during compression and the nonlinear problems caused by non-Newtonian polymer melt. In this study, a 3D simulation method was developed for injection-compression molding. In this method, arbitrary Lagrangian- Eulerian was introduced to model the moving-boundary flow problem in the compression stage. The non-Newtonian characteristics and compressibility of the polymer melt were considered. The melt flow and pressure distribution in the cavity were investigated by using the proposed simulation method and compared with those of injection molding. Results reveal that the fountain flow effect becomes significant when the cavity thickness increases during compression. The back flow also plays an important role in the flow pattern and redistribution of cavity pressure. The discrepancy in pressures at different points along the flow path is complicated rather than monotonically decreased in injection molding.

Derivative spectrophotometric method for simultaneous determination of clindamycin phosphate and tretinoin in pharmaceutical dosage forms.

PubMed

Barazandeh Tehrani, Maliheh; Namadchian, Melika; Fadaye Vatan, Sedigheh; Souri, Effat

2013-04-10

A derivative spectrophotometric method was proposed for the simultaneous determination of clindamycin and tretinoin in pharmaceutical dosage forms. The measurement was achieved using the first and second derivative signals of clindamycin at (1D) 251 nm and (2D) 239 nm and tretinoin at (1D) 364 nm and (2D) 387 nm.The proposed method showed excellent linearity at both first and second derivative order in the range of 60-1200 and 1.25-25 μg/ml for clindamycin phosphate and tretinoin respectively. The within-day and between-day precision and accuracy was in acceptable range (CV<3.81%, error<3.20%). Good agreement between the found andadded concentrations indicates successful application of the proposed method for simultaneous determination of clindamycin and tretinoin in synthetic mixtures and pharmaceutical dosage form.

Spectrophotometric Determination of Poorly Water Soluble Drug Rosiglitazone Using Hydrotropic Solubilization technique.

PubMed

Sherje, A P; Desai, K J

2011-09-01

In the present investigation, hydrotropic solution of urea was employed as a solubilizing agent for spectrophotometric determination of poorly water-soluble drug rosiglitazone maleate. In solubility determination study, it was found that there was more than 14-folds enhancement in solubility of rosiglitazone maleate in a 6M solution of urea. Rosiglitazone maleate obeys Beer's law in concentration range of 5-300 μg/ml. Linearity of rosiglitazone maleate was found in the range of 80-120% of the label claim. The proposed method has been applied successfully to the analysis of the cited drug in pharmaceutical formulations with good accuracy and precision. The method herein described is new, simple, eco-friendly, economic, and accurate and can be utilized in routine analysis of rosiglitazone maleate in bulk drug and tablet dosage form.

Spectrophotometric Determination of Poorly Water Soluble Drug Rosiglitazone Using Hydrotropic Solubilization technique

PubMed Central

Sherje, A. P.; Desai, K. J.

2011-01-01

In the present investigation, hydrotropic solution of urea was employed as a solubilizing agent for spectrophotometric determination of poorly water-soluble drug rosiglitazone maleate. In solubility determination study, it was found that there was more than 14-folds enhancement in solubility of rosiglitazone maleate in a 6M solution of urea. Rosiglitazone maleate obeys Beer's law in concentration range of 5-300 μg/ml. Linearity of rosiglitazone maleate was found in the range of 80-120% of the label claim. The proposed method has been applied successfully to the analysis of the cited drug in pharmaceutical formulations with good accuracy and precision. The method herein described is new, simple, eco-friendly, economic, and accurate and can be utilized in routine analysis of rosiglitazone maleate in bulk drug and tablet dosage form. PMID:22923874

Spectrophotometric determination of titanium with tannin and thioglycollic acid and its application to titanium-treated steels and ferrous and non-ferrous alloys.

PubMed

Banerjee, S

1986-04-01

A sensitive spectrophotometric method for the determination of titanium by formation of its complex with tannin and thioglycollic acid at pH 4 has been developed. The intense yellow colour is measured at 400 nm and the system obeys Beer's law over the range 0.2-5 ppm titanium in the solution measured. The method is applicable to titanium-treated steels, stainless steels, permanent magnet alloys and duralumin alloys. The interference of Co, Ni, Cr, Mn, V, Mo and W can be eliminated by prior separation of titanium by controlled addition of cupferron in the presence of thioglycollic acid (TGA). Copper can be quantitatively separated by precipitation with TGA and determined complexometrically with EDTA, with PAN as indicator. Niobium interferes even in traces.

Downhole steam quality measurement

DOEpatents

Lee, D.O.; Montoya, P.C.; Muir, J.F.; Wayland, J.R. Jr.

1985-06-19

The present invention relates to an empirical electrical method for remote sensing of steam quality utilizing flow-through grids which allow measurement of the electrical properties of a flowing two-phase mixture. The measurement of steam quality in the oil field is important to the efficient application of steam assisted recovery of oil. Because of the increased energy content in higher quality steam it is important to maintain the highest possible steam quality at the injection sandface. The effectiveness of a steaming operation without a measure of steam quality downhole close to the point of injection would be difficult to determine. Therefore, a need exists for the remote sensing of steam quality.

Injection System for Multi-Well Injection Using a Single Pump

PubMed Central

Wovkulich, Karen; Stute, Martin; Protus, Thomas J.; Mailloux, Brian J.; Chillrud, Steven N.

2015-01-01

Many hydrological and geochemical studies rely on data resulting from injection of tracers and chemicals into groundwater wells. The even distribution of liquids to multiple injection points can be challenging or expensive, especially when using multiple pumps. An injection system was designed using one chemical metering pump to evenly distribute the desired influent simultaneously to 15 individual injection points through an injection manifold. The system was constructed with only one metal part contacting the fluid due to the low pH of the injection solutions. The injection manifold system was used during a three-month pilot scale injection experiment at the Vineland Chemical Company Superfund site. During the two injection phases of the experiment (Phase I = 0.27 L/min total flow, Phase II = 0.56 L/min total flow), flow measurements were made 20 times over three months; an even distribution of flow to each injection well was maintained (RSD <4%). This durable system is expandable to at least 16 injection points and should be adaptable to other injection experiments that require distribution of air-stable liquids to multiple injection points with a single pump. PMID:26140014

Evaluation of centrifugal compressor performance with water injection

NASA Technical Reports Server (NTRS)

Beede, William L; Hamrick, Joseph T; Withee, Joseph R , Jr

1951-01-01

The effects of water injection on a compressor are presented. To determine the effects of varying water-air ratio, the compressor was operated at a constant equivalent impeller speed over a range of water-air ratios and weight flows. Operation over a range of weight flows at one water-air ratio and two inlet air temperatures was carried out to obtain an indication of the effects of varying inlet air temperature. Beyond a water-air ratio of 0.03 there was no increase in maximum air-weight flow, a negligible rise in peak total-pressure ratio, and a decrease in peak adiabatic efficiency. An increase in inlet air temperature resulted in an increase in the magnitude of evaporation. An analysis of data indicated that the magnitude of evaporation within the compressor impeller was small.

The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

PubMed

Altiokka, G; Atkosar, Z; Can, N O

2002-10-15

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively. Copyright 2002 Elsevier Science B.V.

An analytical study of the effect of coolant flow variables on the kinetic energy output of a cooled turbine blade flow

NASA Technical Reports Server (NTRS)

Prust, H. W., Jr.

1971-01-01

The results of an analytical study to determine the effect of changes in the amount, velocity, injection location, injection angle, and temperature of coolant flow on blade row performance are presented. The results show that the change in output of a cooled turbine blade row relative to the specific output of the uncooled blade row can be positive, negative, or zero. Comparisons between the analytical results and experimental results for four different cases of coolant discharge, all at a coolant temperature ratio of unity, show good agreement for three cases and rather poor agreement for the other. To further test the validity of the method, more experimental data is needed, particularly at different coolant temperature ratios.

Analysis of tests of subsurface injection, storage, and recovery of freshwater in the lower Floridan aquifer, Okeechobee County, Florida

USGS Publications Warehouse

Quinones-Aponte, Vicente; Kotun, Kevin; Whitley, J.F.

1996-01-01

A series of freshwater subsurface injection, storage, and recovery tests were conducted at an injection-well site near Lake Okeechobee in Okeechobee County, Florida, to assess the recoverability of injected canal water from the Lower Floridan aquifer. At the study site, the Lower Floridan aquifer is characterized as having four local, relatively independent, high-permeability flow zones (389 to 398 meters, 419 to 424 meters, 456 to 462 meters, and 472 to 476 meters below sea level). Four subsurface injection, storage, and recovery cycles were performed at the Lake Okeechobee injection-well site in which volumes of water injected ranged from about 387,275 to 1,343,675 cubic meters for all the cycles, and volumes of water recovered ranged from about 106,200 to 484,400 cubic meters for cycles 1, 2, and 3. The recovery efficiency for successive cycles 2 and 3 increased from 22 to 36 percent and is expected to continue increasing with additional cycles. A comparison of chloride concentration breakthrough curves at the deep monitor well (located about 171 meters from the injection well) for cycles 1, 4, and test no. 4 (from a previous study) revealed unexpected finings. One significant result was that the concentration asymptote, expected to be reached at concentration levels equivalent or close to the injected water concentration, was instead reached at higher concentration levels. The injection to recovery rate ratio might affect the chloride concentration breakthrough curve at the deep monitor well, which could explain this unexpected behavior. Because there are four high-permeability zones, if the rate of injection is smaller than the rate of recovery (natural artesian flow), the head differential might not be transmitted through the entire open wellbore, and injected water would probably flow only through the upper high- permeability zones. Therefore, observed chloride concentration values at the deep monitor well would be higher than the concentration of the injected water and would represent a mix of water from the different high-permeability zones. A generalized digital model was constructed to simulate the subsurface injection, storage, and recovery of freshwater in the Lower Floridan aquifer at the Lake Okeechobee injection-well site. The model was constructed using a modified version of the Saturated-Unsaturated TRAnsport code (SUTRA), which simulates variable-density advective-dispersive solute transport and variable-density ground-water flow. Satisfactory comparisons of simulated to observed dimensionless chloride concentrations for the deep monitor well were obtained when using the model during the injection and recovery phases of cycle 1, but not for the injection well during the recovery phase of cycle 1 even after several attempts. This precluded the determination of the recovery efficiency values by using the model. The unsatisfactory comparisons of simulated to observed dimensionless chloride concentrations for the injection well and failure of the model to represent the field data at this well could be due to the characteristics of the Lower Floridan aquifer (at the local scale), which is cavernous or conduit in nature. To test this possibility, Reynolds numbers were estimated at varying distances from the injection well, taking into consideration two aquifer types or conceptual systems, porous media and cavernous. For the porous media conceptual system, the Reynolds numbers were greater than 10 at distances less than 1.42 meters from the injection well. Thus, application of Darcy's law to ground-water flow might not be valid at this distance. However, at the deep monitor well (171 meters from the injection well), the Reynolds number was 0.08 which is indicative of laminar porous media flow. For the cavernous conceptual system, the Reynolds numbers were greater than 2,000 at distances less than 1,000 meters from the well. This number represents the upper limit of laminar flow, which is the fundamental assumption

Numerical Simulation of Atomization in Nozzle Injection Flow

NASA Astrophysics Data System (ADS)

Fan, Qinyin; Guo, Chenhai; Takagi, Tosimi; Narumiya, Kikuo; Hattori, Hiroshi

At the initial stage of injection, the injection flow has not yet broken up and in a range of small atmosphere pressure (16˜500KPa), the tip of the injection flow always forms a shape of mushroom. [1] [2] Moreover, the umbrella of the mushroom is always very big and its root is always very thin, especially when the atmosphere pressure is relatively low (88KPa, or 100mmHg). These phenomena are not known popularly and the reason of mushroom formation is not clear. In this paper, with the MARS method for simulating free surface, analysis of injection flow is practiced. The phenomena are reproduced and the reason is cleared that the formation of the mushroom is induced by the momentum exchange between the injection fuel flow with very high speed and the very complex flow of the air.

Comparison of HPLC & spectrophotometric methods for estimation of antiretroviral drug content in pharmaceutical products.

PubMed

Hemanth Kumar, A K; Sudha, V; Swaminathan, Soumya; Ramachandran, Geetha

2010-10-01

Simple and reliable methods to estimate drugs in pharmaceutical products are needed. In most cases, antiretroviral drug estimations are performed using a HPLC method, requiring expensive equipment and trained technicians. A relatively simple and accurate method to estimate antiretroviral drugs in pharmaceutical preparations is by spectrophotometric method, which is cheap and simple to use as compared to HPLC. We undertook this study to standardise methods for estimation of nevirapine (NVP), lamivudine (3TC) and stavudine (d4T) in single tablets/capsules by HPLC and spectrophotometry and to compare the content of these drugs determined by both these methods. Twenty tablets/capsules of NVP, 3TC and d4T each were analysed for their drug content by HPLC and spectrophotometric methods. Suitably diluted drug solutions were run on HPLC fitted with a C18 column using UV detection at ambient temperature. The absorbance of the diluted drug solutions were read in a spectrophotometer at 300, 285 and 270 nm for NVP, 3TC and d4T respectively. Pure powders of the drugs were used to prepare calibration standards of known drug concentrations, which was set up with each assay. The inter-day variation (%) of standards for NVP, 3TC and d4T ranged from 2.5 to 6.7, 2.1 to 7.7 and 6.2 to 7.7, respectively by HPLC. The corresponding values by spectrophotometric method were 2.7 to 4.7, 4.2 to 7.2 and 3.8 to 6.0. The per cent variation between the HPLC and spectrophotometric methods ranged from 0.45 to 4.49 per cent, 0 to 4.98 per cent and 0.35 to 8.73 per cent for NVP, 3TC and d4T,respectively. The contents of NVP, 3TC and d4T in the tablets estimated by HPLC and spectrophotometric methods were similar, and the variation in the amount of these drugs estimated by HPLC and spectrophotometric methods was below 10 per cent. This suggests that the spectrophotometric method is as accurate as the HPLC method for estimation of NVP, 3TC and d4T in tablet/capsule. Hence laboratories that do not have HPLC equipment can also undertake these drug estimations using spectrophotometer.

Photometric changes on Saturn's Titan: Evidence for active cryovolcanism

USGS Publications Warehouse

Nelson, R.M.; Kamp, L.W.; Lopes, R.M.C.; Matson, D.L.; Kirk, R.L.; Hapke, B.W.; Wall, S.D.; Boryta, M.D.; Leader, F.E.; Smythe, W.D.; Mitchell, K.L.; Baines, K.H.; Jaumann, R.; Sotin, Christophe; Clark, R.N.; Cruikshank, D.P.; Drossart, P.; Lunine, J.I.; Combes, M.; Bellucci, G.; Bibring, J.-P.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Formisano, V.; Filacchione, G.; Langevin, Y.; McCord, T.B.; Mennella, V.; Nicholson, P.D.; Sicardy, B.; Irwin, P.G.J.; Pearl, J.C.

2009-01-01

We report infrared spectrophotometric variability on the surface of Saturn's moon Titan detected in images returned by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini Saturn Orbiter. The changes were observed at 7??S, 138??W and occurred between October 27, 2005 and January 15, 2006. After that date the surface was unchanged until the most recent observation, March 18, 2006. We previously reported spectrophotometric variability at another location (26??S, 78??W). Cassini Synthetic Aperture RADAR (SAR) images find that the surface morphology at both locations is consistent with surface flows possibly resulting from cryovolcanic activity (Wall et al., companion paper, this issue). The VIMS-reported time variability and SAR morphology results suggest that Titan currently exhibits intermittent surface changes consistent with present ongoing surface processes. We suggest that these processes involve material from Titan's interior being extruded or effiised and deposited on the surface, as might be expected from cryovolcanism. ?? 2009.

Spectrophotometric Determination of Chromium (III) with the Disodium Salt of (Ethylenediamine) tetraacetic Acid (Complexon III); DETERMINACION ESPECTROFOTOMETRICA DE CROMO (III) CON LA SAL DISODICA DEL ACIDO ETILEN-DIAMINO-TETRA-ACETICO (COMPLEXONA III)

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

Cellini, R.F.; Valiente, E.A.

1956-01-01

A spectrophotometric method for Cr (III) determination is established: hot and weak acid solutions are treated by disodium (ethylenediamine)tetraacetic acid (complexoneIII) yielding a very stable violet chelate, which follows Beer's law between 1 and 7 gamma Cr(III)/ml. These concentrations are employed in the experiences of this work. The absorption spectrum of Cr(III)-complexone-III has two maximums at 396 and 538 m mu . The maximum at 538 mu m is utilized in this method. Time, temperature, pH, and complexone-III concentration are studied and the best experimental conditions are fixed. (auth)

UV Spectrophotometric Simultaneous Determination of Paracetamol and Ibuprofen in Combined Tablets by Derivative and Wavelet Transforms

PubMed Central

Hoang, Vu Dang; Ly, Dong Thi Ha; Tho, Nguyen Huu; Minh Thi Nguyen, Hue

2014-01-01

The application of first-order derivative and wavelet transforms to UV spectra and ratio spectra was proposed for the simultaneous determination of ibuprofen and paracetamol in their combined tablets. A new hybrid approach on the combined use of first-order derivative and wavelet transforms to spectra was also discussed. In this application, DWT (sym6 and haar), CWT (mexh), and FWT were optimized to give the highest spectral recoveries. Calibration graphs in the linear concentration ranges of ibuprofen (12–32 mg/L) and paracetamol (20–40 mg/L) were obtained by measuring the amplitudes of the transformed signals. Our proposed spectrophotometric methods were statistically compared to HPLC in terms of precision and accuracy. PMID:24949492

UV spectrophotometric simultaneous determination of paracetamol and ibuprofen in combined tablets by derivative and wavelet transforms.

PubMed

Hoang, Vu Dang; Ly, Dong Thi Ha; Tho, Nguyen Huu; Nguyen, Hue Minh Thi

2014-01-01

The application of first-order derivative and wavelet transforms to UV spectra and ratio spectra was proposed for the simultaneous determination of ibuprofen and paracetamol in their combined tablets. A new hybrid approach on the combined use of first-order derivative and wavelet transforms to spectra was also discussed. In this application, DWT (sym6 and haar), CWT (mexh), and FWT were optimized to give the highest spectral recoveries. Calibration graphs in the linear concentration ranges of ibuprofen (12-32 mg/L) and paracetamol (20-40 mg/L) were obtained by measuring the amplitudes of the transformed signals. Our proposed spectrophotometric methods were statistically compared to HPLC in terms of precision and accuracy.

A simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

NASA Technical Reports Server (NTRS)

Dupraw, W. A.

1972-01-01

A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.

3-D numerical evaluation of density effects on tracer tests.

PubMed

Beinhorn, M; Dietrich, P; Kolditz, O

2005-12-01

In this paper we present numerical simulations carried out to assess the importance of density-dependent flow on tracer plume development. The scenario considered in the study is characterized by a short-term tracer injection phase into a fully penetrating well and a natural hydraulic gradient. The scenario is thought to be typical for tracer tests conducted in the field. Using a reference case as a starting point, different model parameters were changed in order to determine their importance to density effects. The study is based on a three-dimensional model domain. Results were interpreted using concentration contours and a first moment analysis. Tracer injections of 0.036 kg per meter of saturated aquifer thickness do not cause significant density effects assuming hydraulic gradients of at least 0.1%. Higher tracer input masses, as used for geoelectrical investigations, may lead to buoyancy-induced flow in the early phase of a tracer test which in turn impacts further plume development. This also holds true for shallow aquifers. Results of simulations with different tracer injection rates and durations imply that the tracer input scenario has a negligible effect on density flow. Employing model cases with different realizations of a log conductivity random field, it could be shown that small variations of hydraulic conductivity in the vicinity of the tracer injection well have a major control on the local tracer distribution but do not mask effects of buoyancy-induced flow.

High-pressure liquid chromatography with direct injection of gas sample.

PubMed

Astanin, Anton I; Baram, Grigory I

2017-06-09

The conventional method of using liquid chromatography to determine the composition of a gaseous mixture entails dissolving vapors in a suitable solvent, then obtaining a chromatograph of the resulting solution. We studied the direct introduction of a gaseous sample into a C18 reversed-phase column, followed by separation of the components by HPLC with UV detection. Since the chromatography was performed at high pressure, vapors readily dissolved in the eluent and the substances separated in the column as effectively as in liquid samples. Samples were injected into the column in two ways: a) through the valve without a flow stop; b) after stopping the flow and relieving all pressure. We showed that an injectable gas volume could reach 70% of column dead volume. When an injected gaseous sample volume was less than 10% of the column dead volume, the resulting peaks were symmetrical and the column efficiency was high. Copyright © 2017 Elsevier B.V. All rights reserved.

Determination of phenformin hydrochloride using molecular imprinting technology coupled with flow-injection chemiluminescence.

PubMed

Liu, Zhenbo; Jia, Fengyan; Wang, Wenwen; Wang, Cuixia; Liu, Yongming

2012-01-01

A novel method was developed using molecular imprinting technology (MIT) coupled with flow-injection chemiluminescence (FI-CL) for highly sensitive detection of phenformin hydrochloride (PH). The phenformin imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. Newly synthesized molecularly imprinted polymer (MIP) particles were packed into a column as a selective recognition element for determination of PH. A CL method for the determination of PH was developed based on the CL reaction of PH with N-bromosuccinimide sensitized by eosin Y in basic media. The optimization of detection conditions was investigated. The CL intensity responded linearly to the concentration of PH in the range 0.09-2.0 µg/mL, with a correlation coefficient of 0.9920. The detection limit was 0.031 µg/mL. The relative standard deviation for the determination of 1.0 µg/mL PH solution was 1.0% (n = 11). The method was applied to the determination of PH in urine samples, with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Applied Spectrophotometry: Analysis of a Biochemical Mixture

ERIC Educational Resources Information Center

Trumbo, Toni A.; Schultz, Emeric; Borland, Michael G.; Pugh, Michael Eugene

2013-01-01

Spectrophotometric analysis is essential for determining biomolecule concentration of a solution and is employed ubiquitously in biochemistry and molecular biology. The application of the Beer-Lambert-Bouguer Lawis routinely used to determine the concentration of DNA, RNA or protein. There is however a significant difference in determining the…

Assessment of the viability of skin grafts

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

Wahner, H.W.

1988-07-01

A number of tests are available to monitor the blood flow in free and distant pedicle skin grafts. The information from these tests aids in the development of measures to enhance vascularization and is occasionally needed to make clinical decisions in patients with distant pedicle grafts. Measurements of the disappearance of an intradermally injected small amount of /sup 133/Xe allows determination of a clearance rate and blood flow before and after clamping the original blood supply through the base. With /sup 99m/Tc, which is generally more readily available, a flow index and block index can be determined. Clinically both proceduresmore » give equally good results in determining a safe time for pedicle base separation. The fluorescein test allows assessment of regional blood flow distribution within the pedicle.« less

Determination of local values of gas and liquid mass flux in highly loaded two-phase flow

NASA Technical Reports Server (NTRS)

Burick, R. J.; Scheuerman, C. H.; Falk, A. Y.

1974-01-01

A measurement system using a deceleration probe was designed for determining the local values of gas and liquid mass flux in various gas/liquid droplet sprayfields. The system was used to characterize two-phase flowfields generated by gas/liquid rocket-motor injectors. Measurements were made at static pressures up to 500 psia and injected mass flow ratios up to 20. The measurement system can also be used at higher pressures and in gas/solid flowfields.

Validation of four different spectrophotometric methods for simultaneous determination of Domperidone and Ranitidine in bulk and pharmaceutical formulation.

PubMed

Abdel-Ghany, Maha F; Abdel-Aziz, Omar; Mohammed, Yomna Y

2015-01-01

Four simple, specific, accurate and precise spectrophotometric methods were developed and validated for simultaneous determination of Domperidone (DP) and Ranitidine Hydrochloride (RT) in bulk powder and pharmaceutical formulation. The first method was simultaneous ratio subtraction (SRS), the second was ratio subtraction (RS) coupled with zero order spectrophotometry (D(0)), the third was first derivative of the ratio spectra ((1)DD) and the fourth method was mean centering of ratio spectra (MCR). The calibration curve is linear over the concentration range of 0.5-5 and 1-45 μg mL(-1) for DP and RT, respectively. The proposed spectrophotometric methods can analyze both drugs without any prior separation steps. The selectivity of the adopted methods was tested by analyzing synthetic mixtures of the investigated drugs, also in their pharmaceutical formulation. The suggested methods were validated according to International Conference of Harmonization (ICH) guidelines and the results revealed that; they were precise and reproducible. All the obtained results were statistically compared with those of the reported method, where there was no significant difference. Copyright © 2015 Elsevier B.V. All rights reserved.

Investigation of Wall Shear Stress Behavior for Rough Surfaces with Blowing

NASA Astrophysics Data System (ADS)

Helvey, Jacob; Borchetta, Colby; Miller, Mark; Martin, Alexandre; Bailey, Sean

2014-11-01

We present an experimental study conducted in a turbulent channel flow wind tunnel to determine the modifications made to the turbulent flow over rough surfaces with flow injection through the surfaces. Hot-wire profile results from a quasi-two-dimensional, sinusoidally-rough surface indicate that the effects of roughness are enhanced by momentum injection through the surface. In particular, the wall shear stress was found to show behavior consistent with increased roughness height when surface blowing was increased. This observed behavior contradicts previously reported results for regular three-dimensional roughness which show a decrease in wall shear stress with additional blowing. It is unclear whether this discrepancy is due to differences in the roughness geometry under consideration or the use of the Clauser fit to estimate wall shear stress. Additional PIV experiments are being conducted for a three-dimensional fibrous surface to obtain Reynolds shear stress profiles. These results provide an additional method for estimation of wall-shear stress and thus allow verification of the use of the Clauser chart approach for flows with momentum injection through the surface. This research is supported by NASA Kentucky EPSCoR Award NNX10AV39A, and NASA RA Award NNX13AN04A.

Sustained subconjunctival protein delivery using a thermosetting gel delivery system.

PubMed

Rieke, Erin R; Amaral, Juan; Becerra, S Patricia; Lutz, Robert J

2010-02-01

An effective treatment modality for posterior eye diseases would provide prolonged delivery of therapeutic agents, including macromolecules, to eye tissues using a safe and minimally invasive method. The goal of this study was to assess the ability of a thermosetting gel to deliver a fluorescently labeled protein, Alexa 647 ovalbumin, to the choroid and retina of rats following a single subconjunctival injection of the gel. Additional experiments were performed to compare in vitro to in vivo ovalbumin release rates from the gel. The ovalbumin content of the eye tissues was monitored by spectrophotometric assays of tissue extracts of Alexa 647 ovalbumin from dissected sclera, choroid, and retina at time points ranging from 2 h to 14 days. At the same time points, fluorescence microscopy images of tissue samples were also obtained. Measurement of intact ovalbumin was verified by LDS-PAGE analysis of the tissue extract solutions. In vitro release of Alexa 488 ovalbumin into 37 degrees C PBS solutions from ovalbumin-loaded gel pellets was also monitored over time by spectrophotometric assay. In vivo ovalbumin release rates were determined by measurement of residual ovalbumin extracted from gel pellets removed from rat eyes at various time intervals. Our results indicate that ovalbumin concentrations can be maintained at measurable levels in the sclera, choroid, and retina of rats for up to 14 days using the thermosetting gel delivery system. The concentration of ovalbumin exhibited a gradient that decreased from sclera to choroid and to retina. The in vitro release rate profiles were similar to the in vivo release profiles. Our findings suggest that the thermosetting gel system may be a feasible method for safe and convenient sustained delivery of proteins to choroidal and retinal tissue in the posterior segments of the eye.

Sustained Subconjunctival Protein Delivery Using a Thermosetting Gel Delivery System

PubMed Central

2010-01-01

Purpose: An effective treatment modality for posterior eye diseases would provide prolonged delivery of therapeutic agents, including macromolecules, to eye tissues using a safe and minimally invasive method. The goal of this study was to assess the ability of a thermosetting gel to deliver a fluorescently labeled protein, Alexa 647 ovalbumin, to the choroid and retina of rats following a single subconjunctival injection of the gel. Additional experiments were performed to compare in vitro to in vivo ovalbumin release rates from the gel. Methods: The ovalbumin content of the eye tissues was monitored by spectrophotometric assays of tissue extracts of Alexa 647 ovalbumin from dissected sclera, choroid, and retina at time points ranging from 2 h to 14 days. At the same time points, fluorescence microscopy images of tissue samples were also obtained. Measurement of intact ovalbumin was verified by LDS-PAGE analysis of the tissue extract solutions. In vitro release of Alexa 488 ovalbumin into 37°C PBS solutions from ovalbumin-loaded gel pellets was also monitored over time by spectrophotometric assay. In vivo ovalbumin release rates were determined by measurement of residual ovalbumin extracted from gel pellets removed from rat eyes at various time intervals. Results: Our results indicate that ovalbumin concentrations can be maintained at measurable levels in the sclera, choroid, and retina of rats for up to 14 days using the thermosetting gel delivery system. The concentration of ovalbumin exhibited a gradient that decreased from sclera to choroid and to retina. The in vitro release rate profiles were similar to the in vivo release profiles. Conclusions: Our findings suggest that the thermosetting gel system may be a feasible method for safe and convenient sustained delivery of proteins to choroidal and retinal tissue in the posterior segments of the eye. PMID:20148655

Effect of vertebral shell on injection pressure and intravertebral pressure in vertebroplasty.

PubMed

Baroud, Gamal; Vant, Christianne; Giannitsios, Demetri; Bohner, Marc; Steffen, Thomas

2005-01-01

An experimental biomechanical study conducted on osteoporotic cadaveric vertebrae. 1) To measure the intravertebral shell pressure and injection pressure; and 2) to determine the effect of the vertebral shell on the intravertebral shell pressure and on the injection pressure. Forces that govern cement flow are an essential component of the cement injection process in vertebroplasty. The vertebral shell may play a significant role in confining the flow of cement in the vertebral body and thereby affecting the intravertebral pressure and injection pressure. A small fenestration was created in the left lateral vertebral shell of 14 vertebrae. A valve to open and close the fenestration and a sensor to measure the intravertebral pressure were attached to the opening. A closed fenestration simulated an intact shell, whereas an open fenestration represented a vented shell. Injection pressure and intravertebral pressure at the shell were recorded during a controlled injection. A closed fenestration resulted in a significant increase in the intravertebral pressure at the shell. During the injection, the shell pressure increased on average to approximately 3.54 +/- 2.91 kPa. Conversely, an open fenestration resulted in an instant relaxation of the shell pressure to the ambient pressure of 0 kPa. Additionally, the injection pressure was approximately 97 times higher than the shell pressure. The presence of vertebral shell seems to be important for intravertebral pressure. However, the intravertebral shell pressure adds very little to the injection pressure.

Medial prefrontal cortex acetylcholine injection-induced hypotension: the role of hindlimb vasodilation

NASA Technical Reports Server (NTRS)

Crippa, G. E.; Lewis, S. J.; Johnson, A. K.; Correa, F. M.

2000-01-01

The injection of acetylcholine (ACh) into the cingulate region of the medial prefrontal cortex (MPFC) causes a marked fall in arterial blood pressure which is not accompanied by changes in heart rate. The purpose of the present study was to investigate the hemodynamic basis for this stimulus-induced hypotension in Sprague-Dawley rats. The study was designed to determine whether a change in the vascular resistance of hindlimb, renal or mesenteric vascular beds contributes to the fall in arterial pressure in response to ACh injection into the cingulate cortex. Miniature pulsed-Doppler flow probes were used to measure changes in regional blood flow and vascular resistance. The results indicated that the hypotensive response was largely due to a consistent and marked vasodilation in the hindlimb vascular bed. On this basis, an additional experiment was then undertaken to determine the mechanisms that contribute to hindlimb vasodilation. The effect of interrupting the autonomic innervation of one leg on the hindlimb vasodilator response was tested. Unilateral transection of the lumbar sympathetic chain attenuated the cingulate ACh-induced vasodilation in the ipsilateral, but not in the contralateral hindlimb. These results suggest that the hypotensive response to cingulate cortex-ACh injection is caused by skeletal muscle vasodilation mediated by a sympathetic chain-related vasodilator system.

Spectrophotometric Determination of Nitrogen Oxides in the Air with 2-N-Ethyl-5-Naphthol-7-Sulfonic Acid

NASA Astrophysics Data System (ADS)

Huang, Y.; Shi, W.; Zhang, C.; Wen, H.

2017-09-01

For the determination of nitrogen oxides in the air, the structure of diazo and coupling compounds was studied and tested by experiments. The conditions and methods of diazo and coupling reactions were investigated. Furthermore, a spectrophotometric method using sulfanilamide as a diazo compound and 2-N-ethyl-5-naphthol-7-sulfonic acid (N-ethyl J acid) as a coupling compound was proposed. The maximum absorption wavelength of sulfanilamide-Nethyl J acid azo compound was at 478 nm. The molar absorptivity was 4.31 × 104 L/(mol × cm) with a recovery of 98.7-100.9% and RSD of 1.85%. For nitrogen oxides, the determinate limit of this measurement was 0.015 mg/m3 and the determinate range 0.024-2.0 mg/m3. Moreover, a high degree of correlation was observed between the results obtained by the proposed method and the standard methods. The proposed method can be easily applied to determine nitrogen oxides in the air.

Spectrophotometric determination of uric acid and some redeterminations of its solubility

USGS Publications Warehouse

Norton, D.R.; Plunkett, M.A.; Richards, F.A.

1954-01-01

The present study was initiated in order to develop a rapid and accurate method for the determination of uric acid in fresh, brackish, and sea water. It was found that the spectrophotometric determination of uric acid based upon its reaction with arsenophosphotungstic acid reagent in the presence of cyanide ion meets this objective. The absorbancy of the blue complex was measured at 890 m??. Slight variations from Beer's law were generally found. The results show the effects of pH, reaction time, concentration of reagents, and temperature upon color development and precipitate formation. Disodium dihydrogen ethylenediamine tetraacetate (Versene) was used as a buffering and complexirig agent. The results are significant in that they give the absorption spectrum of the blue complex and the effects of variables upon its absorbancy. Studies were made with the method to determine the stability of reagents and standard solutions and to determine the rate of bacterial decomposition of uric acid. Measurements of the solubility of uric acid are reported.

The effect of initial flow nonuniformity on second-stage fuel injection and combustion in a supersonic duct. [supersonic combustion ramjet engine

NASA Technical Reports Server (NTRS)

Russin, W. R.

1975-01-01

The effects of flow nonuniformity on second-stage hydrogen fuel injection and combustion in supersonic flow were evaluated. The first case, second-stage fuel injection into a uniform duct flow, produced data indicating that fuel mixing is considerably slower than estimates based on an empirical mixing correlation. The second-case, two-stage fuel injection (or second-stage fuel injection into a nonuniform duct flow), produced a large interaction between stages with extensive flow separation. For this case the measured wall pressure, heat transfer, and amount of reaction at the duct exit were significantly greater than estimates based on the mixing correlation. Substantially more second-stage fuel burned in the second case than in the first case. Overall effects of unmixedness/chemical kinetics were found not to be significant at the exit for stoichiometric fuel injection.

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

PubMed

Altunay, Nail; Gürkan, Ramazan; Kır, Ufuk

2016-01-01

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

Spectrophotometric Determination of Phenolic Antioxidants in the Presence of Thiols and Proteins

PubMed Central

Avan, Aslı Neslihan; Demirci Çekiç, Sema; Uzunboy, Seda; Apak, Reşat

2016-01-01

Development of easy, practical, and low-cost spectrophotometric methods is required for the selective determination of phenolic antioxidants in the presence of other similar substances. As electron transfer (ET)-based total antioxidant capacity (TAC) assays generally measure the reducing ability of antioxidant compounds, thiols and phenols cannot be differentiated since they are both responsive to the probe reagent. In this study, three of the most common TAC determination methods, namely cupric ion reducing antioxidant capacity (CUPRAC), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt/trolox equivalent antioxidant capacity (ABTS/TEAC), and ferric reducing antioxidant power (FRAP), were tested for the assay of phenolics in the presence of selected thiol and protein compounds. Although the FRAP method is almost non-responsive to thiol compounds individually, surprising overoxidations with large positive deviations from additivity were observed when using this method for (phenols + thiols) mixtures. Among the tested TAC methods, CUPRAC gave the most additive results for all studied (phenol + thiol) and (phenol + protein) mixtures with minimal relative error. As ABTS/TEAC and FRAP methods gave small and large deviations, respectively, from additivity of absorbances arising from these components in mixtures, mercury(II) compounds were added to stabilize the thiol components in the form of Hg(II)-thiol complexes so as to enable selective spectrophotometric determination of phenolic components. This error compensation was most efficient for the FRAP method in testing (thiols + phenols) mixtures. PMID:27529232

Utilization of N-Bromosuccinimide as a Brominating Agent for the Determination of Sumatriptan Succinate in Bulk Drug and Tablets

PubMed Central

Prashanth, Kudige N.; Basavaiah, Kanakapura; Raghu, Madihalli S.

2013-01-01

One titrimetric and two spectrophotometric methods which are simple, sensitive, and economic are described for the determination of sumatriptan succinate (STS) in bulk drug and in tablet dosage form using N-bromosuccinimide (NBS) as a brominating agent. In titrimetry, aqueous solution of STS is treated with a measured excess of NBS in acetic acid medium, and after the bromination of STS is judged to be complete, the unreacted NBS is determined iodometrically (method A). Spectrophotometric methods entail addition of a known excess of NBS in acid medium followed by the determination of residual NBS by its reaction with excess iodide, and the liberated iodine (I3 −) is either measured at 370 nm (method B) or liberated iodine is reacted with starch followed by the measurement of the blue colored starch-iodine complex at 570 nm (method C). Titrimetric method is applicable over range 1.0–10.0 mg STS (method A), and the reaction stoichiometry is found to be 1 : 3 (STS : NBS). The spectrophotometric methods obey Beer's law for concentration range 0.6–15.0 μg mL−1 (method B) and 0.2–4.0 μg mL−1 (method C). The calculated apparent molar absorptivity values were found to be 2.10 × 104 and 7.44 × 104 L mol−1 cm−1, for method B and method C, respectively. PMID:23935625

A mathematical approach for the simultaneous in vitro spectrophotometric analysis of rifampicin and isoniazid from modified-release anti-TB drug delivery systems.

PubMed

du Toit, Lisa; Pillay, Viness; Choonara, Yahya

2010-01-01

Dissolution testing with subsequent analysis is considered as an imperative tool for quality evaluation of the combination rifampicin-isoniazid (RIF-INH) combination. Partial least squares (PLS) regression has been successfully undertaken to select suitable predictor variables and to identify outliers for the generation of equations for RIF and INH determination in fixed-dose combinations (FDCs). The aim of this investigation was to ascertain the applicability of the described technique in testing a novel oral FDC anti-TB drug delivery system and currently available two-drug FDCs, in comparison to the United States Pharmacopeial method for analysis of RIF and INH Capsules with chromatographic determination of INH and colorimetric RIF determination. Regression equations generated employing the statistical coefficients satisfactorily predicted RIF release at each sampling point (R(2)>or=0.9350). There was an acceptable degree of correlation between the drug release data, as predicted by regressional analysis of UV spectrophotometric data, and chromatographic and colorimetric determination of INH (R(2)=0.9793 and R(2)=0.9739) and RIF (R(2)= 0.9976 and R(2)=0.9996) for the two-drug FDC and the novel oral anti-TB drug delivery system, respectively. Regressional analysis of UV spectrophotometric data for simultaneous RIF and INH prediction thus provides a simplified methodology for use in diverse research settings for the assurance of RIF bioavailability from FDC formulations, specifically modified-release forms.

An automated flow injection system for metal determination by flame atomic absorption spectrometry involving on-line fabric disk sorptive extraction technique.

PubMed

Anthemidis, A; Kazantzi, V; Samanidou, V; Kabir, A; Furton, K G

2016-08-15

A novel flow injection-fabric disk sorptive extraction (FI-FDSE) system was developed for automated determination of trace metals. The platform was based on a minicolumn packed with sol-gel coated fabric media in the form of disks, incorporated into an on-line solid-phase extraction system, coupled with flame atomic absorption spectrometry (FAAS). This configuration provides minor backpressure, resulting in high loading flow rates and shorter analytical cycles. The potentials of this technique were demonstrated for trace lead and cadmium determination in environmental water samples. The applicability of different sol-gel coated FPSE media was investigated. The on-line formed complex of metal with ammonium pyrrolidine dithiocarbamate (APDC) was retained onto the fabric surface and methyl isobutyl ketone (MIBK) was used to elute the analytes prior to atomization. For 90s preconcentration time, enrichment factors of 140 and 38 and detection limits (3σ) of 1.8 and 0.4μgL(-1) were achieved for lead and cadmium determination, respectively, with a sampling frequency of 30h(-1). The accuracy of the proposed method was estimated by analyzing standard reference materials and spiked water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Optimization of Dendritic Cell-Mediated Cytotoxic T-Cell Activation by Tracking of Dendritic Cell Migration Using Reporter Gene Imaging.

PubMed

Lee, Hongje; Lee, Ho Won; La Lee, You; Jeon, Yong Hyun; Jeong, Shin Young; Lee, Sang-Woo; Lee, Jaetae; Ahn, Byeong-Cheol

2018-06-01

The aim of this study is to optimize the dendritic cell (DC)-mediated T-cell activation using reporter gene imaging and flow cytometric analysis in living mice. A murine dendritic cell line (DC2.4) co-expressing effluc and Thy1.1 genes were established by transfection with retroviral vectors. Thy1.1 positive cells were sorted by magnetic bead separation system (DC2.4/effluc). Cell proliferation assay and phenotype analysis to determine the effects of gene transduction on the function of dendritic cells between parental DC2.4 and DC2.4/effluc were performed. To optimize the DC-mediated immune response by cell number or frequency, different cell numbers (5 × 10 5 , 1 × 10 6 , and 2 × 10 6  DC2.4/effluc) or different frequencies of DC2.4/effluc (first, second, and third injections) were injected in the right footpad of mice. The migration of the DC2.4/effluc into the draining popliteal lymph node of mice was monitored by bioluminescence imaging (BLI). Flow cytometric analysis was performed with splenocytes to determine the cytotoxic T-cell population after injection of DC2.4/effluc. Parental DC2.4 and DC2.4/effluc exhibit no significant differences in their proliferation and phenotype. BLI signals were observed in the draining popliteal lymph node at day 1 after injection of DC2.4/effluc in 1 × 10 6 and 2 × 10 6 cells-injected groups. The highest BLI signal intensity was detected in 2 × 10 6 cells-injected mice. On day 11, the BLI signal was detected in only 2 × 10 6 cell-injected group but not in other groups. Optimized cell numbers (2 × 10 6 ) were injected in three animal groups with a different frequency (first, second, and third injection groups). The BLI signal was detected at day 1 and maintained until day 7 in the first injection group, but there is low signal intensity in the second and the third injection groups. Although the expression levels of Thy1.1 gene in the first injection group were very high, there reveals no expression of Thy1.1 gene in the second and the third injection groups. The number of tumor-specific CD8 + T-cells in the spleen significantly increased, as the number of DC injections increases. Successful optimization of DC-mediated cytotoxic T-cell activation in living mice using reporter gene imaging and flow cytometric analysis was achieved. The optimization of DC-mediated cytotoxic T-cell activation could be applied for the future DC-based immunotherapy.

Influences of Detection Pinhole and Sample Flow on Thermal Lens Detection in Microfluidic Systems

NASA Astrophysics Data System (ADS)

Liu, Mingqiang; Franko, Mladen

2014-12-01

Thermal lens microscopy (TLM), due to its high temporal () and spatial resolution (), has been coupled to lab-on-chip chemistry for detection of a variety of compounds in chemical or biological fields. Due to the very short optical path length (usually below 100 ) in a microchip, the sensitivity of TLM is unfortunately still 10 to 100 times lower than conventional TLS with 1 cm sample length. Optimization of the TLM optical configuration was made with respect to different pinhole aperture-to-beam size ratios for the best signal-to-noise ratio. In the static mode, the instrumental noise comes mainly from the shot noise of the probe beam when the chopper frequency is over 1 kHz or from the flicker noise of the probe beam at low frequencies. In the flowing mode, the flow-induced noise becomes dominant when the flow rate is high. At a given flow rate, fluids with a higher density and/or a higher viscosity will cause larger flow-induced noise. As an application, a combined microfluidic flow injection analysis ()-TLM device was developed for rapid determination of pollutants by colorimetric reactions. Hexavalent chromium [Cr(VI)] was measured as a model analyte. Analytical signals for 12 sample injections in 1 min have been recorded by the FIA-TLM. For injections of sub-L samples into the microfluidic stream in a deep microchannel, a limit of detection of was achieved for Cr(VI) in water at 60 mW excitation power.

Spectrophotometric studies on the complexation equilibria of Ni and Pb with 2-carboxy-2-hydroxy-5'-sulfo-formazylbenzene. Simultaneous determination of trace amounts of Ni and Pb.

PubMed

Hashem, Elham Y; Abu-Bakr, Mohamed S; Hussain, Sawsan M

2004-01-01

Spectrophotometric studies have been made to investigate the reaction of Nickel and Lead with 2-carboxy-2'-hydroxy-5'-sulfoformazyl-benzene (zincon) in 50%(v/v) ethanol-water at 25 degrees C and an ionic strength of 0.1 M NaClO4. A complete picture of the complexation equilibria in the pH range (4.2-12.0) for nickel and (1.9-11.5) for lead are presented. Simple, rapid, selective and sensitive methods for the spectro-photometric determination of nickel and lead has been developed based on the color reaction of their complexes with zincon. The methods allow the determination of 4.69 microg mL(-1) of nickel at pH = 6.3 (lambdamax = 665 nm) and 10.3 microg ml(-1) of lead at pH = 5.6 (lambdamax = 610 nm). The apparent molar absorptivities were epsilon = 1.3 x 10(4) L mol(-1) cm(-1) for nickel and epsilon = 0.6 x 10(4) L mol(-1) cm(-1) for lead. The interference of a large number of foreign ions and complexing agents has been studied. Thiosulphate, as masking agent allows the simultaneous determination of nickel and lead in the presence of high concentrations of copper. Ascorbic acid, sodium cyanide and or sodium fluoride provide the elimination of many other interferences. The methods have been applied successfully to the simultaneous determination of nickel and lead in an aluminium and non-ferrous alloy.

Standard test method for nitrogen dioxide content of the atmosphere (Griess-Saltzman reaction)

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

Not Available

1975-01-01

This method covers the manual determination of nitrogen dioxide (NO/sub 2/) in the atmosphere in the range from 4 to 10,000 ..mu..g/m/sup 3/ (0.002 to 5 ppM) when sampling is conducted in fritted-tip bubblers. For concentrations of NO/sub 2/ in excess of 10 mg/m/sup 3/ (5 ppM), as occur in industrial atmospheres, gas burner stacks, or automotive exhaust, or for samples relatively high in sulfur dioxide content, other methods should be applied. The maximum sampling period is 60 min at a flow rate of 0.4 liter/min. The NO/sub 2/ is absorbed in an azo-dye-forming reagent. A red-violet color is producedmore » within 15 min, the intensity of which is measured spectrophotometrically at 550 nm.« less

Flow-injection chemiluminescence determination of acetylsalicylic acid based on its enhancing effect on the lucigenin–hydrogen peroxide system.

PubMed

Wabaidur, S M; Alam, S M; Alothmana, Z A; Eldesokya, Gaber

2014-09-01

A sensitive flow-injection chemiluminescence method for the determination of acetylsalicylic acid is described. It is based on the enhanced chemiluminescent emission of the alkaline lucigenin–H2O2 system by acetylsalicylic acid. The difference in chemiluminescent intensity of alkaline lucigenin–H2O2 in the presence of acetylsalicylic acid from that in the absence of acetylsalicylic acid was linear at acetylsalicylic acid concentrations in the range of 0.0029–47.37 μg/mL, with detection and quantification limits of 0.0011 and 0.0029 μg/mL, respectively. The correlation coefficient of the working curve was 0.9983. The relative standard deviation (n = 10) for 25 μg/mL acetylsalicylic acid is 1.95%. All experimental parameters were optimized. The method was successfully applied to the determination of acetylsalicylic acid in pharmaceutical preparations. The recovery results obtained by the method were satisfactory.

Online Determination of Trace Amounts of Tannic Acid in Colored Tannery Wastewaters by Automatic Reference Flow Injection Analysis

PubMed Central

Wei, Liang

2010-01-01

A simple, rapid and sensitive method was proposed for online determination of tannic acid in colored tannery wastewater by automatic reference flow injection analysis. Based on the tannic acid reduction phosphotungstic acid to form blue compound in pH 12.38 alkaline solutions, the shade of blue compound is in a linear relation to the content of tannic acid at the point of the maximum absorption peak of 760 nm. The optimal experimental conditions had been obtained. The linear range of the proposed method was between 200 μg L−1 to 80 mg L−1 and the detection limit was 0.58 μg L−1. The relative standard deviation was 3.08% and 2.43% for 500 μg L−1 and 40 mg L−1 of tannic acid standard solution, respectively, (n = 10). The method had been successfully applied to determination of tannic acid in colored tannery wastewaters and the analytical results were satisfactory. PMID:20508812

Flow injection chemiluminescent determination of tetracycline using a tris(2,2'-bipyridine)ruthenium(II)-cerium(IV) sulphate system.

PubMed

Guo, Liangqia; Xie, Zenghong; Lin, Xucong; Liu, Xiaohua; Zhang, Weilin; Chen, Guonan

2004-01-01

A flow-injection chemiluminescence method for the determination of tetracycline was developed. The method is based on an enhancement by tetracycline of the chemiluminescence light emission of tris(2,2'-bipyridine)ruthenium(II). In sulphuric acid medium, the chemiluminescence is generated by the continuous oxidation of tris(2,2'-bipyridine)ruthenium(II) by cerium (IV) sulphate. The light-emission intensity is greatly enhanced in the presence of tetracycline. Under the optimum conditions, the calibration curve is linear over the range 3.75 x 10(-8) g/mL-1.5 x 10(-5) g/mL for tetracycline with the linear equation: deltaINT = 205.898 x C - 20.442 (R2 = 0.9974). The detection limit is 3.27 x 10(-8) g/mL. The proposed method was also successfully used to determine tetracycline in pharmaceutical formulation (mean recovery of tetracycline, 100.7%). Copyright 2004 John Wiley & Sons, Ltd.

Flow-injection analysis with electrochemical detection of reduced nicotinamide adenine dinucleotide using 2,6-dichloroindophenol as a redox coupling agent.

PubMed

Tang, H T; Hajizadeh, K; Halsall, H B; Heineman, W R

1991-01-01

The determination of reduced nicotinamide adenine dinucleotide (NADH) by electrochemical oxidation requires a more positive potential than is predicted by the formal reduction potential for the NAD+/NADH couple. This problem is alleviated by use of 2,6-dichloroindophenol (DCIP) as a redox coupling agent for NADH. The electrochemical characteristics of DCIP at the glassy carbon electrode are examined by cyclic voltammetry and hydrodynamic voltammetry. NADH is determined by reaction with DCIP to form NAD+ and DCIPH2. DCIPH2 is then quantitated by flow-injection analysis with electrochemical detection by oxidation at a detector potential of +0.25 V at pH 7. NADH is determined over a linear range of 0.5 to 200 microM and with a detection limit of 0.38 microM. The lower detection potential for DCIPH2 compared to NADH helps to minimize interference from oxidizable components in serum samples.

N-bromosuccinimide-fluorescein based sensitive flow-injection chemiluminescence determination of phenformin.

PubMed

Wang, Zhouping; Zhang, Zhujun; Fu, Zhifeng; Fang, Luqiu; Zhang, Xiao

2004-02-01

A novel and highly sensitive method for the determination of phenformin over the range of 6 x 10(-9) - 1 x 10(-5) g ml(-1) in pharmaceutical formulations with flow-injection chemiluminescence (CL) detection is proposed. The method is based on the CL produced during the oxidation of N-bromosuccinimide (NBS) in an alkaline medium in the presence of fluorescein as an effective energy transfer agent. The use of cetyltrimethylammonium bromide (CTAB) as a sensitizer enhances the signal magnitude by about 100 times. The detection limit is 2 x 10(-9) g ml(-1) (3sigma) with a relative standard deviation of 2.3% (n = 11) at 1 x 10(-7) g ml(-1) phenformin. Ninety samples can be determined per hour. The method was evaluated by carrying out a recovery study and by the analysis of commercial formulations. The obtained results compared well with those by an official method, and demonstrated good accuracy and precision. The possible CL mechanism of the proposed system was also briefly analyzed.

Fuel cell membrane hydration and fluid metering

DOEpatents

Jones, Daniel O.; Walsh, Michael M.

2003-01-01

A hydration system includes fuel cell fluid flow plate(s) and injection port(s). Each plate has flow channel(s) with respective inlet(s) for receiving respective portion(s) of a given stream of reactant fluid for a fuel cell. Each injection port injects a portion of liquid water directly into its respective flow channel. This serves to hydrate at least corresponding part(s) of a given membrane of the corresponding fuel cell(s). The hydration system may be augmented by a metering system including flow regulator(s). Each flow regulator meters an injecting at inlet(s) of each plate of respective portions of liquid into respective portion(s) of a given stream of fluid by corresponding injection port(s).

Verification of a three-dimensional resin transfer molding process simulation model

NASA Technical Reports Server (NTRS)

Fingerson, John C.; Loos, Alfred C.; Dexter, H. Benson

1995-01-01

Experimental evidence was obtained to complete the verification of the parameters needed for input to a three-dimensional finite element model simulating the resin flow and cure through an orthotropic fabric preform. The material characterizations completed include resin kinetics and viscosity models, as well as preform permeability and compaction models. The steady-state and advancing front permeability measurement methods are compared. The results indicate that both methods yield similar permeabilities for a plain weave, bi-axial fiberglass fabric. Also, a method to determine principal directions and permeabilities is discussed and results are shown for a multi-axial warp knit preform. The flow of resin through a blade-stiffened preform was modeled and experiments were completed to verify the results. The predicted inlet pressure was approximately 65% of the measured value. A parametric study was performed to explain differences in measured and predicted flow front advancement and inlet pressures. Furthermore, PR-500 epoxy resin/IM7 8HS carbon fabric flat panels were fabricated by the Resin Transfer Molding process. Tests were completed utilizing both perimeter injection and center-port injection as resin inlet boundary conditions. The mold was instrumented with FDEMS sensors, pressure transducers, and thermocouples to monitor the process conditions. Results include a comparison of predicted and measured inlet pressures and flow front position. For the perimeter injection case, the measured inlet pressure and flow front results compared well to the predicted results. The results of the center-port injection case showed that the predicted inlet pressure was approximately 50% of the measured inlet pressure. Also, measured flow front position data did not agree well with the predicted results. Possible reasons for error include fiber deformation at the resin inlet and a lag in FDEMS sensor wet-out due to low mold pressures.

Titrimetric and Spectrophotometric Methods for the Assay of Ketotifen Using Cerium(IV) and Two Reagents

PubMed Central

Raghu, Madihalli Srinivas; Basavaiah, Kanakapura; Prashanth, Kudige Nagaraj; Vinay, Kanakapura Basavaiah

2013-01-01

One titrimetric and two spectrophotometric methods are described for the determination of ketotifen fumarate (KTF) in bulk drug and in tablets using cerium(IV) as the oxidimetric agent. In titrimetry (method A), the drug was treated with a measured excess of cerium(IV) in H2SO4 medium and after a standing time of 10 min, the surplus oxidant was determined by back titration with iron(II). The spectrophotometric procedures involve addition of a known excess of cerium(IV) to KTF in acid medium followed by the determination of unreacted oxidant by reacting with either p-dimethyl amino benzaldehyde and measuring the resulting colour at 460 nm (method B) or o-dianisidine and subsequent measurement of the absorbance of coloured product at 470 nm (method C). Titrimetric assay is based on a 1 : 2 reaction stoichiometry between KTF and cerium(IV) and the method is applicable over 2–18 mg range. In spectrophotometry, regression analysis of Beer's law plots showed a good correlation in 0.4–8.0 and 0.4–10.0 g mL−1 KTF ranges for method B and method C, respectively, and the corresponding molar absorptivity coefficients are calculated to be 4.0 × 104 and 3.7 × 104 L mol−1 cm−1. PMID:24324496

Heat-exchanger concepts for neutral-beam calorimeters

NASA Astrophysics Data System (ADS)

Thompson, C. C.; Polk, D. H.; McFarlin, D. J.; Stone, R.

1981-10-01

Advanced cooling concepts that permit the design of water cooled heat exchangers for use as calorimeters and beam dumps for advanced neutral beam injection systems were evaluated. Water cooling techniques ranging from pool boiling to high pressure, high velocity swirl flow were considered. Preliminary performance tests were carried out with copper, inconel and molybdenum tubes ranging in size from 0.19 to 0.50 in. diameter. Coolant flow configurations included: (1) smooth tube/straight flow; (2) smooth tube with swirl flow created by tangential injection of the coolant; and (3) axial flow in internally finned tubes. Additionally, the effect of tube L/D was evaluated. A CO2 laser was employed to irradiate a sector of the tube exterior wall; the laser power was incrementally increased until burnout occurred. Absorbed heat fluxes were calculated by dividing the measured coolant heat load by the area of the burn spot on the tube surface. Two six element thermopiles were used to accurately determine the coolant temperature rise. A maximum burnout heat flux near 14 kW/sq cm was obtained for the molybdenum tube swirl flow configuration.

Using a tracer technique to identify the extent of non-ideal flows in the continuous mixing of non-Newtonian fluids

NASA Astrophysics Data System (ADS)

Patel, D.; Ein-Mozaffari, F.; Mehrvar, M.

2013-05-01

The identification of non-ideal flows in a continuous-flow mixing of non-Newtonian fluids is a challenging task for various chemical industries: plastic manufacturing, water and wastewater treatment, and pulp and paper manufacturing. Non-ideal flows such as channelling, recirculation, and dead zones significantly affect the performance of continuous-flow mixing systems. Therefore, the main objective of this paper was to develop an identification protocol to measure non-ideal flows in the continuous-flow mixing system. The extent of non-ideal flows was quantified using a dynamic model that incorporated channelling, recirculation, and dead volume in the mixing vessel. To estimate the dynamic model parameters, the system was excited using a frequency-modulated random binary input by injecting the saline solution (as a tracer) into the fresh feed stream prior to being pumped into the mixing vessel. The injection of the tracer was controlled by a computer-controlled on-off solenoid valve. Using the trace technique, the extent of channelling and the effective mixed volume were successfully determined and used as mixing quality criteria. Such identification procedures can be applied at various areas of chemical engineering in order to improve the mixing quality.

Derivative spectrophotometric method for simultaneous determination of clindamycin phosphate and tretinoin in pharmaceutical dosage forms

PubMed Central

2013-01-01

A derivative spectrophotometric method was proposed for the simultaneous determination of clindamycin and tretinoin in pharmaceutical dosage forms. The measurement was achieved using the first and second derivative signals of clindamycin at (1D) 251 nm and (2D) 239 nm and tretinoin at (1D) 364 nm and (2D) 387 nm. The proposed method showed excellent linearity at both first and second derivative order in the range of 60–1200 and 1.25–25 μg/ml for clindamycin phosphate and tretinoin respectively. The within-day and between-day precision and accuracy was in acceptable range (CV<3.81%, error<3.20%). Good agreement between the found and added concentrations indicates successful application of the proposed method for simultaneous determination of clindamycin and tretinoin in synthetic mixtures and pharmaceutical dosage form. PMID:23575006

A simple spectrophotometric method for the determination of arsenic in industrial and environmental samples using 2,4-Dihydroxy benzophenone-2-amino thiophenol.

PubMed

Deepa, K; Lingappa, Y

2014-04-24

2,4-Dihydroxy benzophenone-2-amino thiophenol (BPBT) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of arsenic. The reagent reacts with arsenic in acidic medium (pH=6.0, sodium acetate-acetic acid buffer) to form light greenish yellow colored 1:1 (M:L) complex. Maximum absorbance was obtained at 343 nm and remains constant for over 24 h. The molar absorptivity and Sandell's sensitivity of BPBT are found to be 6.01×10(4) L mol(-1)cm(-1) and 0.0016 μg cm(-2) respectively. The system obeys Beer's law in the range of 0.125-2.637 μg/ml of As (III). Since BPBT method is more sensitive, it was applied for the determination of arsenic in some environmental water samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Peroxydisulfate Oxidation of L-Ascorbic Acid for Its Direct Spectrophotometric Determination in Dietary Supplements

NASA Astrophysics Data System (ADS)

Salkić, M.; Selimović, A.; Pašalić, H.; Keran, H.

2014-03-01

A selective and accurate direct spectrophotometric method was developed for the determination of L-as cor bic acid in dietary supplements. Background correction was based on the oxidation of L-ascorbic acid by potassi um peroxydisulfate in an acidic medium. The molar absorptivity of the proposed method was 1.41 · 104 l/(mol · cm) at 265 nm. The method response was linear up to an L-ascorbic acid concentration of 12.00 μg/ml. The detection limit was 0.11 μg/ml, and the relative standard deviation was 0.9 % (n = 7) for 8.00 μg/ml L-ascorbic acid. Other compounds commonly found in the dietary supplements did not interfere with the detection of L-ascorbic acid. The proposed procedure was successfully applied to the determination of L-ascorbic acid in these supplements, and the results obtained agreed with those obtained by iodine titration.

Convenient UV-spectrophotometric determination of citrates in aqueous solutions with applications in the pharmaceutical analysis of oral electrolyte formulations.

PubMed

Krukowski, Sylwester; Karasiewicz, Mateusz; Kolodziejski, Waclaw

2017-07-01

Herein, we present a convenient method for quantitative spectrophotometric determination of citrate ions in aqueous solutions in the middle-UV range. It involves measuring the absorbance of citric acid at 209 nm under suppressed dissociation at pH < 1.0 in the presence of hydrochloric acid. Validation of the method was performed according to the guidelines of the International Conference on Harmonization. A very good linear dependence of the absorbance on concentration (r 2  = 0.9999) was obtained in a citrate concentration range of 0.5-5.0 mmol/L. This method is characterized by excellent precision and accuracy; the coefficient of variation in each case is below the maximal permissible value (%RSD < 2). The proposed analytical procedure has been successfully applied to the determination of citrates in oral electrolyte formulations. Copyright © 2017. Published by Elsevier B.V.

Spectrophotometric determination of phenylephrine HCl and orphenadrine citrate in pure and in dosage forms.

PubMed

Shama, S A

2002-11-07

A simple and rapid spectrophotometric methods have been estimated for the microdetermination of phenylephrine HCl (I) and orphenadrine citrate (II). The proposed methods are based on the formation of ion-pair complexes between the examined drugs with alizarine (Aliz), alizarine red S (ARS), alizarine yellow G (AYG) or quinalizarine (Qaliz), which can be measured at the optimum lambda(max). The optimization of the reaction conditions is investigated. Beer's law is obeyed in the concentration ranges 2-36 microgram ml(-1), whereas optimum concentration as adopted from Ringbom plots was 3.5-33 microgram ml(-1). The molar absorptivity, Sandell sensitivity, and detection limit are also calculated. The correlation coefficient was >/=0.9988 (n=6) with a relative standard deviation of

Simultaneous determination of rifampicin, isoniazid and pyrazinamide in tablet preparations by multivariate spectrophotometric calibration.

PubMed

Goicoechea, H C; Olivieri, A C

1999-08-01

The use of multivariate spectrophotometric calibration is presented for the simultaneous determination of the active components of tablets used in the treatment of pulmonary tuberculosis. The resolution of ternary mixtures of rifampicin, isoniazid and pyrazinamide has been accomplished by using partial least squares (PLS-1) regression analysis. Although the components show an important degree of spectral overlap, they have been simultaneously determined with high accuracy and precision, rapidly and with no need of nonaqueous solvents for dissolving the samples. No interference has been observed from the tablet excipients. A comparison is presented with the related multivariate method of classical least squares (CLS) analysis, which is shown to yield less reliable results due to the severe spectral overlap among the studied compounds. This is highlighted in the case of isoniazid, due to the small absorbances measured for this component.

Selection of Wavelengths for Optimum Precision in Simultaneous Spectrophotometric Determinations.

ERIC Educational Resources Information Center

DiTusa, Michael R.; Schilt, Alfred A.

1985-01-01

Although many textbooks include a description of simultaneous determinations employing absorption spectrophotometry and treat the mathematics necessary for analytical quantitations, treatment of analytical wavelength selection has been mostly qualitative. Therefore, a general method for selecting wavelengths for optimum precision in simultaneous…

On the thermodynamic and kinetic investigations of a [c2]daisy chain polymer

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

Hmadeh, Mohamad; Fang, Lei; Trabolsi, Ali

2010-01-01

We report a variety of [c2]daisy chain molecules which undergo quantitative, efficient, and fully reversible molecular movements upon the addition of base/acid in organic solvents. Such externally triggered molecular movements can induce the contraction and extension of the [c2]daisy chain molecule as a whole. A linear polymer of such a bistable [c2]daisy chain exerts similar types of movements and can be looked upon as a candidate for the development of artificial muscles. The spectrophotometric investigations of both the monomeric and polymeric bistable [c2]daisy chains, as well as the corresponding model compounds, were performed in MeCN at room temperature, in ordermore » to obtain the thermodynamic parameters for these mechanically interlocked molecules. Based on their spectrophotometric and thermodynamic characteristics, kinetic analysis of the acid/base-induced contraction and extension of the [c2]daisy chain monomer and polymer were conducted by employing a stopped-flow technique. These kinetic data suggest that the rates of contraction and extension for these [c2]daisy chain molecules are determined by the thermodynamic stabilities of the corresponding kinetic intermediates. Faster switching rates for both the contraction and extension processes of the polymeric [c2]daisy chain were observed when compared to those of its monomeric counterpart. These kinetic and thermodynamic investigations on [c2]daisy chain-based muscle-like compounds provide important information for those seeking an understanding of the mechanisms of actuation in mechanically interlocked macromolecules.« less

Simulation of the Transverse Injection of a Pulsed Jet from the Surface of a Flat Plate into a Supersonic Flow

NASA Astrophysics Data System (ADS)

Volkov, K. N.; Emelyanov, V. N.; Yakovchuk, M. S.

2017-11-01

The transverse injection of a pulsed jet into a supersonic flow for thrust vectoring in solid rocket motors is investigated. The gas flow through the injection nozzle is controlled by a piston which performs reciprocating motion. Reynolds-averaged Navier-Stokes equations and the ( k- ɛ) turbulence model equations are discretized using the finite volume method and moving grids. The pressure distributions on the plate surface obtained using various approaches to the description of the flow field and difference schemes are compared. The solution obtained for the case of injection of a pulsed jet is compared with the solution for the case where a valve prevents gas flow through the injection nozzle. The dependence of the control force produced by gas injection on time is investigated.

Universality Results for Multi-Layer Hele-Shaw and Porous Media Flows

NASA Astrophysics Data System (ADS)

Daripa, Prabir

2012-11-01

Saffman-Taylor instability is a well known viscosity driven instability of an interface. Motivated by a need to understand the effect of various injection policies currently in practice for chemical enhanced oil recovery, we study linear stability of displacement processes in a Hele-Shaw cell involving injection of an arbitrary number of immiscible fluid phases in succession. This is a problem involving many interfaces. Universal stability results have been obtained for this multi-layer (multi-region) flow in the sense that the results hold with arbitrary number of interfaces. These stability results have been applied to design injection policies that are considerably less unstable than the pure Saffman-Taylor case. In particular, we determine specific values of the viscosity of the fluid layers corresponding to smallest unstable band. Moreover, we discuss universal selection principle of optimal viscous profiles. The talk is based on following papers. Qatar National Fund (a member of the Qatar Foundation).

Simulation of Orientation in Injection Molding of High Aspect Ratio Particle Thermoplastic Composites

NASA Astrophysics Data System (ADS)

Vélez-García, Gregorio M.; Ortman, Kevin C.; Eberle, Aaron P. R.; Wapperom, Peter; Baird, Donald G.

2008-07-01

A 2D coupled Hele-Shaw flow approximation for predicting the flow-induced orientation of high aspect ratio particles in injection molded composite parts is presented. For a highly concentrated short glass fiber PBT suspension, the impact of inter-particle interactions and the orientation at the gate is investigated for a center-gated disk using material parameters determined from rheometry. Experimental orientation is determined from confocal laser micrographs using the methods of ellipses. The constitutive equations are discretized using discontinuous Galerkin Finite Elements. Model predictions are significantly improved by using a localized orientation measured experimentally at the gate region instead of random or averaged gapwise measured orientation assumed in previous studies. The predicted profile in different radial positions can be related to the layered structure along the gapwise direction. Model modifications including interactions have lower impact than the initial conditions.