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Real Samples (real + sample)

Distribution by Scientific Domains

Chemistry	76%
Polymers and Materials Science	3%

Distribution within Chemistry

Analytical Chemistry	50%
Mass Spectrometry	19%

Selected Abstracts

New Methylene Blue (NMB) Encapsulated in Mesoporous AlMCM-41 Material and Its Application for Amperometric Determination of Ascorbic Acid in Real Samples

ELECTROANALYSIS, Issue 15 2007
Shabnam Sohrabnezhad
Abstract New methylene blue (NMB) dye incorporated into AlMCM-41 surfactant-free and hybrid surfactant-AlMCM-41 mesophase. UV-vis evidence shows that new methylene blue dye protonated in both cases of zeolites. New methylene blue is electroactive in zeolites and their electrochemical activity has been studied by cyclic voltammetry and compared to that of NMB in aqueous solutions. New methylene blue molecules are not released to the solution during CV measurements and are accessible to H3O+ ions. The presence of surfactant affects the kinetics of the redox process through proton ions diffusion. The midpoint potentials (Em) values show that new methylene blue dye incorporated into AlMCM-41 can be reduced easily with respect to solution new methylene blue. New methylene blue interacting with surfactant polar heads and residual Br, ions as a results, it shows a couple of peaks in high potential with respect to new methylene blue solution. The electrode made with methylene blue-AlMCM-41 without surfactant was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. The calibration plot was linear over the ascorbic acid concentration range 1.0×10,5 to 5.0×10,4 M. The detection limit of the method is 1.0×10,5 M, low enough for trace ascorbic acid determination in various real samples. [source]

On-line solid-phase extraction with a monolithic weak cation-exchange column and simultaneous screening of ,1-adrenergic receptor antagonists in human plasma

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007
Xiaoyi Wei
Abstract An on-line SPE,HPLC method, using a monolithic poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (poly(GMA-EDMA)) based weak cation-exchange (WCX) column, was developed for simultaneous determination of ,1-adrenergic receptor antagonists in human plasma. The monolithic WCX column was prepared by an in-situ polymerization protocol and modified stepwise with ethylenediamine and chloroacetic acid. On connecting this column to an injection valve, an on-line SPE protocol could be established for removal of matrices (mainly proteins and lipids) and preconcentration of four ,1-adrenergic receptor antagonists in human plasma. This method was validated and then used for determination of terazosin, alfuzosin, prazosin, and doxazosin in clinical plasma samples. For all analytes, each calibration curve was found to be linear over a range of 0.005,5 ,g/mL (R >0.997), and the limit of detection for each analyte was 0.5 ng/mL. Recovery (> 80%) and precision (RSD <15%) for inter- and intra-day assay were tested at three concentration levels of each analyte and showed acceptable results for quantitative assay. Real samples from hypertensive patients were monitored and results were in agreement with those of the conventional liquid,liquid extraction-HPLC method. Furthermore, due to its good permeability and biocompatibility, the monolithic WCX sorbent could be reused more than 300 times. The proposed method was especially appropriate for multi-analyte monitoring in plasma samples. [source]

Properties of Poly(sodium 4-styrenesulfonate)-Ionic Liquid Composite Film and Its Application in the Determination of Trace Metals Combined with Bismuth Film Electrode

ELECTROANALYSIS, Issue 5 2008
Jianbo Jia
Abstract A new kind of bismuth film modified electrode to sensitively detect trace metal ions based on incorporating highly conductive ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF6) in solid matrices at glassy carbon (GC) was investigated. Poly(sodium 4-styrenesulfonate) (PSS), silica, and Nafion were selected as the solid matrices. The electrochemical properties of the mixed films modified GC were evaluated. The electron transfer rate of Fe(CN)64,/Fe(CN)63, can be effectively improved at the PSS-BMIMPF6 modified GC. The bismuth modified PSS-BMIMPF6 composite film electrodes (GC/PSS-BMIMPF6/BiFEs) displayed high mechanical stability and sensitive stripping voltammetric performances for the determination of trace metal cations. The GC/PSS-BMIMPF6/BiFE exhibited well linear response to both Cd(II) and Pb(II) over a concentration range from 1.0 to 50,,g L,1. And the detection limits were 0.07,,g L,1 for Cd(II) and 0.09,,g L,1 for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120,s, respectively. Finally, the GC/PSS-BMIMPF6/BiFEs were successfully applied to the determination of Cd(II) and Pb(II) in real sample, and the results of present method agreed well with those of atomic absorption spectroscopy. [source]

Electrochemical Detection of Arsenic(III) in the Presence of Dissolved Organic Matter (DOM) by Adsorptive Square-Wave Cathodic Stripping Voltammetry (Ad-SWCSV)

ELECTROANALYSIS, Issue 4 2008
Tsanangurayi Tongesayi
Abstract This study has demonstrated that As(III) can be electrochemically detected and quantified in the presence of fulvic acid (FA) and dissolved organic matter (DOM). This eliminates the need to remove DOM prior to measurement of As(III) in environmental samples. Apart from reducing analysis time and the cost of the analysis, this could be potentially useful for the development of electrochemical methods for the detection and measurement of As(III) onsite. Both synthetic samples in which FA was added and a real sample with 22.16,mg/L total organic carbon (TOC) were analyzed. [source]

A Cobalt Film Electrode for Nitrite Determination in Natural Water

ELECTROANALYSIS, Issue 24 2007
Koïkoï Soropogui
Abstract In this study a cobalt film electrodeposited on a copper disk (Ø=3.1,mm) was tested as electrode to measure nitrite ions in raw water. This electrode was able to determine the nitrite ions concentration in nondeaerated synthetic media and in natural water. The electrode reached a detection limit of 0.2,,mol L,1 and has a linear concentration range of 0.4 to 2,,mol L,1 NO2,. The influence of several ions such as NO3,, Cl,, SO42,, Mg2+, HCO3, and NH4+ was also tested. The electrode was used to determine the concentration of nitrite ions in a real sample. [source]

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine on the Tetrabromo- p -Benzoquinone Modified Carbon Paste Electrode

ELECTROANALYSIS, Issue 5 2007
Jahan-Bakhsh Raoof
Abstract The electrochemical properties of hydrazine studied at the surface of a carbon paste electrode spiked with p -bromanil (tetrabromo- p -benzoquinone) using cyclic voltammetry (CV), double potential-step chronoamperometry and differential pulse voltammetry (DPV) in aqueous media. The results show this quinone derivative modified carbon paste electrode, can catalyze the hydrazine oxidation in an aqueous buffered solution. It has been found that under the optimum conditions (pH,10.00), the oxidation of hydrazine at the surface of this carbon paste modified electrode occurs at a potential of about 550,mV less positive than that of a bar carbon paste electrode. The electrocatalytic oxidation peak current of hydrazine showed a linear dependent on the hydrazine concentrations and linear analytical curves were obtained in the ranges of 6.00×10,5 M,8.00×10,3 M and 7.00×10,6 M,8.00×10,4 M of hydrazine concentration with CV and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3,) were determined as 3.6×10,5 M and 5.2×10,6 M by CV and DPV methods. This method was also used for the determination of hydrazine in the real sample (waste water of the Mazandaran wood and paper factory) by standard addition method. [source]

Dual CD system-modified MEEKC method for the determination of clemastine and its impurities

ELECTROPHORESIS, Issue 19 2010
Serena Orlandini
Abstract A dual system of CDs was used for the first time in MEEKC with the aim of determining clemastine and its three main related impurities in both drug substances and tablets. The addition of methyl-,-cyclodextrin and heptakis(2,6-di- O -methyl)-,-cyclodextrin to the microemulsion pseudo-stationary phase was essential to increase the resolving power of the system to obtain a baseline separation among the compounds. The best microemulsion composition was identified by mixture design and the effects of the factors concentrations of CDs and voltage were investigated by a response surface study applying a Central Composite Design. In both cases, Derringer's desirability function made it possible to find the global optimum, which corresponded to the following combination: microemulsion, 89.8% 10,mM borate buffer pH 9.2, 1.5% n -heptane and 8.7% of SDS/n -butanol in 1:2 ratio; 18,mM methyl-,-cyclodextrin, 38,mM heptakis(2,6-di- O -methyl)-,-cyclodextrin, 17,kV. By applying these conditions, the separation was completed in about 5.5,min. The method was validated following International Conference on Harmonisation guidelines and was applied to a real sample of clemastine tablets. [source]

Testing of the influenza virus purification by CIEF

ELECTROPHORESIS, Issue 2 2010
Marie Horká
Abstract In virological practice, the pre-concentration, purification and subsequent determination of the purity and concentration of the viruses from the cultural medium and/or from the real sample are required. The conventional techniques used today are equipment demanding, time-consuming and laborious. In this study, the CIEF of influenza viruses with UV detection has been developed and subsequently used to test the purification of the virus from the biological samples. The equine and swine influenza viruses present in infected allantoic fluid of specific pathogen free embryonated chicken eggs were precipitated by using PEG 6000 and sodium chloride. The precipitated viruses were centrifuged at 14,000×g, and the impurities of different densities were removed by using the sucrose gradients. The efficiency of the virus purification technique was examined by the CIEF and compared to the results of real-time PCR. The pIs of both influenza viruses were determined. Simultaneously, the CIEF was found to be a suitable method for the rapid testing of the efficiency of the virus purification. [source]

A new strategy to filter out false positive identifications of peptides in SEQUEST database search results

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 22 2007
Jiyang Zhang
Abstract Based on the randomized database method and a linear discriminant function (LDF) model, a new strategy to filter out false positive matches in SEQUEST database search results is proposed. Given an experiment MS/MS dataset and a protein sequence database, a randomized database is constructed and merged with the original database. Then, all MS/MS spectra are searched against the combined database. For each expected false positive rate (FPR), LDFs are constructed for different charge states and used to filter out the false positive matches from the normal database. In order to investigate the error of FPR estimation, the new strategy was applied to a reference dataset. As a result, the estimated FPR was very close to the actual FPR. While applied to a human K562 cell line dataset, which is a complicated dataset from real sample, more matches could be confirmed than the traditional cutoff-based methods at the same estimated FPR. Also, though most of the results confirmed by the LDF model were consistent with those of PeptideProphet, the LDF model could still provide complementary information. These results indicate that the new method can reliably control the FPR of peptide identifications and is more sensitive than traditional cutoff-based methods. [source]

Quantitative Analysis of Prometrine Herbicide by Liquid,Liquid Extraction Procedures Coupled to Electrochemical Measurements

ELECTROANALYSIS, Issue 6 2009
V. Juarez
Abstract A sensitive method is proposed for the preconcentration and quantification of the herbicide Prometrine (PROM) at a liquid-liquid interface employing square-wave voltammetry. The preconcentration stage was based on liquid-liquid extraction methodology and the PROM quantification was carried out from the peak current of square-wave voltammograms. Under the experimental conditions employed, linear calibration curves in the concentration range 1.0×10,6,M,5.0×10,5,M, with detection limit equal to 1.5×10,6,M were obtained without pretreatment of the samples. This linear range, as well as detection limit could be extended towards lower concentrations when a pretreatment procedure was employed. In this way, linearity of calibration curves between 8.0×10,8,M and 2.4×10,7,M and detection limit of 1.0×10,7,M, were observed. On the other hand, the standard addition method was also used as an alternative and an appropriated quantification technique for this system. A linear concentration range between 1.0×10,6,M and 2.7×10,5,M, with a correlation coefficient of 0.997, was obtained. This procedure has also a promising application in the separation of herbicides from other interferents, present in real samples, previous to their quantification. [source]

Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping Voltammetry

ELECTROANALYSIS, Issue 12 2008
B. Gholivand
Abstract A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N,-bis(salicylaldehydo)4-carboxyphenylenediamine (BSCPDA),complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02,mol L,1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42,,M, pH,9.6 and adsorption potential at ,50,mV versus Ag/AgCl. With an accumulation time of 20,s, the peaks current are proportional to the concentration of nickel and cadmium over the 1,180, and 0.5,200,ng mL,1 with detection limits of 0.06 and 0.03,ng mL,1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98,nA mL ng,1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results. [source]

Lead(II) Potentiometric Sensor Based on 1,4,8,11-Tetrathiacyclotetradecane Neutral Carrier and Lipophilic Additives

ELECTROANALYSIS, Issue 11 2008
Mohamed
Abstract A potentiometric sensor for lead(II) ions based on the use of 1,4,8,11-tetrathiacyclotetradecane (TTCTD) as a neutral ionophore and potassium tetrakis-(p -chlorophenyl)borate as a lipophilic additive in plasticized PVC membranes is developed. The sensor exhibits linear potentiometric response towards lead(II) ions over the concentration range of 1.0×10,5,1.0×10,2,mol L,1 with a Nernstian slope of 29.9,mV decade,1 and a lower limit of detection of 2.2×10,6,mol L,1 Pb(II) ions over the pH range of 3,6.5. Sensor membrane without a lipophilic additive displays poor response. The sensor shows high selectivity for Pb(II) over a wide variety of alkali, alkaline earth and transition metal ions. The sensor shows long life span, high reproducibility, fast response and long term stability. Validation of the method by measuring the lower limit of detection, lower limit of linear range, accuracy, precision and sensitivity reveals good performance characteristics of the proposed sensor. The developed sensor is successfully applied to direct determination of lead(II) in real samples. The sensor is also used as an indicator electrode for the potentiometric titration of Pb(II) with EDTA and potassium chromate. The results obtained agree fairly well with data obtained by AAS. [source]

Stripping Voltammetry of Cerium(IIl) with a Chemically Modified Carbon Paste Electrode Containing Functionalized Nanoporous Silica Gel

ELECTROANALYSIS, Issue 2 2008
Mehran Javanbakht
Abstract This research introduces the design of an adsorptive stripping voltammetric method for the cerium(III) determination at a carbon paste electrode, chemically modified with dipyridyl-functionalized nanoporous silica gel (DPNSG-CPE). The electroanalytical procedure comprised two steps: the Ce(III) chemical accumulation at ,200,mV followed by the electrochemical detection of the Ce(III)/dipyridyl complex, using anodic stripping voltammetry. The factors, influencing the adsorptive stripping performance, were optimized including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The resulting electrode demonstrated a linear response over a wide range of Ce(III) concentration (1.0,28,ng mL,1). The precision for seven determinations of 4 and 10,ng mL,1 Ce(III) was 3.2% and 2.5% (relative standard deviation), respectively. The prepared electrode was used for the cerium determination in real samples and very good recovery results were obtained. [source]

Voltammetric Analysis of Trace Levels of Platinum Group Metals , Principles and Applications

ELECTROANALYSIS, Issue 21 2007
2Article first published online: 4 OCT 200, Clinio Locatelli
Abstract The compelling use of autocatalytic converters, containing platinum group metals (PGMs), has been the cause, in the environmental and biological matrices, of an increasing concentration of such metals. For this reason, in the last decade, the literature has reported several papers regarding analytical procedures for the determination of Pt(II), Pd(II) and Rh(III) in real samples, generally employing spectroscopic methods. The present review intends to highlight the contribution of the voltammetric techniques for the determination of these metals, including also those less investigated, i.e. Iridium, Osmium and Ruthenium. [source]

New Methylene Blue (NMB) Encapsulated in Mesoporous AlMCM-41 Material and Its Application for Amperometric Determination of Ascorbic Acid in Real Samples

Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide

ELECTROANALYSIS, Issue 6 2007
Aminur Rahman
Abstract A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly-5, 2,: 5,, 2,-terthiophine-3-carboxylic acid), poly-TTCA through the formation of amide bond between carboxylic acid groups of poly-TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly-TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X-ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly-TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73,s,1. The biosensor efficiently detected xanthine through oxidation at +0.35,V and reduction at ,0.25,V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10,6,1.0×10,4 M and 5.0×10,7 to 1.0×10,4,M, respectively. The detection limits were determined to be of 1.0×10,6,M and 9.0×10,8,M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples. [source]

Simultaneous and Direct Determination of Tryptophan and Tyrosine at Boron-Doped Diamond Electrode

ELECTROANALYSIS, Issue 8 2006
Guohua Zhao
Abstract A facile method for the simultaneous measurement of tryptophan (Trp) and tyrosine (Tyr) was firstly exploited at unmodified boron-doped diamond (BDD) electrode. The experimental results indicated that by using differential pulse voltammetry, the oxidative peaks of these two kinds of amino acids could be completely separated at BDD electrode. The peak separation of Trp and Tyr was developed to be 0.64,V when Na2PO4/NaOH buffer solution with the optimized pH,11.2 was employed. The detection limit of Trp was obtained to be 1×10,5,M, while that of Tyr was achieved to be 1×10,6,M. The present method was also evidenced to be available to the determination of real samples of amino acids. [source]

Voltammetric Monitoring and Speciation of Copper Ions in Italian "Grappa" with Platinum Microelectrodes

ELECTROANALYSIS, Issue 7 2006
Antonietta Baldo
Abstract A linear sweep voltammetric (LSV) investigation and the anodic stripping voltammetric (ASV) detection of copper ions in ethanol-water mixtures and grappa samples are reported. The measurements are carried out by using platinum microdisk electrodes. Ethanol-water mixtures with ethanol content in the range 40,100,vol%, commercially available and raw grappa samples having ethanol content in the above range are examined. From LSV measurements of copper (II) ions added to the samples, the formation of intermediate copper (I) soluble species, which are stabilized mainly by the naturally occurring organic compounds present in the real samples, is observed. The analysis of LSV and ASV current responses against added Cu2+ ions provides linear trends over the concentration range 5×10,5,5×10,3,M and 5×10,7,5×10,5,M, respectively. The sensitivity depends on the ethanol content in the mixture and, as expected, it is the higher the lower the viscosity of the medium. In particular, it varies from 1.54 to 3.53,nA mM,1 and from 0.114 to 0.263,nA ,M,1 for LSV and ASV measurements, respectively, upon changing the ethanol content from 40 to 100,vol%. In the same range of ethanol content, detection limits obtained by ASV vary from 0.27 to 0.15,,M, respectively. Labile or total copper contents in the grappa samples are determined by ASV measurements performed in the untreated matrices or in the samples acidified with 0.1,M HClO4, respectively. Finally, acidification of the samples with different amounts of HClO4 allows also some speciation investigations to be performed. [source]

Highly Sensitive and Selective Measurement of Bismuth in Seawater and Drug with 1,2-Phenylenedioxydiacetic Acid by Cathodic Adsorptive Stripping Voltammetry

ELECTROANALYSIS, Issue 7 2006
B. Gholivand
Abstract A new method is presented for determination of bismuth based on cathodic adsorptive stripping of complex bismuth with 1,2-phenylenedioxydiacetic acid (PDA) at a hanging mercury drop electrode (HMDE). The effect of various parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum conditions for determination of bismuth include nitric acid concentration 0.01,M, 8.0×10,4,M PDA and accumulation time 120,s, accumulation potential of ,200,mV. The limits of detection are 0.25 and 0.05,nM, and responses are linear 1,1000 and 0.1,400,nM at tacc of 60 and 120,s, respectively. Many common anions and cations do not interfere in the determination of bismuth. The method was applied to the determination of bismuth in some real samples such as sea , and spring water and drug. [source]

Trace Determination of Chromium by Square-Wave Adsorptive Stripping Voltammetry on Bismuth Film Electrodes

ELECTROANALYSIS, Issue 21 2004
Eleni Chatzitheodorou
Abstract This works reports the use of adsorptive stripping voltammetry (AdSV) for the trace determination of chromium on a rotating-disk bismuth-film electrode (BFE). During the reductive accumulation step, all the chromium species in the sample were reduced to Cr(III) which was complexed with cupferron and the complex was accumulated by adsorption on the surface of a preplated BFE. The stripping step was carried out by using a square-wave (SW) potential-time voltammetric signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements in the presence of dissolved oxygen. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3, limit of detection for chromium was 100,ng L,1 (for 120,s of preconcentration) and the relative standard deviation was 3.6% at the 2,,g L,1 level (n=8). Finally, the method was applied to the determination of chromium in real samples with satisfactory results. [source]

Heavy Metals in Matrices of Food Interest: Sequential Voltammetric Determination at Trace and Ultratrace Level of Copper, Lead, Cadmium, Zinc, Arsenic, Selenium, Manganese and Iron in Meals

ELECTROANALYSIS, Issue 18 2004
Clinio Locatelli
Abstract The voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices. The present work, regarding the sequential determination of Cu(II), Pb(II), Cd(II), Zn(II) by square-wave anodic stripping voltammetry (SWASV), As(III), Se(IV) by square-wave cathodic stripping voltammetry (SWCSV) and Mn(II), Fe(III) by square-wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal, are an interesting example of the possibility to sequentially determine each single element in real samples. Besides the set up of the analytical method, particular attention is aimed either at the problem of possible signal interference or to show that, using the peak area Ap as instrumental datum, it is possible to achieve lower limits of detection. The analytical procedure was verified by the analysis of the standard reference materials: Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. Precision, as repeatability, and accuracy, expressed as relative standard deviation and relative error, respectively, were lower than 6% in all cases. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed. [source]

Voltammetric Determination of ,-Tocopheryl Acetate in Pharmaceutical Dosage Forms

ELECTROANALYSIS, Issue 11 2004
Slawomir Michalkiewicz
Abstract A simple and rapid voltammetric method has been developed for the quantitative determination of ,-tocopheryl acetate (,-TOAc) in pharmaceutical preparations. Studies with linear scan (LSV), square-wave (SQWV) and differential pulse voltammetry (DPV) were carried out using platinum microelectrodes. A well-defined, irreversible oxidation wave/peak was obtained at 1.30,V (vs. Ag/AgCl reference electrode.) The use of SQWV or DPV technique provides a precise determination of ,-tocopheryl acetate using the multiple standard addition method. The statistical parameters and the recovery study data clearly indicate good reproducibility and accuracy of the method. Accuracy of the results assessed by recovery trials was found within the 99.3% to 103.5%, and 99.1% to 101.4%, for SQWV and DPV, respectively. The quantification limits for the both voltammetric techniques were found to be 6×10,5,M (SQWV) and 7×10,5,M (DPV). Analysis of the authentic samples containing ,-TOAc showed no interference with common additives and excipients, such as unsaturated fatty acids (co-formulated as glycerine esters) and vitamin A (as retinol or ,-carotene). The method proposed does not require any pretreatment of the pharmaceutical dosage forms. A gas chromatography determination of ,-TOAc in real samples was also performed for comparison. [source]

Analysis and Speciation of Traces of Arsenic in Environmental, Food and Industrial Samples by Voltammetry: a Review

ELECTROANALYSIS, Issue 9 2004
Andrea Cavicchioli
Abstract Voltammetric approaches for the determination of arsenic and speciation at trace levels are critically appraised in a review covering the literature from 1970 to 2002. Special attention is devoted to stripping modes and to issues related to the choice of working material and supporting electrolyte. A section is dedicated to the management of real samples and aspects of sample preparation. An extensive compilation, organized by real sample type, gathers essential experimental conditions. Potentiometric stripping analysis is introduced for sake of comparison. The coupling of voltammetric detection or preaccumulation with FIA, chromatography, capillary electrophoresis and ICP techniques is also addressed. [source]

Total analysis of endocrine disruptors in a microchip with gold nanoparticles

ELECTROPHORESIS, Issue 18 2010
Hui-Bog Noh
Abstract The development of a simple, sensitive, and direct method for the total analysis of certain endocrine disruptors was performed by integrating preconcentration steps to a separation step on a microchip through the modification of the field-amplified sample stacking and field-amplified sample injection steps. To improve the preconcentration and separation performances, the preconcentration and separation buffers were modified with citrate-stabilized gold nanoparticles (AuNPs). For the detection of the separated samples, cellulose-dsDNA/AuNPs-modified carbon paste electrodes were used at the channel end. The experimental parameters affecting the analytical performances, such as the buffer concentration, water plug length, SDS concentration in the separation buffer, AuNPs concentration, preconcentration time, detection potential and electrode to channel distance, were examined. The detection limits of the test compounds were between 7.1 and 11.1,fM and that for 4-pentylphenol was 7.1 (±1.1) fM. Dynamic ranges were in the range from 0.15 to 600.0,pM. The experiments with real samples were performed to evaluate the reliability of the proposed method. [source]

Analytical characterization of PEG polymers by MEKC

ELECTROPHORESIS, Issue 4 2010
María R. Plata
Abstract Characterization of PEGs with average molecular masses of up to 2000 has been achieved using MEKC with UV detection. A rapid derivatization procedure with phenyl isocyanate using microwave radiation, in order to introduce chromophore groups in PEGs, has been developed involving a reaction time of 60,s. Different optimized conditions in accordance with the molecular weight have been studied to obtain the oligomer separation. The weight-average molecular mass the number-average molecular mass and the degree of polydispersity (molecular mass distribution) were calculated for the different PEGs obtaining similar results with those certified for standards. A good precision was obtained for characterizing the different oligomers. Ethylene glycol was used as the internal standard for the analysis of low-molecular-weight PEGs. The developed method was satisfactorily applied to the characterization of these polymers in several real samples, such as lubricant eye drops, toothpaste, tap water and eye make-up remover. [source]

Mercury speciation by CE: An update

ELECTROPHORESIS, Issue 1 2009
Petr Kubán
Abstract This review provides an update on mercury speciation by CE. It includes a brief discussion on physicochemical properties, toxicity and transformation pathways of mercury species (i.e. methyl-, ethyl-, phenyl- and inorganic mercury) and outlines recent trends in Hg speciation by CE. CE is presented as a complementary technique to chromatographic separation techniques, especially in cases when speed, high efficiency and low sample volumes are required. The development of suitable sample preconcentration/isolation (sample stacking, ion exchange, liquid,liquid,liquid extraction, dual-cloud point extraction) to achieve low LODs for analysis of trace concentrations of mercury species in real samples is emphasized. Hyphenation of CE to element specific detectors (i.e. electrothermal atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry) is discussed as well as a potential of CE in interaction studies that may provide useful information on interaction of various Hg species with selected bio-macromolecules. [source]

Atmospheric molding of ionic copolymer MALDI-TOF/MS arrays: A new tool for protein identification/profiling

ELECTROPHORESIS, Issue 24 2006
Alexander Muck
Abstract An atmospheric molding protocol has been used to prepare an ionic methacrylate-based copolymer sample support chips for MALDI (pMALDI)-MS by targeting selected groups of various monomers copolymerized during molding, namely, carboxy, sulfo, dimethylalkyamino, and trimethylalkylammonium groups. The new disposable array chips provide analyte-oriented enhancement of protein adsorption to the modified substrates without requiring complicated surface coating or derivatization. The MALDI-MS performance of the new ionic copolymer chips was evaluated for lysozyme, ,-lactoglobulin,A, trypsinogen and carbonic anhydrase,I using washing with solutions prepared in pH or ionic strength steps. On cationic chips, the proteins are washed out at pH lower than their pI values, and on anionic chips at pH higher than their pI values. The ability of the microfabricated pMALDI chip set to selectively adsorb different proteins from real samples and to significantly increase their MS-signal was documented for the transmembrane photosystem,I protein complex from the green alga Chlamydomonas reinhardtii. The proteins were almost exclusively adsorbed according to calculated pI values and grand average of hydropathy (GRAVY) indexes. The new disposable chips reduce manipulation times and increase measurement sensitivity for real-world proteomic samples. The simple atmospheric molding procedure enables additional proteomic operations to be incorporated on disposable MALDI-MS integrated platforms. [source]

A self-contained polymeric 2-DE chip system for rapid and easy analysis

ELECTROPHORESIS, Issue 18 2006
Keisuke Usui
Abstract We developed a polymeric 2-DE chip system. The chip consisted of an IEF region, an SDS-PAGE region, a valveless connection port, and a sample introduction port. A "junction structure" as a valveless connection port, which allowed separating and connecting the first- and second-dimensional gels, was fabricated between their regions. A "solution inlet" as a sample introduction port was fabricated to perform the liquid and sample introductions without solution leakage. Simultaneous sample monitoring was performed using the on-chip detection system. The performances of the system were demonstrated using commercially available proteins as a standard specimen and tissue-extracted proteins as the real samples. All procedures were employed without any movement of relocation part. This new 2-D separation system realized improved labor-intensive operations and a reduced experimental time. [source]

Rapid determination of aliphatic amines in water samples by pressure-assisted monolithic octadecylsilica capillary electrochromatography-mass spectrometry

ELECTROPHORESIS, Issue 18-19 2004
Bricio Santos
Abstract A pressure-assisted capillary chromatography-mass spectrometry method based on the use of a monolithic octadecylsilica (ODS) capillary is proposed for the determination of aliphatic amines. A 25 mM citric acid buffer containing 10% methanol is used as running electrolyte. Separation is achieved by simultaneously applying a capillary electrophoresis (CE) voltage of 13 kV and an overimposed pressure of 8 bar. The use of pressure is required to ensure stable electrospray conditions. Analysis times are reduced by using a capillary column consisting of a 30 cm long monolithic silica capillary column bound with ODS and a fused-silica capillary column also 30 cm long. The proposed method was successfully applied to the determination of low-molecular-weight aliphatic amines in tap and river water. The analysis of real samples requires cleanup and preconcentration, which can be performed automatically by inserting a minicolumn in the replenishment system of the commercial instrument. [source]

Integrated on-chip derivatization and electrophoresis for the rapid analysis of biogenic amines

ELECTROPHORESIS, Issue 14 2004
Nigel P. Beard
Abstract We demonstrate the monolithic integration of a chemical reactor with a capillary electrophoresis device for the rapid and sensitive analysis of biogenic amines. Fluorescein isothiocyanate (FITC) is widely employed for the analysis of amino-group containing analytes. However, the slow reaction kinetics hinders the use of this dye for on-chip labeling applications. Other alternatives are available such as o -phthaldehyde (OPA), however, the inferior photophysical properties and the UV ,max present difficulties when using common excitation sources leading to a disparity in sensitivity. Consequently, we present for the first time the use of dichlorotriazine fluorescein (DTAF) as a superior in situ derivatizing agent for biogenic amines in microfluidic devices. The developed microdevice employs both hydrodynamic and electroosmotic flow, facilitating the creation of a polymeric microchip to perform both precolumn derivatization and electrophoretic analysis. The favorable photophysical properties of the DTAF and its fast reaction kinetics provide detection limits down to 1 nM and total analysis times (including on-chip mixing and reaction) of <60 s. The detection limits are two orders of magnitude lower than current limits obtained with both FITC and OPA. The optimized microdevice is also employed to probe biogenic amines in real samples. [source]