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Simultaneous Determination (simultaneous + determination)
Selected AbstractsPoly(pyridine-3-boronic acid)/Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrodes for Simultaneous Determination of Ascorbic Acid, 3,4-Dihydroxyphenylacetic Acid and Uric AcidELECTROANALYSIS, Issue 19 2010Zhijiao Wu Abstract Poly(pyridine-3-boronic acid) (PPBA)/multiwalled carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was used for the simultaneous determination of ascorbic acid (AA), 3,4-dihydroxyphenylacetic acid (DOPAC) and uric acid (UA). The anodic peaks for AA, DOPAC and UA at the PPBA/MWCNTs/GCE were well resolved in phosphate buffer solution (pH,7.4). The electrooxidation of AA, DOPAC and UA in the mixture solution was investigated. The peak currents increase with their concentrations increasing. The detection limits (S/N=3) of AA, DOPAC and UA are 5,µM, 3,µM and 0.6,µM, respectively. [source] Differential Pulse Anodic Stripping Voltammetric Simultaneous Determination of Copper(II) and Silver(I) with Bis(2-hydroxyacetophenone) Butane-2,3-dihydrazone Modified Carbon Paste ElectrodesELECTROANALYSIS, Issue 19 2010M. B. Gholivand Abstract The behavior of a modified carbon paste electrode (CPE) for simultaneous determination of copper(II) and silver(I) by anodic adsorptive stripping voltammetry (ASV) was studied. The electrode was built incorporating the bis(2-hydroxyacetophenone) butane-2,3-dihydrazone (BHAB) as a complexing agent to a Nujol-graphite base paste. The resulting electrode demonstrated linear responses over the range of Cu(II) and Ag(I) concentrations 0.1,20 and 0.01,2.0,µM respectively. The relative standard deviation (RSD) for the determination of 5.0,µM of both metal ions were 2.9 and 3.1,% for Cu(II) and Ag(I), respectively. The method has been applied to the analysis of copper in wheat and barley seed samples and silver in developed radiological film. [source] A Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotube/Chitosan Composite as a New Sensor for Simultaneous Determination of Acetaminophen and Mefenamic Acid in Pharmaceutical Preparations and Biological SamplesELECTROANALYSIS, Issue 15 2010Ali Babaei Abstract A new chemically modified electrode is constructed based on multiwalled carbon nanotube/chitosan modified glassy carbon electrode (MWCNTs-CHT/GCE) for simultaneous determination of acetaminophen (ACT) and mefenamic acid (MEF) in aqueous buffered media. The measurements were carried out by application of differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA) methods. Application of DPV method showed that the linear relationship between oxidation peak current and concentration of ACT and MEF were 1,,M to 145,,M, and 4,,M to 200,,M, respectively. The analytical performance of this sensor has been evaluated for detection of ACT and MEF in human serum, human urine and a pharmaceutical preparation with satisfactory results. [source] Simultaneous Determination of Ascorbic Acid, Dopamine and Uric Acid at Pt Nanoparticles Decorated Multiwall Carbon Nanotubes Modified GCEELECTROANALYSIS, Issue 10 2010Zekerya Dursun Abstract A modified electrode was fabricated by electrochemically deposition of Pt nanoparticles on the multiwall carbon nanotube covered glassy carbon electrode (Pt nanoparticles decorated MWCNT/GCE). A higher catalytic activity was obtained to electrocatalytic oxidation of ascorbic acid, dopamine, and uric acid due to the enhanced peak current and well-defined peak separations compared with both, bare and MWCNT/GCE. The electrode surfaces were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Individual and simultaneous determination of AA, DA, and UA were studied by differential pulse voltammetry. The detection limits were individually calculated for ascorbic acid, dopamine, and uric acid as being 1.9×10,5,M, 2.78×10,8,M, and 3.2×10,8,M, respectively. In simultaneous determination, LODs were calculated for AA, DA, and UA, as of 2×10,5,M, 4.83×10,8,M, and 3.5×10,7,M, respectively. [source] Silver Doped Poly(L -valine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Uric Acid, Ascorbic Acid and DopamineELECTROANALYSIS, Issue 5 2010Wenna Hu Abstract In this paper, a silver doped poly(L -valine) (Ag-PLV) modified glassy carbon electrode (GCE) was fabricated through electrochemical immobilization and was used to electrochemically detect uric acid (UA), dopamine (DA) and ascorbic acid (AA) by linear sweep voltammetry. In pH,4.0 PBS, at a scan rate of 100,mV/s, the modified electrode gave three separated oxidation peaks at 591,mV, 399,mV and 161,mV for UA, DA and AA, respectively. The peak potential differences were 238,mV and 192,mV. The electrochemical behaviors of them at the modified electrode were explored in detail with cyclic voltammetry. Under the optimum conditions, the linear ranges were 3.0×10,7 to 1.0×10,5,M for UA, 5.0×10,7 to 1.0×10,5,M for DA and 1.0×10,5 to 1.0×10,3,M for AA, respectively. The method was successfully applied for simultaneous determination of UA, DA and AA in human urine samples. [source] Simultaneous Determination of Cadmium, Lead, Copper and Mercury Ions Using Organofunctionalized SBA-15 Nanostructured Silica Modified Graphite,Polyurethane Composite ElectrodeELECTROANALYSIS, Issue 1 2010Ivana Cesarino Abstract A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite,polyurethane composite electrode with SBA-15 silica organofunctionalized with 2-benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at ,1.1,V vs. SCE where they complex with 2-benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd2+, Pb2+, Cu2+ and Hg2+ in natural waters was achieved. [source] Simultaneous Determination of Trace Zinc(II) and Cadmium(II) by Differential Pulse Anodic Stripping Voltammetry Using a MWCNTs,NaDBS Modified Stannum Film ElectrodeELECTROANALYSIS, Issue 23 2009Qing Tian Abstract A multiwalled carbon nanotubes,sodium dodecyl benzene sulfonate (MWCNTs,NaDBS) modified stannum film electrode was employed for the determination of cadmium(II) and zinc(II). The Sn/MWCNTs-NaDBS film electrode was prepared by applying MWCNTs,NaDBS suspension to the surface of the GCE, while the Sn film was plated in situ simultaneously with the target metal ions. Under optimal conditions, linear calibration curves were obtained in a range of 5.0 ,100.0,,g L,1 with detection limits of 0.9,,g L,1 for zinc(II) and 0.8,,g L,1 for cadmium(II), respectively. This film electrode was successfully applied to the determination of Zn(II) and Cd(II) in tap water sample. [source] Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano-Gold Self-Assembled Glassy Carbon ElectrodeELECTROANALYSIS, Issue 10 2009Guangzhi Hu Abstract Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self-assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self-assembling gold nanoparticles on the surface of L -cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well-defined redox peaks of DA on the GNP/LC/GCE was obtained at Epa=0.197,V and Epc=0.146,V, respectively. And the peak separation between DA and AA is about 0.2,V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10,8,8.5×10,5 mol L,1 and 1.0×10,6,2.5×10,3 mol L,1, with the detection limit of 2.0×10,8 mol L,1 and 3.0×10,7 mol L,1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result. [source] The Fabrication and Characterization of a Bismuth Nanoparticle Modified Boron Doped Diamond Electrode and Its Application to the Simultaneous Determination of Cadmium(II) And Lead(II)ELECTROANALYSIS, Issue 16 2008Kathryn Abstract We report the simultaneous electroanalytical determination of Pb2+ and Cd2+ by square-wave anodic stripping voltammetry (SWASV) using a bismuth nanoparticle modified boron doped diamond (Bi-BDD) electrode. Bi deposition was performed in situ with the analytes, from a solution of 0.1,mM Bi(NO3)3 in 0.1,M HClO4 (pH,1.2), and gave detection limits of 1.9,,g L,1 and 2.3,,g L,1 for Pb(II) and Cd(II) respectively. Pb2+ and Cd2+ could not be detected simultaneously at a bare BDD electrode, whilst on a bulk Bi macro electrode (BiBE) the limits of detection for the simultaneous determination of Pb2+ and Cd2+ were ca. ten times higher. [source] Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping VoltammetryELECTROANALYSIS, Issue 12 2008B. 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] Chitosan Incorporating Cetyltrimethylammonium Bromide Modified Glassy Carbon Electrode for Simultaneous Determination of Ascorbic Acid and DopamineELECTROANALYSIS, Issue 17 2007Xuelian Zou Abstract Simultaneous determination of a neurotransmitter, dopamine (DA), and ascorbic acid (AA) is achieved at neutral pH on a chitosan incorporating cetyltrimethylammonium bromide (CTAB) modified glassy carbon (GC) electrode. Differential pulse voltammetry (DPV) technique was used to investigate the electrochemical response of DA and AA at a glassy carbon electrode modified with chitosan incorporating CTAB. An optimum 6.0,mmol L,1 of CTAB together with 0.5 wt% of chitosan was used to improve the resolution and the determination sensitivity. In 0.1,mol L,1 aqueous phosphate buffer solution of pH,6.8, the chitosan-CTAB modified electrode showed a good electrocatalytic response towards DA and AA. The anodic peak potential of DA shifted positively, while that of AA shifted negatively. Thus, the difference of the anodic peaks of DA and AA reached 0.23,V, which was enough to separate the two anodic peaks very well. The presented method herein could be applied to the direct simultaneous determination of DA and AA without prior treatment. The anodic peak currents (Ipa) of DPV are proportional to DA in the concentration range of 8,,M to 1000,,M, to that of AA 10,,M to 2000,,M, with correlation coefficients of 0.9930 and 0.9945, respectively. The linear range is much wider than previously reported. [source] Simultaneous Determination of Quinoline and Pyridine Compounds in Gasoline and Diesel by Differential Pulse VoltammetryELECTROANALYSIS, Issue 6 2007Leonardo Abstract The presence of trace basic organonitrogen compounds such as quinoline and pyridine in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic nitrogen compounds in fuel samples such as gasoline and diesel. This method utilizes preconcentration on an ion,exchange resin (Amberlyte IR,120,H) followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline and pyridine as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by an irreversible chemical reaction. Very well resolved diffusion-controlled voltammetric peaks were obtained in dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBAF4 0.1,mol L,1) for quinoline (,1.95,V) and pyridine (,2.52,V) vs. Ag|AgCl|KClsat reference electrode. The proposed DPV method displayed a good linear response from 0.10 to 300,mg L,1 and a limit of detection (LOD) of 5.05 and 0.25,,g L,1 for quinoline and pyridine, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline samples yielded 25.0±0.3 and 33.0±0.7,mg L,1 and in diesel samples yielded 80.3±0.2 and 131±0.4,mg L,1, respectively. Spike recoveries were 94.4±0.3% and 101±0.5% for quinoline and pyridine, respectively, in the fuel determinations. This proposed method was also compared with UV-vis spectrophotometric measurements. Results obtained for the two methods agreed well based on F and t student's tests. [source] Simultaneous Determination of Uric Acid and Ascorbic Acid Using Edge Plane Pyrolytic Graphite ElectrodesELECTROANALYSIS, Issue 8 2006Roohollah, Torabi Kachoosangi Abstract Edge plane pyrolytic graphite electrodes have been applied for the determination of uric acid and ascorbic acid. The separate determination of uric acid was found to produce three linear ranges from 100,nM to 3400,,M with a detection limit of 30,nM found to be possible. Uric acid detection was also explored in the presence of 200,,M ascorbic acid where a detection limit of 52,nM was found to be possible. The detection of ascorbic acid in the presence of uric acid was also explored over three linear ranges of ascorbic acid with a limit of detection of 80,nM. Last the simultaneous determination of both uric acid and ascorbic acid is investigated over the range 100,nM to 1000,,M where detection limits of 50,nM and 120,nM were obtained respectively. Analysis of uric acid in a growth tissue medium was found to be successful, confirming the applicability of the methodology to real matrices. This protocol is shown to provide low detection limits, easy handling (no electrode modification), good voltammetric peak separation of uric acid and ascorbic acid and a wide linear dynamic range. [source] Direct Simultaneous Determination of ,- and ,-Naphthol Isomers at GC-Electrode Modified with CNTs Network Joined by Pt Nanoparticles Through Derivative VoltammetryELECTROANALYSIS, Issue 5 2006Xiao-Gang Wang Abstract The semi-derivative technique was adopted to improve the resolution and surfactant was added to sample solution to enhance the sensitivity, , - and , -naphthol isomers could be determined directly and simultaneously at glassy carbon electrode modified with carbon nanotubes network joined by Pt nanoparticles. In 0.1,mol,L,1 HAc-NaAc buffer solution (pH,5.8), the linear calibration ranges were 1.0×10,6 to 8.0×10,4 mol,L,1 for both , - and , -naphthols, with detection limits of 5.0×10,7 for , - and 6.0×10,7,mol,L,1 for , -naphthol. The amount of naphthol isomers in artificial wastewater has been tested with above method, and the recovery was from 98% to 103%. [source] Simultaneous Determination of Copper and Bismuth by Anodic Stripping Voltammetry Using H-Point Standard Addition Method with Simultaneous Addition of AnalytesELECTROANALYSIS, Issue 17 2005Esmaeil Shams Abstract Simultaneous determination of bismuth and copper by anodic stripping voltammetry using H-point standard addition method (HPSAM) with simultaneous addition of analytes is described. The effect of various parameters including acid concentration, accumulation time, accumulation potential and concentration ratio of analytes in the standard solution on the sensitivity and accuracy of method were investigated. The results of applying the H-point standard addition method showed that Cu2+ and Bi3+ could be determined simultaneously with the concentration ratios of Cu2+ to Bi3+ varying from 1,:,15 to 16,:,1 in the mixed sample. The method was successfully applied to the simultaneous determination of copper and bismuth in some synthetic mixtures. [source] Simultaneous Determination of Hydroquinone and Catechol at a Glassy Carbon Electrode Modified with Multiwall Carbon NanotubesELECTROANALYSIS, Issue 10 2005Honglan Qi Abstract A simply and high selectively electrochemical method for simultaneous determination of hydroquinone and catechol has been developed at a glassy carbon electrode modified with multiwall carbon nanotubes (MWNT). It was found that the oxidation peak separation of hydroquinone and catechol and the oxidation currents of hydroquinone and catechol greatly increase at MWNT modified electrode in 0.20,M acetate buffer solution (pH,4.5). The oxidation peaks of hydroquinone and catechol merge into a large peak of 302,mV (vs. Ag/AgCl, 3,M NaCl) at bare glassy carbon electrode. The two corresponding well-defined oxidation peaks of hydroquinone in the presence of catechol at MWNT modified electrode occur at 264,mV and 162,mV, respectively. Under the optimized condition, the oxidation peak current of hydroquinone is linear over a range from 1.0×10,6,M to 1.0×10,4,M hydroquinone in the presence of 1.0×10,4,M catechol with the detection limit of 7.5×10,7,M and the oxidation peak current of catechol is linear over a range from 6.0×10,7,M to 1.0×10,4,M catechol in the presence of 1.0×10,4,M hydroquinone with the detection limit of 2.0×10,7 M. The proposed method has been applied to simultaneous determination of hydroquinone and catechol in a water sample with simplicity and high selectivity. [source] Direct Simultaneous Determination of Cu, Ni and V in Seawater Using Adsorptive Cathodic Stripping Voltammetry with Mixed LigandsELECTROANALYSIS, Issue 10 2005A. Cobelo-García Abstract An analytical procedure is proposed for the direct simultaneous determination in a single scan of Cu, Ni and V in seawater by means of adsorptive cathodic stripping voltammetry (ACSV) with mixed ligands (DMG and catechol). Optimum conditions for the determination of these three elements were studied. Detection limits of the technique depended upon the reproducibility of the procedura blank, and were found to be 0.5,nM for Cu, 0.4,nM for Ni and 0.3,nM for V. The method is suitable for the analysis of estuarine, coastal and open-ocean waters, and especially to study the metal contamination in areas subject to oil spill events. [source] Simultaneous Determination of Fluorine, Chlorine, Bromine and Iodine in Six Geochemical Reference Materials Using Pyrohydrolysis, Ion Chromatography and Inductively Coupled Plasma-Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 4 2009Hélène Balcone-Boissard halogènes; pyrohydrolyse; chromatographie ionique; spectrométrie de masse couplée à une source de plasma induit; matériaux géologiques de référence Concentrations of halogens (fluorine, chlorine, bromine and iodine) were determined in six geochemical reference materials (BHVO-2, GS-N, JG-1, JR-1, JB-1b, JB-2). Halogens were first extracted from powdered samples using a pyrohydrolysis technique, then hydrolysis solutions were analysed by ion chromatography for F and Cl and inductively coupled plasma-mass spectrometry for Br and I. The detection limits in solutions were 100 ,g l,1 for both F and Cl and 10 ng l,1 for Br and I. Considering the extraction procedure, performed on a maximum of 500 mg of sample and producing 100 ml of pyrohydrolysis solution, detection limits in rock samples were 20 mg kg,1 for F and Cl and 2 ,g kg,1 for Br and I. The mean analytical errors on the studied composition ranges were estimated at 10 mg kg,1 for F and Cl, 100 ,g kg,1 for Br and 25 ,g kg,1 for I. The concentration values, based on repeated (generally > 10) sample analysis, were in good agreement generally with published values and narrowed the mean dispersion around mean values. Large dispersions are discussed in terms of samples heterogeneity and contaminations during sample preparation. Basaltic RMs were found to be more suitable for studies of halogen compositions than differentiated rock material, especially granites , the powders of which were heterogeneous in halogens at the 500 mg level. Les concentrations en halogènes (fluor, chlore, brome et iode) on été déterminées dans 6 matériaux géologiques de référence (BHVO-2, GS-N, JG-1, JR-1, JB-1b, JB-2), distribués par le GSJ, l'USGS et le CRPG. Les halogènes étaient d'abord extraits des échantillons, disponibles sous forme de poudre, par pyrohydrolyse. F et Cl sont ensuite analysés par chromatographie ionique, Br et I par spectrométrie de masse couplée à une source de plasma induit. Les limites de détection sont de 100 ,g l,1 pour F et Cl, et de 10 ng l,1 pour Br et I, respectivement. L'extraction des halogènes était réalisée sur 500 mg de poudre de roche, produisant 100 ml de solution d'extraction. Ainsi, pour les échantillons de roche, les limites de détection étaient de 20 mg kg,1 pour F et Cl, et 2 ,g kg,1 pour Br et I. L'erreur analytique moyenne sur la gamme de concentration étudiée est estimée à 10 mg kg,1 pour F et Cl, 100 ,g kg,1 pour Br et 25 ,g kg,1 pour I. Les valeurs de concentrations données, obtenues par l'analyse répétée (> 10) du même échantillon étaient en accord avec les valeurs reportées dans la littérature. Elles présentent en général une plus faible dispersion autour de la valeur moyenne. Dans le cas d'une importante dispersion des résultats, celle-ci est discutée en terme d'hétérogénéité de l'échantillon analysé et de contamination durant la préparation du matériel de référence. Les échantillons de référence de composition basaltique se révèlent être plus appropriés pour étudier les compositions en halogènes que les matériaux correspondant à des roches différenciées, en particulier des granites dont la distribution en halogènes apparaît hétérogène dans les poudres à l'échelle d'un aliquot de 500 mg. [source] Simultaneous Determination of Gibbs Free Energies of Formation of Sr2RhO4(s) and Sr4RhO6(s) Using Solid-State Electrochemical Cells.CHEMINFORM, Issue 1 2005Aparna Banerjee No abstract is available for this article. [source] Simultaneous Determination of Epinephrine, Noradrenaline and Dopamine in Human Serum Samples by High Performance Liquid Chromatography with Chemiluminescence DetectionCHINESE JOURNAL OF CHEMISTRY, Issue 7 2007Fu-Nan Chen Abstract A simple, rapid and accurate high performance liquid chromatographic (HPLC) technique coupled with chemiluminescence (CL) detection was developed for the simultaneous determination of epinephrine (E), noradrenaline (NA) and dopamine (DA). It was based on the analyte enhancement effect on the CL reaction between luminol and potassium ferricyanide. The effects of various parameters, such as potassium ferricyanide concentration, luminol concentration, pH value and component of the mobile phase on chromatographic behaviors of the analytes (E, NA and DA) were investigated. The separation was carried out on C18 column using the mobile phase of 0.01 mol/L potassium hydrogen phthalate solution and methanol (92:8, V/V). Under the optimum conditions, E, NA and DA showed good linear relationships in the range of 1×10,8,5×10,6, 5.0×10,9,1.0×10,6 and 5.0×10,9,1.0×10,6 g/mL respectively. The detection limits for E, NA and DA were 4.0×10,9, 1.0×10,9 and 8.0×10,10 g/mL. The proposed method has been applied successfully to the analysis of E, NA and DA in human serum samples. [source] Capillary Electrophoresis for the Simultaneous Determination of Metals by Using Ethylenediamine Tetraacetic Acid as Complexing Agent and Vancomycin as Complex SelectorCHINESE JOURNAL OF CHEMISTRY, Issue 12 2006Jirasak Threeprom Abstract A new separation system of capillary electrophoresis for the simultaneous determination of metals by using ethylenediamine tetraacetic acid (EDTA) as complexing agent and employing vancomycin as complex selector was described. The Z-shape cell capillary electrophoresis was used to enhance the sensitivity for the determination of the complexes of Cu(II), Ni(II), Co(II) and Fe(III) with EDTA. The partial filling method (co-current mode) was used in order to increase the selectivity of the electrophoretic method, meanwhile vancomycin was not present at the detector path during the detection of metal-EDTA complexes. The vancomycin concentration, phosphate concentration and pH of the buffer strongly influenced mobility, resolution and selectivity of the studied analytes. Under the optimal condition, the relative standard deviations (n=5) of the migration time and the peak area were less than 3.14% and 7.35%, respectively. Application of the Z-shape cell capillary electrophoresis method with UV detection and vancomycin loading led to the reliable determination of these metal ions in tap water and the recoveries were97%,101%. The detection limits based on a signal to noise ratio of 3:1 were found in the range of 2,10 µg·L,1. [source] ,-Cyclodextrin Incorporated Carbon Nanotube-coated Electrode for the Simultaneous Determination of Dopamine and EpinephrineCHINESE JOURNAL OF CHEMISTRY, Issue 3 2005Wang Ge-Yun Abstract An ,-cyclodextrin (,-CD) incorporated carbon nanotube (CNT)-coated electrode was fabricated and applied to the simultaneous determination of dopamine (DA) and epinephrine (EP). It has been found that the modified electrode shows strong catalytic effects on the electro-separation of DA and EP, and the cathodic potential difference between DA and EP is about 390 mV. The reducing peak current is proportional to DA and EP concentrations in the range of 2.0×10 -6,1.0×10 -3 and 1.0×10 -6,1.0×10 -3 mol·L -1, respectively. Their detection limits can reach 1×10 -6 and 5×10 -7 mol·L -1, respectively. Because the oxidation of ascorbic acid (AA) is an irreversible reaction in ,-CD/CNT film, the interference of AA in determination of DA and EP is eliminated. [source] Comparison of Artificial Neural Networks with Partial Least Squares Regression for Simultaneous Determinations by ICP-AESCHINESE JOURNAL OF CHEMISTRY, Issue 11 2007Mohamad KHAYATZADEH MAHANI Abstract Simultaneous determination of several elements (U, Ta, Mn, Zr and W) with inductively coupled plasma atomic emission spectrometry (ICP-AES) in the presence of spectral interference was performed using chemometrics methods. True comparison between artificial neural network (ANN) and partial least squares regression (PLS) for simultaneous determination in different degrees of overlap was investigated. The emission spectra were recorded at uranium analytical line (263.553 nm) with a 0.06 nm spectral window by ICP-AES. Principal component analysis was applied to data and scores on 5 dominant principal components were subjected to ANN. A 5-5-5 (input, hidden and output neurons) network was used with linear transfer function after both hidden and output layers. The PLS model was trained with five latent variables and 20 samples in calibration set. The relative errors of predictions (REP) in test set were 3.75% and 3.56% for ANN and PLS respectively. [source] Simultaneous determination of metronidazole and spiramycin in bulk powder and in tablets using different spectrophotometric techniquesDRUG TESTING AND ANALYSIS, Issue 1 2010Fatma I. Khattab Abstract Metronidazole (MZ) is an anti-infective drug used in the treatment of anaerobic bacterial and protozoa infections in humans. It is also used as a vetinary antiparasitic drug. Spiramycin (SP) is a medium-spectrum antibiotic with high effectiveness against Gram-positive bacteria. Three simple, sensitive, selective and precise spectrophotometric methods were developed and validated for the simultaneous determination of MZ and SP in their pure form and in pharmaceutical formulations. In methods A and B, MZ was determined by the application of direct spectrophotometry and by measuring its zero-order (D0) absorption spectra at its ,max = 311 nm. In method A, SP was determined by the application of first derivative spectrophotometry (D1) and by measuring the amplitude at 218.3 nm. In method B, the first derivative of the ratio spectra (DD1) was applied, and SP was determined by measuring the peak amplitude at 245.6 nm. Method C entailed mean centring of the ratio spectra (MCR), which allows the determination of both MZ and SP. The methods developed were used for the determination of MZ and SP over a concentration range of 5,25 µg ml,1. The proposed methods were used to determine both drugs in their pure, powdered forms with mean percentage recoveries of 100.16 ± 0.73 for MZ in methods A and B, 101.10 ± 0.90 in method C, 100.09 ± 0.70, 100.02 ± 0.88 and 100.49 ± 1.26 for SP in methods A, B and C, respectively. The proposed methods were proved using laboratory-prepared mixtures of the two drugs and were successfully applied to the analysis of MZ and SP in tablet formulation without any interference from each other or from the excipients. The results obtained by applying the proposed methods were compared statistically with a reported HPLC method and no significant difference was observed between these methods regarding both accuracy and precision. Copyright © 2010 John Wiley & Sons, Ltd. [source] Chitosan Incorporating Cetyltrimethylammonium Bromide Modified Glassy Carbon Electrode for Simultaneous Determination of Ascorbic Acid and DopamineELECTROANALYSIS, Issue 17 2007Xuelian Zou Abstract Simultaneous determination of a neurotransmitter, dopamine (DA), and ascorbic acid (AA) is achieved at neutral pH on a chitosan incorporating cetyltrimethylammonium bromide (CTAB) modified glassy carbon (GC) electrode. Differential pulse voltammetry (DPV) technique was used to investigate the electrochemical response of DA and AA at a glassy carbon electrode modified with chitosan incorporating CTAB. An optimum 6.0,mmol L,1 of CTAB together with 0.5 wt% of chitosan was used to improve the resolution and the determination sensitivity. In 0.1,mol L,1 aqueous phosphate buffer solution of pH,6.8, the chitosan-CTAB modified electrode showed a good electrocatalytic response towards DA and AA. The anodic peak potential of DA shifted positively, while that of AA shifted negatively. Thus, the difference of the anodic peaks of DA and AA reached 0.23,V, which was enough to separate the two anodic peaks very well. The presented method herein could be applied to the direct simultaneous determination of DA and AA without prior treatment. The anodic peak currents (Ipa) of DPV are proportional to DA in the concentration range of 8,,M to 1000,,M, to that of AA 10,,M to 2000,,M, with correlation coefficients of 0.9930 and 0.9945, respectively. The linear range is much wider than previously reported. [source] Simultaneous Determination of Copper and Bismuth by Anodic Stripping Voltammetry Using H-Point Standard Addition Method with Simultaneous Addition of AnalytesELECTROANALYSIS, Issue 17 2005Esmaeil Shams Abstract Simultaneous determination of bismuth and copper by anodic stripping voltammetry using H-point standard addition method (HPSAM) with simultaneous addition of analytes is described. The effect of various parameters including acid concentration, accumulation time, accumulation potential and concentration ratio of analytes in the standard solution on the sensitivity and accuracy of method were investigated. The results of applying the H-point standard addition method showed that Cu2+ and Bi3+ could be determined simultaneously with the concentration ratios of Cu2+ to Bi3+ varying from 1,:,15 to 16,:,1 in the mixed sample. The method was successfully applied to the simultaneous determination of copper and bismuth in some synthetic mixtures. [source] Simultaneous determination of nine endogenous steroids in human urine by polymeric-mixed micelle capillary electrophoresisELECTROPHORESIS, Issue 19 2010Sabrina Flor Abstract A new CE system based on the use of polymeric-mixed micelles (cholic acid, SDS and the poloxamine Tetronic® 1107) was developed for the simultaneous determination of nine steroids in human urine. This method allows the baseline separation and quantitation of cortisol, androstenedione, estriol, dehydroepiandrosterone sulfate, testosterone, dehydroepiandrosterone, estrone, progesterone and estradiol in less than 25,min showing to be sensitive enough to detect low concentrations of these steroids in urine samples (5,45,ng/mL). The optimized electrophoretic conditions were performed using a 50,cm×75,,m capillary, 18,kV, 25°C, with 44,mM cholic acid, 10,mM SDS, 0.05%,w/v tetronic® 1107, 2.5%,v/v methanol, 2.5%,v/v tetrahydrofuran in 5,mM borate , 5,mM phosphate buffer (pH=8.0) as a background electrolyte and a dual 210/254 UV-detection. The method can simultaneously determine 0.1,120,,g/mL, which corresponds to 5,6000,ng/mL of steroids in 2,mL urine. The recoveries ranged between 82.4 and 101.5%. Due to its simplicity, speed, accuracy and reliability, the proposed method could be a potential alternative to the traditional methodologies used with clinical purposes. [source] Simultaneous determination of six non-polar heterocyclic amines in meat samples by supercritical fluid extraction,capillary electrophoresis under fluorimetric detectionELECTROPHORESIS, Issue 13 2010Fernando De Andrés Abstract A novel, sensitive and selective method for the separation and quantification of a group of non-polar heterocyclic amines (9H-pyrido-[3,4-b] indole, norharmane; 1-methyl-9H-pyrido-[3,4-b] indole, harmane; 2-amino-9H-pyrido-[2,3-b] indole, A,C; 2-amino-3-methyl-9H-pyrido-[2,3-b] indole, MeA,C; 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b] indole, Trp-P-1 and 3-amino-1-methyl-5H-pyrido-[4,3-b] indole, Trp-P-2) in commercial meat samples has been developed. This methodology is faster than others previously described. The method is based on the combination of a supercritical fluid extraction procedure, followed by the analysis of the extracted plug by CE with fluorescence detection. The supercritical fluid extraction procedure was optimized for the clean-up of the samples and the extraction of the analytes. For the electrophoretic separation, the effect of composition, pH and concentration of buffer, organic modifier content, pressure and time of injection, capillary temperature and voltage applied were studied. A 10,mmol/L formic acid,ammonium formate,ACN (10%, v/v) solution at pH 1.5 was selected as the running electrolyte. With 5-s hydrodynamic injection, linear responses in the range from 100 to 1000,ng/mL and detection limits ranging from 15.9 to 28.1,ng/mL were obtained for different amines in less than 13,min. ACN,water (1:1 in volume) was used as a sample solvent. Fluorescence detection enhances the sensitivity and avoids interferences coming from non-fluorescent compounds present in the matrices of the sample extracts. [source] Simultaneous determination of memantine and amantadine in human plasma as fluorescein derivatives by micellar electrokinetic chromatography with laser-induced fluorescence detection and its clinical applicationELECTROPHORESIS, Issue 11 2010Hsin-Hua Yeh Abstract A nonionic surfactant MEKC method with LIF detection was developed for the simultaneous determination of memantine, an anti-Alzheimer's disease agent, and amantadine, an anti-Parkinson's disease drug, in human plasma. Before analysis, the plasma samples were pretreated by liquid,liquid extraction with ethyl acetate, and derivatized with 6-carboxyfluorescein N -hydroxysuccinimide ester. The chemical derivatization is performed with 6-carboxyfluorescein N -hydroxysuccinimide ester in ACN , 5,mM pH 9.0 borate buffer (40:60, v/v) at 35°C for 3,h. After the derivatization reaction, hydrodynamic injection (0.5,psi, 8,s) was used to introduce the derivatized solution, and the separation was performed in borate buffer (30,mM, pH 9.5) with the nonionic surfactant Brij-35® (0.07%, w/v); the separation voltage was 6,kV. The linear ranges of the method for the determination of memantine and amantadine in human plasma were over a range of 2.0,60.0,ng/mL. The detection limit was 0.5,ng/mL (S/N=3). This method was applied successfully to monitor the concentration of memantine or amantadine in patients with Alzheimer's disease or Parkinson's disease. [source] Simultaneous determination of Zr(IV) and Hf(IV) by CE using precolumn complexation with a [PW11O39]7, ligandELECTROPHORESIS, Issue 10 2007Sadayuki Himeno Professor Abstract A CE method was developed for the simultaneous determination of Zr(IV) and Hf(IV) at trace levels. A lacunary Keggin-type [PW11O39]7, ligand reacted quantitatively with a mixture of trace amounts of Zr(IV) and Hf(IV) to form the so-called ternary Keggin-type anions [P(ZrIVW11)O40]5, and [P(HfIVW11)O40]5, in 0.010,M monochloroacetate buffer (pH,2.2). Since both ternary anions possessed different electrophoretic mobilities and high molar absorptivities in the UV region, Zr(IV) and Hf(IV) were determined simultaneously with direct UV detection at 258,nm. Each peak height was linearly dependent on the concentration of Zr(IV) or Hf(IV) in the range of 5.0×10,7,1.0×10,5,M; a detection limit of 2×10,7,M was achieved. The utility of the proposed CE method was demonstrated for the simultaneous determination of Zr(IV) and Hf(IV) in natural water samples with satisfactory results. [source] | |||||||||||||||||||||||||||||||