Differential Pulse Adsorptive Stripping Voltammetry Research Articles

Determination of pantoprazole by adsorptive stripping voltammetry at carbon paste electrode

A voltammetric method was described for the determination of pantoprazole by differential-pulse adsorptive stripping voltammetry at a carbon paste electrode. Accumulation of pantoprazole was found to be optimized in Britton–Robinson buffer (0.04 M, pH 4.0) solution following 5 min accumulation time at open circuit condition. Under optimized conditions, the current showed a linear dependence with concentration in the range 1.0×10 −7–1.0×10 −5 M. The detection limit was 2.0×10 −8 M. The method was applied successfully for the analysis of pantoprazole in tablet dosage form. The results of accuracy and precision were comparable to those obtained by spectrophotometry.

Voltammetric Determination of Carcinogenic Nitrobiphenyls at a Hanging Mercury Drop Electrode

Differential pulse voltammetry (DPV) and adsorptive stripping voltammetry (AdSV) at a hanging mercury drop electrode (HMDE) was used for the determination of trace amounts of carcinogenic nitrobiphenyls, namely 2-nitrobiphenyl (2-NBP), 3-nitrobiphenyl (3-NBP) and 4-nitrobiphenyl (4-NBP) within the concentration range from 2.10-8 to 1.10-5 mol⋅L-1 for DPV and from 2.10-9 to 1.10-7 mol⋅L-1 for AdSV using a Britton-Robinson buffer – methanol (1:1) mixture with resulting pH 12 as a base electrolyte. The practical applicability of newly developed methods was verified using model samples of drinking and river water and liquid-liquid extraction for a preliminary separation and preconcentration.

Determination of the antibacterial trovafloxacin by differential-pulse adsorptive stripping voltammetry

A differential-pulse adsorptive stripping voltammetric method for the determination of trace amounts of the antibacterial trovafloxacin (TRFLX) is proposed. The optimal experimental parameters for the drug assay were: accumulation potential=−0.30 V (vs. Ag/AgCl), accumulation time=120 s, pulse amplitude=50 mV and scan rate=5 mV s −1 in Britton–Robinson buffer (pH 4.5). The linear concentration range of application was 2.0–20.0 ng ml −1 of TRFLX, with a relative standard deviation of 3.6% (for a level of 5.0 ng ml −1) and a detection limit of 0.6 ng ml −1. The method was applied to determination of TRFLX in human urine and serum samples. It was validated using HPLC as a reference method. Recovery levels of the method reached 100% in all cases

Simultaneous determination of chromium(VI) and chromium(III) at trace levels by adsorptive stripping voltammetry

A new methodology was proposed for the speciation of chromium by differential pulse adsorptive stripping voltammetry (DPAdSV) using pyrocatechol violet (PCV) and N-(2-hydroxyethyl)ethylenediamine- N, N′, N′-triacetic acid (HEDTA) as complexing agents. In this procedure, a partial least squares (PLS) regression was used for the resolution of the strongly overlapping voltammetric signals from mixtures of Cr(III) and Cr(VI) in the presence of PCV and HEDTA. The relative error in absolute value was <6% when concentrations of several mixtures were calculated. The analysis of the possible effect of the presence of foreign ions in the solution was performed. The procedure was successfully applied to the speciation of chromium in different samples of natural water.

Optimization Procedure, Applying the Experimental‐Design Methodology, for the Determination of Rifampicin after Metal Complexation by Differential Pulse Adsorptive Stripping Voltammetry

A procedure for the determination of rifampicin (RIF) after CuII complexation by differential pulse adsorptive stripping voltammetry (DPAdSV) was optimized. The selection of the experimental conditions was made on the basis of the experimental-design methodology. The calibrations were performed under these conditions by means of a robust regression method that allows for the elimination of anomalous points. Once the detection limit was calculated, this method was successfully applied to the analysis of RIF in pharmaceutical preparations. The analysis of urine samples was also performed. The complexity of these samples made it necessary to apply multivariate-regression techniques to obtain satisfactory results.

Optimization Procedure, Applying the Experimental-Design Methodology, for the Determination of Rifampicin after Metal Complexation by Differential Pulse Adsorptive Stripping Voltammetry

Optimization Procedure, Applying the Experimental-Design Methodology, for the Determination of Rifampicin after Metal Complexation by Differential Pulse Adsorptive Stripping Voltammetry

Application of an Optimization Procedure in Adsorptive Stripping Voltammetry for the Determination of Chromium with Ammonium Pyrrolidine Dithiocarbamate

A procedure for the determination of chromium by differential pulse adsorptive stripping voltammetry (DPAdSV), using ammonium pyrrolidine dithiocarbamate (APDC) as complexing agent, has been optimized. The new method allows the selective determination of Cr(VI) in the presence of Cr(III) at pH equal to or below 3. The selection of the experimental conditions was made using experimental design methodology, and it was under these conditions where the calibrations were made, using a robust regression method which allows the elimination of anomalous points. The detection limit obtained was 1.09×10−9 M. The procedure was successfully applied to the determination of Cr(VI) and total chromium in different water samples.

DIFFERENTIAL PULSE ADSORPTIVE STRIPPING VOLTAMMETRY DETERMINATION OF EPINEPHRINE WITH β-MERCAPTOETHANOL SELF-ASSEMBLED MONOLAYERS MODIFIED ELECTRODE

ABSTRACT β-Mercaptoethanol self-assembled monolayer modified electrode (ME/Au SAMs) has been fabricated on bare gold. ATR-FTIR was used for the characterization and surface structure of the films. The films, as mediator, accelerated the electron transfer and showed an excellent electrocatalytic activity for the oxidation of the EP. The electrochemical behavior of epinephrine at ME/Au SAMs has been studied by cyclic voltammetry. The electrocatalytic mechanism has been explored. At potential of −0.044 V (vs SCE) in pH 4.0 aqueous buffer, a first oxidation wave is observed for epinephrine at the modified electrode (electrochemical oxidation of leucoepinephrine to epinechrome). In contrast, the first oxidation wave is not observed for norepinephrine or dopamine at the same condition. Under the conditions chosen, the modified electrode provides a linear response for epinephrine in the concentration range from 1.0 × 10−7 to 1.0 × 10−4 mol/L by differential pulse adsorptive stripping voltammetry. The detection limit (three times the signal blank/slope) was 3.3 × 10−8 mol/L. The modified electrode could eliminate the interference of norepinephrine, dopamine, and glucose at 10-, 40- and 1000-fold concentration of epinephrine (at 8.0 × 10−6 mol/L), and it has been satisfactorily used for the determination of epinephrine in injection.

Determination of Disulfiram by Adsorptive Stripping Voltammetry at Gold Disk Microelectrodes

Gold disk microelectrodes (AuMEs, 50 μm O) have been used for the determination of the fungicide disulfiram (DSF) at low concentration levels by differential pulse adsorptive stripping voltammetry (dp-AdSV). The AuMEs were fabricated in the laboratory and characterized by scanning electron microscopy and cyclic voltammetry. The AuME was pretreated daily by polishing with 3-μm diamond powder for 60 s, and by applying successively potentials of −0.4, −0.8, −1.0, −1.2 and −1.5 V for 30 s each in 0.1 mol L−1 H2PO4−/HPO42− (pH 6.0). In between measurements, the application of a potential of −1.5 V for 30 s was only necessary. The DSF adsorption on the AuME surface allows its determination at trace levels by dp-AdSV using low supporting electrolyte concentrations (3.0 mmol L−1) with an accumulation time of 120 s, a pulse amplitude of 50 mV, and a scan rate of 50 mV s−1. A detection limit of 6.3×10−8 mol L−1 and a RSD of 1.3% at a 5.0×10−7 mol L−1 DSF concentration level (n=10) were obtained with a two-electrode system and no stirring during the deposition step. The effect of the presence of several potential interferences on the DSF stripping signal has been tested. The developed method has been applied to the determination of DSF in spiked pea seeds with good results.

Differential pulse adsorptive stripping voltammetry of osmium-modified peptides

Complexes of osmium tetroxide with nitrogen ligands were developed and used in our laboratory as probes of the DNA structure. Here, we show that the complex of osmium tetroxide with 2,2′-bipyridine (Os,bipy) can be used for modification and electrochemical detection of proteins at neutral pH. Salmon luteinizing hormone (SLH) containing two tryptophan (Trp) residues and human luteinizing hormone (HLH) containing one Trp were modified by Os,bipy and measured by differential pulse adsorptive stripping voltammetry (DPAdSV) at a hanging mercury drop electrode (HMDE). The intensity of the DPAdSV catalytic signals corresponded to the number of Trp residues in the peptide molecule. Decreasing pH of the background electrolyte from 6.6 to 3.8 led to the increase of DPAdSV signals, suggesting that at pH 3.8, the DPAdSV detection limit might be well below 1 ng/ml. Our results suggest that Os,bipy is potentially useful for chemical modification of proteins.

Determination of the antibacterial enrofloxacin by differential-pulse adsorptive stripping voltammetry

Two new methods for the determination of enrofloxacin in commercial formulations and canine urine samples, based on adsorptive stripping voltammetry (AdSV), are proposed. One of the proposed method uses univariate calibration to analyse enrofloxacin in commercial formulations and the other applies principal component regression (PCR) to the voltammetric measurements to determine enrofloxacin in the presence of its metabolite ciprofloxacin. The linear concentration ranges of application were 4–25 and 18–55 ng ml −1 by using an accumulation potential of −0.3 V and a 180 or 60 s accumulation time, respectively for the univariate method. The first concentration range was used for the multivariate method. Both methods were successfully applied to the analysis of commercial formulations and spiked canine urine samples, respectively.

Polarographic and Voltammetric Determination of Trace Amounts of 9-Nitroanthracene

The polarographic behavior of 3-nitrofluoranthene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, differential pulse voltammetry (DPV) and adsorptive stripping voltammetry (AdSV), both at a hanging mercury drop electrode. Optimum conditions have been found for its determination by the given methods in the concentration ranges of 1 × 10 -6 -1 × 10 -4 mol l -1 (DCTP), 1 × 10 -7 -1 × 10 -4 mol l -1 (DPP), 1 × 10 -8 -1 × 10 -6 mol l -1 (DPV) and 1 × 10 -9 -1 × 10 -7 mol l -1 (AdSV), respectively. Practical applicability of these techniques was demonstrated on the determination of 3-nitrofluoranthene in drinking and river water after its preliminary separation and preconcentration using liquid-liquid and solid phase extraction with the limits of determination 4 × 10 -10 mol l -1 (drinking water) and 2 × 10 -9 mol l -1 (river water).

Electrochemical behavior and voltammetric determination of the herbicide metribuzin at mercury electrodes.

The electrochemical behavior of the herbicide metribuzin (4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one) at mercury electrodes was studied in aqueous solutions by direct current (DC) and tast polarography, differential pulse (DPV) and cyclic voltammetry (CV), and controlled-potential coulometry. The electrolysis products were separated and identified by chromatographic techniques combined with mass spectrometric detection. The reduction process in acid media includes two irreversible steps. In the first four-electron step the N-NH2 and the 1,6-azomethine bonds are reduced. The second step leads to the formation of 5-tert-butyl-2,3,4,5-tetrahydroimidazol-4-one at the mercury-pool electrode. The first reduction step combined with adsorptive accumulation of the herbicide molecule at the mercury electrode surface was used for its determination by differential pulse adsorptive stripping voltammetry (DPAdSV). Calibration curves were linear in the range 1-30 microg L(-1) with a detection limit of 0.27 microg L(-1) (1 nmol L(-1)) under the conditions used (buffer pH 4.5, Eacc = -0.45 V relative to Ag/AgCl and tacc = 10 s). Preconcentration on solid-phase extraction columns (SPE-phenyl) was used for the determination of very small amounts of metribuzin in river water samples. Recovery was approximately 97%. The reproducibility of the analytical procedure including SPE treatment and DPV determination was expressed as relative standard deviations of 2.53 and 3.66% for 2 and 6 microg L(-1) metribuzin, respectively.

Determination of cadmium by differential pulse adsorptive stripping voltammetry

A study of the adsorptive stripping voltammetry of cadmium on a mercury drop electrode is reported in which 2-mercapto-5-phenil-ammino-1,3,4-thiadiazole (MPATD), synthesized at home has been used as a chelating agent. The most suitable operating conditions and parameters such as buffer, pH, deposition potential, deposition time, ligand concentration, scan rate and others were selected and the determination of cadmium from aqueous solutions using the standard additions method was possible. As validation criteria, the linearity and range, repeatability of the signal, repeatability of the concentration and accuracy were investigated. A limit of detection of 4.67×10 −10 M and a limit of quantification of 1.55×10 −9 M were achieved. The interference of other metals and organic substances was studied. Concerning a possible catalytic effect, no one was found. The method was designed in order to determine Cd from biological samples.

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode.

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.

Optimization of the experimental parameters in the determination of rifamycin SV by adsorptive stripping voltammetry

A procedure for the determination of rifamycin SV by adsorptive stripping voltammetry (AdSV) has been optimized. Two different voltammetric techniques, namely differential pulse adsorptive stripping voltammetry (DPAdSV) and square wave adsorptive stripping voltammetry (SWAdSV) were used. In order to determine the most sensitive technique, an optimization of the experimental parameters was carried out for every technique using experimental design methodology. A canonical analysis of the response surface was carried out, which was adjusted to determine the optimum and the influence of the experimental factors. When this lay outside the ambit of the experiment, the optimum path method was used for the optimising process. The detection limits obtained, 3.108 × 10 −8 mol dm −3 for DPAdSV and 1.233 × 10 −8 mol dm −3 for SWAdSV, show that SWAdSV is a more sensitive technique for the analysis of rifamycin SV. Finally, this method was used to determine rifamycin SV in real samples.

Voltammetric and spectrophotometric techniques for the determination of the antihypertensive drug Prazosin in urine and formulations

A sensitive method was developed to determine Prazosin using a nafion modified carbon paste electrode (NMCPE). Prazosin was accumulated at a potential of 750 mV in Britton–Robinson buffer (pH 6.0) and then a negative sweep was made obtaining a cathodic peak close to 0 V. Cyclic voltammetric studies indicated that the process was quasi-reversible, and fundamentally controlled by adsorption. To obtain a good sensitivity, the instrumental and accumulation variables were studied using differential pulse voltammetry (DPV). Adsorptive voltammetric peak currents showed a linear response for Prazosin concentrations in the range between 4.0×10 −11 and 4.0×10 −8 M with two different slopes, and a detection limit (LOD) of 3.1×10 −11 M was obtained. The variation coefficient (CV) for a 8.0×10 −10 M solution ( n=10) was 4.08%. A spectrophotometric study of Prazosin was also carried out and two absorption bands were obtained at 246 and 329 nm (pH 1.8). The band at 329 nm was pH-dependent and its height and position changed with the pH values, so this allowed the p K a′ determination (7.14±0.20) using different methods. The detection limit reached by means of UV-spectrophotometry was 0.9×10 −7 M, and the variation coefficient for 1.5×10 −5 M Prazosin solutions was 1.14% ( n=10). Although the sensitivity of the UV-spectrophotometric method was lower than that obtained using adsorptive stripping-differential pulse voltammetry (AdS-DPV), it could be applied to the determination of Prazosin in Minipres tablets. The voltammetric method was used for the determination of the drug in human urine samples at trace levels with good recoveries.

Polarographic and voltammetric determination of selected nitrated polycyclic aromatic hydrocarbons

The use of differential pulse polarography, differential pulse voltammetry and adsorptive stripping voltammetry for the determination of trace amounts of selected nitrated polycyclic aromatic hydrocarbons (1-nitropyrene, 9-nitroanthracene, 2-nitrofluorene and 2,7-dinitrofluorene were chosen as model substances) were studied. The influence of pH and the composition of the base electrolyte on the polarographic and voltammetric behaviour of these substances was investigated and the optimum conditions for their determination in the concentration range of 1×10 −4–1×10 −9 mol l −1 were found. Practical applicability of these methods was demonstrated on the determination of trace amounts of selected chemical carcinogens in river water and on monitoring the chemical destruction of the test substances.

Adsorptive Stripping Voltammetric Determination of Albendazole at a Hanging Mercury Drop Electrode

ABSTRACT Albendazole is determined by differential-pulse adsorptive cathodic stripping voltammetry at a hanging mercury drop electrode using the reduction peak of its copper(II) complex at −0.28V at an accumulation potential 0.0V vs. Ag/AgCl electrode. The optimum conditions of pH, accumulation potential and accumulation time were studied. The calibration graph for the determination of albendazole was linear in the range 3.0X10−8 - 9X10−7M with a relative standard deviation of 2.8%. The detection limit was 1.0X10−8M after 180s accumulation at 0.0V. The effect of common excipients and metal ions on the peak height of albendazole was studied. The presence of Cu2+ ions forms a stable complex with albendazole which is strongly adsorbed at the mercury electrode surface. The method was applied to the determination of the drug in commercially available dosage forms.

Combined use of differential pulse adsorptive and anodic stripping techniques for the determination of antimony(III) and antimony(V) in zinc electrolyte

A knowledge of the concentration of both antimony(III) and antimony(V) is required in zinc plant electrolyte. In this paper, it is shown that an interference-free method to determine the low concentration of antimony in both oxidation states in zinc matrices is achieved by the combined use of differential pulse anodic stripping voltammetry (DPASV) after addition of concentrated hydrochloric acid (total antimony) and differential pulse adsorptive stripping voltammetry (DPAdSV) after addition of dilute hydrochloric and chloranilic acid (antimony(III)). The antimony(V) concentration is therefore calculable from the difference in the DPASV and DPAdSV determinations. In principle, antimony(III) could be determined by DPASV and antimony(V) by DPAdSV. However, in zinc electrolyte, the antimony(III) DPASV method suffers from a small level of interference when antimony(V) is present, while the DPAdSV method for the determination of antimony(V) is significantly interefered with by the presence of antimony(III). Consequently, only the combined use of both the DPASV and DPAdSV gives the required selectivity to achieve a completely interference-free determination of antimony in each oxidation state in zinc plant electrolyte.