Simultaneous Differential Pulse Voltammetric Determination Research Articles

De-bundled single-walled carbon nanotube-modified sensors for simultaneous differential pulse voltammetric determination of ascorbic acid, dopamine, and uric acid

De-bundled SWCNTs modified glassy carbon electrode for the simultaneous differential pulse voltammetric determination of ascorbic acid, dopamine, and uric acid.

A tantalum electrode coated with graphene nanowalls for simultaneous voltammetric determination of dopamine, uric acid, L-tyrosine, and hydrochlorothiazide

The authors describe a voltammetric sensor for simultaneous determination of dopamine (DA), uric acid (UA), L-tyrosine (Tyr), and the diuretic drug hydrochlorothiazide (HCTZ). The assay is based on the use of graphene nanowalls deposited on a tantalum substrate. The nanowalls are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and cyclic voltammetry. The nanowalls are vertically grown on the substrate by direct-current arc plasma jet chemical vapor deposition. The modified electrode is shown to enable simultaneous differential pulse voltammetric determination of DA, UA, Tyr, and HCTZ. The graphene nanowalls display a large specific surface, high conductivity, and a large number of catalytically active sites for oxidation of analytes. Simultaneous detection is performed best at a pH value of 7.0 and at peak potentials of 0.124 V (vs. SCE) for DA, 0.256 V for UA, 0.536 V for Tyr and 0.708 V for HCTZ. The respective detection limits are 0.04 μM, 0.1 μM, 0.6 μM and 0.4 μM. The results show that this graphene wall modified electrode is a promising tool for the design of sensitive, selective, and stable sensors.

A glassy carbon electrode modified with porous gold nanosheets for simultaneous determination of dopamine and acetaminophen

Porous gold nanosheets modified glassy carbon electrode (GCE) was facilely prepared by one-step electrodeposition, using N-methylimidazole as a growth-directing agent. The porous gold nanosheets modified GCE was characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction spectroscopy. The modified electrode displayed improved sensitivity for individual and simultaneous differential pulse voltammetric determination of dopamine (DA; at 180 mV) and acetaminophen (AC; at 450 mV vs. Ag/AgCl) even in the presence of ascorbic acid. The oxidation peak currents linearly increased with the concentrations of DA and AC in the ranges from 2.0 to 298.0 μM and 3.0 to 320.0 μM, respectively, and the detection limits are 0.28 μM for DA and 0.23 μM for AC. The relative standard deviations (n = 20) are 1.5 % for DA and 0.4 % for AC.

An adaptive wavelength interval selection by modified particle swarm optimization algorithm: simultaneous spectral or differential pulse voltammetric determination of multiple components with overlapping peaks

The elimination of wavelengths which contain useless or irrelevant information for calibration model is becoming one of the key steps in multicomponent spectral analysis even in situations where the partial least-squares (PLS) regression is applied. Because of the continuity of most kinds of spectral responses, the adaptive wavelength interval selection by modified particle swarm optimization (PSO) could be proposed in the present study. The proposed method was used for simultaneous spectrophotometric determination of caffeine, aspirin, and phenacetin and simultaneous differential pulse voltammetric determination of nitrophenol isomers. The method was eventually applied to commercial drugs. For comparison, a conventional full-spectrum PSO analysis was also performed. Experimental results demonstrate that the adaptive wavelength interval selection by modified PSO is capable of improving the future predictive ability of the model.

Improvement of the prediction ability of multivariate calibration by a method based on the combination of data fusion and least squares support vector machines

This paper suggests a novel method named DF-LS-SVM, which is based on least squares support vector machines (LS-SVM) regression combined with data fusion (DF) to enhance the ability to extract characteristic information and improve the quality of the regression. Simultaneous multicomponent determination of Fe(III), Co(II) and Cu(II) was conducted for the first time by using the proposed method. Data fusion is a technique that integrates information from disparate sources to produce a single model or decision. The LS-SVM technique allows for learning a high-dimensional feature with fewer training data, and reduces the computational complexity by only requiring the solution of a set of linear equations instead of a quadratic programming problem. Experimental results showed that the DF-LS-SVM method was successful for simultaneous multicomponent determination even when severe overlap of spectra existed. The DF-LS-SVM method is an attractive and promising hybrid approach that combines the best properties of the two techniques. The results obtained from an additional test case, simultaneous differential pulse voltammetric determination of o-nitrophenol, m-nitrophenol and p-nitrophenol, also demonstrated that the DF-LS-SVM method performed somewhat better than LS-SVM and PLS methods.

Simultaneous Differential Pulse Voltammetric Determination of Sulfamethoxazole and Trimethoprim on a Boron‐Doped Diamond Electrode

AbstractThe performance of hydrogen‐ (HT) and oxygen‐terminated (OT) boron‐doped diamond (BDD) electrodes (electrochemically pretreated) on the simultaneous differential pulse voltammetric determination of sulfamethoxazole and trimethoprim in pharmaceutical products is presented. Under the optimum analytical experimental conditions, the HT‐BDD electrode presented two well‐defined oxidation peaks at 920 and 1100 mV vs. Ag/AgCl for sulfamethoxazole and trimethoprim, respectively. On the other hand, when the OT‐BDD electrode was used, the sulfamethoxazole oxidation current peak was decreased twenty fold. The calculated LOD values for sulfamethoxazole and trimethoprim using the HT‐BDD electrode were 3.65 μg L−1 and 3.92 μg L−1, respectively. The results obtained in the simultaneous determination of sulfamethoxazole and trimethoprim in three different commercial formulations were similar to those obtained using a standard HPLC method at 95% confidence level.

Combining direct orthogonal signal correction and wavelet packet transform with partial least squares to analyze overlapping voltammograms of nitroaniline isomers

A novel method named DOSCWPTPLS approach based on partial least squares (PLS) regression with direct orthogonal signal correction (DOSC) and wavelet packet transform (WPT) as pre-processed tools was proposed for the simultaneous differential pulse voltammetric determination of o-nitroaniline, m-nitroaniline and p-nitroaniline with overlapping peaks. The method combines the ideas of DOSC and WPT with PLS regression for enhancing the ability in the extraction of characteristic information and the quality of regression. Data reduction was performed using DOSC, WPT and PLS algorithm. DOSC is used to remove information in the response matrix D by subtracting the structured noise that is orthogonal to the concentration matrix C. Wavelet packet representations of signals provide a local time–frequency description, thus in the wavelet packet domain, the quality of the noise removal, data compression, and relevant information extraction can be improved. PLS was applied for multivariate calibration and reduced noise by eliminating the less important latent variables. In this case, by optimization, the kind of wavelet function, the decomposition level, and the number of DOSC components, tolerance factor and the number of PLS factors for the DOSCWPTPLS method were selected as Coiflet 2, 3, 3, 0.001 and 3, respectively. A program (PDOSCWPTPLS) was designed to perform the simultaneous voltammetric determination of o-nitroaniline, m-nitroaniline and p-nitroaniline. The relative standard errors of prediction (RSEP) obtained for all components using DOSCWPTPLS, DOSCPLS, WPTPLS and PLS were compared. Experimental results demonstrated that the DOSCWPTPLS method had the best result among the four methods and was successful even when there was severe overlap of voltammograms.

Simultaneous differential pulse voltammetric determination of L-dopa and carbidopa in pharmaceuticals using a carbon paste electrode modified with lead dioxide immobilized in a polyester resin

A carbon paste electrode modified with lead dioxide immobilized in a polyester resin has been developed for simultaneous differential pulse voltammetric determination of L-dopa and carbidopa in pharmaceutical formulations. The analytical curves were linear in the concentration ranges from 2.6 ´ 10-4 to 1.2 ´ 10-3 mol L-1 and from 3.2 ´ 10-5 to 1.5 ´ 10-4 mol L-1 for L-dopa and carbidopa, respectively. The detection limits were 2.5 ´ 10-5 mol L-1 and 3.7 ´ 10-6 mol L-1 for L-dopa and carbidopa, respectively and recoveries of L-dopa and carbidopa from two samples ranged from 98.1 to 103% of the added amount. The relative standard deviations were lower than 2.5% for 1.2 ´ 10-4 and 1.2 ´ 10-3 mol L-1 of these catecholamines solutions and the results obtained for L-dopa and carbidopa in pharmaceutical formulations using the proposed voltammetric procedure are in close agreement with the labeled values and/or those obtained using an enzymatic method at the 95% confidence level.

Simultaneous determination of uric acid, xanthine and hypoxanthine with an electrochemically pretreated carbon paste electrode

A simple method is presented for the simultaneous differential pulse voltammetric determination of uric acid, xanthine and hypoxanthine. It is based on the improved current responses of the three analytes at carbon paste electrodes polarized in a dilute alkaline medium (0.002 mol/l NaOH, 0.1 mol/l NaClO4) at 1.3 V vs. SCE for a short time. Compared with the methods reported in the literature, this procedure has a much wider linear range (2 to 3 orders of magnitude in concentration), lower detection limits (5 to 10 μg l−1) and less interference by ascorbic acid. The electrochemical responses were found to be dependent on the pre-anodization potential and the time imposed on the electrodes as well as on the alkalinity of the supporting electrolyte. The proposed procedure was used to determine uric acid, xanthine and hypoxanthine in human urine without any preliminary treatment.