Differential Pulse Stripping Voltammetry Research Articles

Sodium dodecyl sulfate-modified carbon paste electrodes for selective determination of dopamine in the presence of ascorbic acid

A carbon paste electrode (CPE) modified by a monolayer film of sodium dodecyl sulfate (SDS) was used for detection of dopamine (DA). Cyclic voltammetry demonstrated improved response of the DA sensor. This suggests the effectivity of surface modification of CPE by SDS. Impedance spectroscopy was used for the characterization of CPE surface properties. The effect of SDS concentration on the electrode quality also reveals that SDS formed a monolayer on CPE surface with a high density of negative-charged end directed outside the electrode. As a result, the carbon paste electrode modified with SDS (SDS/CPE) exerted discrimination against ascorbic acid in physiological circumstance. Thus, it can selectively determine dopamine even in the presence of 220-fold AA combined with differential pulse stripping voltammetry. In pH 7.40 phosphate buffer solution, the oxidation peak current on differential pulse voltammograms increases linearly with the concentration of DA in the range of 5.0 × 10 − 7 to 8.0 × 10 − 4 mol · L − 1 with a detection limit of 5.0 × 10 − 8 mol · L − 1 . Satisfying results are achieved when detecting the DA in injection and simulated biology sample.

Determination of iodide ions at poly(3-methylthiophene)-modified electrode by differential pulse stripping voltammetry

A voltammetric electrode based on a poly(3-methylthiophene) (PMT) film for the differential pulse stripping voltammetric (DPSV) determination of iodide was developed. Gold electrodes were first coated with PMT, and iodide was then doped into the polymer film by electrochemical oxidation of iodide at 0.75 V. The effects of various electrochemical parameters, such as electroyte type and its pH, deposition potential, deposition time, and precipitation time, were examined. Using DPSV, the PMT electrode was found to be suitable for the measurement of iodide concentrations above 1 × 10−9 M.

Simultaneous determination of lead and cadmium at a glassy carbon electrode modified with Langmuir–Blodgett film of p- tert-butylthiacalix[4]arene

A glassy carbon electrode (GCE) modified with a Langmuir–Blodgett (LB) film of p- tert-butylthiacalix[4]arene (TCA) has been investigated as a disposable sensor for measuring the trace levels of lead and cadmium. The possibility of determining lead and cadmium at trace levels was examined with differential pulse stripping voltammetry in the measurement step. The electrochemical response was characterized with respect to supporting electrolyte, pH of solution, accumulation time, accumulation potential, layers of the LB films, and possible interferences. Calibration plots were found to be linear in the range 2 × 10 −7 to 5 × 10 −5 mol l −1 (Cd 2+) and 1 × 10 −7 to 2.5 × 10 −5 mol l −1 (Pb 2+); the detection limits were 2 × 10 −8 mol l −1 (Cd 2+) and 8 × 10 −9 mol l −1 (Pb 2+). Possible recognition mechanism was also discussed. From the analysis of real samples (river, lake and tap water) it can be concluded that the method is sensitive and reproducible in determining of these elements and can be used in the analysis of natural water samples.

The Determination of Nonelectroactive Anticancer Drug 6‐Thioguanine on DNA‐Modified Gold Electrode

A nonelectroactive anticancer drug 6‐thioguanine was determined by differential pulse stripping voltammetry on the DNA‐modified gold electrode. The electrode was prepared by the dry adsorptive method, which is simple and direct. Potassium ferricyanate [K3Fe(CN)6] was chosen as an appropriate electroactive indicator to probe and characterize the interaction since the 6‐thioguanine and DNA both are nonelectroactive over the potential range studied. The reductive peak current of K3Fe(CN)6 is linear with the concentration of 6‐thioguanine in the range of 2.0×10−8∼8.0×10−7 mol L−1. The detection limit is 6.0×10−9 mol L−1. The established method was successfully applied to determining trace 6‐thioguanine with the recoveries between 95.7% and 105.6%.

Determination of Trace Amounts of Lorazepam by Adsorptive Cathodic Differential Pulse Stripping Method in Pharmaceutical Formulations and Biological Fluids

A new adsorptive cathodic differential pulse stripping voltammetry method for the direct determination of lorazepam at trace levels in pharmaceutical formulations and biological fluids is proposed. The procedure involves an adsorptive accumulation of lorazepam on a hanging mercury drop electrode (HMDE), followed by reduction of adsorbed lorazepam by voltammetric scan using differential pulse modulation. The optimum conditions for the analysis of lorazepam are pH=2 using Britton‐Robinson (B‐R) buffer, accumulation potential of −0.2 V (vs. Ag/AgCl), and accumulation time of 40 sec. The peak current is proportional to the concentration of lorazepam, and a linear calibration graph is obtained at 0.05–1.15 µg mL−1. A relative standard deviation of 2.41% (n=3) was obtained, and the limit of detection was 0.019 µg mL−1. The capability of the method for the analysis of real samples was evaluated by determination of lorazepam in pharmaceutical preparations and biological (urine and plasma) fluids with satisfactory results.

Voltammetric Determination of Phenylglyoxylic Acid in Urine Using Graphite Composite Electrode

A composite electrode prepared from graphite powder and epoxy resin was applied as a working electrode for the determination of phenylglyoxylic acid (one of the metabolites of styrene) in human urine. Cathodic differential pulse stripping voltammetry was used and optimum conditions have been found giving the limit of determination about 5 mg L−1. All results were compared with those obtained using hanging mercury drop electrode. For the confirmation of suggested mechanism of the electrochemical reaction the elimination voltammetry with linear scan was used.

Chemical analysis of CuInSe2 thin films prepared by evaporation through a multistage process

The chemical composition of CuInSe2 (CIS) thin films was determined through an electrochemical method implemented in our laboratory. The CIS thin films were grown on soda lime glass substrates by the chemical reaction of their precursors occurred in a multistage process. The quantitative determination of the elements constituting the CIS films was carried out by Differential Pulse Stripping Voltammetry (DPSV). Comparing the results obtained by the electrochemical analysis with the phases identified in the CIS samples by XRD (X-ray diffraction) measurements, it was found that the DPSV method is reliable. The studies revealed that the samples grow in the α-phase (CuInSe2) and crystallize in the chalcopyrite structure, which is of technological interest in the photovoltaic industry. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Simultaneous determination of three organophosphorus pesticides by differential pulse stripping voltammetry and chemometrics

A differential pulse stripping voltammetry method (DPSV) is proposed for the determination of parathion-methyl (PTM), fenitrothion (FT) and parathion (PT) at a hanging mercury drop electrode (HMDE). The voltammograms of these three compounds overlap strongly, and it is difficult to determine the compounds individually from their mixtures. Quantitative analysis for each of the pesticide compounds in a mixture has been investigated with the aid of chemometrics and the prediction performance of the different methods such as classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), Kalman filter (KF) and radial basis function-artificial neural networks (RBF-ANN), was compared. A set of synthetic mixtures of the three compounds was analysed by using the proposed methods, and it was found that the lowest relative prediction error (RPE) and satisfactory % recovery were achieved with the RBF-ANN procedure. The proposed method was also applied to several vegetable samples spiked with known amounts of the pesticides with satisfactory results.

Measurement of zinc in Mongolia patent drug Zhuangxiyin Powder with pulse stripping voltammetry

To determine the content of zinc in Mongolia patent drug Zhuangxiyin Powder. Differential pulse stripping voltammetry was employed for measurement of zinc. The zinc content in three samples of the drug was (493+/-11.95)microg/g, (526+/-13.74)microg/g and (554+/-9.84) microg/g respectively, and the relative standard deviation (RSD) was 2.42%, 2.61% and 1.78% respectively. The content of zinc in Zhuangxiyin Powder of daily dosage is higher than the needed daily intake of healthy people.

Silver Composite Electrode for Voltammetric Determination of Halogenides

The application of the silver composite electrode prepared from silver, graphite powder and methacrylate resin for the voltammetric determination of halogenide ions was studied. Cathodic direct current (DC) as well as differential pulse (DP) stripping voltammetry (DPV) enable direct determination of chloride, bromide, as well as iodide ions. The achieved limits of detection for all determined ions are sufficient for practical analytical purposes (tap water, natural water, etc.) and results reported in this paper are fully comparable with results achieved using other electrodes. The possibilities of sample analysis without elimination of the presence of surface‐active substances or of dissolved oxygen were studied. The silver composite electrode represents a suitable sensor for analytical purposes and seems to be promising for replacement of mercury electrodes in many cases.

Differential Pulse Stripping Voltammetric Determination of Paracetamol and Phenobarbital in Pharmaceuticals Assisted by Chemometrics

A voltammetric method, aided by chemometrics, was developed for the simultaneous determination of paracetamol and phenobarbital in pharmaceuticals. Both of these analytes gave well‐defined oxidation peaks in the Britton–Robinson buffer (pH 5.72) when analyzed by differential pulse‐stripping voltammetry (DPSV) at a glassy carbon electrode. The experimental conditions were optimized: 200 mV—deposition potential, 160 s—deposition time, 4 mV—increment potential, 50 mV—amplitude, and 60 ms—pulse width. Under these selected conditions, the oxidation current had a linear relationship with concentration of paracetamol [ranges: 0.09–0.93 mg l−1 (r 2 = 0.999) and 0.9–11.7 mg l−1 (r 2 = 0.999)], and phenobarbital [1.0–22.0 mg l−1 (r 2 = 0.999)]. Due to the overlapping voltammograms from the two analytes, two chemometrics methods, partial least squares (PLS), and principal component regression (PCR), were used for building calibration models from voltammograms of mixtures. These models were applied for prediction of the analytes from unknown samples. It was found that the two chemometrics methods gave good results for analysis of mixtures of these two compounds. The proposed method was verified by an established HPLC method, and its practical application was demonstrated with the determination of paracetamol and phenobarbital in several commercial tablets with satisfactory results.

Evaluations of solid electrodes for use in voltammetric monitoring of heavy metals in samples from metallurgical nickel industry.

Evaluation of different solid electrode systems for detection of zinc, lead, cobalt, and nickel in process water from metallurgical nickel industry with use of differential pulse stripping voltammetry has been performed. Zinc was detected by differential pulse anodic stripping voltammetry (DPASV) on a dental amalgam electrode as intermetallic Ni-Zn compound after dilution in ammonium buffer solution. The intermetallic compound was observed at -375 mV, and a linear response was found in the range 0.2-1.2 mg L(-1) (r(2)=0.98) for 60 s deposition time. Simultaneous detection of nickel and cobalt in the low microg L(-1) range was successfully performed by use of adsorptive cathodic stripping voltammetry (AdCSV) of dimethylglyoxime complexes on a silver-bismuth alloy electrode, and a good correlation was found with corresponding AAS results (r(2)=0.999 for nickel and 0.965 for cobalt). Analyses of lead in the microg L(-1) range in nickel-plating solution were performed with good sensitivity and stability by DPASV, using a working electrode of silver together with a glassy carbon counter electrode in samples diluted 1:3 with distilled water and acidified with H(2)SO(4) to pH 2. A new commercial automatic at-line system was tested, and the results were found to be in agreement with an older mercury drop system. The stability of the solid electrode systems was found to be from one to several days without any maintenance needed.

Simultaneous determination of lead(II) and cadmium(II) at a diacetyldioxime modified carbon paste electrode by differential pulse stripping voltammetry

A simple and effective chemically modified carbon paste electrode (CMCPE) for the simultaneous determination of lead(II) and cadmium(II) was developed in this work. The electrode was prepared by the addition of diacetyldioxime into a carbon paste mixture. Pb 2+ and Cd 2+ were preconcentrated on the surface of the modified electrode by complexing with diacetyldioxime and reduced at a negative potential (−1.10 V). Then the reduced products were oxidized by differential pulse stripping. The fact that two stripping peaks appeared on the voltammograms at the potentials of −0.65 V (Cd 2+) and −0.91 V (Pb 2+) demonstrates the possibility of simultaneous determination of Pb 2+ and Cd 2+. Under the optimized working conditions, calibration graphs were linear in the concentration ranges of 1.0×10 −7–1.5×10 −5 mol l −1 (Pb 2+) and 2.5×10 −7–2.5×10 −5 mol l −1 (Cd 2+), respectively. For 5 min preconcentration, detection limits of 1×10 −8 mol l −1 (Pb 2+) and 4×10 −8 mol l −1 (Cd 2+) were obtained at the signal noise ratio (SNR) of 3. To evaluate the reproducibility of the newly developed electrode, the measurements of 5×10 −7 mol l −1 Pb 2+ and Cd 2+ were parallel carried out for six times at different electrodes and the relative standard deviations were 2.9% (Pb 2+) and 3.2% (Cd 2+), respectively. Interferences by some metals were investigated. Only Ni 2+ and Hg 2+ apparently affected the peak currents of Pb 2+ and Cd 2+. The diacetyldioxime modified carbon paste electrode was applied to the determination of Pb 2+ and Cd 2+ in water samples. The results indicate that this electrode is sensitive and effective for the simultaneous determination of Pb 2+ and Cd 2+.

Simultaneous determination of urinary cadmium, cobalt, lead, and nickel concentrations in steel production workers by differential pulse stripping voltammetry.

Screening for metals in urine is important because toxic levels of these elements are linked to disease. In the current study, the authors used differential pulse stripping voltammetry on a hanging mercury drop electrode for the simultaneous determination of cadmium, cobalt, lead, and nickel in the urine of 63 production and 63 quality control workers in a steel production plant, along with 63 matched normal controls. Urinary sampling is a noninvasive procedure, and in this study participants had good compliance. Metal levels for both the production and quality control workers were significantly higher than for controls. The results reveal the need for immediate improvements in workplace ventilation and industrial hygiene practices for this cohort.

Electrochemical Reduction of 6-Benzylaminopurine at Mercury Electrodes and Its Analytical Application

The commercial exploitation of modern, in vitro plant micropropagation methods, featuring synthetic cytokinins as essential components of the cultivation media, is rapidly increasing. Thus, development of rapid, inexpensive and less labour-intensive methods for monitoring cytokinin levels could help to optimise media consumption and reduce costs. Therefore, we studied the electrochemical behaviour of the highly active and widely used cytokinin, 6-benzylaminopurine (BAP), in aqueous solutions by DC polarography, cyclic and differential pulse voltammetry and constant potential coulometry. The BAP molecule undergoes a six-electron irreversible reduction process that starts with four-electron reduction of the protonated pyrimidine skeleton. As a result of elimination of the amine from the side chain, the N1=C6 electrochemically active bond is re-established and the last two-electron step follows. The intermediates of constant potential electrolysis were identified using mass spectrometric analysis. The dissociation constant (pKa) of BAP was found, spectrophotometrically, to be 4.16. BAP concentrations were measured using two voltammetric techniques, fast-scan differential pulse (FSDPV) and adsorptive stripping voltammetry (AdSV). The relative standard deviations for these two methods were lower than 4.5% (c < 28.7 ng ml-1) and 1.2% (c < 20 ng ml-1), while the detection limits were 7.88 and 0.80 ng ml-1, respectively. Using these techniques, BAP was determined in two types of nutrition media used for the micropropagation of plants in vitro (Gerbera and banana media). In the case of media samples containing the interfering agent adenine (i.e. Gerbera plant medium), the analyte was preconcentrated by ion-exchange chromatography and immunoaffinity chromatography. This preconcentration process gives 92% recovery. In contrast, it was possible to determine BAP levels in simple banana cultivation medium directly, without any pre-purification process. Both methods, reported here (FSDPV and AdSV), were found to be useful for rapidly monitoring BAP consumption by plants during their growth under in vitro conditions.

Voltammetric studies of the interaction of lumazine with cyclodextrins and DNA

The interaction of lumazine, an antibacterial drug, with α-, β-cyclodextrins and DNA in aqueous solution was studied by differential pulse stripping voltammetry and cyclic voltammetry as well as UV–vis spectroscopy. The electrochemical and absorption spectral data indicated a 1:1 complex formation of lumazine with α-, β-cyclodextrins and DNA. The nature of the process, taking place at the hanging mercury drop electrode, was clarified. It was found that the complexation of lumazine molecules enhances the stacking interactions which might facilitate the formation of a perpendicularly stacked layer of lumazine-α-cyclodextrin complex on the electrode surface. Based on the variations in the current or absorbance, the formation constants and consequently, the Gibbs energy of these complexes were determined. The small size cavity of α-cyclodextrin was found to have a greater affinity for lumazine than the β-cyclodextrin. Moreover, the interactions of lumazine-α-cyclodextrin or lumazine-β-cyclodextrin inclusion complex with DNA have been investigated by means of voltammetry. The results suggest that lumazine displayed high affinity for DNA and the inclusion complex decomposed when it binds to DNA.

Determination of arsenic in gold samples using matrix exchange differential pulse stripping voltammetry

A method comprising matrix exchange differential pulse stripping voltammetry (DPSV) at a gold film electrode has been proposed for the determination of small quantities of arsenic in pure gold. A wall-jet cell (WJC) and an on-line deoxygenation system were used to facilitate matrix exchange. The gold(I) cyanide complex was formed to avoid gold deposition on the electrode together with the arsenic. The pH of the sample solutions were adjusted to 3, as alkaline solutions gold(I) cyanide produced interference and the uncomplexed cyanide led to passivation of the gold film electrode. Matrix exchange electrolytes consisting of 4 mol l −1 hydrochloric acid or a combination of 2 mol l −1 sulphuric acid and 0.2 mol l −1 hydrochloric acid could be utilised. Arsenic concentrations as low as 0.1 mg l −1, could readily be detected in a gold matrix with a 60 s deposition time. While, cobalt and silver did not interfere with the arsenic determination, copper interfered even when present at similar concentrations to that of arsenic.

Determination of nanogram quantities of osmium-labeled single stranded DNA by differential pulse stripping voltammetry

Earlier, we showed that using differential pulse cathodic stripping voltammetry with hanging mercury drop electrode (HMDE), single-stranded (ss) DNA modified with osmium tetroxide, pyridine reagent (Os,py) can be determined at concentrations down to about 10–5 ng/ml. Here, we show that by exchanging Os,py for osmium tetroxide, 2,2′-bipyridine (Os,bipy) and decreasing the pH of the background electrolyte from neutrality to about pH 4, ssDNA can be determined at concentrations lower by one order of magnitude. Determination of DNA at such low concentrations may find use in various areas of molecular biology and in biotechnologies, including the development of DNA sensors.

Voltammetric determination of chlorpromazine hydrochloride and promethazine hydrochloride with the use of multivariate calibration

The voltammetric behavior of antipsychotic drugs, such as, chlorpromazine hydrochloride and promethazine hydrochloride has been investigated at a glassy carbon electrode in Britton–Robinson buffer of pH 9. It was found by applying the differential pulse stripping voltammetry (DPSV) that both chlorpromazine hydrochloride and promethazine hydrochloride had well formed oxidation voltammetric waves, with the peak potential for chlorpromazine hydrochloride at 620 mV, and for the two peaks of promethazine hydrochloride at 444 and 668 mV. The calibrations were linear for chlorpromazine hydrochloride and promethazine hydrochloride in the concentration ranges of 0.05–1.2 and 0.1–1 mg l −1, respectively. However, the voltammetric peaks of these two drugs, seriously overlap and it is difficult to determine them individually from a response of a drug mixture. In this work, a method for the simultaneous determination of these two drugs is proposed, and is based on their oxidation at the glassy carbon electrode. The interpretation of the complex voltammograms is achieved with the aid of chemometric methods, such as, classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). The proposed method was applied to determine these two drugs in a set of synthetic mixtures and blood samples, and in general, satisfactory results were obtained.

An Oscillating and Renewing Silver Electrode for Cadmium and Lead Detection in Differential Pulse Stripping Voltammetry

Issues concerning the use of mercury electrode in environmental analyses has led to considerable research effort aimed at finding alternative tools with acceptable performance. A renewing silver working electrode is investigated. This system has shown a good response to lead and cadmium. Concentrations as low as 10 µg L−1 have been detected for both ions in 0.1 M HCl solutions. The system shows also little interference from copper. A detection limit of 0.5 µg L−1 is estimated for these systems. The electrode system may be used repeatedly without maintenance over a considerable period of time as a new silver film is formed prior to each scan. The silver electrode has been excited, oscillated with both triangular and sinusoidal audio frequency waves. The results indicate that the reproducibility of the response is increased when the electrode is oscillated sinusoidally. A study of the oscillating frequency has also been carried out. The result shows that the detection sensitivity improved considerably when low frequencies typically in the range 40 to 80 Hz are used. Good detection sensitivity, along with the simplicity of use and maintenance renders this system potentially attractive for use in online and field instruments.