Square-Wave Cathodic Stripping Voltammetry of Marcellomycine. A Sensitive Analytical Method

Abstract

Square-wave adsorptive stripping voltammetry has been applied to the determination of a new cytostatic anthracyclinic compound, marcellomycine. 100-fold and 1000-fold increases of sensitivity have been found with regard to the differential pulse stripping voltammetry and differential pulse polarography respectively. The detection limit is fixed at 5 × 10^?9 M.     

Simultaneous Trace Determination of Nickel and Cobalt in Natural Waters by Differential Pulse Polarography

Abstract

A differential pulse polarographic method has been developed for the simultaneous low level determination of nickel and cobalt in the presence of furildioxime in natural waters. The nature of the electrode processes was studied with cyclic voltammetry. Limits of determination of 0.4 μg/L and 0.15 μg/L were achieved for nickel and cobalt respectively     

A Determination of 6-Mercaptopurine and 6-Thio-Guanine By Anodic Differential Pulse Voltammetry

Abstract

The anodic oxidation of 6-mercaptopurine and 6-thioguanine has been studied on a rotating and stationary disk electrode of glassy carbon, using d.c. and differential pulse potential program. Conditions have been found for determination of these substances by anodic differential pulse voltammetry on a rotating disk electrode, with a detection limit of about 2 × 10^?5 mol 1^?1.     

Application of an optimization procedure in adsorptive stripping voltammetry for the determination of trace contaminant metals in aqueous medium

A procedure for the determination of the contaminant metal In(III) by differential pulse adsorptive stripping voltammetry (DPAdSV) using ammonium pyrrolidine dithiocarbamate (APDC) as a complexing agent, has been optimized. The selection of the experimental conditions was made using experimental design methodology by means of a robust regression method which allows the elimination of anomalous points. The detection limit obtained was 1.3×10⁻⁹ mol dm⁻³. Possible interferences from concomitant metal ions were evaluated. Among all the metals analyzed, only Cd(II) was found to create an interference. This fact made impossible to carry out the determination of In(III) in the presence of Cd(II) using a univariate calibration. This problem was solved using multivariate regression techniques such as partial least squares (PLS). The procedure was successfully applied to the determination of indium in different aqueous samples.     

Quantitative Analysis of Irbesartan in Pharmaceuticals and Human Biological Fluids by Voltammetry

Abstract

A differential pulse (DP) and square wave (SW) voltammetric techniques were developed for the determination of irbesartan. The electrochemical behavior of irbesartan was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) at the hanging mercury drop electrode (HMDE). Different parameters were tested to optimize the conditions of the determination. It was found that in the range of 8 × 10^?6–1 × 10^?4 M, the currents measured by both of methods presented a good linear property as a function of the concentration of irbesartan. In addition, validation parameters, such as reproducibility, sensitivity, and recovery were evaluated as well. The slope of the log Ip- log ν linear plot was 0.58 indicating the diffusion control for 0.5 M sulphuric acid without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances.

The methods were successfully applied to the analysis of irbesartan in the pharmaceutical tablet formulations and in human serum samples.     

Electrochemical Behaviour and Square Wave Voltammetry of the Rice Herbicides Molinate,Bensulfuron-Methyl,Mefenacet and Thiobencarb

Abstract

Cyclic, differential pulse and square wave voltammetry were applied to develop an electroanalytical procedure for the determination of a group of herbicides used to treat rice crops: molinate, bensul-ruron-methyl, mefenacet and thiobencarb. The oxidation mechanism causes adsorption problems and consequent poisoning of the electrode surface by the products of the electrochemical reaction. Parameters such as pH, frequency and electrochemical electrode surface treatment were optimized. The analytical methodology developed using square wave voltammetry was applied to the determination of molinate and bensulfuron-methyl in simple or mixed commercial products.     

Determination of Anticholinesterase Activity for Pesticides Monitoring Using a Thiocholine Sensor

Abstract

An acetylthiocholine sensor based on a disposable screen-printed carbon electrode has been assembled for measuring organophosphorus and carbamate pesticides in river water samples through the degree of inhibition of the enzyme acetylcholinesterase (AChE). The carbon working electrode surface was modified by deposition of a mediator, tetracyanoquinodimethane (TCNQ), and Nafion. Acetylcholinesterase catalyses the cleavage of acetylthiocholine to thiocholine, which is measured by differential pulse voltammetry and directly related to the enzyme activity. The scan speed, the pulse amplitude of the differential pulse voltammetry and several parameters in the procedure were optimised. An inhibition calibration curve was obtained using carbofuran. The method was also applied to water samples, showing its suitability as a rapid screening assay (15 min per test) for anticholinesterase activity detection.     

Effect of ethylenediamine on the anodic stripping voltammetric determination of heavy metals in the presence of humic acid

Ligand competition coupled with differential pulse anodic stripping voltammetry has been investigated for the determination of copper, lead and cadmium. Ethylenediamine displaces humic acid in its metal complexes forming kinetically labile compounds. It also eliminates interferences associated with the oxidation of copper. This enhances the sensitivity of the determination of the metals over a wide range of humic acid concentration (up to 30 mg/l). The procedure has been applied to the determination of heavy metals in a real water sample.     

Analyse de la fraction labile du zinc,cadmium, plomb et du cuivre dissous en milieu marin côtier par la redissolution anodique à impulsions différentielles

Analysis of the labile fraction of zinc, cadmium, lead and copper dissolved in the coastal marine environment using differential pulse anodic stripping voltammetry. The determination of the optimal experimental conditions for the dosage of labile concentrations of heavy metals such as cadmium, copper lead and zinc, in a coastal marine environment has been performed. The method used was differential pulse anodic stripping voltammetry (DPASV) with hanging mercury drop. To cite this article: M. El Makhfouk et al., C. R. Chimie 6 (2003).     

Electrochemical Oxidation and Determination of Theophylline at a Carbon Paste Electrode Using Cetyltrimethyl Ammonium Bromide as Enhancing Agent

Abstract

The oxidation of theophylline was studied at a carbon paste electrode in the presence of cetyltrimethyl ammonium bromide by cyclic and differential pulse voltammetry. The results indicated that the electrochemical responses of theophylline are apparently improved by cetyltrimethyl ammonium bromide, due to the enhanced accumulation of theophylline at carbon paste electrode surface. Under optimal conditions the peak current was proportional to theophylline concentration in the range of 8.0 × 10^?7 to 2.0 × 10^?4 M with a detection limit of 1.85 × 10^?7 M by differential pulse voltammetry. The proposed method was applied to the determination of theophylline in tablet and urine samples.     

Electrochemical Behaviour of Loprazolam and its Determination in Pharmaceutical Formulations

Abstract

The electrochemical behaviour of Loprrzoiam has been determined in aqueous solution at 37 > Cusing DC polarography, differential pulse polarography and voltammetry and linear sweep cyclic voltammetry. Loprazolam can be quantitavely determined up to 3.9 10^?6 M at pH 6.5 using DP polarography, the detection limit being established at 1.6 10^?7 M. The method developed was applied to the determination of the compound in its formulations, Somnovit 1 mg, obtaining errors lower than 4%.     

Microdetermination of Mercury in Industrial Waste Waters by Stripping Voltammetry

Abstract

Low levels of mercury have been determined in industrial waste waters by differential pulse anodic stripping voltammetry with a precision of ±3.6 standard deviation. The limit of determination was observed to be 1.0 μg/L.     

Decomposition of vegetables for determination of Zn,Cd, Pb and Cu by stripping voltammetry

A simple and accurate digestion method using nitric acid, perchloric acid and hydrogen peroxide has been developed for use in trace analysis for heavy metals in vegetables by differential pulse anodic stripping voltammetry. The recovery of the metals from the samples is lower if the hydrogen peroxide is omitted from the digestion mixture. Standard reference materials have been analysed satisfactorily by this method.     

Simultaneous Determination of Chromium(VI) and Aluminum(III) by Adsorptive Stripping Voltammetry with Pyrocatechol Violet

A new methodology is presented for the simultaneous determination of chromium(VI) and aluminum(III) by differential‐pulse adsorptive stripping voltammetry (DPAdSV) with Pyrocatechol Violet (PCV) as a complexing agent. In this procedure, a partial least‐squares regression (PLS) is used for the resolution of the strongly overlapping voltammetric signals from mixtures of Cr^VI and Al^III in the presence of PCV. The procedure was successfully applied to the determination of these metals in river water.     

Nafion‐Coated Bismuth Film Electrodes for the Determination of Trace Lead and Cadmium in Herbal Medicines by Anodic Stripping Voltammetry

A novel analytical procedure for the determination of Pb(II) and Cd(II) in herbal medicines by differential pulse anodic stripping voltammetry (DPASV) on Nafion‐coated bismuth film electrode (NCBFE) was proposed and experimentally validated. Various experimental parameters, which influenced the response of the NCBFE to these metals in real samples, were optimized. The results showed that there were well‐defined peaks of Pb and Cd in herb samples at deposition potential of ?1.2 V and deposition time of 300 s. The analytical performance of the NCBFE was evaluated in the presence of dissolved oxygen, with the determination limits of 0.35 µg·L^?1 for Pb and 0.72 µg·L^?1 for Cd and recoveries of 87.8% –105.4% for Pb and 89.5% –108.5% for Cd obtained from different samples. The Pb and Cd concentrations in the studied samples have been also determined by graphite furnace atomic absorption spectrometry (GFAAS), suggesting that there was a satisfactory agreement between the two techniques, with relative errors lower than 6.5% in all cases. The great advantages of the proposed method over the spectroscopic method were characterized by its simplicity, selectivity and short analysis time, simultaneous analysis of different metals and cost‐efficiency.     

Present potential of electrochemical methods for metal determinations in reference materials

Summary Based on high-pressure ashing, the potential to determine some trace metals (Zn, Cd, Pb, Cu, Ni, Co, Al, Tl, Cr, Fe) by anodic or cathodic stripping voltammetry in the square wave (SWV) and differential pulse modes (DPASV) is described. In comparison to the differential pulse mode, the square wave mode shows advantages for cathodic stripping and for zinc determination.New developments by use of potentiometric stripping analysis (PSA) permit the determination of Pb and Cd in whole blood without sample pretreatment and Pb, Cd, and Cu in milk and milk powder with simple pretreatment.Mercury film microelectrodes prepared by electrodeposition of Hg onto a carbon fiber were used for the rapid multicomponent trace determination of heavy metals in very small (5 l) samples by voltammetry and potentiometry.

---

Gegenwärtiges Potential elektrochemischer Methoden für Metallbestimmungen in Referenzmaterialien

     

Determination of zinc, cadmium, lead and copper in soils and sewage sludges by microprocessor-controlled voltammetry in comparison with atomic absorption spectrometry

Summary Information on the heavy metal contents in soils and sewage sludges is of strong ecological interest. For control of the maximum allowed concentrations photometric and atomic absorption spectrometric methods have been developed for the determination of the single elements; sample digestion is carried out using hydrochloric acid and nitric acid.Differential pulse polarography and differential pulse anodic stripping voltammetry allow the simultaneous determination of different heavy metals in one digestion solution according to their electrochemical behaviour. This possibility is given, for instance, for zinc, cadmium, lead and copper. The adequate procedure was tested with a microprocessor-controlled polarograph. Flame atomic absorption spectrometry was used as reference method.

---

Bestimmung von Zink, Cadmium, Blei und Kupfer in Böden und Klärschlämmen durch mikroprozessorgesteuerte Voltammetrie im Vergleich mit der Atomabsorptionsspektrometrie

     

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

Abstract

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.     

Determination of Ni and Co using 2-quinolinethiol by adsorptive voltammetry

Summary A new method for the simultaneous determination of cobalt and nickel has been developed by differential pulse adsorptive voltammetry using 2-quinolinethiol as chelate. A separation of the two peaks by 0.3 V was achieved, allowing the determination of the two metals in a wide range of concentrations. The influence of pH, nature of the supporting electrolytes, preconcentration time and applied potential was investigated. Pb, Cd, Fe, Zn and Cr do not interfere. The determination limits were 10^–8 mol/l for Co and 10^–9 mol/l for Ni. The method was applied to mussel tissues and wines.     

Electrochemical Study of Interaction Between Clozapine and DNA and Its Analytical Application

Abstract

The interaction between clozapine (CLZ) as an orally administrated antipsychotic drug with double stranded calf thymus DNA (dsDNA) was investigated at electrode surface using differential pulse voltammetry (DPV). Activated carbon paste electrode (CPE) was modified with dsDNA and used for monitoring the changes of the characteristics peak of CLZ in 0.05 M acetate buffer (pH 4.3). The adsorptive stripping voltammetry on dsDNA‐modified carbon paste electrode (dsDNA‐CPE) was used for determination of very low concentration of CLZ. Under optimal conditions, the oxidation peak current is proportional to CLZ concentration in the range of 7×10^?9?1.2×10^?6 mol l^?1 with a detection limit of 1.5×10^?9 mol l^?1 for 180 s accumulation time by DPV. The proposed dsDNA‐CPE was successfully used for determination of CLZ in human serum samples with recovery of 97.0±2.5%.