Katarzyna Tyszczuk

Determination of uranium by adsorptive stripping voltammetry at a lead film electrode.

An adsorptive stripping voltammetric procedure for the determination of U(VI) at an in situ plated lead film electrode is described. The U(VI) complex with cupferron was accumulated from an acetate buffer solution of pH 4.2 at the potential -0.65V. The measurements were carried out from undeaerated solutions. The calibration graph for an accumulation time of 180s was linear from 5x10(-10) to 2x10(-8)molL(-1). The detection limit was 2x10(-10)molL(-1), the relative standard deviation for 2x10(-8)molL(-1) U(VI) was 4.3%. The proposed procedure was validated in the course of U(VI) determination in water certified reference materials.

Sensitive voltammetric determination of rutin at an in situ plated lead film electrode

A highly sensitive sensor for the determination of rutin by adsorptive stripping voltammetry was described. It consists of a lead film modified glassy carbon electrode (LF/GCE). In the proposed procedure rutin was accumulated by adsorption on the lead film electrode and then during the stripping step a lead film and the accumulated rutin were oxidised. The electrochemical behaviour of rutin at the lead film electrode was investigated by square-wave voltammetry. In the optimal conditions the anodic peak currents (measured by square-wave voltammetry) increased linearly with the concentration of rutin in the range of 5 x 10(-10) to 1 x 10(-8)mol L(-1). The detection limit for rutin following 30s of accumulation time was equal to 2.5 x 10(-10) mol L(-1). The method was successfully applied to the determination of rutin content in the tablets without previous separation.

Voltammetric method for the determination of sildenafil citrate (Viagra) in pure form and in pharmaceutical formulations

A highly sensitive and simple voltammetric method for the determination of sildenafil citrate (SC) was developed. The method is based on the accumulation by adsorption of SC on a lead film modified glassy carbon electrode (LF/GCE) and then the reduction of SC throughout the stripping step. During the determinations of SC at the lead film electrode three adsorptive stripping voltammetric peaks at -1.2, -1.33 and -1.45V were observed. The respective response selected for identification and quantification has been evaluated with respect to the composition and pH of the supporting electrolyte, the potential and the time of the lead film formation, the potential and the time of the SC accumulation and other variables. Experimental results indicate an excellent linear correlation between the peak current and concentration in the range of 2x10(-9)-1.5x10(-7)mol/L (for peaks 1 and 2) and 1x10(-8)-1.5x10(-7)mol/L (for the peak 3). The detection limits (LOD) for SC following 30s of accumulation time were equal to 9x10(-10)mol/L (for peaks 1 and 2) and 4.5x10(-9)mol/L (for the peak 3). The method was successfully applied to the determination of SC in the tablets (Viagra 25 and Viagra 50) and average the contents were in close agreement with those quoted by the manufacturer and with those obtained by the reported spectrophotometric method and voltammetric method using a hanging mercury drop electrode.

Adsorptive stripping voltammetric determination of trace concentrations of molybdenum at an in situ plated lead film electrode.

An in situ plated lead film electrode has been applied for adsorptive stripping voltammetric determination of trace concentrations of molybdenum in the presence of Alizarin S. The procedure is based on the preconcentration of the molybdenum-Alizarin S complex at an in situ plated lead film electrode held at -0.6 V (versus Ag/AgCl), followed by a negatively sweeping square wave voltammetric scan. The peak current is proportional to the concentration of molybdenum over the range 2x10(-9) to 5x10(-8) mol L(-1), with a 3sigma detection limit of 9x10(-10) mol L(-1) with an accumulation time of 60 s. The measurements were carried out from underaerated solutions. The proposed procedure was validated in the course of Mo(VI) determination in water certified reference materials.

Application of gallium film electrode for elimination of copper interference in anodic stripping voltammetry of zinc

For elimination of copper interference in anodic stripping determinations of zinc at mercury and bismuth film electrodes gallium ions are usually added to the supporting electrolyte. In the presented studies novel ex situ formed gallium film electrode was applied for this purpose. The proposed electrode is less toxic than mercury one while the detection limit for zinc was lower than for bismuth film electrode following the same deposition time. The calibration graph for deposition time of 60s was linear from 5x10(-8) to 2x10(-6)mol L(-1). The determinations of zinc were carried out from undeaerated solutions. The proposed procedure was applied to zinc determination in certified reference material and tap water sample.

Analysis of organic compounds using an in situ plated lead film electrode.

For many years mercury electrodes were commonly used in stripping voltammetry for determination of organic compounds, owing to their high sensitivity, reproducibility and renewability. However, because of the toxicity of mercury, alternative (less toxic) electrode materials are searched. The review describes recent results regarding adsorptive stripping voltammetric determination of trace concentration of biologically active organic substances using an in situ plated lead film electrode (LFE). Such an electrode exhibits the distinct advantage of simple preparation, good reproducibility and electrochemical surface renewal. The article reviews the development, behaviour and application of a lead film electrode for stripping voltammetry of biologically active organic compounds.

Determination of cadmium by stripping voltammetry at a lead film electrode

A procedure for trace cadmium determination by stripping voltammetry at a lead film electrode is presented. Measurements consist of three steps: simultaneous in situ formation of lead film and a deposition of metallic cadmium at a lead film electrode, oxidation of cadmium for 1 s and in the last step registering the current corresponding to Cd(II) reduction. The calibration graph was linear from 2 × 10−9 to 1 × 10−6 mol L−1 for a deposition time of 300 s. A detection limit for cadmium following deposition time of 300 s was 6 × 10−10 mol L−1. The relative standard deviation at cadmium concentration 2 × 10−8 mol L−1 was 3.6%. The measurements were carried out from undeaerated solutions. The procedure proposed was validated by analysis of rain water certified reference material.