Iwona Rutyna

An adsorptive stripping voltammetry procedure for ultra-trace determination of U(VI) using double accumulation step on two lead-film working electrodes

We report a very sensitive stripping voltammetric procedure for determination of ultra-trace quantity of U(VI) in water samples. A very low detection limit was achieved owing to the application of a new construction of the voltammetric electrode cell with two built-in working electrodes that differed significantly in their surface area. The procedure was based on the double adsorptive accumulation of the U(VI)-cupferron complex onto two lead film working electrodes. Under optimal conditions the detection limit for accumulation time of 120 s for the big electrode and 120 s for the small electrode was about 3.1 × 10(-11) mol L(-1), whereas for accumulation time of 480 s for the big electrode and 240 s for the small electrode it was about 1.1 × 10(-11) mol L(-1). The proposed method was successfully validated using certified reference material seawater NASS-5.

Determination of As(III) by anodic stripping voltammetry following double deposition and stripping steps at two gold working electrodes.

The double deposition and stripping steps were proposed to minimize interference and increase the sensitivity in anodic stripping voltammetry of As(III). Two working electrodes of drastically different surface areas were used for the measurements. Arsenic was first deposited at the gold film electrode of a large surface area. When the deposition step at this electrode finished, the electrode was moved at a short distance to the second electrode consisting of four gold microelectrodes. The arsenic stripped from the first electrode was partially deposited at the microelectrodes and the analytical signal was obtained by its oxidation. Due to double deposition of arsenic the interference of Cu(II) was minimized and the detection limit of As(III) was lowered by one order of magnitude. The calibration graph was linear from 5×10(-10) to 1×10(-8) mol L(-1) following deposition time of 300 s at the first and the second electrode.

Determination of cobalt by adsorptive stripping voltammetry with double accumulation and stripping steps

A double accumulation and stripping steps were proposed to increase the sensitivity of Co(II) determination by catalytic adsorptive stripping voltammetry (AdSV). Electrodes with large and small surface area were used for the first and second accumulation step, respectively. As the accumulation of Co(II) complex at the first electrode was finished, the electrode was placed at a short distance opposite the second one. Then the Co(II) complex desorbed from the first electrode was accumulated at the second electrode. Taking into account the small volume of space between the electrodes, the concentration of the Co(II) complex in solution between the electrodes was drastically higher than that in the bulk solution. The accumulation step at the second electrode was performed from the solution with higher concentration of Co(II) and therefore the detection limit was lowered. The calibration graph of Co(II) determination for accumulation time of 120 s at both electrodes was linear from 1.18 to 58.9 ng L−1. The detection limit for Co(II) was equal to 0.47 ng L−1 and it is so far the lowest detection limit obtained for Co(II) using mercury-free electrodes. The proposed method was applied to Co(II) determination in water certified reference material.

Determination of Folic Acid at a Bismuth Film Electrode by Adsorptive Stripping Voltammetry

This article reports a new simple and sensitive method for the determination of folic acid by adsorptive stripping voltammetry. The method is based on the accumulation of folic acid at a bismuth film plated in situ on a glassy carbon substrate. In order to stabilize bismuth ions, sodium potassium tartrate was added to the supporting electrolyte. The bismuth film formation and folic acid accumulation conditions were optimized and measurements were carried without solution deaeration. The calibration graph was linear from 5 × 10−10 to 2 × 10−8 mole per liter with an accumulation time of 180 seconds with a limit of detection of 2 × 10−10 mole per liter. The relative standard deviation for 5 × 10−9 mole per liter of folic acid was 3.1 percent (n = 5). The method was successfully applied for determination of folic acid in pharmaceutical preparations.

Adsorptive stripping voltammetry of nickel at a bare glassy carbon electrode

A bare glassy carbon electrode is applied to nickel determination by adsorptive stripping voltammetry in the presence of dimethylglyoxime as a complexing agent. A procedure of nickel determination and electrode regeneration was proposed. The calibration graph for Ni(II) for an accumulation time of 120 s was linear from 2 × 10−9 to 1 × 10−7 mol L−1. The detection limit was 8.2 × 10−10 mol L−1. The relative standard deviation for a solution containing 2 × 10−8 mol L−1 of Ni(II) was 4.1%. The proposed procedure was applied for Ni(II) determination in certified water reference materials.