Witold Ciesielski

Square wave adsorptive stripping voltammetric determination of famotidine in urine

Electrochemical studies of famotidine were carried out using voltammetric techniques: cyclic voltammetry, linear sweep and square wave adsorptive stripping voltammetry. The dependence of the current on pH, buffer concentration, nature of the buffer, and scan rate was investigated. The best results for the determination of famotidine were obtained in MOPS buffer solution at pH 6.7. This electroanalytical procedure enabled to determine famotidine in the concentration range 1x10(-9)-4x10(-8)molL(-1) by linear sweep adsorptive stripping voltammetry (LS AdSV) and 5x10(-10)-6x10(-8)molL(-1) by square wave adsorptive stripping voltammetry (SW AdSV). Repeatability, precision and accuracy of the developed methods were checked. The detection and quantification limits were found to be 1.8x10(-10) and 6.2x10(-10)molL(-1) for LS AdSV and 4.9x10(-11) and 1.6x10(-10)molL(-1) for SW AdSV, respectively. The method was applied for the determination of famotidine in urine.

Application of improved iodine-azide procedure for the detection of thiouracils in blood serum and urine with planar chromatography.

The application of iodine-azide reaction for the determination of thiouracils in thin-layer chromatography and high-performance thin-layer chromatography is described. The developed plates were sprayed with a freshly prepared mixture of sodium azide, adjusted to a proper pH, and starch solution, and exposed to iodine vapour for 5 s. The detection limits were established at pmol level. The factors depending on the detection limits were described. A comparison of iodine-azide tests reaction with other procedures is presented. The developed method was applied to detection of thiouracils in blood serum and urine. The possibility of detection of a thiouracils mixture was demonstrated.

A new method for the iodometric determination of sulphoxides

A method is described for determination of sulphoxides through their reaction with iodide in a trifluoroacetic acid/acetone medium to produce iodine, which is then titrated with thiosulphate.

Spectrophotometric determination of methimazole, D-penicillamine, captopril, and disulfiram in pure form and drug formulations

A spectrophotometric method for the determination of methimazole (MT), D-penicillamine (PA), captopril (CA), and disulfiram (DM) was proposed. The method is based on the reaction of sulfur compound with N,N-dimethyl-p-phenylenediamine (DMPD) in acidic solution, in the presence of Fe3+ ions as oxidizing agent. The Beer’s law was obeyed in the range 16–110 mg of MT, 19–260 mg of PA, 29–160 mg of CA, and 36–110 mg of DM. The method was successfully applied to the quantification of these compounds in pharmaceuticals.

Methods of extraction and thin-layer chromatography determination of phospholipids in biological samples

Abstract Phospholipids (PLs) are a class of compounds essential for living organisms, including human beings. This paper presents a brief review concerning the extraction as well as thin-layer chromatographic separation and determination of phospholipids. After a short introduction regarding phospholipids and their specific characteristics, the extraction techniques will be discussed. Then, phospholipid separation and system detection for thin-layer chromatography (TLC) will be presented. The focus will be on phospholipids that are most abundant in biological systems; that is why chosen examples of PLs determination in biological samples will be revealed as well as general PL determination schemes. In the Summary section, there will also be a short discussion about advantages and disadvantages of PL determination with the use of TLC.

Voltammetric behaviour and quantitative determination of pesticide iminoctadine

Iminoctadine (IOD) was determined in spiked river water samples by square wave voltammetry (SWV) using a cyclic renewable silver amalgam film electrode (Hg(Ag)FE). It was found that the compound can act as an electrocatalyst. In Britton–Robinson buffer at pH 6.5 a signal connected with the catalytic hydrogen evolution reaction was detected at −1.8 V versus Ag/AgCl. Validation of the method was carried out. The LOD and LOQ have been estimated to be 2.6 × 10−9 mol L−1 and 8.5 × 10−9 mol L−1, respectively.

Organothiophosphorus compounds as inductors of the iodine-azide reaction. Analytical application.

Thiophosphoryl compounds were found to exhibit strong induction activity in the iodine-azide reaction. On this basis three procedures for their determination: titrimetric (0.15-1 mumol), coulometric (1-20 nmol) and spectrophotometric (0.5-5 nmol) have been developed. RSD in all applied methods (techniques) have been found at the 1-7% level. The induction coefficients were dependent on the type of compound applied and on the reaction condition and varied from 90 to 450.

Electrochemical study of the fungicide acibenzolar-s-methyl and its voltammetric determination in environmental samples

The electrochemical behavior of new generation fungicide acibenzolar-s-methyl (S-methyl 1,2,3-benzothiadiazole-7-carbothioate, ASM) on the hanging mercury drop electrode (HMDE) was investigated using square wave adsorptive stripping voltammetry. This method of determination is based on the irreversible reduction of ASM at the HMDE. The well-defined ASM peak was observed at −0.4 V (vs. Ag/AgCl) in BR buffer at pH 2.2. The reduction peak current was proportional to concentration of ASM from 1.0 × 10−8 to 6.0 × 10−8 mol L−1 with detection and quantification limit 3.0 × 10−9 and 1.0 × 10−8 mol L−1, respectively. The applicability of the developed method for analysis of spiked samples of tap water, river water, and soil is illustrated. The effect of adsorption on the mercury electrode was studied in detail using the AC impedance method. Possible interferences with other common pesticides and heavy metal ions were examined. Clarification of the electrode mechanism was made using cyclic voltammetry (CV) technique.

Voltammetric behavior and quantitative determination of ambazone concentrations in urine and in a pharmaceutical formulation

The use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the analytical determination of ambazone in urine samples and pharmaceutical formulations is described. A single reduction peak in Britton-Robinson buffer at pH 4.0 was detected at about −1.4 V versus Ag/AgCl. Mechanistic studies have shown that the compound can act as an electrocatalyst. The method was validated. The analytical curve was linear in the concentration range from 1.0×10−9 to 1.0×10−7 mol L−1. The detection and quantification limits were found to be 3.0×10−10 mol L−1 and 1.0×10−9 mol L−1, respectively. The proposed method was successfully applied to ambazone determination in real samples.

Thin Layer Chromatography with Post-Chromatographic Iodine-Azide Reaction for Thiuram Analysis in Food Samples

Abstract A simple, sensitive, precise, and rapid planar chromatographic method for thiuram analysis was elaborated. Reaction between iodine and azide ions induced by thiuram was applied as a detection system. The developed plates were sprayed with freshly prepared mixtures of sodium azide and starch solution adjusted to pH 6.0, and exposed to iodine vapor. The spots became visible as white spots on a violet-grey background. The iodine-azide detection system was proved to be the most favorable and enabled detection of quantities at the level 0.5 pmol per spot. The iodine-azide test was compared with other visualizing techniques commonly used in planar chromatography: iodine vapor, UV254, Cu(II). Certain factors that influence detection with iodine-azide reaction as a detection system were checked. The developed method was linear over the concentration range of 2–9 pmol per spot. The proposed technique was applied to detect thiuram in food samples.