Monika Skowron

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.

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.

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.

Application of image analysis technique for the determination of organophosphorus pesticides by thin-layer chromatography

A simple and convenient thin-layer chromatography (TLC) method combined with image analysis technique was developed to determine malathion and fenthion in apple and orange juices. The detection of pesticides was based on iodine—azide reaction. Digital images of TLC plate chromatograms were analyzed using TLSee® software, and quantitative analysis was conducted. The linearity, sensitivity, accuracy, and precision of the system were investigated.

Application of thin-layer chromatography image analysis technique in quantitative determination of sphingomyelin

A sensitive and convenient method for sphingomyelin determination was developed based on thinlayer chromatography (TLC) and image-processing analysis. The mobile phase composition, detection and quantification conditions were systematically investigated through several trials. The molybdenum blue reaction allowed specific detection of the phospholipid with a high sensitivity and a wide linear range. Digital images of TLC plate chromatograms were captured with flatbed scanner and converted into peak chromatograms using TLSee® software and quantitative analysis was conducted. The linearity, sensitivity, accuracy and precision of the system were evaluated. The limits of detection and quantification were 0.5 and 1.7 μg/spot, respectively. Separation of the mixture consisting of sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine was also carried out.

Image analysis of phenylisothiocyanate derivatised and charge-couple device-detected glyphosate and glufosinate in food samples separated by thin-layer chromatography

ABSTRACT The paper presents the application of pre-chromatographic derivatisation reaction of aminophosphonic acids (glyphosate and glufosinate) with phenylisothiocyanate in thin-layer chromatography (TLC). Silica gel as stationary phase and a mixture of methanol–water–diethyl ether (2:1:1, v/v/v) and ethanol–water–diethyl ether (4:1:2, v/v/v) were used as the mobile phase, respectively. Detection was performed by spraying TLC plates with a freshly prepared mixture of sodium azide (1%), starch solution (1% for glyphosate and 2% for glufosinate), and potassium iodide (1.0 × 10–2 mol L−1) adjusted to pH 6.0 and exposed to iodine vapour for 15 s. Both glyphosate and glufosinate as phenylthiocarbamates (PTC-derivatives) were visible as white spots against a violet background which were converted into chromatograms using TLSee software. The calibration curves for glyphosate and glufosinate were within the ranges of 8.45–84.5 ng and 1.98–79.2 ng per spot, respectively. The limits of detection and quantification for glyphosate were at a level of 4 and 8.45 ng per spot, and for glufosinate were 0.99 and 1.78 ng per spot, respectively. The proposed method was successfully used in the determination of aminophosphonic acids in spiked plants samples.

Thin-layer chromatographic image analysis for the determination of sulfide ions using pyrylium cations

A highly specific and sensitive chromatographic method for the determination of sulfide ions was developed. The procedure is based on the sensitive and specific reaction of sulfide ions with 4-[p-(N,N-dimethylamino)phenyl]-2,6-diphenylpyrylium cations. The product of the reaction is a thiopyrylium derivative which can be quantitatively determined. Separations were performed on cellulose thin-layer chromatography (TLC) plates with a mixture of phosphoric buffer (pH 3.0), propan-2-ol, and acetonitrile (4:4:0.5, v/v) as the mobile phase. The thiopyrylium derivative was visible in the form of blue spots against a colorless background, which were converted into a chromatogram using TLSee software. Linearity was obtained in the range of 40–500 pmol per spot. The limits of detection and quantification were 10 pmol per spot and 33 pmol per spot, respectively. The proposed method was successfully used for the detection and determination of sulfide ions in water samples from the Busko Zdrój health resort.

Determination of some thiophosphorus insecticides based on coulometric titration with the anodically generated chlorine: a further insight in the reaction mechanism in aqueous medium

A new method of analytical determination of some thiolo (PS) and thiono (PS) group containing phosphorus insecticides using a coulometric titration with the anodically generated chlorine and biamperometric end-point detection was described. The method worked well for compounds containing one (methamidophos) or two PS bonds (iso-malathion) or one PS bond (fenitrothion) but failed for compounds containing both PS and PS bonds (malathion, dimethoate) or additional sterically hindered CSC bond (fenthion). Based on the found number z of electrons transferred per mol of oxidized compounds, mechanistic pathways for chlorination of PS and PS containing thiophosphorus insecticides with molecular chlorine in aqueous, acidic medium were proposed.

Application of image analysis technique for the determination of thiophanate methyl by thin-layer chromatography

ABSTRACT A simple and convenient thin-layer chromatography (TLC) method combined with image analysis technique was developed to determine thiophanate methyl. The detection of pesticide was based on iodine–azide reaction. Digital images of TLC plate chromatograms were analysed using TLSee software, and quantitative analysis was conducted. The linearity (0.3–3.0 µg per spot), sensitivity, accuracy and precision of the system were investigated.

Quantitative Method of Disulfiram Determination by Thin-Layer Chromatographic Image Analysis Technique

A simple and sensitive thin-layer chromatographic (TLC) method coupled with an image analysis technique was developed for the quantitative determination of disulfiram. Separation was performed on RP-18 plates with methanol—water 90:10 (v/v) as mobile phase. Disulfiram was detected using copper(II) ions (producing a yellow complex). Digital images of TLC plate chromatograms were converted into peak chromatograms using TLSee software, and quantitative analysis was conducted. Linearity was obtained in the range of 1.0–10 µg/spot. The limits of detection and quantification were 0.26 µg/spot and 0.86 µg/spot, respectively. Quantitative determination of disulfiram in Anticol was also performed, with a recovery of 100.3%. The method was applied for the determination of disulfiram in a urine-spiked sample.