Determination of pharmaceutical dosage forms via diffusion layer titration at an interdigitated microelectrode array

This paper presents a method for the analysis of drugs in dosage form. It is based on galvanostatic generation of oxidation agent from a suitable precursor on one segment of interdigitated microelectrode array (IDA) and its consecutive amperometric detection on second segment. High collection efficiency of this process in comparison to rotational ring disc electrode (RRDE) is a unique feature of IDA system. The transfer of oxidation agent can be influenced by addition of species, which reacts with oxidant. This influence can be used for its determination. Evaluation of generator–collector current dependence (diffusion layer titration curve) reveals the value of generator current IgenE of the end-point of titration. IgenE is proportional to the bulk phase concentration of determined species. The method was applied to the analysis of pharmaceuticals Antabus (Disulfiram Alpharma NOR, tetraethylthiuram disulfide (TETD)), a popular drug for alcoholism treatment, and Celaskon (vitamin C, Léčiva CZE, ascorbic acid (AA)). From model samples analysis rather low detection limits, 9×10−7 mol dm−3, respectively, 4×10−6 mol dm−3, were estimated which enables trace content analysis of the drugs. A small size of IDA sensor also makes it suitable for microanalytical improvement.