Highly sensitive voltammetric determination of captopril on renewable amalgam film electrode

New highly sensitive voltammetric method for captopril (CPT) determination was developed. The main novelty of the work was the application of a renewable amalgam film electrode (Hg(Ag)FE) for this purpose. During the research instrumental parameters of the developed method were optimized and were as follows: t_w = t_s = 5 ms, E_s = 5 mV, ΔE = 100 mV. Preconcentration potential and time were equal to 100 mV and 20 s, respectively. All measurements were conducted in electrolyte consisted of 0.1 M HClO₄. Limit of detection was calculated and was equal to 1.9 nM (0.39 ng mL^-1) for 20 s preconcentration time and Hg(Ag)FE surface area approximately 11.2 mm². Linearity was achieved in the concentration range 0.05-1 μM. Repeatability of the method expressed as variation coefficient was estimated at 3.5% (0.15 μM CPT, n = 10). Applicability of the method was confirmed by analysis of tablets containing CPT and urine. Recoveries were in the range from 95 to 109% suggesting that the method might be assumed as accurate. Obtained results were also in good agreement with the producer declaration.