Bismuth-coated screen-printed carbon electrodes for quantitative voltammetric determination of formaldehyde in urotropin

For the first time, a bismuth-modified electrode is used for the quantitative voltammetric determination of formaldehyde (FA) in urotropin. The well-established method of forming formaldehyde hydrazone (FAH) in the presence of hydrazine sulphate (HRZ) was employed to transform the hydrated form of FA into its electrochemically active derivative. The reduction current of FAH was recorded in a phosphate buffer solution (PBS, pH 5.2±0.1) in the presence of 0.09 M HRZ on a screen-printed carbon electrode that had been preliminarily modified with a bismuth film. A 20-second electrolysis at an applied potential of –0.28 V in a solution comprising 1 M HCl, 0.5 M NaBr, and 4 g/L Bi(III) resulted in the formation of a well-developed metal layer with an active surface. The determination of FA in technical urotropin yielded satisfactory results, indicating the potential for further applications of Bi/SPCE in pharmaceutical analysis.