Polarographic studies of the oxidation of vitamin K5 in aqueous solution.

Electrochemical behavior of 4-amino-2-methyl-1-naphthol hydrochloride (VK₅) has been studied by de and ac polarography in order to determine the applicability of these methods to the determination of VK₅ in aqueous solution. VK₅ exhibits two well-defined anodic waves on dc polarograms, one of which is due to the oxidation of VK₅ to the corresponding quinoimine and the other, to the formation of mercurous chloride on a dropping mercury electrode. Complete preremoval of dissolved oxygen makes the former wave reproducible, and its limiting current is found to be proportional to the VK₅ concentration ranging from 1.0 × 10^?5 to 1.0 × 10^?3m. On ac polarograms, electrooxidation of VK₅ also gives rise to a distinct peak whose height is proportional to the VK₅ concentration in the range of 5.0 × 10^?7 to 1.0 × 10^?5m. These facts can be applied to the microdetermination of VK₅ present in concentrations as low as the 0.1-ppm range.