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Determination of Nicotinic Acid and Metabolites in Urine, Cosmetics, and Pharmaceuticals by High-Performance Liquid Chromatography with Novel Electrochemical Detection

ABSTRACT Silver and gold electrodes were used with high-performance liquid chromatography and an electrochemical detector to determine nicotinic acid and its metabolites (1-methylnicotinamide chloride, nicotinic acid hydroxamate, nicotinamide, nicotinic acid, and methyl nicotinate). Nicotinic acid derivatives were more efficiently oxidized on a gold electrode than on a silver electrode. In direct current mode, with the current at a constant potential and with suitable experimental parameters, linear dynamic range for these derivatives was from 0.4 to 8.0 mg L−1. The limits of quantification were less than 1.0 ng. The developed method was used to determine nicotinic acid and its derivatives in human urine, cosmetics, and pharmaceuticals. The results for high-performance liquid chromatography with electrochemical and ultraviolet detection were comparable.