The determination of 2-hydroxynicotinic acid and its major metabolite in blood and urine by spectro-photofluorimetry and differential pulse polarography

A sensitive and specific spectrofluorimetric assay was developed for the determination of 2-hydroxynicotinic acid (1) and its major metabolite, the N-1-riboside (11) in blood and urine. Both compounds exhibit strong fluorescence in acidic media. Thin-layer chromatography is employed to separate the drug from its metabolite; the compounds are eluted from the silica gel into methanol—0.1 M hydrochloric acid (80+20). The sensitivity is 0.04–0.05 μg of I and 0.10–0.12 μg of II per ml of blood or urine. The two compounds can also be determined by differential pulse polarography, which is especially suitable for urine. The fluorimetric method was applied to the determination of blood levels and the urinary excretion of the drug in man after single oral 500-mg doses.