Quantitative estimation of nicotinic acid in urine

Abstract

An account is given of a technique for the quantitative estimation in urine of nicotinic acid and nicotinic acid conjugates by the colorimetric method involving the use of CNBr and metol described in a previous paper [see B. A. 13 (5) entry 7289]. The urine must be subjected to alkaline (and not to acid) hydrolysis before the color reaction is performed, in order to liberate the nicotinic acid from the nicotinic acid conjugates. The method is very accurate, and added nicotinic acid is refound quantitatively. In 10 normal persons the color producing substances excreted in 24 hrs. were equivalent to 1.5-5 mg nicotinic acid. Nicotine will give a slight color reaction with CNBr and metol. After oral inj. of 90 mg nicotinic acid 14% is excreted, chiefly during the 1st hour and, partially, in a combined form which is hydrolysed under the same conditions as in synthetic nicotinuric acid (nicotinyl glycine).