Spectrophotometric determination of nitrate in vegetable products using 2-sec-butylphenol
A procedure is described for the determination of nitrate in vegetable products, based on the quantitative reaction of nitrate and 2-sec-butylphenol in sulphuric acid (5 + 7), and the subsequent extraction and measurement of the yellow complex formed in alkaline medium. The colour reaction is sensitive and stable and absorbances measured at 418 nm obey Beer's law for concentrations of nitrate-nitrogen between 0.13 and 2.50 µg ml–1. Various possible interferents in vegetable products do not interfere with the nitration of 2-sec-butylphenol. Recoveries of nitrate from vegetable products were satisfactory and the standard deviation for the whole procedure was 1.41% for the 42 determinations; the detection limit of the method is 1.3 p.p.m. for nitratenitrogen.