Abstract
A simple and practical method for the simultaneous determinations of nitrite and nitrate in various foods is described. It is based on the formation of tetrazolophthalazine, by the reaction of nitrite and hydralazine in an acidic medium (pH 1.0-3.0) at 70°C for 10min, and the formation of 4-nitro-2-sec-butylphenol, by the reaction of nitrate and 2-sec-butylphenol in aqueous (5+7) sulfuric acid at room temperature for 15min and subsequent pentafluorobenzoylation to form the pentafluorobenzyl ester of 4-nitro-2-sec-butylphenol in the alkaline range. The two products were simultaneously analyzed by means of gas liquid chromatography with a flame-ionization detector and a column of 5% OV-17 on Chromosorb W, HP; the detection limits are 0.05μg/ml for nitrite and 0.10μg/ml for nitrate.
For the determinations of nitrite and nitrate in foods, clean-up of crude extracts by florisil column chromatography and by addition of silver sulfate allows the satisfactory elimination of interfering compounds. The recoveries from several foods were 95.1-98.1 for nitrite and 95.7-98.3 for nitrate, and the standard deviations for the whole procedure (28 determinations) were 1.1% for nitrite and 1.0% for nitrate.
