Determination of Nitrite and Nitrate by High Performance Liquid Chromatograpy

Abstract

A simple and practical method for the determination of nitrite and nitrate in various foods, river water and human saliva is described. It is based on the formation of 4-nitroso-2, 6-xylenol. by the reaction of nitrite and 2, 6-xylenol in a solution of sulfuric acid-water-acetic acid (1:8:1) at 40°C for 30min, and the formation of 4-nitro-2, 6-xylenol by the reaction of nitrate and 2, 6-xylenol in a solution of sulfuric acid-phosphoric acid-water-acetic acid (6:2:1:1) at 40°C for 5 min. The two products are extracted with chloroform and simultaneously analyzed by means of high performane liquid chromatography with an ultraviolet detector (310nm) and a column of Zorbax SIL with chloroform-methanol-acetic acid (98:1:1) as the mobile phase. The detection limits are 0.05μg/ml for nitrite nitrogen and 0.5μg/ml for nitrate nitrogen. For the determination of nitrite and nitrate in foods, river water and human saliva, addition of silver sulfate and sulfamic acid allows the satisfactory elimination of interfering compounds. The recoveries from several samples were 98.46-100.27% for nitrite and 98.47-101.78% for nitrate, and the relative standard deviations for the whole procedure were 1.47-6.44% for nitrite and 2.07-5.35% for nitrate. © 1983, Japanese Society for Food Hygiene and Safety. All rights reserved.