Abstract
A gas chromatographic method was developed for the determination of the nitrite ion (NO2-) in foods. The method is based on the Sandmeyer reaction.
The procedure can be outlined as follows. (a) Extraction of food by homogenizing it with water at 80°C. (b) Precipitation of proteins by addition of alkaline ZnSO4 solution and removal of the precipitate by filtration. (c) Diazotization of p-bromoaniline by NO2- in the aqueous extract followed by reaction with a solution of copper (I) chloride in hydrochloric acid to form p-bromochlorobenzene. (d) Quantitative determination of the reaction product by gas chromatography, employing an electron-capture detector.
The product yield was more than 90%. There was no apparent interference with this method by dimethylamine, sodium chloride, nitrate ion and so on. Various ham and sausage samples were analyzed by this method and the results agreed well with those obtained by the diazotization-coupling colorimetric method prescribed in the Standard Methods of Analysis for Hygienic Chemists authorized by the Pharmaceutical Society of Japan (1980). The limit of determination of NO2- was 0.02μg/g.
