Gas-liquid chromatographic determination of trace amounts of nitrite in egg, egg white, and egg yolk

A simple, sensitive, and practical method is described for determination of nitrite in egg, egg white, and egg yolk. Egg is deproteinized by adding a mixture of ammonium thiocyanate, mercuric chloride, and zinc acetate, and centrifuged. Nitrite in the supernate is converted to tetrazolophthalazine by reaction with hydralazine in acidic solution and then determined by gas-liquid chromatography with an electron-capture detector (GLC-ECD) and a column of OV-225 on Chromosorb W(HP). Nitrite concentrations from 5 to 50 ng/mL are calculated from peak height; the detection limit is 3 ng/mL extract. Recoveries from eggs, egg whites, and egg yolks ranged from 91.7 to 98.0%. The mean nitrite concentration in 50 egg samples was 0.04 ppm (0.01-0.11 ppm) with a detection limit of 4 ng nitrite/g.