Ion selective method for the determination of nitrite in smoked fish.

In a direct ion selective electrode method for determining nitrite in smoked fish, the nitrite extracted from the sample is converted to nitrous acid with a measured addition of an acid buffer. The released nitrous acid is measured by a nitrogen oxide electrode. A known addition procedure is used to accurately measure the amount of nitrite in solution and the nitrite concentration is determined directly from Gran's plot paper. Recoveries of nitrite from spiked smoked chub samples ranged from 94.0 to 100.0% with an average of 96.7 and a relative standard deviation of +/-1.9% at the 100 ppm level. Results from the ion selective method were comparable with those from the official first action AOAC method 24.037-24.038.