Ultra-trace analysis of nitrite in food samples by flow injection with spectrophotometric detection

A flow injection system with spectrophotometric detection is proposed for t he determination of low levels of nitrite based on its catalytic effect on the oxidation of gallocyanine by bromate in acidic media. Various analytica l parameters such as acidity, reagent concentration, flow rate, sample size , time, temperature, and interfering species were studied. The calibration graph was linear for 0.020-0.500 mu g/mL of nitrite. The method is successf ully applied to food samples. Up to 30 +/- 5 samples can be analyzed per ho ur.