Rapid and selective electrochemical determination of nitrite in cured meat in the presence of ascorbic acid

A simple, fast and selective amperometric procedure for nitrite determination in cured meat based on the use of a carbon paste electrode is presented. Direct interference of ascorbic acid, which interferes with electrochemical detection, was eliminated by applying a cellulose acetate membrane of 100 Da molecular weight cut-off on the electrode. Indirect interference of ascorbic acid due to its auto-oxidation reaction and its reaction with nitrite is discussed. In order to stabilise the ascorbic acid, metaphosphoric acid and EDTA were added. In contrast to the standard spectrophotometric method, which requires careful control of pH and the use of carcinogenic reagents, amperometric determination of nitrite is simple, rapid, and works without reagents. Also, sample preparation is simpler because it requires neither heating to 80 degreesC nor the centrifugation steps of the official spectrophotometric method. The detection limit achieved was 14 ppb (0.2 muM) nitrite in the solution, which corresponds to a detection of 2.8 ppm in meat samples. The method was compared with the standard spectrophotometric procedure and applied to the detection of nitrites in cured meat samples with satisfactory results.