Development of a sequential injection analysis system for the potentiometric determination of nitrite in meat products by using a Gran's plot method

This article describes a potentiometric multi-task flow system, based on the sequential injection analysis (SIA) concept, developed to quantify the nitrite contained in cured meat products. The manifold includes a mixing chamber to provide the automatic on-line generation of the solutions required for the multiple standard additions method, adopted as potentiometric analytical technique of measurement. The assessment of nitrite concentration was accomplished by using the Gran's plot approach. A 0.16 mol L-1 silver sulphate solution, prepared in ammonia hydroxide, was used to remove the salt present in the samples since chloride ion is one of the most important interfering agents of the nitrite selective electrode. The procedure, when applied to different types of meat samples, showed relative standard deviations better than 3% with a sampling rate of 20 samples h(-1). The results obtained statistically agreed with those obtained by application of a modification of the well-known Griess spectrophotometric method adopted as a reference technique.