A simple automated method for the determination of nitrate and nitrite in infant formula and milk powder using sequential injection analysis

Abstract

A fast and efficient automated method using a sequential injection analysis (SIA) system, based on the Griess, reaction was developed for the determination of nitrate and nitrite in infant formulas and milk powder. The system enables to mix a measured amount of sample (previously constituted in the liquid form and deproteinized) with the chromogenic reagent to produce a colored substance whose absorbance was recorded. For nitrate determination, an on-line prereduction step was added by passing the sample through a Cd minicolumn. The system was controlled from a PC by means of a user-friendly program. Figures of merit include linearity (r2 > 0.999 for both analytes), limits of detection (0.32mg kg-1 NO3-N, and 0.05mg kg-1 NO2-N), and precision (sr%) 0.8-3.0. Results were statistically in good agreement with those obtained with the reference ISO-IDF method. The sampling frequency was 30 hour-1 (nitrate) and 80 hour-1 (nitrite) when performed separately. Copyright © 2011 Mariela Pistn et al.