DETERMINATION OF NITRITE LEVELS IN REFRIGERATED AND FROZEN SPINACH BY ION CHROMATOGRAPHY

The determination of nitrites in samples of spinach after different times of refrigeration and freezing was studied. After cooking, the liquid and solid obtained were analysed. Ion chromatography with electrochemical detection, in which cell is composed of a single large porous graphite working electrode, was used as these solutions had, in many instances, concentrations of nitrites around 50 ng/ml; these levels are close to, or even below, the determination limits of other analytical methods usually employed. However, using this electrochemical detection, the determination of levels around 20 ng/ml was performed with good accuracy. The results obtained indicate that the freezing procedure does not modify the nitrite levels of the samples. In contrast, the refrigeration technique produces a considerable increase in their concentration 4-8 days later.