Development of a New Methodology for Indirect Determination of Nitrite, Nitrate, and Total Nitrite in the Selected Two Groups of Foods by Spectrophotometry

A new indirect preconcentration procedure was developed for micellar sensitive detection of trace nitrite as analyte by spectrophotometry. The method is based on ion association of triiodide ion, I-3 (-) or I-2, produced by the reaction of nitrite at low concentrations with excess iodide in presence of ion-pairing agent, Coomassie brilliant blue R 250 (CBB), and electrophilic attack of nitrosyl cation produced by disproportionation of nitrite depending on concentration to ion-pairing agent at higher concentrations than 5 mu g L-1 in acidic medium, and then extraction of the ion-pairing complex formed from aqueous solution into the micelles of Triton X-114 at sodium acetate medium. The calibration graphs were rectilinear in the range of 0.5-5 and 5-200 mu g L-1 with increasing and decreasing slopes in micellar phase, respectively. The detection and quantification limits of the method were 0.15 and 0.50 mu g L-1, and the precision (as RSD) for five replicate measurements of different concentrations of nitrite was in the range of 2.3-4.8%. The average recoveries of spiked nitrite residues ranged from 97 to 104%. The method is free of matrix interferences and successfully applied to the indirect determination of nitrite, nitrate, and total nitrite in selected two groups of foods. Also, the accuracy was validated by analysis of a certified reference material as well as recoveries of spiked samples. The objective of the study is to provide an alternate economical method to determine the contents of nitrite, nitrate, and total nitrite after homogenization, extraction, reduction, and preconcentration from sample matrix.