Preconcentration and indirect quantification of trace nitrite, nitrate and total nitrite in selected beverage and milk samples using ion-pairing cloud-point extraction with acridine orange

Abstract

A new indirect preconcentration method was developed for micellar-sensitive detection of trace nitrite as analyte by spectrophotometry. It is based on selective ion-pairing complex formation of triiodide ion, I3 ? with acridine orange, AOH+ (3,6-bis(dimethylamino) acridine) at pH 4.0 and its cloud-point extraction (CPE) with Triton X-114 as extracting agent. The extracted surfactant-rich phase is diluted with acetonitrile, and its absorbance is measured against analyte blank at 450 nm. The variables affecting CPE efficiency were investigated, and a set of optimized conditions was obtained. The calibration graph was rectilinear in the range of 1.5–150 ?g L?1. The detection limit was 0.42 ?g L?1 with a precision lower than 4.1%. The validation was statistically confirmed by analysis of a certified reference material. The method was successfully applied to determination of nitrite, nitrate and total nitrite in selected beverage and milk samples before and after reduction with two different reducing agents. © 2018