Application of oxygen scavenger in gel electromembrane extraction for determination of nitrite and nitrate

Abstract

Gel electromembrane microextraction (G-EME) have been proven as a promising extraction method due to its effectiveness for extraction and preconcentration of charged analytes and its compliance with the principle of green chemistry. G-EME consists of two phases (donor and acceptor phases), separated by a gel membrane made of agarose. The driving force is the electrical potential applied across the membrane. Despite of all the advantages, the common problem was the oxygen generated in the acceptor solution due to the electrolysis of water that could affect the analysis of easily oxidized analyte species such as nitrite/nitrate species. In this work, application of oxygen scavenger to the acceptor solution has been attempted and studied to prevent or minimize this effect in G-EME for determination of nitrite and nitrate ions. Several oxygen scavengers such as ascorbic acid, iron, sulfite, and bisulfite were tested and examined. Ion chromatography was used for quantitative analysis of nitrite and nitrate ions. The mixture of sulfite and bisulfite (14 ppm) in the acceptor solution could prevent the oxidation of nitrite to nitrate effectively. After optimizing all the parameters, the method was successfully applied for speciation of nitrite and nitrate in water samples giving the linear calibration curves in the range of 10 to 200 µg L-1, the limits of detection were 12 µg L-1 and 13 µg L-1, respectively, for both nitrite and nitrate ions. This method was successfully applied to the simultaneous determination of nitrite and nitrate spiked into sausage and water samples at the sub-ppm range.