Application of silica coated magnetite nanoparticles modified with Cu(I)-neocuproine as nanosorbent to simultaneous separation-preconcentration of trace amounts of nitrate and nitrite.

A novel, inexpensive and sensitive type of magnetic nanosorbent based on the functionalized silica-coated Fe3O4 nanoparticles was prepared and used for the adsorption of trace amounts of nitrite and nitrate ions. The work is based on selective ion-pairing complex formation of nitrate and nitrite with Cu(I)-neocuproine which are covalently bounded on nanoparticles. Nitrite was determined according to its reaction with barbituric acid to give violuric acid and determination of nitrate was based on its reduction to nitrite in the presence of Zn/NaCl. After formation of violuric acid, the absorbance was measured spectrophotometrically at 310 nm. The quantitative recoveries were obtained at pH 5.5 for the analytes. Under optimum conditions, the limits of detection in the original solutions were 0.49 µg L-1 and 0.40 µg L-1 for nitrate and nitrite, respectively. The linearity ranges were found to be 1.5 to 2.8 × 103 µg L-1(NO3-) and 1.2 to 1.9 × 103 µg L-1 (NO2-). The preconcentration factor was 120 for nitrate and 150 for nitrite. This method has been successfully applied to the determination of trace amounts of nitrite and nitrate in various water and food samples and also accuracy was confirmed by the analysis of the spiked recovery test.