Multi-pumping flow system for the determination of nitrite and nitrate in water samples

Abstract

A multi-pumping flow system for the spectrophotometric determination of nitrite and nitrate is described. The determination of nitrite is based on the Griess-Ilosvay reaction. Nitrate can be determined after its on-line reduction to nitrite using hydrazine sulphate in alkaline medium. Calibration was linear up to 3 mg NO2 − L−1 with a limit of detection (3sb/S) of 0.013 mg NO2 − L−1 an injection throughput of 55 injections h−1 and a repeatability (RSD) of 0.5% for the direct determination of nitrite. Two calibration graphs within the ranges 0.039–7 mg NO3 − L−1 and 0.026–5 mg NO2 − L−1 were run for the determination of nitrate and nitrite under reducing conditions, respectively. A limit of detection of 0.039 mg NO3 − L−1 was obtained. An injection throughput of 27 injections h−1 and an RSD lower than 1.5% were achieved. The method was successfully applied to the determination of nitrite and nitrate in water samples.