Determination of nitrite in water samples using atmospheric pressure glow discharge microplasma emission and chemical vapor generation of NO species

Abstract

In this work, a low-power (<25 W), portable direct current (dc) atmospheric pressure glow discharge microplasma (4 mm × 10 mm) molecular emission spectrometer (APGD-MES) is developed for the determination of nitrite by using chemical vapor generation. Nitrite is on-line reduced to volatile nitric oxide (NO) by 1.5% (m/v) ascorbic acid and 1.0 mol L−1 hydrochloric acid. Then, the generated NO was separated and transferred into the APGD microplasma by an argon stream (100 mL min−1) for its excitation, and NO emission was measured by a microspectrometer. The effects of operational parameters of the APGD microplasma source and vapor generation of nitrite were investigated and the analytical figures of merit for nitrite detection was evaluated. The limit of detection of the proposed method was calculated to be 0.26 μg mL−1 of nitrite by measuring NO emission at 237.0 nm. The calibration curve is linear for the nitrite concentration in the range of 2.0–100.0 μg mL−1 and good precision (2.3%, RSD) is readily achieved for 5.0 μg mL−1 nitrite. The accuracy of this procedure was demonstrated by nitrite detection in a certified reference material. Analyte recoveries test were also performed to verify the accuracy of the method for nitrite determination in a series of environmental water samples. It was found that the concentration of nitrite of these samples were all below the LOD, and the obtained recoveries were in the range of 95–117%. The proposed APGD–MES method provides an alternative useful technique for screening potential nitrite pollution of potable waters.