The chemical generation of NO for the determination of nitrite by high-resolution continuum source molecular absorption spectrometry

Abstract

In the present work, we propose a method for the determination of nitrite based on the chemical generation of nitric oxide (NO) and its detection by high-resolution continuum source molecular absorption spectrometry. NO is generated by the reduction of nitrite in acidic media with ascorbic acid as the reducing agent and then transferred into a quartz cell by a stream of argon carrier gas. The conditions under which the NO is generated are as follows: 0.4 mol L−1 hydrochloric acid, 1.5% (w/v) ascorbic acid, an argon gas pressure of 0.03 MPa and an injection time of the reducing agent of 4 s. All measurements of molecular absorption were performed using the NO line at 215.360 nm, and the signal was measured by peak height. Under these conditions, the method described has limits of detection and quantification of 0.045 and 0.150 μg mL−1 of nitrite, respectively. The calibration curve is linear for nitrite concentrations in the range 0.15–15 μg mL−1. The precision, estimated as the relative standard deviation (RSD), was 3.5% and 4.4% for solutions with nitrite concentrations of 0.5 and 5.0 μg mL−1, respectively. This method was applied to the analysis of different water samples (well water, drinking water and river water) collected in Cachoeira City, Bahia State, Brazil. The results were in agreement with those obtained by a spectrophotometric method using the Griess reaction. Addition/recovery tests were also performed to check the validity of the proposed method. Recoveries of 93–106% were achieved.