Determination of Nitrites, Nitrates, and Their Mixtures Using Flow Injection Analysis with Spectrophotometric Detection

Abstract

A new flow injection analysis (FIA) method has been developed for determination of nitrites, nitrates, and their mixtures, based on the reaction of nitrites with rivanol (2-ethoxy-6,9-diaminoacridinium lactate) in HCl medium; the concentration of the diazonium salt formed is evaluated spectrophotometrically (λ = 520 nm). Flow-through determination of nitrates can be carried out by using the same reaction following prior reduction in a flow-through reductor filled with copperised cadmium included in the apparatus. The determination of both ions in a mixture is enabled by the use of a switching solenoid valve, which either excludes the reductor (determination of only nitrites) or connects the reductor in the flow-through system (determination of the sum of nitrites and nitrates). The reaction and flow conditions with the full experimental design were optimized and detection limits for nitrite (0.14 mg L⁻¹) and nitrate (1.2 mg L⁻¹) determination were obtained. Both anions were determined in soil samples and it was found that excellent correlation exists between the proposed method and the standard methods (Griess reaction and ion-selective nitrate electrode).

Keywords:

• Nitrites
• Nitrates
• Flow injection analysis
• Flow-through reductor

Acknowledgments

The authors wish to thank the University Development Fund (Grant No. 2314) and research project (MSM:113100002) for financial support.