Determination of Nitrite and Nitrate in Drinking Water Using Ion Chromatography with Direct UV Detection

Importance of the Topic

Monitoring nitrite and nitrate levels in drinking water is critical for public health and regulatory compliance. Both anions can pose significant health risks at elevated concentrations, making sensitive and selective analytical methods indispensable for environmental and quality control laboratories.

Objectives and Study Overview

This protocol outlines a reliable ion chromatography method with direct UV detection for simultaneous quantification of nitrite and nitrate in drinking water. The study evaluates reagent preparation, chromatographic conditions, and the impact of chemical suppression on analytical performance.

Methodology and Reagents

An eluent composed of 1.8 mM sodium carbonate and 1.7 mM sodium bicarbonate is prepared by diluting a concentrated solution. Stock solutions of 1000 ppm nitrite and nitrate are made from ACS-grade salts, and working standards are freshly diluted to bracket target concentrations. Samples are optionally preserved with sulfuric acid to stabilize analytes.

Used Instrumentation

• Ion chromatograph equipped with a UV-visible absorbance detector at 210 nm
• IonPac AS9 analytical column coupled with an AG9 guard column
• Optional AMMS-II chemical suppressor to reduce background absorbance and eliminate negative peaks

Main Results and Discussion

Baseline separation of nitrite, bromide, and nitrate is achieved in under 10 minutes. Using a 25 µL injection, the method detection limits in drinking water are 10 ppb for nitrite (≈3 ppb N) and 15 ppb for nitrate (≈3.5 ppb N). Nitrite shows linearity from 10 ppb to 50 ppm, while nitrate is linear from 15 ppb to 75 ppm. Incorporation of chemical suppression improves baseline stability and peak shapes.

Benefits and Practical Applications

• High selectivity with minimal ionic interferences via direct UV detection
• Sensitivity suitable for regulatory monitoring of drinking water
• Option to enhance performance through chemical suppression
• Rapid analysis compatible with routine QA/QC workflows

Future Trends and Possibilities

Advances may include coupling with mass spectrometry for confirmation, development of portable field-deployable IC systems, automated sample preparation, and greener eluent formulations. Integration with data analytics and remote monitoring platforms can further strengthen water quality surveillance.

Conclusion

Ion chromatography with direct UV detection offers a robust, accurate, and efficient solution for nitrite and nitrate analysis in drinking water. The method meets stringent detection requirements and can be optimized with chemical suppression, supporting diverse environmental and industrial applications.