Determination of Nitrite and Nitrate in Drinking Water Using Chemically Suppressed Ion Chromatography

Significance of the Topic

Determining nitrite and nitrate in drinking water is critical due to their potential health impacts and strict regulatory limits.
Ion chromatography enables sensitive and selective quantification of these anions even in complex matrices.

Objectives and Study Overview

This work aims to demonstrate a rapid and accurate method for quantifying nitrite and nitrate in acid-preserved drinking water using chemically suppressed ion chromatography.
The method tolerates high chloride and sulfate backgrounds and provides trace-level detection with minimal sample preparation.

Methodology

An IonPac AS9 analytical column with AG9 guard was used on a Dionex ion chromatograph equipped with a conductivity detector.
The eluent consisted of 1.8 mM sodium carbonate and 1.7 mM sodium bicarbonate at 2.0 mL/min.
Suppression employed an Anion MicroMembrane suppressor regenerated with 25 mM sulfuric acid at 6 mL/min via the AutoRegen accessory.
Samples (25 µL) were preserved to pH <2 with sulfuric acid prior to injection.

Instrumentation

• Dionex Ion Chromatograph with conductivity detector
• IonPac AS9 analytical column and AG9 guard column
• Anion MicroMembrane suppressor
• AutoRegen suppressor regeneration accessory

Main Findings and Discussion

A representative chromatogram of drinking water spiked with 3.3 ppm nitrite and 22.0 ppm nitrate demonstrated clear, baseline separation.
The method tolerated up to 150 ppm chloride and 0.5% sulfuric acid, with sulfate levels up to five times higher than the analytes.
Detection limits were 10 ppb for both nitrite (3.0 ppb nitrogen) and nitrate (2.3 ppb nitrogen).
Linearity ranged from 10 ppb to 50 ppm for nitrite and 20 ppb to 100 ppm for nitrate, confirming robust quantitation over a wide concentration span.

Benefits and Practical Applications

• High sensitivity suitable for trace-level monitoring in water quality control
• Rapid analysis with minimal sample preparation and strong interference tolerance
• Reliable performance in acid-preserved samples
• Applicable for regulatory compliance testing and routine QA/QC in water treatment facilities

Future Trends and Applications

• Integration with mass spectrometry for enhanced selectivity and sensitivity
• Development of online sample pretreatment and automated workflows for high throughput
• Advances in microfluidic ion chromatography for portable field analysis
• Extension of the method to additional anions and emerging contaminants in water

Conclusion

The chemically suppressed ion chromatography method offers a reliable, sensitive, and rapid approach for nitrite and nitrate determination in drinking water.
Its robustness against matrix effects and broad linear range make it well suited for both regulatory compliance and routine laboratory monitoring.

References

No specific literature references were provided in the original document.