Measuring Nitrite and Nitrate in Rain and River Water Samples Using a Portable Ion Chromatograph in Step-gradient...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Water Quality Monitoring

Background:

• Growing environmental pollution necessitates sensitive, real-time pollutant monitoring.
• Nitrite and nitrate are key water quality indicators.
• Assessing water quality in Tasmania presents unique challenges.

Purpose of the Study:

• To enhance nitrate and nitrite detection capabilities using the portable Aquamonitrix analyzer.
• To optimize the system for ultra-low detection limits (LODs).
• To validate the system for environmental water quality assessment in Tasmania.

Main Methods:

• Utilized a portable ion chromatography-based nutrient analyzer (Aquamonitrix).
• Employed step-gradient mode with 3D printed flow cells (5 cm and 10 cm optical path length).
• Optimized eluent (KOH and NaCl) and injection loop (300 µL) for ultra-low LODs.

Main Results:

• Achieved LODs of 0.004 µg/mL for nitrite and 0.023 µg/mL for nitrate.
• Further improved nitrate LOD to 0.008 µg/mL with a 10 cm flow cell.
• Demonstrated high repeatability (RSD < 1.42% for peak area, < 0.49% for retention time) and salinity tolerance (up to 5 ppt).
• Detected significantly lower nitrate levels in Tasmanian rainwater compared to Ireland.
• Real-time analysis showed average nitrate concentrations of 2.08 µg/mL in the Tamar River and 0.17 µg/mL in the Derwent River.
• Validation against standard ion chromatography showed no significant differences (p > 0.05).

Conclusions:

• The optimized Aquamonitrix system provides robust, reliable, and accurate field-based monitoring of nitrite and nitrate.
• The system is suitable for real-time water quality assessment, even under challenging environmental conditions.
• This technology addresses the need for sensitive and efficient environmental monitoring.