Fast anion determinations in environmental waters using a compact IC system

Significance of the Topic

Inorganic anions such as fluoride, chloride, nitrite, bromide, sulfate, nitrate, and phosphate are critical parameters for assessing environmental water quality. Rapid, reliable detection of these species supports regulatory compliance, pollution tracking, and public health protection.

Objectives and Study Overview

This study demonstrates a streamlined method for fast anion analysis in municipal drinking water using a novel compact ion chromatography (IC) system with electrolytic eluent generation. It builds on Thermo Fisher Scientific’s Application Update 200, aiming to enhance throughput and automation.

Methodology

The method employs gradient elution with potassium hydroxide (KOH) generated in situ. Key conditions:

• Eluent profile: 15–44 mM KOH (0.2–6 min), 44 mM KOH (6–9 min), 15 mM KOH (9–12 min)
• Flow rate: 1.0 mL/min
• Injection volume: 10 µL
• Column temperature: 30 °C
• Detection: suppressed conductivity in recycle mode at constant current (109 mA)
• Run time: 12 min

Instrumentation Used

The analysis was performed on a Thermo Scientific Dionex Inuvion IC system equipped with:

• AS-DV autosampler
• IonPac AS18-Fast-4 µm analytical column (4 × 150 mm) with AG18 guard (4 × 30 mm)
• EGC 500 KOH eluent generator with CR-ATC 600 anion trap column
• RFIC eluent degasser
• ADRS 600 (4 mm) suppressor in recycle mode

Main Findings and Discussion

The method achieved baseline separation of seven common inorganic anions within 12 minutes. Typical results for a standard mixture and a municipal sample included:

• Fluoride: retention ~1 min, 0.63 mg/L in sample
• Chloride: ~12 min, 9.7 mg/L
• Nitrite: ~8 min, 0.023 mg/L
• Bromide: ~9 min (no concentration in sample)
• Sulfate: ~10 min, 16.3 mg/L
• Nitrate: ~9 min, 1.3 mg/L
• Phosphate: ~6.5 min, 0.085 mg/L

Background conductivity drift was 0.38 µS/min and noise remained below 1.5 nS, demonstrating stable baseline and high sensitivity.

Benefits and Practical Implications

The automated eluent generation eliminates manual preparation and reduces chemical waste. High-pressure compact design allows rapid analysis with minimal footprint. The robust system delivers reproducible retention times and low detection limits, suitable for routine environmental monitoring and regulatory labs.

Future Trends and Potential Applications

Advancements may include integration with mass spectrometry for improved selectivity, on-line sample preparation modules for direct field monitoring, microfluidic IC platforms for portable analysis, and AI-driven data interpretation to accelerate result validation.

Conclusion

This application note confirms that the compact IC system with electrolytic eluent generation provides a fast, reliable method for simultaneous determination of key inorganic anions in environmental waters. Its automation and performance characteristics support high-throughput and routine water quality testing.

References

1. Thermo Scientific Application Update 200: Fast Anion Determinations in Environmental Waters Using a High-Pressure Compact Ion Chromatography System.