Fast Anion Determinations in Environmental Waters Using a High-Pressure Compact Ion Chromatography System

Importance of the Topic

Anions such as fluoride, chloride, nitrate, nitrite, sulfate, phosphate and bromide are monitored in surface, ground, drinking and wastewater to protect public health and comply with regulatory frameworks like the U.S. Safe Drinking Water Act and Clean Water Act. Rapid and reliable detection of these species supports pollutant control, process optimization and routine compliance testing.

Study Objectives and Overview

This work updates a previous Thermo Fisher application note by implementing a high-pressure, compact ion chromatography system (Integrion HPIC) with a shorter 4×150 mm, 4 µm IonPac AS18-4µm column to reduce analysis time from 20 min to 12 min while preserving resolution and sensitivity. The goal was to evaluate chromatographic performance, precision, detection limits and method accuracy for seven anions in various environmental waters.

Methodology

Analyses employed an electrolytically generated hydroxide gradient (15–44 mM KOH) at 1.0 mL/min, with a 10 µL injection volume and column temperature of 35 °C. Suppressed conductivity detection was performed using a self-regenerating Dionex AERS 500 suppressor at 15 °C. Sample types included municipal drinking water, surface water, wastewater and well water, filtered through 0.2 µm membranes and, where needed, diluted.

Instrumentation Used

• Thermo Scientific Dionex Integrion HPIC system with RFIC up to 5000 psi
• Thermo Scientific Dionex AS-AP autosampler (10 mL trays)
• Dionex EGC 500 KOH electrolytic eluent generator and CR-ATC 600 trap column
• Dionex HP EG degasser module
• Dionex IonPac AG18-4µm guard column (4×30 mm) and AS18-4µm separation column (4×150 mm)
• Dionex AERS 500 self-regenerating suppressor (4 mm, recycle mode)
• Thermo Scientific Chromeleon 7.2 SR4 CDS software

Main Results and Discussion

All seven anions eluted in under 9 min, with total run time of 12 min. The 4 µm resin provided sharper peaks and improved resolution of critical pairs (carbonate/bromide, sulfate/nitrate) compared to 7.5 µm media. Retention time precision (n=7) was <0.1 % RSD and peak area precision <0.2 % RSD. Method detection limits ranged from 0.1 to 2.6 µg/L. Spiked recoveries in diverse water matrices were 89–105 %, demonstrating accuracy across real samples.

Benefits and Practical Applications

• High throughput: 12-minute cycle supports large sample loads.
• Regulatory compliance: meets U.S. EPA Method 300.1 requirements.
• Reagent-free operation: electrolytic eluent generation reduces preparation time and contamination risk.
• Versatility: applicable to drinking water, wastewater, surface and industrial effluents.

Future Trends and Potential Applications

Advances in IC instrumentation may include higher-pressure capabilities to adopt sub-2 µm particles for ultrafast separations, integration of multi-detector modules for comprehensive profiling, and AI-driven method optimization. Expansion into on-line and field-deployable systems could further streamline water quality monitoring.

Conclusion

The updated method using the Integrion HPIC system and AS18-4µm column delivers a robust, fast and accurate protocol for routine anion determination in environmental waters. Improved resolution, precision and lower detection limits support stringent regulatory requirements and diverse laboratory workflows.

References

1. U.S. EPA Method 300.1: Determination of Inorganic Anions in Drinking Water, 1997.
2. Thermo Fisher Scientific Application Note 154: Inorganic Anions in Environmental Waters Using Hydroxide-Selective Column, 2003.
3. Dionex Integrion HPIC System Installation and Operator’s Manual, Thermo Fisher Scientific, 2015.
4. Dionex IonPac AS18-4µm Column Product Manual, Thermo Fisher Scientific, 2014.
5. Dionex AERS 500 Suppressor Product Manual, Thermo Fisher Scientific, 2013.