Thermo Scientific Dionex IonPac AS23 Anion-Exchange Column

Importance of the Topic

Reliable detection and quantification of oxyhalides and common inorganic anions in water are critical for environmental monitoring, drinking water safety and regulatory compliance. Bromate, a toxic byproduct of ozone disinfection, and other oxyhalides require sensitive analytical methods at trace levels to protect public health.

Study Objectives and Overview

This work presents the development and application of a high-capacity carbonate-based anion-exchange chromatography method using the Thermo Scientific™ Dionex™ IonPac™ AS23 column. The study aims to separate and quantify oxyhalides (bromate, chlorite, chlorate), halides and major anions in diverse matrices including drinking water, wastewater and industrial effluents. Special emphasis is placed on trace bromate determination using isocratic elution and large-loop injection.

Methodology and Instrumentation

The AS23 column features a hyper-branched polymer resin with quaternary ammonium functionality (320 μeq capacity for 4 × 250 mm format), optimized for high selectivity and resolution. An isocratic eluent of 4.5 mM sodium carbonate/0.8 mM sodium bicarbonate at 1.0 mL/min and 30 °C is employed with suppressed conductivity detection (ASRS ULTRA II or ACES 300 suppressors). Large-loop injections (200 μL for analytical, 2 μL scaled for capillary) enable trace bromate (<0.01 mg/L) quantification. Gradient mode with KOH from 5–40 mM is demonstrated for extended anion coverage.

Main Results and Discussion

• Baseline separation of fluorides, oxyhalides and common anions in under 23 minutes using the 4 × 250 mm column.
• Capillary (0.4 mm) format achieves high mass sensitivity with 100-fold eluent reduction and 10 μL/min flow.
• Drinking water samples with carbonate >300 mg/L show clear nitrate-carbonate resolution.
• Wastewater and industrial effluents yield reliable quantitation of organic acids alongside oxyhalides and inorganics.
• Trace bromate detection down to 5 μg/L meets EPA Methods 300.0/300.1 without preconcentration.

Benefits and Practical Applications

• High capacity and selectivity minimize matrix interferences in diverse water types.
• RFIC operation with on-board eluent generation and pH modulation reduces reagents and manual preparation.
• Scalable formats (4 mm, 2 mm, 0.4 mm) support routine and capillary chromatography.
• Cost-effective operation with low eluent consumption and waste for high-throughput labs.

Future Trends and Opportunities

Integration with mass spectrometry promises enhanced selectivity and identification. Automated online preconcentration and miniaturized capillary systems will improve sensitivity and reduce sample volumes. Development of novel stationary phases may expand the range of target analytes including emerging oxyacids and organic anions. Smart workflow integration and remote monitoring can further streamline environmental compliance.

Conclusion

The Dionex IonPac AS23 column provides a versatile, high-resolution solution for anion analysis in environmental and industrial waters. Its robust performance, regulatory compliance and flexible format options make it well-suited for trace oxyhalide monitoring and routine quality control.

Instrumentation Used

• Ion chromatography systems: Thermo Scientific Dionex ICS-5000+, ICS-4000 HPIC, ICS-2100 RFIC.
• Eluent generators: EGC II KOH cartridge, Dionex Eluent Generator Cartridge with CR-ATC trap.
• Suppression modules: ASRS ULTRA II, ACES 300 suppressors.
• Columns: Dionex IonPac AG23/AS23 in 4×250 mm, 2×250 mm, and 0.4×250 mm formats; AG23 and AS23 guard columns.