Thermo Scientific Dionex IonPac AS9-SC and AS9-HC Anion-Exchange Column

Significance of the Topic

Chromatographic determination of inorganic anions and oxyhalides is critical for environmental monitoring, industrial quality control, and public health. Trace bromate, a regulated disinfection byproduct in drinking water, and other anionic species in complex matrices demand sensitive, robust, and efficient analytical methods. The Thermo Scientific Dionex IonPac AS9-SC and AS9-HC columns have been developed to address these needs by offering high selectivity, capacity, and compatibility with carbonate-based isocratic eluents.

Study Objectives and Overview

This application note evaluates the performance of two anion-exchange columns—Dionex IonPac AS9-SC (solvent-compatible) and the high-capacity AS9-HC—for the rapid isocratic separation of fluoride, chlorite, bromate, chloride, nitrite, bromide, chlorate, nitrate, phosphate, and sulfate in diverse sample types. Key goals include:

• Assessing separation efficiency and runtime under isocratic carbonate conditions.
• Demonstrating trace bromate quantification in drinking water down to low µg/L levels.
• Illustrating column versatility across analytical, guard, and capillary formats.
• Exploring sample pretreatment and detection options for high-salt and solvent-miscible matrices.

Methodology and Instrumentation Used

A suite of Thermo Scientific™ Dionex™ components was employed:

• Columns: IonPac AS9-SC and AS9-HC analytical (4×250 mm, 2×250 mm) and capillary (0.4×250 mm) with matching AG9-SC/AG9-HC guard columns.
• Eluent: Isocratic carbonate/bicarbonate or pure carbonate (3–9 mM) at flow rates from 10 µL/min (capillary) to 2 mL/min.
• Detection: Suppressed conductivity (Dionex ASRS or ACES 300 suppressors) and UV at 214 nm for enhanced nitrite sensitivity.
• Pretreatment: OnGuard Ag and H cartridges to remove excess chloride and silver ions when required.

Main Results and Discussion

Comparison of AS9-SC and AS9-HC columns shows:

• AS9-SC achieves complete anion separation in under 10 minutes using 1.8 mM carbonate/1.7 mM bicarbonate.
• AS9-HC increases capacity (190 µeq for 4×250 mm) and retention times (~22 min) to resolve critical pairs such as bromate/chloride and chlorate/nitrate.
• Capillary AS9-HC (0.4 mm) delivers comparable resolution with 100× reduced eluent consumption and high mass sensitivity.
• Trace bromate at 5 ppb in simulated and real drinking water matrices is quantified with large-loop injection (200 µL on 4 mm; 2 µL on capillary) and isocratic 9 mM carbonate eluent.
• OnGuard pretreatment effectively removes high chloride backgrounds, eliminating peak overlap and enabling accurate bromate measurement.
• Applications extend to rapid chloride/sulfate analysis in polymeric catalysts (<8 min), trace anion monitoring in semiconductor solvents, and nitrite detection in high-ionic-strength wastewaters (up to 111 000:1 chloride/nitrite ratio) by UV detection.

Benefits and Practical Applications

The Dionex IonPac AS9-SC and AS9-HC columns offer:

• Fast, robust isocratic methods compatible with standard IC systems.
• High capacity for trace analyte detection in challenging matrices.
• Solvent compatibility for flexible sample cleanup and extended column life.
• Scalable formats from analytical to capillary, optimizing sample volume and cost.
• Validated performance in regulatory methods (e.g., EPA 300.0/300.1).

Future Trends and Applications

Ongoing developments in ion chromatography will focus on miniaturized high-capacity packings, integration with mass spectrometry for structural identification, novel suppressor designs for lower background noise, and further enhancement of throughput for high-volume environmental and industrial screening. Increased demand for ultra-trace analysis and multiplatform compatibility will drive next-generation column technologies.

Conclusion

Thermo Scientific Dionex IonPac AS9-SC and AS9-HC columns demonstrate exceptional performance for the isocratic separation and quantification of a broad range of inorganic anions and oxyhalides. Their high capacity, solvent compatibility, and compatibility with suppressed conductivity and UV detection make them versatile tools for water quality, industrial, and research laboratories.

Instrumentation Used

• Dionex IonPac AS9-SC/AS9-HC columns and AG9-SC/AG9-HC guard columns.
• Dionex ACES 300 and ASRS suppressors (auto-regenerating or recycle modes).
• Thermo Scientific Dionex OnGuard Ag and H cartridges for sample pretreatment.
• Conductivity and UV (214 nm) detectors.