Fast Determinations of Inorganic Ions in Salton Sea Samples Using a High-Pressure IC System

Significance of the Topic

Monitoring inorganic ions in high-salinity waters is critical for environmental and industrial applications. Rapid and accurate ion profiling supports water quality assessment, ecosystem health monitoring, and regulatory compliance. High-pressure ion chromatography enables fast, high-resolution separations even in challenging saline matrices.

Goals and Study Overview

This study demonstrates accelerated separations of inorganic anions and cations in Salton Sea surface water and a neighboring municipal drinking water sample using a Thermo Scientific Dionex ICS-5000+ HPIC Reagent-Free IC system. The key objective was to reduce analysis times while maintaining baseline resolution.

Used Instrumentation

• Thermo Scientific Dionex ICS-5000+ HPIC RFIC system with high-pressure pump (SP/DP), eluent generator (EG), and detector/chromatography (DC) modules
• Dionex AS-AP autosampler and Chromeleon CDS
• IonPac AS18-4 µm anion-exchange column (2 × 150 mm) with AG18 guard (2 × 30 mm)
• IonPac CS12A-5 µm cation-exchange column (3 × 150 mm) with CG12A guard (3 × 30 mm)
• Dionex EGC 500 KOH and MSA eluent generator cartridges with CR-ATC and CR-CTC trap columns
• Dionex ASRS-300 anion and CSRS-300 cation self-regenerating suppressors

Methodology and Sample Preparation

• Anion analysis: 23 mM KOH eluent at flow rates of 0.25–0.38 mL/min, 5 µL injection, detection by suppressed conductivity (ASRS-300).
• Cation analysis: 35 mM methanesulfonic acid eluent at flow rates up to 0.75 mL/min, 25 µL injection, detection by suppressed conductivity (CSRS-300).
• Salton Sea surface water diluted 1 000×, filtered through 0.20 µm IC syringe filter to remove particulates; municipal drinking water analyzed undiluted or at 5× dilution for anions.
• High-pressure connectors and ferrules used to support system pressures of 2 000–5 000 psi.

Main Results and Discussion

• Anion separations achieved near-baseline resolution of nine anions in under 6 minutes at 0.38 mL/min (system backpressure ~3 600 psi).
• Cation separations of six cations completed in ~4 minutes at 0.75 mL/min (system backpressure ~3 100 psi), compared to ~10 minutes in standard methods.
• Salton Sea sample showed high concentrations of sodium (20 g/L), chloride, and sulfate, with lower magnesium and calcium; municipal water exhibited typical mg/L levels.
• Throughput increased from ~50 to over 110 samples per day without compromising resolution.

Benefits and Practical Applications

• Significant reduction in analysis time improves laboratory productivity and sample throughput.
• Reagent-Free IC eliminates manual eluent preparation, reducing variability and contamination risks.
• High-pressure capability enables use of microbore and capillary columns for enhanced efficiency and sensitivity.
• Applicable to environmental monitoring, desalination process control, and quality assurance in saline and drinking water analysis.

Future Trends and Applications

Advancements in capillary and microfluidic HPIC, combined with on-line sample preconcentration and automated data processing, will further increase sensitivity and throughput. Integration with portable or field-deployable systems may enable in situ water quality monitoring and real-time decision support.

Conclusion

The Dionex ICS-5000+ HPIC system delivers fast, high-resolution inorganic ion separations in saline matrices, dramatically reducing run times and enhancing laboratory efficiency. Reagent-Free operation and high-pressure compatibility support robust, reproducible analyses across a range of environmental and industrial applications.

Reference

1. Ponce VM. The Salton Sea: An Assessment. 2005.
2. Christison T, Lopez L. Technical Note 129: Configuring High Pressure IC at Analytical Flow Rates. 2012.
3. Thermo Fisher Scientific. Dionex Product Manual for Anion and Cation Self-Regenerating Suppressors. 2009.
4. Thermo Fisher Scientific. Dionex ICS-5000+ HPIC Installation Manual. 2011.
5. Thermo Fisher Scientific. Dionex AS-AP Operator’s Manual. 2012.
6. Thermo Fisher Scientific. AN141: Determination of Inorganic Cations in Environmental Waters. 2001.
7. Thermo Fisher Scientific. AN154: Determination of Inorganic Anions in Environmental Waters. 2003.
8. Thermo Fisher Scientific. AN260: Monitoring Inorganic Anions and Cations During Desalination. 2010.
9. Pang F et al. Application Brief 141: Fast Determination of Inorganic Anions by Capillary IC. 2012.
10. Thermo Fisher Scientific. Environmental Capillary IC Applications, Capillary IC Library. 2012.