Determination of cations and ammonium in environmental waters using a compact RFIC ion chromatography system

Importance of Topic

The accurate measurement of alkali and alkaline earth cations together with ammonium in drinking and environmental waters is critical for water quality assessment, regulatory compliance, and environmental monitoring.

Objectives and Study Overview

This application note evaluates the performance of a compact reagent-free ion chromatography system for simultaneous determination of lithium, sodium, ammonium, potassium, magnesium, and calcium in various water matrices. It compares results with a previously published method to demonstrate the suitability of the new Inuvion IC platform.

Materials and Methods

• Reagents: Type I deionized water, standard salts of Ca, Mg, K, Na, Li, and a certified ammonium standard
• Calibration: Multi‐point calibration covering low µg/L to mg/L ranges for each ion
• Detection: Suppressed conductivity detection with a recycle suppressor in recycle mode
• Eluent: 30 mM methanesulfonic acid generated in situ via RFIC
• Run time: 22 minutes per injection, 10 µL injection volume

Used Instrumentation

• Dionex Inuvion IC system with built-in pump degasser, column heater, and eluent generator
• Thermo Scientific AS-DV autosampler with 5 mL vials and filter caps
• Dionex IonPac CS16-4 µm (4 × 250 mm) analytical column with CG16 guard column
• EGC 500 MSA cartridge and CR-CTC 600 eluent control module
• CDRS 600 suppressor and Chromeleon CDS software version 7.3.2

Results and Discussion

Calibration exhibited excellent linearity with coefficients of determination above 0.996 for all analytes. Method detection limits ranged from 0.11 µg/L for magnesium to 11.9 µg/L for calcium, ensuring sensitivity for trace-level monitoring. Analysis of drinking water and secondary effluent demonstrated accurate quantitation across a wide concentration span. In the tested wastewater effluent, sodium and calcium were observed at higher levels compared to drinking water, while ammonium remained below 1 mg/L in both matrices.

Benefits and Practical Applications

• Wide dynamic range accommodates trace to high concentrations in a single run
• Reagent‐free operation reduces maintenance and chemical consumption
• Compact footprint suitable for routine laboratory environments
• Reliable detection of environmentally relevant cations for QA/QC, regulatory compliance, and research

Future Trends and Opportunities

Advances in RFIC technology and suppressor design will further lower detection limits and expand applicability to more challenging matrices such as industrial effluents. Integration with automated sample preparation and data analytics platforms will enhance throughput and data quality for large‐scale monitoring programs.

Conclusion

The Dionex Inuvion IC system combined with the IonPac CS16 column provides robust, sensitive, and high‐throughput analysis of key cations and ammonium in environmental waters, meeting the demands of modern water quality laboratories.

References

• Thermo Scientific Application Update 204: Analysis of Environmental Waters for Cations and Ammonium Using a Compact Ion Chromatography System, 2016