Determination of Low Concentrations of Perchlorate in Drinking and Groundwaters Using Ion Chromatography

Importance of the Topic

The precise quantification of trace levels of perchlorate in drinking and groundwater is critical due to its widespread use in rocket propellants and potential interference with thyroid function. Regulatory bodies have set low allowable limits (4–18 µg/L), and reliable analytical data are required for water quality monitoring and remediation decision-making.

Objectives and Study Overview

This application note describes an improved ion chromatography (IC) method for determining perchlorate at low microgram-per-liter levels in drinking and groundwaters. The study aims to optimize separation, sensitivity, and robustness against common anionic interferences and high salt matrices.

Methodology and Instrumentation

Reagents and sample preparation:

• Type I deionized water and ACS-grade salts (sodium perchlorate, other anions).
• Stock perchlorate standard (1000 mg/L) diluted to working levels (2–100 µg/L).
• OnGuard Ag and H cartridges used for chloride removal in extreme matrices.

Chromatographic conditions:

• System: Thermo Scientific Dionex DX-500 IC with GP50 pump, AS40 autosampler, LC30 oven, CD20 conductivity detector, EG40 eluent generator.
• Column: Dionex IonPac AG16 guard + AS16 analytical (4×250 mm).
• Eluent: 65 mM KOH from EG40 generator; flow 1.2 mL/min; temperature 30 °C.
• Injection: Large-loop 1000 µL; suppressed conductivity detection (ASRS ULTRA, external water mode, 300 mA).

Main Results and Discussion

The method exhibits excellent linearity from 2 to 100 µg/L (r2 > 0.9985) and a method detection limit (MDL) of 151 ng/L. Perchlorate elutes at ~9.6 min with a symmetrical peak shape, thanks to the high capacity and hydrophilic nature of the AS16 column. Interference tests with 22 common anions (arsenate, bromide, nitrate, sulfate etc.) show that all elute prior to perchlorate, ensuring no coelution. Recovery studies in the presence of 50–1000 mg/L carbonate, chloride, or sulfate yield quantitative recoveries (93–110%) at 20 µg/L. In extreme chloride matrices (10 000 mg/L Cl–), sample dilution or OnGuard Ag cartridge treatment enables accurate perchlorate measurement; a 1:5 dilution plus 35 mM KOH eluent improved resolution when perchlorate >40 µg/L.

Benefits and Practical Applications

• Robust trace-level determination of perchlorate for regulatory compliance and environmental monitoring.
• Compatibility with automated EG40 eluent generation reduces manual preparation and improves throughput.
• Effective suppression of interferences from common anions and high salt waters.
• Large-loop injection enhances sensitivity without compromising peak shape.

Future Trends and Applications

Emerging needs include coupling IC with mass spectrometry for isotope analysis, miniaturization for field-deployable systems, and expanding the method to simultaneous determination of other polarizable anions. Advances in suppression technology and high-capacity columns may further lower detection limits and improve resilience against complex matrices.

Conclusion

The described IC approach using the Dionex IonPac AS16 column and EG40 eluent generator provides sensitive, selective, and reliable quantification of perchlorate in drinking and groundwaters. Its high linearity, low MDL, and robustness against interferences make it a valuable tool for environmental and regulatory laboratories.

Reference

1. California Department of Health Services. “Perchlorate in California Drinking Water” Update; September 1999.
2. California Department of Health Services. Determination of Perchlorate by Ion Chromatography; June 1997.
3. Okamoto HS, Rishi DK, Steeber WR, Baumann FJ, Perera SK. J Am Water Works Assoc. 1999;91(10):73–84.
4. Dionex Corporation (Thermo Scientific). Analysis of Low Concentrations of Perchlorate in Drinking Water and Ground Water by Ion Chromatography. Application Note 121; Sunnyvale, CA.
5. Jackson PE, Laikhtman M, Rohrer JS. J Chromatogr A. 1999;850:131–135.
6. Federal Register. Unregulated Contaminant Monitoring Rule; Vol. 64, No. 180, 50555–50620; September 17, 1999.
7. U.S. EPA Method 300.0. The Determination of Inorganic Anions in Water by Ion Chromatography; August 1993.
8. Chaudhuri S, Okamoto HS, Pia S, Tsui D. Inter-Agency Perchlorate Steering Committee Analytical Subcommittee Report; 1999.