Determination of Perchlorate in Drinking Water Using a Reagent-Free Ion Chromatography System

Significance of the Topic

Perchlorate is a persistent anion contaminant found in drinking, surface and groundwater as a result of the widespread use of ammonium perchlorate in aerospace propellants and fireworks. Due to its chemical similarity to iodide, perchlorate can disrupt thyroid function and pose health risks, prompting regulatory agencies and states such as California to establish monitoring guidelines and action levels. Reliable, sensitive, and reagent-free analytical methods are essential for ensuring water quality and public health.

Objectives and Study Overview

This work presents an updated implementation of U.S. EPA Method 314.0 for perchlorate determination using an improved suppressor device. The goals are to demonstrate method performance—accuracy, precision, method detection limit (MDL), minimum reporting level (MRL), linear range, and matrix conductivity threshold (MCT)—and to validate recoveries in field samples. Small modifications to chromatographic conditions and the adoption of a Thermo Scientific Dionex AERS 500 suppressor in external water mode form the core of the update.

Methodology and Instrumentation Used

An integrated reagent-free ion chromatography system (Thermo Scientific Dionex ICS-2100 or ICS-5000+) was configured with:

• Dionex IonPac AS16 analytical column (4 × 250 mm) and AG16 guard column (4 × 50 mm)
• Dionex EGC III KOH eluent generator cartridge delivering 50 mM KOH at 1.2 mL/min
• Dionex AERS 500 external water-mode suppressor (4 mm)
• Suppressed conductivity detection at 30 °C column and 35 °C cell temperature
• Autosampler capable of 1,000 µL large-loop injections and 2,000 µL DI water wash

Standards were prepared from a 1,000 mg/L sodium perchlorate stock diluted to calibration levels (1–50 µg/L). Mixed common anion solutions (chloride, sulfate, carbonate) were prepared to assess matrix effects. Samples were filtered through 0.2 µm PES filters and, if necessary, diluted or pretreated with OnGuard cartridges to reduce high ionic strength.

Main Results and Discussion

The initial demonstration of capability yielded recoveries of 99.9% (±0.72% RSD) at 25 µg/L perchlorate, meeting EPA requirements. The MDL in DI water was determined to be 0.2 µg/L, and the laboratory MRL was set at 4 µg/L. Calibration was linear over 1.5 orders of magnitude (R² = 0.999). The matrix conductivity threshold (MCT) was found to be approximately 5,311 µS/cm (range 5,311–5,794 µS/cm) at 25 µg/L perchlorate, with successful MCT verification (74.7% recovery at 618 mg/L mixed anions). Field samples spiked at 4 µg/L perchlorate showed recoveries of 82.4–101.3%, demonstrating good tolerance to drinking water matrices. Use of the AERS 500 suppressor reduced baseline noise (<2 nS/min) and improved peak efficiency compared to the previous ULTRA II device. Recycle-mode suppression can generate ghost peaks and is not recommended for quantification.

Benefits and Practical Applications

This updated method offers:

• Reagent-free operation and simplified maintenance
• Lower background noise and improved detection limits
• High suppressor capacity and fast startup
• Robust performance for routine monitoring under EPA Method 314.0 criteria
• Flexibility for a range of drinking and environmental water matrices

Future Trends and Opportunities

Advances in column technology (e.g., 2 mm formats), on-line sample preparation, coupling to mass spectrometry for increased selectivity, and higher-throughput automation will further enhance perchlorate analysis. Expanded applications to industrial effluents and complex matrices can benefit from the improved suppressor resilience and minimal reagent consumption.

Conclusion

The revised EPA Method 314.0 procedure incorporating a Dionex AERS 500 suppressor and optimized chromatographic parameters delivers sensitive, accurate, and precise determination of perchlorate in drinking water. Method validation data confirm MDL of 0.2 µg/L, robust linearity, controlled matrix effects, and compliance with U.S. EPA performance requirements, supporting its use for regulatory and quality‐control monitoring.

References

• Jackson PE, Gokhale GT, Streib T, Rohrer JS, Pohl CA. J Chromatogr A. 2000;888:151.
• Gilbert ME, Sui L. Environ Health Perspect. 2008;116(6):752.
• California Department of Public Health. Perchlorate in Drinking Water. Effective October 2007.
• Thermo Fisher Scientific. Determination of Perchlorate in Drinking Water using a Reagent-Free Ion Chromatography System. Application Note 148, 2016.
• Thermo Fisher Scientific. Determination of Perchlorate in Drinking Water by Ion Chromatography. Application Update 145, Sunnyvale, CA.