Determining Sub-ppb Perchlorate in Drinking Water Using Preconcentration/ Matrix Elimination Ion Chromatography with Suppressed Conductivity Detection by U.S. EPA Method 314.1

Importance of the Topic

Perchlorate is a persistent and highly soluble anion used in rocket propellants, pyrotechnics, airbags and industrial explosives. Its mobility in soil and water has led to widespread contamination of groundwater, surface water and certain food items. Chronic exposure to even trace levels of perchlorate can disrupt thyroid hormone production by inhibiting iodide uptake, posing a particular risk to fetuses and infants. Various U.S. states have adopted advisory or public health goal levels as low as 1–6 µg/L, necessitating analytical methods capable of reliably quantifying sub-ppb concentrations in complex drinking water matrices.

Objectives and Study Overview

This application note evaluates U.S. EPA Method 314.1, which integrates on-line preconcentration and matrix elimination with ion chromatography (IC) and suppressed conductivity detection to achieve a method reporting limit of 0.5 µg/L and detection limits near 0.02 µg/L. The study compares two different separation columns—Dionex IonPac AS16 and AS20—for primary and confirmatory analyses, demonstrates performance in reagent water and diverse drinking water samples, and highlights tolerance to high-ionic strength matrices without dilution or extensive pretreatment.

Methodology

• Samples (2 mL) are drawn into a dual-pump IC system and loaded onto a Dionex IonPac Cryptand C1 concentrator column.
• Matrix ions (chloride, sulfate, bicarbonate at 100–1000 mg/L) are diverted to waste by a rinse step with 10 mM NaOH.
• Perchlorate is refocused and eluted onto the analytical column using a NaOH gradient (0.5–100 mM) generated reagent-free.
• A primary separation on AS16 is complemented by confirmation on AS20 to distinguish perchlorate from co-eluting anions.
• Calibration uses quadratic regression over 0.5–10 µg/L; performance checks include mid-level precision/recovery and matrix-fortified sample recovery tests.

Used Instrumentation

• Thermo Scientific Dionex ICS-3000 Reagent-Free Ion Chromatography System (DP dual pump, EG eluent generator, DC detector)
• Dionex AS Autosampler with sequential concentration capability
• Dionex IonPac Cryptand C1 Concentrator Column (4×35 mm)
• Dionex IonPac AG16/AS16 and AG20/AS20 analytical and guard columns (2×250 mm/2×50 mm)
• Thermo Scientific Dionex ASRS ULTRA II suppressed conductivity suppressor (2 mm external water mode)

Key Results and Discussion

• Calibration curves on both AS16 and AS20 yield r² = 0.9999, with recoveries of 99–105% at 5 µg/L.
• Method detection limits (~0.02 µg/L) and reporting limits (MRL = 0.5 µg/L) meet EPA specifications; prediction intervals remain within ±50%.
• Precision (%RSD) at mid-level (5 µg/L) is <6%, and recoveries in six drinking water matrices (0.5 and 5 µg/L fortifications) range from 93–112% on the primary column and 95–120% on the confirmatory column.
• The concentrator effectively removes >90% of high concentrations of matrix anions, eliminating the need for sample dilution or off-line cleanup.
• Comparative analyses demonstrate the importance of dual-column confirmation to avoid false positives from co-eluting species.

Benefits and Practical Applications

• Achieves sub-ppb perchlorate detection with a simple on-line workflow.
• Tolerates high-ionic strength samples without additional pretreatment.
• Automated eluent generation and sample concentration reduce manual preparation and risk of contamination.
• Dual-column confirmation provides high specificity in regulatory compliance testing.

Future Trends and Potential Applications

• Incorporation of inline carbonate removal devices to further improve baseline stability and sensitivity.
• Integration with mass spectrometric detection to enhance selectivity and lower detection limits.
• Application of multidimensional chromatography for simultaneous anion profiling in environmental and food samples.
• Development of fully automated platforms for high-throughput monitoring of drinking water quality.

Conclusion

EPA Method 314.1, as implemented with Thermo Scientific Dionex IC systems, offers a robust, sensitive and selective approach for quantifying trace perchlorate in drinking water down to 0.5 µg/L. The combination of online preconcentration, matrix elimination and dual-column confirmation streamlines sample analysis, accommodates challenging matrices, and meets regulatory performance criteria.

Reference

1. Jackson, P. E.; Gokhale, S.; Streib, T.; Rohrer, J. S.; Pohl, C. A. Improved Method for the Determination of Trace Perchlorate in Ground and Drinking Waters by Ion Chromatography. J. Chromatogr. A 2000, 888, 151.
2. Hedrick, E.; Munch, D. Measurement of Perchlorate in Water by Use of an 18O-Enriched Isotopic Standard and Ion Chromatography with Mass Spectrum Detection. J. Chromatogr. A 2004, 1039, 83.
3. U.S. Government Accountability Office. Perchlorate: A System to Track Sampling and Cleanup Results is Needed. GAO-05-462, May 2005.
4. Urbansky, E. T. Review and Discussion of Perchlorate Chemistry as Related to Analysis and Remediation. Biorem. J. 1998, 2, 81.
5. California Department of Health Services. Perchlorate in California Drinking Water: Overview and Links. January 2006.
6. U.S. EPA Method 314.0. Determination of Perchlorate in Drinking Water Using Ion Chromatography. 1999.
7. Dionex Corporation. Application Update 148: Determination of Perchlorate in Drinking Water Using Reagent-Free Ion Chromatography. 2005.
8. U.S. EPA Method 314.1. Determination of Perchlorate in Drinking Water Using In-Line Column Concentration/Matrix Elimination IC with Suppressed Conductivity Detection. 2005.
9. Dionex Corporation. Application Note 1789: Improved Determination of Trace Concentrations of Perchlorate in Drinking Water Using Preconcentration with Two-Dimensional Ion Chromatography. 2006.