Determination of Perchlorate in Drinking Water using Suppressed Anion Chromatography Coupled with Single Quadrupole MS

Importance of the Topic

Perchlorate is a persistent environmental contaminant capable of disrupting thyroid hormone production by inhibiting iodide uptake. Although no federal drinking water standard exists yet, several states have imposed maximum contaminant levels for perchlorate. Sensitive and selective analytical methods are essential to detect trace levels of perchlorate in drinking water and to ensure public health protection and regulatory compliance.

Goals and Overview of the Study

This study presents the development and validation of an anion chromatography–mass spectrometry (IC-MS) method using a novel electrolytically regenerated suppressor in a modular IC system coupled to a single quadrupole LCMS-2020. The aim was to achieve high sensitivity and selectivity for perchlorate determination at sub‐ppb concentrations in drinking water matrices.

Methodology and Instrumentation

An IC system with an electrolytically regenerated anion suppressor provided a stable, low-noise background for conductivity detection. A three‐pump arrangement delivered (1) the sample eluent, (2) suppressor regeneration flow, and (3) an acetonitrile post-suppressor stream to enhance MS response. A conductivity detector monitored all anions; a diverter valve directed only the perchlorate fraction to the MS, preventing salt buildup. The LCMS-2020 single quadrupole with electrospray ionization operated in selected ion monitoring (SIM) mode for m/z 99 and 101. Calibration was performed over 0.25–20 ppb perchlorate.

Used Instrumentation

• Shimadzu Prominence IC system with built-in electrolytic anion suppressor
• LCMS-2020 single quadrupole mass spectrometer with ESI interface
• Conductivity detector (CDD)
• Three-pump configuration for eluent delivery, suppressor regeneration, and post-suppressor acetonitrile flow
• Diverter valve for selective MS introduction

Main Results and Discussion

A five-point calibration yielded correlation coefficients (r2) above 0.9999 for both m/z 99 and 101 ions, with quantitative accuracy between 93.8% and 102.3%. The method detection limit was determined to be 0.05 ppb. Precision tests at 0.5 and 1 ppb showed retention time RSDs below 0.1% and peak area RSDs below 2.6%. Spike recovery experiments produced 96% recovery at 2 ppb and 99.3% at 10 ppb. Analysis of laboratory tap water detected 0.315 ppb perchlorate, with an area count ratio of m/z 99 to 101 equal to 2.74, confirming compound identity.

Contributions and Practical Applications of the Method

This IC-MS approach enables reliable quantification of perchlorate at trace levels, well below state regulatory limits. The selective eluent diversion protects the MS from high salt loads, reducing maintenance and downtime. The method is well suited for routine drinking water monitoring laboratories seeking to meet stringent quality assurance and quality control requirements.

Future Trends and Opportunities

• Integration with high-resolution mass spectrometry for enhanced selectivity and multi-analyte screening
• Miniaturized and portable IC-MS platforms for on-site water quality testing
• Automation of sample preparation and system calibration for higher throughput
• Coupling with ion mobility spectrometry to resolve complex anion mixtures
• Development of multi-residue methods targeting emerging water contaminants alongside perchlorate

Conclusion

The combination of a modular IC system with an electrolytically regenerated suppressor and LCMS-2020 single quadrupole MS delivers outstanding sensitivity, selectivity, and reproducibility for perchlorate determination in drinking water. The method meets or exceeds EPA 332.0 criteria for detection limit, precision, and accuracy, representing a robust solution for regulatory compliance and public health protection.

Reference

• EPA Method 332.0. U.S. Environmental Protection Agency.
• Guo H., Marfil-Vega R., Kuhn E. Determination of Perchlorate in Drinking Water using Suppressed Anion Chromatography Coupled with Single Quadrupole MS. Shimadzu Scientific Instruments, Inc.