Determination of perchlorate by U.S. EPA Method 332.0 using a compact ion chromatography system coupled with mass spectrometry

Significance of the Topic

Perchlorate contamination in water supplies is an emerging public health issue due to its disruption of thyroid function and potential carcinogenicity. Federal and state agencies are implementing guidelines to monitor trace levels below microgram-per-liter concentrations.

Objectives and Study Overview

This study evaluates a compact ion chromatography system coupled with a single quadrupole mass spectrometer to comply with U.S. EPA Method 332.0 for perchlorate determination in raw and finished drinking waters. It extends previous work by rigorously validating system performance against regulatory quality criteria.

Methodology

Samples were spiked with an 18O-enriched perchlorate internal standard and injected onto an IonPac AS20 column with in situ KOH eluent generation. The suppressor removed counterions prior to detection. The mass spectrometer operated in negative electrospray ionization and selected ion monitoring of m/z 99, 101, and 107. Calibration, limits of detection and quantification, matrix effects, and robustness were assessed according to EPA 332.0 QC requirements including blanks, mid-level checks, fortified blanks, duplicates, and matrix spike recoveries.

Instrumentation used

• Dionex Integrion HPIC system with EGC 500 KOH eluent generator and CR-ATC 600 trap column
• Dionex AS20 analytical column and Dionex AERS 500e suppressor in external water mode
• Dionex AS-AP autosampler and AXP auxiliary pump
• Thermo Scientific ISQ EC single quadrupole mass spectrometer with HESI-II source
• Peak Scientific Genius 1022 nitrogen generator
• Chromeleon CDS data system

Major Results and Discussion

The method achieved a method detection limit of 26.9 ng/L and a lowest concentration minimum reporting level of 125 ng/L. Calibration was linear (r² = 0.9997) and quadratic (r² = 1.0000) over 125–5000 ng/L, with recoveries of 96–105%. Precision in drinking water and high-ionic matrices was <5% R.S.D. at >MRL levels. Matrix interferences in synthetic waters up to 1000 mg/L chloride, sulfate, carbonate were controlled, and cleanup cartridges restored confirmation ion ratios. Tap and bottled water samples spiked at 200 ng/L and 1000 ng/L yielded recoveries of 100–111%.

Benefits and Practical Applications

• Automated eluent generation eliminates manual errors and enhances reproducibility
• No organic modifiers required for ESI, simplifying operation
• Comprehensive compliance with EPA Method 332.0 QC criteria
• High sensitivity suitable for regulatory monitoring and QA/QC in environmental laboratories

Future Trends and Potential Applications

• Integration of multi-analyte IC-MS workflows for broader anion screening
• Development of field-deployable compact IC-MS instruments
• Advancements in ion suppression and ionization to further lower detection limits
• Application of machine learning for rapid data review and anomaly detection

Conclusion

The combination of the Dionex Integrion HPIC system and ISQ EC mass spectrometer meets all performance criteria of EPA Method 332.0, delivering robust, sensitive, and accurate perchlorate analysis in diverse drinking water matrices. This platform supports laboratories in achieving reliable trace-level determinations with streamlined workflows.

References

1. U.S. Environmental Protection Agency. Method 332.0: Determination of Perchlorate in Drinking Water by IC-MS. Rev. 1.0, 2005.
2. Thermo Fisher Scientific. Application Update 72507: Perchlorate Analysis by Compact IC-MS. 2017.
3. Dean, J.A., Ed. Lange’s Handbook of Chemistry. 15th Ed.; McGraw-Hill, 1999.
4. Thermo Fisher Scientific. Product Manuals for Dionex Eluent Generator Cartridges, Trap Columns, AERS Suppressor, and ISQ EC MS. 2010–2017.