Determination of perchlorate in environmental waters using a compact ion chromatography system coupled with a single quadrupole mass spectrometer

Importance of the topic

Perchlorate is an emerging contaminant in environmental waters due to its historic use as a propellant oxidizer. It disrupts thyroid function and poses a potential carcinogenic risk. Regulatory agencies and several U.S. states have set advisory or enforceable limits in drinking water at low µg/L levels. Reliable, sensitive detection methods are vital for public health protection and compliance with evolving standards.

Objectives and study overview

This study presents a reference method for trace perchlorate quantification in drinking water, surface water, and groundwater. It combines high-pressure ion chromatography (HPIC) on a Dionex IonPac AS20 column with a compact ISQ EC single-quadrupole mass spectrometer. The goal is to achieve low-ng/L detection in matrices containing high levels of chloride, carbonate, and sulfate, while providing confident peak identification.

Methodology and instrumentation

The analytical system comprises a Thermo Scientific Dionex Integrion HPIC with KOH eluent generated in situ, suppressed conductivity detection via an AERS 500e suppressor in external water mode, and an auxiliary pump for eluent delivery to the mass spectrometer. A six-port matrix diversion valve directs early eluting matrix ions to waste, protecting the MS interface. The ISQ EC MS uses electrospray ionization in negative mode without added organic modifiers. Key parameters include 55 mM KOH at 0.3 mL/min, a 30 °C column oven, 20 °C detector compartment, and a 14 min run time with 100 µL injections. Mass detection employs selected ion monitoring at m/z 99 and 101 for native perchlorate and m/z 107 for an 18O-labeled internal standard.

Main results and discussion

Perchlorate is fully resolved from common anions (Cl–, SO4 2–, CO3 2–) on the AS20 column. In a laboratory synthetic matrix (1000 mg/L each of chloride, carbonate, sulfate), the MS method achieved limits of detection between 20 and 60 ng/L. Calibration curves (125–5000 ng/L) showed excellent linearity (R2 ≥ 0.9993) for both internal and external standard approaches. Over 100 sequential injections, raw peak areas varied by less than ±6%, and concentration recoveries remained within 96–120%, demonstrating method robustness in high-ionic-strength samples.

Benefits and practical applications

This IC-MS protocol surpasses conductivity detection in sensitivity and selectivity, enabling perchlorate measurement at sub-µg/L levels without laborious sample cleanup or organic solvent addition. The 18O-labeled internal standard corrects for matrix effects and instrumental drift, facilitating reliable quantification in routine monitoring, regulatory compliance testing, and quality control in water utilities and environmental laboratories.

Future trends and potential applications

Advances may include adaptation to soil and wastewater matrices under ISO guidelines, integration with high-resolution mass spectrometry for multi-residue profiling, and miniaturized chromatography systems. Automation of sample preparation, enhanced source designs for greater ionization efficiency, and broader adoption of isotopic internal standards will further improve throughput and data quality.

Conclusion

The described compact HPIC-MS approach with matrix diversion and 18O internal standard offers a sensitive, selective, and robust solution for perchlorate analysis in complex water matrices. It meets stringent detection requirements, simplifies workflow by eliminating organic modifiers, and aligns with regulatory and ISO methods for environmental monitoring.

References

1. ISO 19340 Water Quality – Determination of Dissolved Perchlorate by Ion Chromatography, 2017.
2. ISO/DIS 20295 Soil Quality – Determination of Perchlorate in Soil by Ion Chromatography, 2016.
3. Thermo Fisher Scientific, Application Note 1513: Determination of Perchlorate in Environmental Waters by IC-ESI-MS, 2017.
4. Dean JA, Lange’s Handbook of Chemistry, 15th Ed., McGraw-Hill, 1999.
5. Thermo Fisher Scientific Product Manual for Dionex Eluent Generator Cartridges, Doc. 065018 Rev.05, 2014.
6. Thermo Fisher Scientific Product Manual for Continuously Regenerated Trap Columns (CR-TC), Doc. 031910, 2010.
7. Thermo Fisher Scientific Product Manual for Dionex ERS 500 Suppressor, Doc. 031956 Rev.11, 2017.
8. Thermo Fisher Scientific ISQ EC Mass Spectrometer Operating Manual, Doc. 1R120591-0002 Rev.A, 2017.
9. U.S. EPA Method 332: Determination of Perchlorate in Drinking Water by IC-Suppressed Conductivity and ESI-MS, Rev.1.0, 2005.