Determination of Perchlorate in Environmental Waters by Ion Chromatography Coupled with Electrospray Mass Spectrometry (IC-MS)

Significance of the Topic

Perchlorate is a persistent inorganic contaminant widely used as an oxidizer in rockets, munitions and fireworks. Its presence in environmental water poses health risks, notably thyroid dysfunction, prompting regulatory limits as low as 1 ppb in drinking water and action levels at 6 ppb in California.

Study Objectives and Overview

This application note outlines the development and validation of an ion chromatography–mass spectrometry (IC-MS) method for trace‐level determination of perchlorate in high‐ionic‐strength environmental waters. Key goals include inline matrix diversion, utilization of a stable-labeled internal standard, and comparison of quantification using 99 and 101 m/z channels.

Materials and Methods

Sample pretreatment is minimized by employing a rear-loading PEEK matrix diversion valve to direct high‐salt fractions to waste. A stable‐labeled 18O-perchlorate internal standard (107 m/z) is added to each sample to compensate for matrix and instrumental variations. Chromatographic separation is achieved on a Dionex IonPac AS16 column (2×250 mm) with a 45 mM KOH eluent at 0.3 mL/min and 28 °C. Suppression is performed by an ASRS ULTRA II 2 mm device operated at 70 mA. Detection is carried out by a Thermo Scientific MSQ mass spectrometer in negative electrospray mode, monitoring SIM channels at 99, 101 and 107 m/z with 0.3 amu span and 1 s dwell time.

Instrumentation Used

• Thermo Scientific Dionex ICS-2500 Ion Chromatography system (GS50 pump, EG50 eluent generator, CD25A conductivity detector, LC30 oven, AS50 autosampler)
• MSQ Enhanced Low‐Mass Option Mass Spectrometer with ESI interface
• Dionex CR-ATC continuously regenerated anion trap and Chromeleon CDS software v6.5
• Auxiliary PEEK matrix diversion valve (Rheodyne 9126) and static mixing tee for acetonitrile/water makeup
• Nitrogen gas supply for electrospray ionization

Main Results and Discussion

The method demonstrated linear calibration from 125 to 5000 ng/L perchlorate in a 1000 mg/L salt matrix (chloride, carbonate, sulfate) with R² > 0.998 at both 99 and 101 m/z. Method detection limits (MDL) in deionized water were 15–30 ng/L; in the salt matrix, MDL was 80 ng/L at 99 m/z and 155 ng/L at 101 m/z. Recoveries for 500 ng/L perchlorate averaged 98–100% across seven replicates (RSD < 10%). A sequence of 100 injections showed consistent area counts (> 75%) and internal standard–corrected recoveries (> 95%), highlighting robustness.

Benefits and Practical Applications

• High selectivity and sensitivity in complex matrices
• No offline sample preparation required
• Quantification well below regulatory limits
• Stable isotope internal standard ensures accuracy and precision
• Automated inline matrix diversion improves throughput

Future Trends and Opportunities

Advances may include coupling IC with high‐resolution and tandem mass spectrometry for enhanced specificity, expanded multi‐anion screening, miniaturized column formats for reduced solvent use, automated online sample cleanup and real‐time field monitoring via portable IC-MS platforms.

Conclusion

The described IC-MS method offers a rapid, robust and sensitive approach for trace perchlorate analysis in environmental waters, combining inline matrix diversion and stable-labeled internal standard quantification to meet stringent regulatory requirements.

References

1. California Department of Health Services. Determination of perchlorate in drinking water, 1997.
2. Thermo Fisher Scientific. Application Note 134: Determination of Low Concentrations of Perchlorate in Drinking and Ground Waters by Ion Chromatography.
3. Thermo Fisher Scientific. Application Update 145: Determination of Perchlorate in Drinking Water by Ion Chromatography.
4. Thermo Fisher Scientific. Application Update 148: Reagent-Free Ion Chromatography for Perchlorate in Water.
5. Roehl R, Slingsby R, Avdalovic N, Jackson PE. J Chromatogr A. 2002;956:245–254.
6. Thermo Fisher Scientific. Dionex Reference Library CD-ROM, August 2002.