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

Importance of the Topic

A reliable and sensitive method for detecting perchlorate in environmental waters is critical due to its widespread use in rocket propellants, munitions, and fireworks and its potential to disrupt thyroid function. Regulatory agencies have set strict limits for perchlorate in drinking water, driving the need for robust analytical tools capable of trace-level quantification in complex matrices.

Objectives and Study Overview

This work presents an ion chromatography–mass spectrometry (IC-MS) approach for perchlorate determination in environmental water samples. The method employs inline matrix diversion to protect the electrospray interface from high ionic strength streams and uses a stable-labeled internal standard to ensure accurate quantification.

Methodology and Instrumentation

The analysis utilizes a Dionex IonPac AS16 column (2 × 250 mm) with eluent generation of 45 mM KOH at 0.3 mL/min and a suppressor current of 70 mA at 28 °C. A Rheodyne diversion valve directs early-eluting salts to waste; after conductivity falls below 1.5 µS, the stream is sent to an ESI-MS detector. The MSQ mass spectrometer operates in negative-ion electrospray mode with SIM channels at 99, 101, and 107 m/z. Cone voltage is set to 70 V, source voltage to –3 kV, and probe temperature to 450 °C. A Dionex AXP-MS auxiliary pump delivers 50/50 acetonitrile/water post-suppressor via a static mixer to enhance ionization.

Main Results and Discussion

Calibration over 125–5000 ng/L perchlorate in a 1000 mg/L chloride–carbonate–sulfate matrix exhibits excellent linearity (R2 > 0.998 at both 99 and 101 m/z). Method detection limits in pure water are 15–30 ng/L. Seven replicates of 500 ng/L perchlorate spiked into the high-salt matrix yielded average recoveries of 98% at 99 m/z (RSD 5.2%) and 100% at 101 m/z (RSD 9.9%). A sequence of 100 injections demonstrated stable recoveries above 95% and consistent raw area counts, confirming reproducibility and robustness.

Benefits and Practical Applications

• Inline matrix diversion removes harsh salts before MS detection, extending probe life and reducing maintenance.
• Use of a stable-labeled 18O-perchlorate internal standard compensates for sample preparation and instrument variability, enabling precise quantification.
• Electrospray-MS detection provides higher selectivity and lower detection limits in complex environmental matrices compared to conductivity detection.
• The reagent-free IC system simplifies operation by generating eluent and suppressor regeneration without manual reagent preparation.

Future Trends and Applications

Advances may include coupling IC to high-resolution or tandem mass spectrometers for simultaneous multi-analyte screening, miniaturized field-deployable systems for on-site monitoring, and integration with automated sample preparation. Expansion of isotope-dilution strategies and data-processing algorithms will further enhance accuracy and throughput for routine environmental surveillance.

Conclusion

The described IC-MS method delivers a sensitive, selective, and reproducible approach for trace perchlorate analysis in challenging environmental water matrices. Inline matrix diversion and isotope dilution ensure robust performance that meets regulatory requirements and supports routine monitoring in water quality laboratories.

References

1. California Department of Health Services. Perchlorate Action Level in Drinking Water; 1997.
2. Thermo Fisher Scientific. Determination of Low Concentrations of Perchlorate in Drinking and Ground Waters Using Ion Chromatography; Application Note 134.
3. Thermo Fisher Scientific. Determination of Perchlorate in Drinking Water by Ion Chromatography; Application Update 145.
4. Thermo Fisher Scientific. Determination of Perchlorate in Drinking Water Using Reagent-Free Ion Chromatography; Application Update 148.
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; 2002.