RAPID ANALYSIS OF ORGANOCHLORINE COMPOUNDS IN WATER USING AUTOMATED SIFT-MS

Importance of topic

Organochlorine volatile organic compounds (VOCs) such as chloroform, trichloroethylene (TCE) and tetrachloroethylene (PCE) continue to pose environmental and health risks due to their persistence in water sources. Routine, high-throughput analysis at trace levels is critical for regulatory compliance, contamination monitoring and safeguarding public health.

Study objectives and overview

This application note presents a streamlined workflow using automated selected ion flow tube mass spectrometry (SIFT-MS) for direct headspace analysis of chlorinated VOCs in water. The main goals are to demonstrate linear quantification from 2 to 100 ppb, to assess method repeatability, and to compare throughput with conventional purge-and-trap gas chromatography methods.

Methodology and instrumentation

Standard preparation involved diluting a 1 000 ppm methanol stock to yield aqueous solutions from 2 to 100 ppb. Samples were incubated at 60 °C for 15 minutes in 20 mL headspace vials. Headspace was withdrawn with a 2.5 mL syringe heated to 150 °C at a fill speed of 200 µL/s and injected at 50 µL/s (total 420 µL/s with makeup nitrogen).
Instrumentation:

• Voice200Ultra SIFT-MS system equipped with eight reagent ions (H3O+, NO+, O2+, O–, OH–, O2–, NO2–, NO3–)
• GERSTEL MPS2 autosampler with Maestro software controlling incubation, injection and syringe flushing
• LabSyft software Method Editor for selected ion mode acquisition

Main results and discussion

Linearity studies across seven concentration levels showed excellent correlation for all three analytes, confirming reliable quantification down to low parts-per-billion. Six replicate injections at 50 ppb yielded relative standard deviations of 3.3% for chloroform, 1.8% for TCE and 1.5% for PCE, reflecting high precision. Continuous injection every 3.8 seconds enabled analysis of at least 12 samples per hour, a threefold improvement over purge-and-trap GC-MS while maintaining comparable sensitivity.

Benefits and practical applications

The automated SIFT-MS headspace approach eliminates sample pre-concentration and moisture removal, reducing analysis time and complexity. High throughput, low detection limits and robust performance under humid conditions make this method suitable for environmental monitoring, drinking water QA/QC and rapid field screening applications.

Future trends and potential uses

Integration of advanced automation, inline sample preparation and expanded reagent ion libraries may further enhance selectivity and throughput. Combining SIFT-MS with chemometric tools could enable multi-analyte fingerprinting for comprehensive water quality profiling. Portable SIFT-MS platforms may support on-site, real-time monitoring of chlorinated VOCs and other emerging contaminants.

Conclusion

Automated SIFT-MS direct headspace analysis delivers sensitive, precise and linear quantification of chlorinated VOCs in water, with significantly higher sample throughput compared to conventional GC-based methods. The technique’s robustness to humidity and minimal sample preparation make it a powerful tool for environmental and water quality laboratories.

References

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2. Smith D, Spanel P. Selected ion flow tube mass spectrometry (SIFT-MS) for on-line trace gas analysis. Mass Spectrom Rev. 2005;24:661.
3. Prince BJ, Milligan DB, McEwan MJ. Application of SIFT-MS to real-time atmospheric monitoring. Rapid Commun Mass Spectrom. 2010;24:1763.
4. Langford VS, Graves I, McEwan MJ. Rapid monitoring of volatile organic compounds: a comparison between gas chromatography/mass spectrometry and SIFT-MS. Rapid Commun Mass Spectrom. 2014;28:10.