Solid Phase Microextraction of Cyanogen Chloride and Other Volatile Organic Compounds in Drinking Water with Fast Analysis by GC-TOFMS

Importance of the Topic

The monitoring of disinfection by-products such as cyanogen chloride (CNCl) and a broad range of volatile organic compounds (VOCs) in drinking water is critical for ensuring public health and regulatory compliance. Traditional methods like purge-and-trap GC-MS or liquid-liquid extraction can be time-consuming, require large sample volumes, or suffer from sensitivity limitations when dealing with highly water-soluble compounds. A rapid, sensitive, and low-cost alternative is needed to support routine quality control in municipal water systems.

Objectives and Study Overview

This study aimed to develop and validate a solid phase microextraction (SPME) headspace sampling protocol coupled with fast gas chromatography-time of flight mass spectrometry (GC-TOFMS) to quantify cyanogen chloride and a suite of 61 VOCs in drinking water. Las Vegas tap water served as the real-world matrix to demonstrate method performance under field-relevant conditions.

Methodology

The experimental workflow included:

• Sample preparation: 2 mL of spiked or tap water were placed in 4 mL vials with a stir bar, sealed with PTFE-lined caps.
• SPME sampling: Carboxen/PDMS fiber was exposed to the headspace while stirring at ambient temperature for 4 minutes.
• Desorption and separation: Fiber was desorbed in a splitless injector at 250 °C; fast GC employed a 20 m × 0.25 mm × 0.71 µm Rtx-TNT column with helium at 5 mL/min flow.
• Temperature program: −40 °C (0.25 min), ramp 120 °C/min to 80 °C, then 80 °C/min to 220 °C, for a total run time under 3 minutes.
• Quantification: Calibration curves established from 0.2 to 40 ppb, with extended range calibration for high-abundance analytes.

Applied Instrumentation

• SPME fiber and holder: Supelco Carboxen/PDMS, manual holder.
• Gas chromatograph: Agilent 6890N with splitless injector and SPME sleeve.
• Column: 20 m × 0.25 mm × 0.71 µm Rtx-TNT (Restek).
• Mass spectrometer: LECO Pegasus III GC-TOFMS, electron ionization at 70 eV, source at 180 °C, acquisition 40 spectra/sec over 47–350 u.
• Data processing: LECO ChromaTOF software with automated peak finding and deconvolution.

Main Results and Discussion

The optimized SPME GC-TOFMS method achieved:

• Rapid analysis: Separation of 61 VOCs in less than 3 minutes.
• Efficient sampling: Maximum CNCl response at a 4 minute headspace extraction time.
• High sensitivity: Estimated detection limits down to 0.0003 ppb for chloroform and 0.03 ppb for CNCl.
• Robust quantification: Calibration linearity from 0.2 to 40 ppb, employing extended range calibration to avoid detector saturation.
• Field validation: Analysis of 14 Las Vegas tap water replicates showed CNCl at 2.8 ppb (RSD 26 %) and total trihalomethanes averaging 45 ppb (RSD < 20 %).

Benefits and Practical Applications

This SPME GC-TOFMS approach offers multiple advantages for water quality laboratories:

• Minimal sample volume and solvent use, reducing waste and cost.
• Short cycle times increase throughput for routine monitoring.
• High sensitivity and selectivity across a wide VOC range support compliance with stringent guidelines.
• Automated data processing streamlines analysis and reduces operator intervention.

Future Trends and Potential Applications

Emerging directions include integration of thicker-film GC columns to eliminate cryogenic cooling, extension to novel disinfection by-products, and coupling with portable TOFMS platforms for on-site monitoring. Advances in SPME coatings could further improve fiber longevity and analyte coverage.

Conclusion

The developed SPME GC-TOFMS method presents a robust, cost-effective, and high-throughput solution for measuring cyanogen chloride and a wide array of VOCs in drinking water. Its combination of rapid analysis, low detection limits, and minimal sample handling makes it well suited for routine environmental monitoring and regulatory compliance.

References

1. World Health Organization. Guidelines for Drinking-water Quality. Water and Sanitation. http://www.who.int/water_sanitation_health/GDWQ/Chemicals/cyanogenchloridefull.htm#General
2. Cancho, B.; Ventura, F.; Galceran, M.T. Simultaneous determination of cyanogen chloride and cyanogen bromide in treated water at sub-µg/L levels by a new GC-ECD method. Journal of Chromatography A. 897 (2000) 307–315.