Analysis of Volatile Hazardous Air Pollutants and Ozone Precursors Using the Cryofocusing GC-MS/MS (MRM) Method

Significance of the topic

Environmental monitoring of volatile organic compounds is critical for understanding health risks and tracing sources of photochemical ozone and fine particulate matter Formation of ground level ozone and PM2 5 is driven by reactive organic species Ozone precursors and hazardous air pollutants require robust multi component analysis in ambient air

Objectives and overview

This study developed a simultaneous analysis method based on cryofocusing GC MS MS using multiple reaction monitoring MRM for a total of ninety six compounds comprising fifty one volatile hazardous air pollutants and fifty five ozone precursor species Ten compounds belong to both categories The method was applied to residential roadside and industrial boundary site samples to assess detection performance and selectivity

Methodology and instrumentation

Sample collection involved canister based sampling of humidified nitrogen spiked with standard mixtures and ambient air samples at multiple locations Standard calibration used diluted HAPS and PAMS source gases and internal standards in pressurized canisters Key analytical steps were cryofocusing preconcentration GC separation and triple quad MS MS detection under various resolution and acquisition modes The main conditions were

• Canister preconcentrator CC2100 with two stage cold traps and cryocooling
• Gas chromatograph GCMS TQ8040 coupled to triple quadrupole mass spectrometer
• InertCap 624 capillary column 60 m 0 25 mm id 1 4 um coating
• Cryofocus at minus 185 degrees for sharp peak shapes
• Measurement modes compared SIM single ion monitoring MRM and pseudo MRM at high unit and low resolution settings

Key results and discussion

MRM provided superior selectivity and lower detection limits than SIM and pseudo MRM despite SIM exhibiting higher ion current Calibration slopes and signal to noise comparisons showed MRM at unit unit resolution most effectively reduced interference but at the expense of sensitivity MRM at unit low resolution offered a compromise Detectability ranking across five sample types was MRM low low MRM unit low SIM unit SIM high pseudo MRM modes varied in performance Evaluation of chromatograms identified specific transitions suffering baseline drift or coelution suggesting the need for transition refinement and optimized collision energies

Benefits and practical applications

The cryofocusing GC MS MS MRM method allows simultaneous quantitation of a wide range of volatile pollutants at sub ppb levels with enhanced confidence in complex matrices Improved selectivity reduces false positives and lowers method detection limits making it suited for regulatory monitoring research into ozone formation and air quality management

Instrumentation used

• Canister preconcentrator CC2100 series GL Sciences
• GC MS MS system GCMS TQ8040 Shimadzu
• InertCap 624 capillary column 6 cyanophenyl 94 methyl polysiloxane
• Helium carrier gas at constant flow and programmable pressure
• Argon collision gas with optimized collision energies

Future trends and potential applications

Further enhancements may include dynamic transition optimization to avoid baseline artifacts adaptive smoothing algorithms and automated MS parameter tuning Advancements in fast GC MS MS and portable cryogenic preconcentration devices may extend applications to real time field monitoring and comprehensive urban air quality mapping Integration with high resolution time of flight MS and two dimensional GC could broaden compound coverage and structural elucidation in complex environments

Conclusion

The study demonstrates that cryofocusing GC MS MS MRM offers a practical and sensitive platform for multi component analysis of volatile hazardous air pollutants and ozone precursors Optimal resolution settings vary by target concentration and matrix complexity The method achieves lower detection limits and higher selectivity compared to conventional SIM and pseudo MRM modes Future work should address transition adjustments and data processing refinements to further improve quantitation accuracy

Reference

• Ministry of the Environment Japan List of Hazardous Air Pollutants 2019
• Schulte H J and Shimadzu Application Note Fast GC MS MS analysis of 76 VOC compounds using headspace trap sampling
• Shimadzu Technical Bulletin Cryofocusing GC MS analysis of volatile organics Application Note 2018