TO-15 65 Component Mix on Rxi®-5Sil MS (30 m, 2.0 mL/min)

Significance of the topic

Environmental monitoring and regulatory compliance often require accurate quantification of trace volatile organic compounds in air samples. The US EPA TO-15 method defines a 65-component mixture of common industrial, chlorinated and aromatic VOCs. Reliable separation and detection of these analytes is critical for air quality assessment, indoor air studies and industrial emissions monitoring.

Study objectives and overview

This application note presents the chromatographic performance of a Restek Rxi®-5Sil MS capillary column under TO-15 conditions. It evaluates retention times, peak resolution and operational parameters for the full 65-component VOC mix. The aim is to demonstrate the method’s suitability for routine trace-level analysis and instrument tuning.

Methodology and instrumentation

The study used a HP-6890 gas chromatograph coupled to a 5973 quadrupole mass spectrometer operated in electron impact mode. Key conditions included:

• Column: Rxi-5Sil MS, 30 m × 0.32 mm ID, 1.0 µm film thickness
• Carrier gas: Helium at 2.0 mL/min (constant flow)
• Oven program: 32 °C (1 min hold), 11 °C/min to 150 °C, then 33 °C/min to 230 °C
• Injection: Direct splitless, 200 mL sample (10 ppbv), cryofocusing with Nutech 8900DS trap
• MS parameters: Scan range 35–250 amu, scan rate 3.32 scans/s, ion source 230 °C, quadrupole 150 °C

Main results and discussion

All 65 target analytes eluted between 1.36 min (propylene) and 12.53 min (hexachlorobutadiene). Early eluters were light hydrocarbons and chlorofluorocarbons, mid-range compounds included solvents such as acetone, MTBE and chlorinated methanes, while heavier aromatics and chlorinated benzenes eluted later. The method provided baseline resolution for most critical pairs. Peaks sharing common ions (e.g., m/z 43 for MEK and hexane) were distinguished by retention time. The tuning compounds and internal standards ensured consistent mass calibration and quantitation.

Benefits and practical applications

The demonstrated method offers rapid cycle times and comprehensive VOC coverage in a single run. It supports:

• Ambient and indoor air quality assessments
• Industrial emissions monitoring and leak detection
• QA/QC in environmental analytical laboratories

Future trends and applications

Advances in multidimensional GC and high-resolution MS promise enhanced separation of isomeric VOCs. Automated sampling, portable GC-MS systems and data-driven processing will expand field deployability. Emerging applications include real-time monitoring of urban air and integration with sensor networks for smart environmental management.

Conclusion

The Rxi-5Sil MS column under TO-15 conditions demonstrated robust retention, reproducible peak resolution and efficient analysis of a complex 65-component VOC mixture. This method is well suited for routine environmental monitoring, regulatory compliance and research applications requiring trace-level VOC quantitation.