TO-15 65 Component Mix on Rxi®-5Sil MS (30 m)

Importance of GC-MS Analysis for Volatile Organic Compounds

This application note outlines a robust approach for the simultaneous determination of 65 volatile organic compounds (VOCs) using EPA Method TO-15 on a capillary GC–MS system. Accurate measurement of VOCs is critical for environmental monitoring, workplace air quality assessment, and compliance with regulatory standards.

Study Objectives and Overview

The main goal was to separate and detect a complex mixture of 65 target analytes spanning light hydrocarbons, chlorinated solvents, ketones, aromatics, and halogenated compounds in a single run. A preconcentration step was incorporated to enhance sensitivity for trace-level quantitation (~10 ppbv).

Methodology and Used Instrumentation

The analysis employed direct injection of a gas sample onto a Nutech 8900DS preconcentrator with a dual-sorbent trap (glass beads and Tenax®) cryofocused at –160 °C. Desorption at 190 °C transferred analytes into the GC inlet.

• GC Column: Rxi®-5Sil MS, 30 m × 0.32 mm ID, 1.0 μm film thickness
• Oven Program: 32 °C (1 min), ramp to 150 °C at 9 °C/min, then to 230 °C at 33 °C/min
• Carrier Gas: Helium at 1.5 mL/min (constant flow)
• Mass Spectrometer: Agilent 5973 MSD in full–scan EI mode (35–250 amu) at 3.32 scans/s, 69.9 eV electron energy

Results and Discussion

Chromatographic separation achieved baseline resolution for most compounds within a 14.9 min run. Early eluters such as propylene and chloromethane appeared within 2 min, while late eluters like naphthalene and hexachlorobutadiene eluted near 15 min. Coelutions were minimal; a notable case involved 2-butanone and hexane sharing m/z 43, which was resolved by retention time. The method demonstrated reproducible retention times (±0.05 min) and clear mass spectral identification across all 65 targets.

Practical Benefits and Applications

• High throughput: single injection for comprehensive VOC profiling
• Low detection limits: sub-ppbv sensitivity via cryofocusing and preconcentration
• Versatility: applicable to ambient air, soil gas, and indoor air quality studies
• Regulatory compliance: meets EPA TO-15 performance criteria

Future Trends and Possibilities

Advances in multidimensional GC, higher-sensitivity MS detectors, and automated sampling will further improve detection limits and isomer resolution. Coupling with real-time data analytics and portable GC-MS units can enable on-site monitoring with immediate feedback.

Conclusion

This method demonstrates reliable, high-resolution analysis of a broad spectrum of VOCs in a single GC–MS run. The integration of efficient preconcentration, precise temperature programming, and mass spectral detection ensures accurate quantitation for environmental and industrial applications.