TO-15 65 Component Mix on Rxi®-1ms (60 m)

Significance of the topic

The reliable detection and quantification of volatile organic compounds (VOCs) at trace levels is critical for environmental monitoring, indoor air quality assessment and regulatory compliance. The TO-15 methodology, widely adopted for ambient air analysis, covers dozens of compounds that range from light hydrocarbons to chlorinated solvents and oxygenates. Achieving complete separation and low detection limits requires optimized thermal desorption, cryofocusing and high-resolution gas chromatography-mass spectrometry workflows.

Study objectives and overview

This work demonstrates a robust method for analyzing a 65-component TO-15 gas standard using a 60 m Rxi-1ms column coupled to a quadrupole GC-MS. The goal was to establish retention times, separation quality and instrument settings that ensure reproducible trace-level performance for all target analytes, including isomeric and coeluting species.

Methodology and Instrumentation

• Column: Rxi-1ms, 60 m × 0.32 mm ID, 1.00 µm film.
• Sample introduction: Direct thermal desorption of 400 mL gas at 10 ppbv using a Nutech 8900DS preconcentrator with Siltek®-treated glass bead traps and Tenax® GR trap.
• Cryofocusing: Dual-stage cryogenic cooling to –160 °C then –155 °C, inject time 140 s.
• GC oven program: 32 °C (1 min) to 150 °C @ 5 °C/min, then to 230 °C @ 15 °C/min.
• Carrier gas: Helium at 1.2 mL/min (constant flow).
• Detector: Agilent 6890 GC with 5973 MSD in EI scan mode (35–250 amu, 3.32 scans/s).
• Instrument temperatures: Transfer line 230 °C, source 230 °C, quadrupole 150 °C.

Main results and discussion

The method achieved baseline separation for the majority of the 65 analytes within a 27 min window. Retention times ranged from 3.96 min (1,1-Difluoroethane) to 28.47 min (Hexachlorobutadiene). Pairs such as methyl tert-butyl ether/propylene oxide and certain isomers share diagnostic ions and require careful deconvolution. The long, low-bleed Rxi-1ms stationary phase provided sharp peaks and minimized interferences, while cryofocusing enhanced the signal-to-noise ratio for early eluters.

Benefits and practical applications

• Comprehensive coverage: Monitors light hydrocarbons, halogenated solvents, oxygenates and aromatics in a single run.
• Regulatory compliance: Meets USEPA TO-15 criteria for ambient and indoor air testing.
• High sensitivity: Detection limits in the low pptv–ppbv range due to efficient preconcentration and cryofocusing.
• Reproducibility: Consistent retention times and peak shapes enable routine QA/QC and method validation.

Future trends and potential uses

Advancements in stationary phase chemistry, ultra-fast GC protocols and high-resolution mass analyzers will further reduce run times and improve isomer resolution. Integration with automated sampling systems and data analytics, including machine learning–based deconvolution, could streamline large-scale air monitoring programs and enable real-time VOC fingerprinting.

Conclusion

This application demonstrates a validated, high-throughput GC-MS approach for 65 regulated VOCs using thermal desorption and a 60 m Rxi-1ms column. The protocol offers robust separation, low detection limits and compliance with standard methods, making it well-suited for environmental and industrial monitoring labs.

Reference

• Restek Application Note: Analysis of TO-15 65 VOC Component Mix on Rxi-1ms Column.