Trace Level Detection of Selected VOCs in Air

As a high speed, portable GC-MS, the new Tridion-9 from Quantitech (UK) has been developed for a wide variety of applications including the onsite analysis of trace levels of volatile organic compounds. Quantitech’s Dr Andrew Hobson says: “The ability to conduct trace level analysis in the field is a major advantage because it avoids the problems and costs associated with the collection and transport of gaseous samples for laboratory analysis.

“Typical applications for this technology include occupational safety, environmental monitoring, process monitoring and research.”

SPME (Solid Phase Micro Extraction) provides a simple, low cost methodology to collect and introduce multiple samples to an analytical instrument.

To highlight the detection capabilities of the Tridion-9 and SPME for a number of analytes at approximately 1 part per billion (ppb) v/v in air, a 10 litre Tedlar bag was spiked with a mixture of VOCs and then a dilution was made to generate a known vapour concentration for the analytes. Concentrations were corrected for atmospheric pressure and temperature using US EPA method 10-2.4. The analytes were extracted from the gas phase at ambient temperature for 60 min using a Custodion SPME syringe with a 65µm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre. Following sample extraction, the SPME syringe was inserted into the TRIDION-9 injection port for analysis.

The data from this experiment showed trace levels of contaminants that are common in sample bags; N,N-Dimethylacetamide and Phenol. However, the target compounds were automatically identified by deconvolution software in the presence of these large interfering compounds. Peaks that chromatographically co-elute are separately identified by target ions in their mass spectrum and peak shape.

This simple experiment demonstrates that the Custodion SPME syringe and Tridion-9 GC-TMS are uniquely suited for rapid onsite analysis.