A Modular Gas Chromatograph for Vocus PTR-ToF-MS: Development and Applications

The recent development of the Vocus Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (Vocus PTR-ToF) offers continuous real-time sampling and unparalleled sensitivity for the detection of gas-phase volatile organic compounds (VOCs). However, known limitations of analysis by ToF-MS are the inability to resolve isomers and often ambiguous identification of detected ions. By incorporating gas chromatography (GC) with ToF-MS systems an additional degree of separation is provided that can solve both limitations. The further development of a thermal desorption preconcentration systems for the GC, makes this technology appropriate for a wide range of environmental applications.

Here, we present recent developments of a modular GC (mod-GC) which has been successfully coupled to both a Vocus PTR-ToF and an EI-ToF-MS separately and as a dual-detector system. Instrument design and characterization (including detection limits and sensitivities), method development, and advances in the data analysis will be discussed using examples from the recent ATHLETIC indoor air campaign at CU-Boulder along with laboratory data that demonstrates the use of this system for the detection and quantification of atmospherically relevant compounds.

These examples will demonstrate how the GC analysis can be used to generate stand-alone data, and provide insight and clarity to results from continuous, on-line Vocus analysis. We will also present initial results applying the mod-GC as an in-situ system for the routine analysis of hazardous air pollutants, such as polycyclic aromatic hydrocarbons, and other atmospherically relevant compounds known to impact both ozone and aerosol production.