An in situ gas chromatograph with automatic detector switching between PTR- and EI-TOF-MS: isomer-resolved measurements of indoor air

Abstract. We have developed a field-deployable gas chromatograph (GC) with thermal desorption preconcentration (TDPC), which is demonstrated here automatic detector switching between two high-resolution time-of-flight mass spectrometers (TOF-MSs) for in situ measurements of volatile organic compounds (VOCs). This system provides many analytical advances, including acquisition fast time–response data tandem molecular speciation and types spectral information each resolved GC peak: ion identification from Vocus proton transfer reaction (PTR) TOF-MS fragmentation pattern electron ionization (EI) detection. was deployed during the 2018 ATHLETIC campaign at University Colorado Dal Ward Athletic Center Boulder, Colorado, where it used to characterize VOC emissions indoor environment. The addition TDPC-GC increased sensitivity by factor 50 due over 6 min sample time versus direct air sampling Vocus, operated resolution 1 Hz. GC-TOF methods average limits detection 1.6 ppt across range monoterpenes aromatics. Here, we describe method use two-detector conclusively identify VOCs hydrocarbons, oxygenates, halocarbons, along detailed results quantification anthropogenic monoterpenes, limonene accounted 47 %–80 % monoterpene composition. also report dimethylsilanediol (DMSD), an organosiloxane degradation product, observed dynamic temporal behavior distinct organosiloxanes (e.g., decamethylcyclopentasiloxane, D5 siloxane). Our suggest DMSD produced humidity-dependent heterogeneous reactions occurring on surfaces environment, rather than formed through gas-phase oxidation siloxanes.