Degradation products of Tenax TA formed during sampling and thermal desorption analysis: Indicators of reactive species indoors

Analyses of indoor air samples of semivolatile organic compounds (SVOCs) from five offices in two office buildings, a school class room, and a room in a day-care center were generally strongly influenced by artifact formation. In the laboratory, the major artifacts could be produced by sampling mixtures of O-3, NO2, and limonene in air on the sorbent, Tenax TA. Several SVOCs from O-3 degradation of Tenax TA were detected, but only few were identified. The NO2 degradation of Tenax TA analyzed by thermal desorption and gas chromatography (TD-GC) almost exclusively formed 2,6-diphenyl-p-benzoquinone (DPQ) and 2,6-diphenyl-p-hydroquinone (DPHQ). The NO2/Tenax TA reaction could be calibrated, thus the NO2 concentration could be determined simultaneously with a SVOC measurement. However, the results indicated that DPQ may be reduced to DPHQ during TD-GC analysis by oxidation of other compounds adsorbed to Tenax TA. Sampling an air mixture of O-2 in excess of limonene on Tenax TA followed by TD-GC analysis exclusively produced DPHQ. O-3 alone produced neither DPQ nor DPHQ. It was found that reactive species (possibly Criegee biradicals and/or other organic radicals) from the O-3/limonene reaction were responsible for the production of DPHQ from Tenax TA. The results indicated that Tenax TA can be used as a trapping agent for some radicals by analysis of the DPQ/DPHQ formation. The present data were not sufficient to obtain evidence for degradation of Tenax TA by other radicals than NO and NO, in indoor SVOC samples. However, the DPQ/DPHQ ratio indicated that DPHQ has been formed from DPQ by oxidation of other adsorbed compounds in some of the samples. Copyright (C) 1996 Elsevier Science Ltd.