Wager, PA; Rothweiler, H; Schlatter, C
The results of studies evaluating the use of Porapak-S as a complementary adsorbent to Tenax-TA for sampling volatile organic compounds (VOCs) in nonindustrial indoor environments were summarized. Porapak and Tenax packed sorption tubes conditioned for 24 hours by hexane and dichloromethane extraction and drying under vacuum at 60 degrees-C were spiked with 500 nanograms per microliter n-hexanal (66251), 1,1,1-trichloroethane (71556) (TCE), alpha-pinene (80568), cyclohexane (110827), and propylene-glycol-diacetate (623847) (PGDA). The air sampling volume was 1 or 5 liters. The compounds were desorbed by heating to 150 degrees in the case of Porapak and 280 degrees in the case of Tenax. The desorbates were analyzed by gas chromatography/mass spectrometry. The percentage recoveries of the compounds were determined from the data. Both sorbents were used to monitor VOC concentrations in 11 new and renovated buildings in Switzerland. Recoveries of n-hexanal, TCE, and alpha-pinene from Tenax ranged from 0 to 101.6%. Recovery of these compounds from Porapak varied from 86.0 to 97.4%. Cyclohexane and PGDA were recovered from Porapak in yields of 78.5 to 83.2 and 89.6 to 99.2%, respectively. Representative air monitoring data indicated that n-decane (124185), cyclohexane, benzene (71432), toluene (108883), ethylbenzene (100414), alpha-pinene, ethyl-acetate (141786), n-hexanal, and PGDA were detected in the buildings. The concentrations ranged from 6 to 7,401 micrograms per cubic meter. Toluene, n-decane, ethylbenzene, and ethyl-acetate were detected equally well with Porapak and Tenax. Cyclohexane and alpha-pinene were better retained on Porapak than on Tenax. The use of Porapak led to higher measured concentrations of cyclohexane and PGDA. Measurements in individual buildings showed significant variability in the measured concentrations of n-hexanal and benzene. The authors conclude that Porapak shows better adsorptive behavior toward VOCs such as alpha-pinene, cyclohexane, and PGDA than Tenax. Because it showers lower thermal stability, Porapak cannot fully replace Tenax.
