A thermal desorption method for determining atmospheric Semi-Volatile Organic Compound concentrations
Creators: name: Fagault, Yoann
Publisher: name: University of Hertfordshire
Year: 2007

description: It is now recognised that indoor environments contribute significantly to human exposure to airborne pollutants. People spend a large amount of time in indoor environments and there are many indoor sources that are not present outdoors. Among the chemicals released in indoor environments, some of them have been identified as hormonally active or carcinogens. Indoor air pollution problems are likely to become more as stricter controls limit outdoor pollution levels. Reduction of air exchange rate and the use of new insulating materials are likely to contribute to the build-up of pollutants in indoor air. The objective of this thesis has been to develop an analytical method based on thermal desorption for the measurement of semivolatile organic compounds (S'\iO:s) to be use for indoor and personal measurements. The sampler consists of a small FMz.s impactor upstream of a sample tube filled with the adsorbent Tenax TA to collect the particulate 'and gaseous phases respectively. The analytical technique was based on thermal desorption to compensate for the low sampling volumes available with the personal sampling pump so that the entire sample can be injected on the analytical system. In addition, the current technique reduces the analytical time and cost because little sample handling is required and it is more environmental friendly because no solvents are used. The experimental work focused on the development of a vapour generation system to determine breakthrough volumes of the least volatile target compounds on the adsorbent Tenax TA, the development of the analytical method for the analysis of both the gaseous and particulate phases and the evaluation of the performance of the developed method. Finally, the applicability of the method was verified by performing a short stUdy involving indoor and personal samplings. The developed vapour generation system permitted vapours to be generated at concentrations that are representative of indoor air concentrations. The apparatus has been evaluated for a number of SIt is now recognised that indoor environments contribute significantly to human exposure to airborne pollutants. People spend a large amount of time in indoor environments and there are many indoor sources that are not present outdoors. Among the chemicals released in indoor environments, some of them have been identified as hormonally active or carcinogens. Indoor air pollution problems are likely to become more as stricter controls limit outdoor pollution levels. Reduction of air exchange rate and the use of new insulating materials are likely to contribute to the build-up of pollutants in indoor air. The objective of this thesis has been to develop an analytical method based on thermal desorption for the measurement of semivolatile organic compounds (S'\iO:s) to be use for indoor and personal measurements. The sampler consists of a small FMz.s impactor upstream of a sample tube filled with the adsorbent Tenax TA to collect the particulate 'and gaseous phases respectively. The analytical technique was based on thermal desorption to compensate for the low sampling volumes available with the personal sampling pump so that the entire sample can be injected on the analytical system. In addition, the current technique reduces the analytical time and cost because little sample handling is required and it is more environmental friendly because no solvents are used. The experimental work focused on the development of a vapour generation system to determine breakthrough volumes of the least volatile target compounds on the adsorbent Tenax TA, the development of the analytical method for the analysis of both the gaseous and particulate phases and the evaluation of the performance of the developed method. Finally, the applicability of the method was verified by performing a short stUdy involving indoor and personal samplings. The developed vapour generation system permitted vapours to be generated at concentrations that are representative of indoor air concentrations. The apparatus has been evaluated for a number of SVOCs including PAHs, phthalates, organophosphate esters and alkylphenol) with as including FW-Is, phthalates, organophosphate esters and alkylphenol) with a broad range of volatility (from naphthalene to pyrene). The breakthrough measurement study performed in the worst conditions (30 0e and 7CJllo relative humidity) demonstrated that the adsorbent Tenax TA was appropriate to quantitatively collect even the least volatile compound naphthalene over a 24 hours sampling period. The analytical method was developed for 16 R\Hs, 6 CB*is, 5 phthalates, 2 organophosphate esters, 3 alkylphenols and 5 pesticides (2 organophosphorous, 1 carbam~te, 1 pyrethro'id and 1 organochlorine). Its applicability for R\Hs measurements was verified with a standard reference material (SRM1649a, NIS1) and by comparison of indoor air filter strips analysed by the Tn method and a conventional solvent extraction method. The 10 method was shown to be quantifiable for R\Hs up to benzo(a)pyrene but less effective for less volatile At\Hs due to their incomplete desorption. A side by side comparison between the developed sampler and a low volume Filter/PUF sampler clearly demonstrate that the developed method was much more efficient than the low volume PUF sampler for the measurement of gaseous low molecular weight compounds (Mw S178 g.mol-1 ). Regarding the particulate phase, measured concentrations from both samplers were highly correlated with the exceptions of the heavy R\Hs (IP, DahA and BghiP). These results suggest that sampling artifact were limited or similar to those of the low volume sampler. The precision of the method was evaluated by the relative standard deviation from co-located measurements in an indoor environment (n=6). A number of target .compounds were detected including R\Hs, CH\Hs, phthalates, organophosphate esters and phenol. The relative standard deviation was generally less than 1CJllo indicating good reprodUcibility. A small demonstration study consisting of twenty four hours indoor and personal measurements was carried during six days. The results obtained in this demonstration study were in agreement with most previous studies reporting indoor heavy At\Hs concentrations lower or similar than outdoor R\Hs concentrations and light R\Hs concentrations higher indoors than in outdoor environments. This demonstration study also confirmed that phthalates and organophosphate esters are ubiquitous in indoor environment.