A New Approach for Diffusive Sampling Based on SPME for Occupational Exposure Assessment

Abstract

Passive sampling is a well-established methodology for the evaluation of exposures to environmental volatile organic compounds (VOCs). The solid-phase microextraction (SPME) technique is a reliable means of sampling VOCs in air. SPME is also being applied as a passive sampler to determine time-weighted average exposure. The use of SPME as a diffusive sampler was evaluated. The passive sampler is based on the use of a cylindrical diffusion cell (porous hydrophobic polyethylene) with an 80 μm carboxen/polydimethylsiloxane fiber to obtain radial diffusion of the analytes to the sorbent. Standard atmospheres of organic vapors in air were used to determine the experimental uptake rates for toluene and chlorobenzene. Toluene concentrations between 2 and 38 mg/m³ with sampling times between 15 and 60 min were evaluated, as well as chlorobenzene concentrations between 2 and 47 mg/m³ with sampling times between 30 and 60 min. The mean diffusive uptake rate was 2.14 mL/min for toluene and 2.57 mL/min for chlorobenzene, and no statistical significant effects of concentration and sampling time were observed under the studied conditions for the two compounds. Relative standard deviation ranged from 2.6 to 6.5%. The performance of the sampler under varying concentrations of toluene was also tested, showing that the sampler reflects the average exposure concentration. Effects of temperature, relative humidity, velocity of the air, back diffusion, competitive adsorption, and the stability of chlorobenzene in the sampler were also studied. Sampler behavior was tested in gas stations, and the results were successfully compared with a 3M-3500 diffusive sampler. The results are promising for using this new SPME device for diffusive monitoring for occupational exposure assessment.

Keywords:

• air monitoring
• fluctuating concentrations
• volatile organic compounds

ACKNOWLEDGMENTS

The authors are indebted to Mr. Christopher Linton and to Mr. Len Sidisky (from Supelco) for kindly providing the first and second sets, respectively, of prototype SPME field samplers, as well as to Mr. René Desquenne (from Porex Technologies) for his kind supply of the PE-cylinders.

This work is dedicated to the memory of our co-author J. Francisco Periago.

Notes

* Deceased