title: Diffusive sampling of methylene chloride with solid phase microextraction.
abstract: This study examined the characteristics of a solid phase microextraction (SPME) assembly as a passive sampler to determine the short-term exposure level (STEL) of methylene chloride. Two types of SPME fibers and six sampling-related factors were chosen and nested in an L(18) Taguchi's orthogonal array. Samples were thermally desorpted and analyzed by gas chromatograph equipped with an electron capture detector (GC/ECD). The use of 85-mum Carboxen/polydimethylsiloxane (Car/PDMS) fibers resulted in greater adsorbed mass, which was highly correlated with the product of concentration and sampling time (r>0.99, p<0.0001), than 85-microm polyacrylate fibers. The sampling rate (SR) of the 85-microm Carboxen/polydimethylsiloxane fibers was not significantly affected by variations in relative humidity (0-80%) and coexistent toluene (none to 100 ppm). Variance of sampling rate was predominantly attributed to the diffusive path length (86.4%) and sampling time (5.7%). With diffusive paths of 3, 10 and 15 mm, the sampling rates of 85-microm Carboxen/polydimethylsiloxane fibers for methylene chloride were 1.4 x 10(-2), 7.7 x 10(-3) and 5.1 x1 0(-3)mL min(-1), respectively. The measured sampling rates were greater than the theoretical values, and decreased with increment of sampling time until they came to constant.
authors.affiliation: Institute of Occupational Safety and Health, Council of Labor Affairs, Executive Yuan, Taipei, Taiwan.
authors.forename: Cheng-Yao
authors.initials: CY
authors.lastname: Chen
authors.forename: Chunming
authors.initials: C
authors.lastname: Hsiech
authors.forename: Jia-Ming
authors.initials: JM
authors.lastname: Lin
mesh_terms: D002849:Chromatography, Gas; D004058:Diffusion; D004781:Environmental Exposure / Q000032:analysis; D008752:Methylene Chloride / Q000032:analysis*; D052617:Solid Phase Microextraction / Q000295:instrumentation / Q000379:methods*
chemical_list: D008752:Methylene Chloride