title: A comparison of exposure methods for SPME-based bioavailability estimates.
abstract: The ability of polydimethlysiloxane coated solid phase microextraction (SPME) fibers to predict bioavailability has been documented for a number of species and compounds. There are also a variety of established methods for establishing SPME-based bioavailability estimates; however, factors such as time until equilibrium and exposure regimen could affect fiber concentrations and have not yet been thoroughly tested. Exposure time may influence SPME fiber concentrations at equilibrium. Co-exposure of the fibers with different animals or the invertebrate species used could yield different estimates than those acquired using a shaker table system to achieve equilibrium between the sediment and SPME fibers. The current study examined the effects of time and exposure method (shaker table versus co-exposure with test species) on SPME fiber concentrations for two hydrophobic compounds: permethrin and p,p'-dichlorodiphenyldichloroethylene (DDE). An additional experiment with permethrin determined whether animal densities or fiber number influenced fiber concentrations. There were significant differences between the time required for SPME fibers to reach equilibrium when co-exposed with different species or separately, but fiber concentrations at equilibrium among treatments for both compounds were similar. Furthermore, among the 12 variations in species and fiber densities, there were no significant differences among treatments indicating that neither the route of exposure, animal density, nor fiber volume influenced SPME fiber estimates. This demonstrated that SPME fiber concentrations at equilibrium were not affected by exposure conditions, increasing their versatility in environmental assessments.
authors: Fisheries and Illinois Aquaculture Center, 1125 Lincoln Dr., Rm. 173, Department of Zoology, Southern Illinois University Carbondale, IL 62901, USA.
authors: Amanda D
authors: AD
authors: Harwood
authors: Peter F
authors: PF
authors: Landrum
authors: Michael J
authors: MJ
authors: Lydy
mesh_terms: D000818:Animals; D003633:Dichlorodiphenyl Dichloroethylene / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007313:Insecta / Q000737:chemistry / Q000378:metabolism; D052617:Solid Phase Microextraction / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism
chemical_list: D004129:Dimethylpolysiloxanes; D014874:Water Pollutants, Chemical; D003633:Dichlorodiphenyl Dichloroethylene