Solid-Phase Microextraction (SPME) Methods to Measure Bioavailable Concentrations in Surface Waters

Due to strong affinity for the solid phase, pyrethroid bioavailability is reduced considerably in surface water containing dissolved organic matter or suspended solids. The bioavailable fraction for water column invertebrates is often considered to be the freely dissolved fraction, because it is that fraction which can cross the cellular membrane. Thus, selective methods that measure the freely dissolved concentration are good indicators of the bioavailability of pyrethroids in surface waters. Solid phase microextraction (SPME) was used in several studies as a selective sampling approach to evaluate the bioavailability of pyrethroids in surface water. The SPME measurements correlated well with the pyrethroid bioaccumulation by Daphnia magna. The LC50 estimated by SPME also correlated well with the observed LC50 to Ceriodaphnia dubia. These results indicate the usefulness of SPME as a tool for evaluating the bioaccumulation and toxicity of pyrethroids to water column invertebrates in the presence of dissolved organic matter or suspended solids. Results from these studies suggest that the presence of dissolved organic carbon and suspended solids should be taken into account when evaluating organism exposure to pyrethroids, especially When monitoring runoff or irrigation effluent which usually contain high levels of dissolved organic matter and suspended solids.