SOLID-PHASE MICROEXTRACTION FOR DETERMINING THE DISTRIBUTION OF CHEMICALS IN AQUEOUS MATRICES

Solid phase microextraction (SPME) can be applied to measure the distr ibution of chemicals in different speciation states. The standard SPME apparatus and procedures can be applied to measure free concentration s of a target compound spiked into pure water and spiked into water co ntaining another pseudophase, such as dissolved humic organic matter ( HOM). Eased on a comparison of results obtained for the two samples, t he partitioning of the target analyte between water and the pseudophas e is calculated. The samples investigated in the present study were fr om heavily contaminated coal wastewater containing dissolved organic p olymers with properties similar to those of HOM. External calibration provides information about freely dissolved analytes. After calibratio n of the SPME signal by addition of an internal standard (e.g., a deut erated surrogate), the results indicate the total concentration of the target analyte in the sample due to the identical partitioning of the internal standard. The concentration determined in this way coincides well with data obtained from liquid-liquid extraction (LLE). Both met hods, SPME with internal calibration and LLE, measure total concentrat ion, composed of a freely dissolved portion and a portion that is reve rsibly bound onto a pseudophase (HOM).