DIRECT ELUTION OF SOLID-PHASE EXTRACTION DISKS FOR THE DETERMINATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND POLYCHLORINATED DIBENZOFURANS IN EFFLUENT SAMPLES

Solvent usage and extraction times can be reduced significantly by solid phase extraction (SPE) over liquid/liquid extraction (LLE). This research adapts existing SPE membrane disk methods to allow for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in industrial effluent and surface water samples containing particulate matter. When several types of filtering media are layered on top of the membrane disk, particulate matter and suspended solids in an effluent sample can be prevented from plugging the disk, allowing an entire sample to be extracted without the need for prefiltering. PCDDs and PCDFs can then be eluted directly from the filtering medium and disk. For 29 effluent samples with particulate matter, the mean values of the internal quantitation standard recovery ranged from 58 to 70% for LLE and from 65 to 77% for SPE. The average recovery was 8% higher for the SPE method over the LLE. Studies in this laboratory have shown that SPE membranes can replace LLE for essentially any aqueous sample. Extensive comparisons of LLE and SPE indicated that these two methods are equivalent statistically. In addition, SPE is quicker and less labor intensive than LLE.