DEVELOPMENT OF A CATION-EXCHANGE METHODOLOGY FOR MARINE TOXICITY IDENTIFICATION EVALUATION APPLICATIONS

In phase I of a standard toxicity identification evaluation (TIE) six manipulations are used to characterize toxicity. The ethylenediaminete traacetic acid addition manipulation is most often used to indicate to xicity caused by divalent metals. An alternative approach for characte rizing/identifying metal toxicity is the use of cation-exchange chroma tography. In this study, five cation-exchange media were compared to d evelop a method for using cation-exchange chromatography as part of a marine TIE. To be considered useful the cation-exchange media must mee t the following criteria: (1) consistently (with minimal variability) extract and elute toxic concentrations of a mixture of metals spiked i nto seawater, (2) demonstrate negligible blank acute toxicity, and (3) function effectively with environmental samples. Two solid-phase extr action media met the criteria: Supelco's LC-WCX column and Alltech's E xtract-Clean IC-Chelate column. In general, these columns were able to remove 80 to 100% of five metals (Cd, Cu, Ni, Pb, Zn) from spiked sea water, and 85 to 100% of metals could be eluted back into solution (ex cept copper for which recovery was 65-75%). Columns functioned effecti vely with seawater spiked with metals concentrations approaching 600 m u g/L and showed low intercolumn variability (coefficient of variation = 1.0-14%). For actual environmental samples, once column breakthroug h was assessed, both columns reduced toxicity and metal concentrations in postcolumn samples. Further, reconstituted column eluates were as toxic as whole samples. The methodology described can be used to assis t in the TIE characterization and identification of toxic metals in en vironmental samples.