SELECTIVE ASSAY FOR HEAVY-METAL TOXICITY USING A FLUOROGENIC SUBSTRATE

Chromogenic substrates have been generally used in enzymatic assays fo r the specific determination of heavy metal toxicity. A toxicity assay based on the specific inhibition of beta-galactosidase by heavy metal s and using a fluorogenic substrate was evaluated for its sensitivity to heavy metals and organic toxicants. The toxicity assay, FluoroMetPL ATE, was specific for heavy metals and was more sensitive than the wid ely used Microtox assay. Except for lead, our assay displayed sensitiv ity similar to that of the 48-h acute Ceriodaphnia dubia assay. Monito ring of industrial samples showed that the FluoroMetPLATE assay gave s imilar results as the daphnid toxicity assay for 22 of 29 samples. For the remaining samples, for which there was no agreement between the t wo tests, it was found that the toxicity was mostly due to organic tox icants, confirming the specificity of FluoroMetPLATE for heavy metal t oxicity.