PHOTOTOXICITY IDENTIFICATION BY SOLID-PHASE EXTRACTION AND PHOTOINDUCED TOXICITY TO DAPHNIA-MAGNA

The photoinduced toxicity of several environmental pollutants (some Po lycyclic Aromatic Hydrocarbons [PAHs]) is a potential threat to aquati c organisms. To identify the cause/s of photoinduced toxicity of a sam ple, it is not sufficient to simply analyze the content of some known phototoxic compounds; so far too few substances of environmental conce rn have ever been tested for their photoinduced toxicity. The PAHs as well as other known phototoxic compounds are hydrophobic and are expec ted to bind to C18 columns. The use of Solid Phase Extraction (SPE) is typically part of the procedure identifying any primary nonpolar toxi cant/s, and adding phototoxicity tests to these manipulations would no t substantially increase the workload. In this study, therefore, the d ifference in acute toxicity to Daphnia magna before and after 2 h of U V irradiation was determined for six PAHs. The ratio between EC50 valu es before and after UV irradiation ranged from 4.6 (for benzo[a]pyrene ) to >244 (for 3,4-benzofluoranthene), demonstrating that the UV enhan ces the PAH-toxicity. A further characterization technique using bindi ng to Sep-Pak SPE C18 columns and recovery with methanol as an eluting agent was then tested in combination with UV irradiation. The mean re covered UV induced toxicity after binding and elution of the six PAHs was 119% according to the phototoxicity tests made. A linear relations hip, between the log(10)K(OW), values for the PAHs and the log(10) for the concentration of methanol at peak elution was found. The combined use of C18 column separation and UV activation may, therefore, be use d in toxicity identification evaluations (TIE) of organic phototoxic c ompounds.