Use of supercritical fluid extraction and fast ion bombardment mass spectrometry to identify toxic chemicals from a refinery effluent adsorbed onto granular activated carbon

Progressively more stringent regulations on effluent toxicity to fish at a U. S. West Coast petroleum refinery have necessitated the use of granular activated carbon (GAC) treatment to further reduce effluent toxicity. Historical studies at this refinery have shown that organic (naphthenic) acids are the most consistent source of effluent toxicity to fish. This paper describes the use of supercritical fluid extraction (SFE) coupled with fast ion bombardment mass spectrometry (FIB-MS) to recover and characterize organic acids from activated carbon as a means to confirm toxicity reduction due to organic acid removal. The extracted organic acids yielded a molecular weight distribution corresponding to carboxylic/naphthenic acid ions which are similar to the distribution in spectra obtained from effluent extracts and commercially available standards. Since toxicity studies have demonstrated that the GAC is effective in removing the toxic components in the effluent, the recovery of naphthenic acids from the GAC lends support that these compounds are the source of fish toxicity.