Nonoxidative metabolism of ethylene glycol monobutyl ether 2 butoxyethanol or BE via fatty acid conjugation was studied in the liver of Fischer 344 male rats following a single 14 oral administration of 500 mg kg body weight ethyl1 2 C BE 70 Ci kg Animals were killed 2 h after the treatment hepatic lipids extracted and the neutrallipids were separated using solid phase extraction The neutral lipid fraction was subjected to preparative thin layer chromatography and the esters corresponding to the relative flow of authentic fatty acid 2 butoxyethylesters were recovered and analyzed by reversed phase high performance liquid chromatography HPLC using methanol water 37 3 v v as solvent Approxi 14 mately 85 of the C label present in the ester fraction was coeluted at retention times corresponding to the different fatty acid 2 butoxyethyl ester standards The radioactive fractions were analyzed by electron impact mass spectrometry Molecular ion peaks and fragmentation patterns similar to that of 16 0 18 0 18 1 18 2 and 20 4 fatty acid 2 butoxyethyl ester standards were detected in the corresponding radioactive HPLC frac tions Fatty acid ethyl ester synthase FAEES purified from the rat liver microsomal frac tion was also found to catalyze the formation of 18 1 fatty acid 2 butoxyethyl ester These studies demonstrate that BE is metabolized nonoxidatively via conjugation with long chain fatty acids and the formation of these esters appears to be catalyzed by the enzyme s involved in fatty acid conjugation of xenobiotic alcohols However the biolog ical significance of BE conjugation with fatty acids remains to be investigated