Capillary gas chromatographic-mass spectrometric determination of fluoroacetate residues in animal tissues

A method for the quantitative determination of fluoroacetate (FAC) residues in animal tissues is described. The procedure involves tungstic acid extraction, partitioning into ethyl acetate, evaporation of ethyl acetate, derivatization with pentafluorobenzyl bromide (PFB), and analysis of the resulting derivative (PFB-FAC) by capillary gas chromatography-mass spectrometry (CGC-MS) with specific ion monitoring (SIM). The tungstic acid system extracted 96.8 +/- 4.2% of the endogenous 14C-1080 residues in rat tissues. Recovery of FAC during the extraction, purification, and derivatization procedures is established by use of a 14C-FAC spike. 1,2-Dibromobenzene is used as an internal standard for the CGC-MS analysis. PFB-FAC is identified on the basis of comparative retention times and the relative intensities of m/z 257.9 and 181.0. PFB-FAC is quantitated by comparing the response at m/z 257.9 to a PFB-FAC standard curve. Routine sensitivity of the method allows determination of 10 ppb fluoroacetate in tissue.