Analytical method for the determination of O,O-diethyl phosphate and O,O-diethyl thiophosphate in faecal samples

A residue analytical method was developed for the determination of the dialkylphosphate metabolites of parathion in faecal samples obtained from rabbits. The faecal pieces were homogenised in water and highly water-soluble O,O-diethyl phosphate (DEP) and O,O-diethyl thiophosphate (DETP) were subsequently alkylated to pentafluorobenzyl esters by a phase transfer reaction. Derivatisation yields depend on the reaction time. The recovery rates were determined over the complete procedure using authentic reference standards in matrix solution. The reference standards allow to observe an effect of the sample matrix on the area of signals while GC-FPD is used. The recoveries over the concentration range from 0.05 to 5 microg/g were 47-62% for O,O-diethyl phosphate and 92-106% for O,O-diethyl thiophosphate potassium salt with FPD.