Poisoning of methamidophos identified by the presence of o,o,s-trimethyl thiophosphate (o,o,s-tmtp)

It was shown by the results of GC-MS-analysis of the testing materials (blood, contents in stomach etc) taken from persons poisoned with methamidophos that O,O,S-TMTP was found in all the samples, and no methamidophos was detected. Through a thorough study on the reason of the above phenomenon, it was confirmed that the presence of O,O,S-TMTP can be taken as a proof of methamidophos poisoning. Conditions of GC-MS determination, including the preparation of sample, were studied and described in detail.