New tools in diagnosis and biomonitoring of intoxications with organophosphorothioates: case studies with chlorpyrifos and diazinon.

Organophosphate (OP) pesticides are neurotoxic compounds that are widely used in agriculture. Classical methods for monitoring OP exposure comprise the measurement of intact OP, its metabolites or cholinesterase activity. Newly developed methods focus on the analysis of the OP adduct bound to proteins such as butyrylcholinesterase (BuChE) and albumin. These adducts can be analyzed by means of fluoride reactivation or by analysis with LC-MS/MS of the pepsin or pronase digest of butyrylcholinesterase and albumin, respectively. The utility of these methods is illustrated through the analysis of plasma samples obtained from patients taken 1-49 days after ingestion of the organophosphate pesticides chlorpyrifos and/or diazinon. Thus, in this particular case several independent methodologies were applied to the biomedical samples, all pointing to the same exposure.

Verification of exposure to cholinesterase inhibitors: generic detection of OPCW Schedule 1 nerve agent adducts to human butyrylcholinesterase.

Phosphylated butyrylcholinesterase is one of the most important biomarkers to verify an exposure to nerve agents, and it can be analyzed with liquid chromatography-tandem mass spectrometry (LC-MS-MS) by detection of a phosphylated nonapeptide that results after digestion of butyrylcholinesterase (BuChE) with pepsin. For a sensitive analysis (low degree of BuChE inhibition), the identity of the cholinesterase inhibitor has to be known in order to use the LC-MS-MS instrument in the most sensitive selected reaction monitoring mode. In practice, the identity of the cholinesterase inhibitor will not be known beforehand, and the number of possible organophosphates is greater than 1000. However, the number of possible molecular masses of organophosphates is approximately 170. A method for which only 34 transitions in the multiple reaction monitoring mode have to be acquired in order to screen for an exposure to all Organization for the Prohibition of Chemical Weapons Schedule 1 nerve agents was developed.