Determination of an acetylcholinesterase inhibitor, MDL 73745, in dog plasma and urine by combined gas chromatography/negative ion chemical ionization mass spectrometry.

A highly sensitive and specific assay has been developed for the determination of MDL 73745 [2,2,2-trifluoro-1-(3-trimethylsilyl-phenyl) ethanone] (I) and the internal standard (MDL 74398) at the nanomolar level in dog plasma and urine by gas chromatography/mass spectrometry. After a single-step extraction process, an aliquot was directly injected onto the gas chromatograph column. The mass spectrometer was run in the negative ion chemical ionization mode with ammonia as reagent gas, and was set to monitor the abundant M-.