Detector for organophosphorus compounds in liquid chromatography based on the cholinesterase inhibition reaction

A sensitive method for the post-column reaction detection of organophosphorus compounds is described. The method relies on cholinesterase and is particularly suitable for the analysis of potent inhibitors such as sarin, soman and tabun. The compounds are separated by reversed-phase chromatography with methanol-water as the mobile phase in a linear gradient system. The reactor used for the detection comprises conventional autoanalyzer equipment with air segmentation of the reactor stream. The detection limits are 10 pg for sarin and soman and 60 pg for tabun. A quantitation method is presented, based on the linear correlation between the residual enzyme activity and the inhibitor concentration. The repeatability is +/- 1%. As a test of the system, the model compounds were detected against a background of urban air.