A miniaturized analytical system for separating and detecting toxic organophosphate nerve agent compounds, based on the coupling of a micromachined capillary electrophoresis chip with a thick-film amperometric detector, is described. Factors influencing the on-chip separation and detection processes have been optimized. Using a MES buffer (20 mM, pH 5.0) running buffer, a 72-mm-long separation channel, and a separation voltage of 2000 V, baseline resolution is observed for paraoxon, methyl parathion, fenitrothion, and ethyl parathion in 140 s. Such miniaturization and speed advantages are coupled to submicromolar detection limits and good precision. Applicability to spiked river water samples is demonstrated, and the implications for on-site environmental monitoring and rapid security screening/warning are discussed.