DETERMINATION OF ORGANOPHOSPHORUS PESTICIDES IN WATER BY SOLID-PHASE EXTRACTION FOLLOWED BY LIQUID-CHROMATOGRAPHY HIGH-FLOW PNEUMATICALLY ASSISTED ELECTROSPRAY MASS-SPECTROMETRY

Priority organophosphorus pesticides in water samples were subjected to analysis by solid-phase extraction followed by liquid chromatography/high-flow pneumatically assisted electrospray mass spectrometry (LC/ESP-MS). The operational parameters of ESP optimized by use of an eluent flow rate of 0.3 mL/min and at a source temperature of 150 degrees C were as follows: drying gas flow rate, 250-300 L/h; ESP nebulizing gas flow, 5-20 L/h; ESP voltage, 2-3.5 kV; HV lens voltage, 0.2-1.0 kV; extraction voltage, 20-130 V; focus voltage, and the ion energy. Water samples (500 mL) were preconcentrated by use of either Empore disks of C-18 and styrene-divinylbenzene or monofunctional C-18 cartridges in an ASPEC XL system. No thermal degradation was observed for the organophosphorus pesticide triclorfon, which usually causes a problem under LC/MS using thermospray interface. The method detection limit was 0.01 mu g/L for most of the organophosphorus pesticides used employing SIM of the [M + Na](+) ion.