Improved analytical performance of photoionization ion mobility spectrometry for the rapid detection of organophosphorus pesticides using patterns with multiple reactant ions.

Ion mobility spectrometry (IMS) has become a potential technique for the rapid detection of organophosphorus pesticides (OPPs). However, using only the commonly-used reactant ion (Ac)H(HO) , some OPPs are difficult to distinguish due to their severely overlapping ion peaks. In this study, the switching of reactant ions ((Ac)H(HO) , O (HO) and Cl(HO) ) in a stand-alone photoionization ion mobility spectrometer was realized by on-line switching the polarity of high voltage and dopant species. Multiple reactant ions were employed to establish the characteristic patterns for the tested OPPs, including fenthion, dursban, dimethoate, malathion, fenitrothion, imidan and isocarbophos. The tested OPPs were represented on a heat map and a three-dimensional coordinate system based on the patterns, from which they could be readily identified. Under optimal conditions, the limits of detection (LODs) of the tested OPPs were evaluated to be 0.3-2.7 ng, and satisfactory repeatability was demonstrated by the obtained relative standard deviations (RSDs) of 4.8% to 14.7%. Finally, Chinese cabbage extract spiked with dursban and malathion was detected by the proposed ion mobility spectrometer, demonstrating its applicability for the simultaneous identification of coexisting OPPs in real samples.