在不需要样品制备、预处理的前提下,将电喷雾解吸串联质谱法用于果蔬表面残留的乙酰甲胺磷、甲拌磷、乐果、乙嘧硫磷、乙硫磷和亚胺硫磷等6种有机磷农药的直接快速检测。在串联质谱中,选择电喷雾离子源,用甲醇作雾化溶剂;以碰撞诱导解离反应正离子检测模式进行定性和定量检测。确定了上述6种有机磷农药的碎片特征峰(m/z)分别为206,261,252,293,407,318。结果表明:6种有机磷农药分子的裂解规律与其分子结构相吻合,排除了检测结果的假阳性。方法的检出限(3S/N)在5.0×10-10~1.0×10-8g·cm-2之间。以1.0×10-8g·cm-2的6种有机磷农药溶液进样,平行测定8次,测定值的相对标准偏差在1.6%~6.5%之间。

Desorption electrospray ionization-tandem mass spectrometry (DESI-MS/MS) was applied to the rapid determination of residual amounts of 6 organophosphorus pesticides (OPP′s), i.e., acephate, thimet, rogor, etrimfos, ethion and phosemet, on surface of fruits and vegetables, without sample preparation and pretreatment. In the MS/MS analysis, ESI was used as ion ization source with methanol as the electrospray solvent, and positive electrospray ionization as well as collision induced dissociation reaction monitoring mode was taken for qualitative and quantitative analysis. The characteristic peaks of the fragments of 6 organophosphorous pesticides with (m/z) 206, 261, 230, 293, 407, 340 respectively were confirmed. It was found that the fragmentation regularity of molecules of the 6 OPP′s were in coincidence with their molecular structures, and the possibility of arising false positiveness of the results of detection was thus eliminated. Values of detection limit (3S/N) found were in the range of 5.0×10-10-1.0×10-8g·cm-2. Precision of the method was tested with sample introduction of 1.0×10-8g·cm-2 of mixture of the 6 OPP′s for 8 determinations, values of RSD′s found were in the range of 1.6%-6.5%.