High throughput residue analysis of paraquat and diquat involving hydrophilic interaction liquid chromatographic separation and mass spectrometric determination

A selective, sensitive and robust LC-MS/MS method is reported for the determination of the residues of paraquat and diquat in various fruit matrices, including grape, apple and pomegranate. The extraction with acidified water (0.1 M HCl) at 80°C (15 min) offered superior recoveries for both analytes with a significantly lower matrix effects as compared to the extraction with acidified methanol by the methods reported in the existing literature. The optimised HPLC conditions on hydrophilic interaction liquid chromatography (HILIC) columns, when coupled with electrospray ionisation-tandem mass spectrometry, offered their limit of quantification at 0.01 mg kg−1. The analysis on an XBridge HILIC column required a thorough optimisation of the gradient programme to induce chromatographic separation and minimise matrix effects. This was not necessary when a CORTECS HILIC column was used, which provided selective and sensitive analysis within 5 min runtime using isocratic flow. Isotopically labelled internal standards corrected the recoveries of both analytes within 70–120% (RSD −1 level. The method has a strong potential for applications in both official control and by those involved in food production for checking compliance with the EU MRLs.

本研究报道了一种选择性优异、灵敏度出众且稳定性极强的液相色谱-串联质谱（LC-MS/MS）分析方法，用于测定葡萄、苹果、石榴等多种水果基质中的百草枯与敌草快残留量。采用酸化水（0.1 mol/L 盐酸）在80℃下萃取15分钟，相较于现有文献报道的酸化甲醇萃取法，该方法对两种分析物均可获得更优异的回收率，且基质效应显著更低。将亲水相互作用液相色谱（HILIC）柱的优化高效液相色谱（HPLC）条件与电喷雾电离串联质谱联用时，该方法的定量限可达0.01 mg/kg。使用XBridge HILIC色谱柱开展分析时，需对梯度洗脱程序进行全面优化，以实现高效色谱分离并最大限度降低基质效应。而采用CORTECS HILIC色谱柱时则无需进行此类优化，该色谱柱可采用等度洗脱模式，在5分钟运行时间内即可完成兼具选择性与灵敏度的分析。采用同位素标记内标进行校正后，两种分析物的回收率均处于70%~120%范围内，相对标准偏差（RSD）符合-1水平。本方法在官方监管以及食品生产从业者核查产品是否符合欧盟最大残留限量（Maximum Residue Limits, MRLs）要求的场景中，均具备极佳的应用潜力。