Recent regulations on food analysis require the screening for pesticides using confirmatory techniques, such as GC-MS(/MS) and LC-MS/MS. With more than 1000 pesticides of more than 100 compound classes there is a demand for powerful and rapid analytical methods, which can detect very low concentrations in food matrices. Matrix effects are a continuous challenge for food laboratories due to the complexity and variety of food samples to be tested. Here we present a high sensitivity and high selectivity LC-MS/MS method that combines quantitation with identification based on Multiple Reaction Monitoring (MRM) and full scan MS/MS data. Food and tea samples were extracted using a QuEChERS procedure and injected into LC-MS/MS after extensive dilution to minimize or possibly eliminate matrix effects. LC separation was performed using a Shimadzu UFLCXRsystem with a Restek Ultra Aqueous C18 column and a gradient of water and methanol with ammonium formate buffer. Total run time was less than 20min. Detection was performed on the AB SCIEX QTRAP� 6500 system using Electrospray Ionization. In addition, SelexION� technology was used differential mobility separation (DMS) to enhanced selectivity to remove matrix interferences. Targeted pesticides were quantified and identified using a Scheduled MRM� method for best accuracy and reproducibility. The superior sensitivity of the MS/MS detector was used to dilute sample extracts extensively (up to 1000x) to completely eliminate matrix effects in most cases. In addition, DMS was used to remove matrix interferences when detecting tricky to analyze (small molecular weight and high polarity analytes).

Elimination of matrix effects and interferences when performing high sensitivity and high selectivity LC-MS/MS screening

248th National Meeting (2014)

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