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Evaluation of matrix effects in different multipesticide residue analysis methods using liquid chromatography-tandem mass spectrometry, including an automated two-dimensional cleanup approach.

Pesticide residue analysis is an important part of food quality control. Three of the most widely used methods are the DFG S19 (extraction with acetone), the ChemElut method (extraction with methanol), and QuEChERS (quick, easy, cheap, effective, rugged, safe; acetonitrile-based). Despite many developments in the field of sample preparation, matrix effects are still one of the most disturbing problems in routine analysis. In this study, we compare the matrix effects in LC-MS analysis after using these three methods in pesticide analysis. Using postcolumn infusion, we were able to visualize all suppressions over the whole chromatogram in matrix-effect profiles. Recently, we also presented a system for the determination of up to 300 pesticides from various kinds of fruit and vegetables. For the measurement, we injected an aliquot of a raw acetonitrile extract. The subsequent cleanup was carried out fully automated by a multidimensional LC. Matrix compounds and analytes are separated in the first dimension on a hydrophilic interaction LC column. In this study, we also compared this new approach with the classical methods. The matrix-effect profiles showed less suppression with the hydrophilic interaction LC-based cleanup. A final evaluation of the partitioning steps of all methods confirmed the benefits of the chromatographic cleanup approach.