Micro Flow UHPLC-MS/MS in Pesticide Analysis of Infant Foods

European Directive 2006/141/EC requires that infant food contains no detectable levels of all pesticide residues above the defined MRL of 10 μg/kg (10 ppb). Furthermore, the directive prohibits the use of certain very toxic pesticides in the production of infant foods and establishes even lower MRLs for a few other very toxic pesticides. Infant foods are recognised as a challenging matrix due to their wide range of fat content and the need to obtain the necessary low limits of detection for a broad range of pesticides.
In this presentation we have compared the use of micro flow-UHPLC, in comparison to conventional higher flow UHPLC for the routine quantitation of pesticide residues. The LC systems were coupled to a triple quadrupole mass spectrometer. The reduction in mobile phase flow rate contributed to increased sensitivity due to the concentration dependant behaviour of electrospray and the greater control of ionisation efficiency at lower LC flow rates. This produced a signal to noise ratio increase in excess of 3 fold when comparing micro flow LC and higher flow LC with the same injection volume. Peak shapes of micro flow LC were comparable to those achieved with higher flow LC due to the low dead volume of the system. Micro flow LC provided further benefits in reduced organic solvent consumption; a potential source of adverse environmental effect and of significant expense to laboratories to purchase. In this presentation we also present validation data for this pesticide method, including system robustness data.