Screening of dimethoate in food by isotope dilution and electrospray ionization tandem mass spectrometry

Crop control is an important issue in both developed and developing countries. An environmentally friendly approach is represented by the so-called Integrated Pest Management (IPM), whereby synthetic pesticides are only applied as a last resort, under the strict control of suitable experts. European and US regulatory authorities, such as the US EPA, are constantly assessing the risks of exposure to the organophosphate (OP) class of pesticides and, among these, specifically dimethoate. The use of dimethoate is still allowed in many crops, including olives, which once was based in the Mediterranean area but now is expanding rapidly throughout the world. An important aspect of IPM protocols is represented by the availability of reliable and sensitive methods to detect pesticides residues. This paper describes an isotope dilution dimethoate assay based on the application of electrospray ionization tandem mass spectrometry (ESI-MS/MS) by means of a deuterium-labeled internal standard. Copyright (C) 2009 John Wiley & Sons, Ltd.