Feasibility of LC/TOFMS and Elemental Database Searching As a Spectral Library for Pesticides in Food
Résumé
Traditionally, the screening of unknown pesticides in food has been accomplished by GC/MS methods using conventional library searching routines. However, many of the new polar and thermally labile pesticides are more readily and easily analysed by LC/MS methods and no searchable libraries currently exist (with the exception of some user libraries, which are limited). Therefore, there is a need for LC/MS libraries that can detect pesticides and their degradation products. This report develops an identification scheme using a combination of LC/MS time-of-flight (accurate mass) and an Access data base of 350 pesticides that are amenable by positive ion electrospray. The approach is different than conventional library searching of fragment ions. The concept here consists of three parts. First is the initial screening of possible pesticides in actual market-place fruit extracts (apple and orange) using accurate mass and generating an accurate mass via an automatic ion extraction routine. Second is searching the Access database manually for a screening identification of a pesticide. Third is identification of the suspected compound by accurate mass of at least one fragment ion and comparison of retention time with an actual standard. Identification of imazalil and iprodione are shown in apple and thiabendazole in oranges using this database approach.
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