Application Note: Pesticide Dynamic MRM Compound Database For Screening And Identification Using The Agilent LC/MS Triple Quadrupole Systems

Over the last century more than 1000 pesticides have been in common use for crop protection. Beyond approved and recommended usage, there always exists the possibility that any of these chemicals can be found in the environment and make their way into the food supply. To protect both the environment and human health, detection and identification in survey type monitoring is very important. Liquid chromatography/tandem mass spectrometry with a triple quadrupole LC/MS meets this need by providing the most sensitive and highly selective detection in complex samples. The system must be run in multiple reaction monitoring (MRM) mode, in order to obtain the maximum sensitivity and selectivity from this technology.

Although the triple quadrupole LC/MS is the most sensitive method for multiresidue analysis, the technique can only detect the pesticides that have been included in the methodology. Each pesticide must contain its predetermined precursor ion and an indicative product ion. This single precursor/product ion pair or transition is required for screening in the MRM mode. For confirmation of a compound at least two transitions must be included in the method so that their presence and correct ratio in a sample can be determined along with the correct chromatographic retention time. Because every compound is different there are specific instrument conditions that will provide an appropriate response for each transition. On the Agilent systems this includes both fragmentor voltage, optimizing transmission of the precursor ion into the mass spectrometer, and the collision energy, optimizing the maximum intensity for a specific product ion. Excellent results are obtained using all other mass spectrometer settings provided by the system's Autotune program.