Development of a LC-MS screening method for plant protection products

Abstract

Plant protection products (ppps) play an important role in food production. They are highly regulated, requiring authorisation prior to their market introduction. Post-authorisation control and monitoring of ppps on the market are of high importance to ensure their safety and efficacy and hinder the use of illegal (e.g. counterfeit) products. Screening by gas chromatography-mass spectrometry (GC-MS) has been successfully used to determine deviations from the approved formulation or the presence of impurities. The limitation of GC-MS screening is that only volatile compounds can be analysed. Therefore, in the course of this diploma thesis a novel liquid chromatography - high resolution mass spectrometry (LC-hrMS) screening method was developed to overcome this limitation. The screening is based on reversed phase LC separation coupled to a quadrupole time of flight (qTOF) mass spectrometer utilizing an in-house database of ppp constituents.A simple sample preparation includes sonication of a methanolic extract and direct injection after a single dilution step (dilute-and-shoot strategy). The LC method is based on a buffered water/2-propanol gradient to cover a broad range of polarities with a balance between separation power and analysis time. An in-house database containing 54 active substances and 25 co-formulants including sum formulae, retention times and at least one characteristic fragment was established. Validation was performed following the SANTE/11312/2021 guideline and 47 active substances and 12 co-formulants met the defined requirements to be included in the qualitative screening.The developed method will be applied to a broad range of ppp samples and extend the analytical scope of market control in Austria.