Microwave-Assisted Extraction Coupled with Liquid Chromatography/Electrospray Ionization Mass Spectrometry for the Simplified Determination of Imidazolinone Herbicides and Their Metabolites in Plant Tissue

The imidazolinones are a significant new class of low-use-rate, reduced-environmental-risk herbicides for protection of a wide variety of agricultural crops. Current residue methodologies for determining the imidazolinones and their metabolites in crops involve laborious, time-consuming cleanup procedures after an aqueous/organic extraction. Using imazethapyr, the most widely utilized member of the class, and its metabolites as representatives, liquid chromatography/electrospray ionization mass spectrometry was found to permit processing as little as 1% of the extract normally processed through the existing methods. Microwave-assisted extraction aided in the shortened cleanup procedure by providing a 100% aqueous initial extract. Over a range of 11 different commodities, average recoveries for imazethapyr, its hydroxy metabolite, and the glucose conjugate were 100%, 102%, and 97%, respectively. The simplicity and general applicability of this analytical approach reduced not only sample analysis time but also, perhaps even more importantly, method development time. Keywords: Imidazolinone; herbicides; determination; MAE; LC/ESMS