The development of new agricultural chemicals requires the identification of a variety of trace level unknowns. Some of the most challenging identification problems in compound development are encountered in the area of metabolite ID. These unknowns are generally present at ultra-trace (low pg) levels, precluding their identification with NMR. In these cases, their identification must be performed using LC/MS.In regulatory metabolite ID, radiolabeled metabolites are typically profiled using conventional LC to allow the injection of sufficient material for radiochemical detection. These metabolite samples may take weeks-months to form, and must be identified rapidly to avoid jeopardizing critical registration deadlines. To utilize these precious samples most efficiently, the post-column effluent is generally split between the MS and a radioactivity detector (RAM), and the effluent from the RAM cell is collected into a 96-well plate to allow the recovery of most of the LC-fractionated sample. In our work, metabolites were generated a combination of soil, plant cell culture, and whole plant systems. These samples were analyzed using LC separations on several LC/MS systems including: 1) a Thermo LTQ-FT Ultra (LIT-FTMS), 2) a Sciex 5600 (QqTOF), and 3) a Thermo Q Exactive (Q- Orbitrap). Radiolabeled metabolites were tracked using RAM detection, and ESI ionization was combined with accurate MS, and MS/MS data acquisition on each instrument.We will discuss the application of each of these techniques in the identification of trace level metabolites produced in whole plant, plant cell culture, and soil metabolism for several agricultural chemicals.SELECTED KEYWORDS: Chromatography, Liquid (LC); Exact Mass Measurement/Accurate Mass Measurement; Fragmentation, Environmental Degradates, Metabolites, Nanospray, NALDI, orbitrap, nanoLC-MS

Metabolite identification using modern Q-TOF and Q-Orbitrap instrumentation

246th National Meeting (2013)

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