The 8th Mass Spectrometry CVG Annual Symposium - Full Day Event!!!

"Analytical, Bioanalytical, Environmental, Proteomics, Forensic and Instrumental Topics "

September 23, 2009, Montreal, Canada

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Presentation No. 15 - Mass Defect Trigger IDA to improve selection of candidate ions for MSMS confirmation of metabolites from in-vivo samples
J.C. Yves Leblanc1; Eva Duchoslav1; Nic Bloomfield2
1MDS Analytical Technologies, Concord, On , Canada ; 2MDS Analytical Tech- Sciex, Concord, ON

Novel Aspect: Real Time Selection of Precursor Ion based on Mass Defect, More Selective Detection and Confirmation of Metabolite.

Introduction: Instrument manufacturers offer the capability to automatically collect MS and MSMS using the following principle; 1) perform a survey scan , 2) select precursor ion (s), 3) perform MSMS on the precursor(s) and 4) repeat process for duration of LC. The challenge in such application is to determine on an LC time scale what are the ion of interest, especially when dealing with complex biological mixture. Mass Defect Filtering is a widely accepted post-acquisition data processing method that enables selective detection of metabolites in the presence of high chemical noise or endogenous species signal. IHere we report on the use of Mass Defect Filtering as a criteria to select precursor ions in real-time with Information Dependant Acquisition (MDf Trigger-IDA)

Methods: Rat and Hhuman liver micorosome incubation of clozapine, buspirone, haloperidol and talinolol were diluted in various matrix to mimic in-vivo metabolism samples (urine, plasma and bile). All standards were obtained from Sigma and used without any additional purification. Separation was performed on a Luna C18 (2) 2.1x100mm, 2u column (Phenomenex) using a Prominance 20-AD XR system (Shimadzu). All analysis were preformed on a research hybrid quadrupole time of flight (QqTOF) system operation equipped with a TurboVTM ionspray source and operated at 30,000 resolution

Results: The Mass Defect of unmodified clozapine and that of the GSH-clozapine conjugate were used with a window of 40mmu as filters for precursor selection in IDA. This approach was compare to more traditional IDA criteria such as dynamic background subtraction (DBS), mass range and intensity threshold. The MDt-IDA method enable detection of all previously reported metabolites of clozapine (total of 11) where as the conventional IDA methodology only detected 6. It was also found that comparison of the post-acquisition Mass-Defect filtering of the survey scan yielded a chromatogram that was identical to the TIC of the precursor ion experiment in the MDf Trigger-IDA, suggesting that all ions detected in post-acquisition processing were effectively selected in real time to perform MSMS with unit resolution selection of the precursor ion. This is a significant improvement over conventional automated MSMS approaches taken in metabolism and data for the other compounds will be shared in the present work.