CPSA Digest 2003

Day 2

Vendor Session - Drug Discovery Technologies & Applications

Accurate and MSn Mass Spectra in Combination with Smart Processing Tools for Metabolite Identification

An integrated strategy for metabolite identification based on standard and high resolution MS and MSn mass spectra, and smart software tools is presented. S9-fractions from rat liver were incubated with testosterone and 14C-testosterone. Full scan LC-MS chromatograms (scan range: 50-1000 m/z) using electrospray ionization were acquired with an Esquire HCTTM quadrupole ion trap and a microTOFTM orthogonal ESI time-of-flight instruments (Bruker Daltonik GmbH, Bremen, Germany). The chromatograms from different time points were compared using the eXpose algorithm of the MetaboliteTools™ software. An especially adapted MSn acquisition method for the quadrupole ion trap was automatically created. Full scan mass spectra of metabolites exclusively detected in the incubation at the respective time point are the result of the comparison by the eXpose algorithm. Various hydroxylated, oxidized metabolites and the glucuronide of testosterone were easily identified. The molecular composition of the metabolites can be directly calculated from accurate mass spectra from the ESI-TOF data. MSn data of the metabolites has been acquired in a targeted MRM experiment with the ion trap. The metabolites can be identified according to characteristic fragmentation. The MSn spectra are saved into a mass spectral library to accelerate future identifications. To confirm the results and 'validate' the new eXpose detection algorithm, the S9-incubations were repeated with 14C-labeled testosterone. The additional radioactive trace allows the unambiguous identification of testosterone metabolites.

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