Abstract
An improved mass defect filter (MDF) method employing both drug and core structure filter templates was applied to the processing of high resolution liquid chromatography/mass spectrometry (LC/MS) data for the detection and structural characterization of oxidative metabolites with mass defects similar to or significantly different from those of the parent drugs. The effectiveness of this approach was investigated using nefazodone as a model compound, which is known to undergo multiple common and uncommon oxidative reactions. Through the selective removal of all ions that fall outside of the preset filter windows, the MDF process facilitated the detection of all 14 nefazodone metabolites presented in human liver microsomes in the MDF-filtered chromatograms. The capability of the MDF approach to remove endogenous interferences from more complex biological matrices was examined by analyzing omeprazole metabolites in human plasma. The unprocessed mass chromatogram showed no distinct indication of metabolite peaks; however, after MDF processing, the metabolite peaks were easily identified in the chromatogram. Compared with precursor ion scan and neutral loss scan techniques, the MDF approach was shown to be more effective for the detection of metabolites in a complex matrix. The comprehensive metabolite detection capability of the MDF approach, together with accurate mass determination, makes high resolution LC/MS a useful tool for the screening and identification of both common and uncommon drug metabolites.
Footnotes
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Part of this work was presented at the 7th International ISSX Meeting, Vancouver, Canada, 29 Aug–2 Sep, 2004 (Zhu et al., 2004).
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.106.009241.
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ABBREVIATIONS: LC/MS, liquid chromatography/mass spectrometry; BPC, base peak chromatogram; FT, Fourier transform; MS/MS, tandem mass spectrometry; HLM, human liver microsome; NEF, nefazodone; m-CPP, meta-chlorophenylpiperazine; MDF, mass defect filter; MH+, protonated molecule; NL, neutral loss; PI, precursor ion; TIC, total ion chromatogram; ToF, time-of-flight; Q-ToF, quadrupole ToF.
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↵1 Current affiliation: Novatia, LLC, Monmouth Junction, New Jersey.
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↵2 Current affiliation: Amgen, Thousand Oaks, California.
- Received January 12, 2006.
- Accepted June 28, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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