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. Author manuscript; available in PMC: 2013 Jan 1.
Published in final edited form as: Mass Spectrom Rev. 2011 Jul 13;31(1):134–178. doi: 10.1002/mas.20342

FIGURE 15.

FIGURE 15

Two-dimensional mass spectrometric analysis of polyunsaturated fatty acid fragmentation pattern with variation of collision gas pressure. Mass spectrometric analysis was performed with a TSQ Quantum Ultra Plus triple-quadrupole mass spectrometer (Thermo Fisher Scientific, San Jose, CA) equipped with an automated nanospray apparatus (i.e., Nanomate HD, Advion Bioscience Ltd., Ithaca, NY) and Xcalibur system software. The first and third quadrupoles were used as independent mass analyzers with a mass resolution setting of 0.7 Thomson while the second quadrupole served as a collision cell for tandem mass spectrometry. Product-ion scan of 8,11,14-eicosatrienoic acid (20:3 FA) (5 pmol/μL) was performed after direct infusion in the negative-ion mode at the fixed collision energy of 16 eV and varied collision gas pressures ranging from 0 to 3 mTorr as indicated. A 2-min period of signal averaging in the profile mode was employed for each scan. All the scans were automatically acquired with a customized sequence subroutine operated under Xcalibur software. All the scans are displayed after being amplified to the 5% of the base peak in each individual scan.