Enhanced product ion scan

Fig. 1.39 LC-MS data dependent analysis of vinpocetin in rat urine using dynamic background substraction (DBS) on a triple quadrupole linear ion trap. (A) Full scan MS (survey scan) trace. (B) Enhanced product ion scan (dependent scan). The major peak at 3.9 min corresponds to apovinpocetin, the minor one at 2.9 min to the hydroxylation product of apovinpocetin (m/z 339).

Sierra Analytics and Applied Biosystems investigated the metabolic profile of indinavir, an HIV protease inhibitor with a very short half-life (2 hours), readily metabolised via CYPs to produce phase I and subsequent II products. Aliquots (10 pL) of indinavir incubated with rat liver S9 fractions were separated by online liquid chromatography and analysed with an Applied Biosystems hybrid triple quadrupole/linear ion trap mass spectrometer in information dependent acquisition (IDA) mode. This consisted of an enhanced MS survey scan followed by enhanced product ion scans for the two most intense parent ions as dependent MS/MS experiments. 

Scholz K, Dekant W, Volkel W, Pahler A. Rapid detection and identification of N-acetyl-L-cysteine thioethers using constant neutral loss and theoretical multiple reaction monitoring combined with enhanced product-ion scans on a linear ion trap mass spectrometer. J Am Soc Mass Spectrom 2005 16 1976-1984. 

S.2.2 Triple Quadrupole Linear Ion Trap Mass Spectrometry Hybrid triple quadrupole linear ion trap mass spectrometry (Q-Trap) can perform NL- and PI-dependent MS/MS acquisition (neutral loss-enhanced product ion scan [NL-EPI] and precursor ion-enhanced... 

The software tools accompanying the QTRAP MS/MS allow set-up of multiple selected reaction monitoring (SRM) transitions for all likely metabolites after the major product ion transitions for the dosed compound are known. Because QTRAP MS/MS can monitor up to 100 SRM transitions during a single assay, the SRM transitions required for quantitation of the dosed compound and internal standard are obtained along with the possible metabolite transitions. During sample analysis, when a possible metabolite transition exceeds a preset threshold value, the QTRAP MS/MS performs an enhanced product ion (EPI) scan. When the assay is complete, the EPI scans can be used to determine whether the hits are metabolites, and if they are metabolites, what part of the molecule has changed. Thus, one analytical run provides both quantitative and metabolite information. 

B) mass spectrum from positive enhanced resolution scan finds the clozapine-GSH adduct at m/z 632 (C) enhanced product ion spectrum of clozapine-GSH adduct at m/z 632. 

The major advantage of this instrument is that qualitative and quantitative analysis can be performed in the same LC-MS run. As an example in a data-dependent experiment, the selected reaction monitoring mode can be used as a survey scan and the enhanced product ion mode (EPI) as a dependent scan. The consequence is that for each quantified analyte a confirmatory MS/MS spectmm can be obtained. 

Enhanced product ion (EPI) Resolving (fixed) Fragment Trap/scan... 

Gao et al., 2007) is used as a survey scan, similar to PI or CNL, to detect metabolites. The MRM transition list can also be generated from metabolites identified from in vitro incubations (Mauriala et al., 2005). The peak, which reaches threshold in MRM transition, triggers the acquisition of a corresponding enhanced product ion (MS/MS) spectrum. This procedure, known as the MRM approach, is an alternative to rapid metabolite detection and structural elucidation with a triple quadrupole mass spectrometer. 

Recently introduced hybrid triple quadruple—linear ion trap (QTRAP) mass spectrometer has scan functions identical to those of classical triple quadruple (PI scan, NL scan, and MRM). It can be used for small-molecule quantification with MRM in both bioanalysis and in vitro ADME studies (Hopfgartner et ah, 2004). The QTRAP also has scan functions (full MS scan and MS/MS scan) similar to an ion trap mass spectrometer. Most importantly, MS, MRM, PI, and NL scans on QTRAP instruments can serve as survey scans to trigger the information-dependent acquisition (IDA) of enhanced product ion spectra (EPI) with polarity switching, which provide product ion spectra with rich fragments with no low-mass cutoff (Xia et al., 2003 Zheng et al., 2007 Wen et al., 2008b Yao et al., 2008 Jian et al., 2009). The information-dependent acquisitions have been widely applied to reactive... 

A QTRAP instrument is capable of a wide variety of scan modes full MS scan (MS), product ion scan (MS and MS ), PI scan, NL scan, MRM, predictive MRM (pMRM), multiple ion monitoring (MIM), enhanced multiply charged (EMC) scan and time-delayed fragmentation (TDF) (Hopfgartner et al., 2004 King and Fernandez-Metzler, 2006). Most of these scan modes can be incorporated into an IDA experiment to achieve metabolite detection and MS/MS spectral recording in a single run. 

Ionization conditions were optimized for individual sulfatide or ganglioside subspecies and enhanced product ion (EPI) scans were selected to provide a greater diversity of product ions. EPI scans were performed with QO trapping set to on, a linear ion trap fill time of 100 ms, and a scan rate of 1,000 amu/s. Example of ESTMS/MS analysis of GAO subspecies is shown in Fig. 7.5a see Note 13). 

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