QTrap system

Li et al. [40-42] used a QTrap system to incorporate both the conventional SRM-only acquisition of parent compounds and the SRM-triggered IDA of potential metabolites within the same scan cycle during the same LC-MS/MS run in plasma sample analysis. The fast scanning capability of the LIT allowed for the IDA of metabolite MS/MS spectra <1 s/scan, in addition to the collection of adequate data points for SRM-only channels. A SRM survey scan containing 30-150 SRM channels was established by running a script in Analyst software. If the intensities in these... 

Figure 4.13 ESI product ion mass spectra of the deprotonated molecules [M-H] of (a) hydrochlorothiazide (mol wt = 297), (b) bumetanide (mol wt = 364), and (c) furo-semide (mol wt = 330) recorded on an API2000 QTrap system.

Figure 5.10 (a) Top-down product ion mass spectrum generated from the 18-fold charged molecule of the 22kDa isoform of hGH and (b) top-down product ion mass spectrum generated from the 14-fold charged molecule (m/z = 1148.3) of the 16kDa artefact of hGH (both measured on a 4000 QTrap system). 

One of the best tools for metabolite profiling is the hybrid QTRAP MS/MS system (Applied Biosystems).119-121 While the hybrid QTRAP MS/MS was initially considered a premier tool for metabolite identification, it has more recently been seen as a tool for quantitation and metabolite profiling. Li et al.122 described the use of a hybrid QTRAP MS/MS system for discovery PK assays plus metabolite profiling in the same analytical procedure. Because QTRAP MS/MS may be used as a triple quadrupole MS system, it can be used as part of a quantitative HPLC/MS/MS system. Because QTRAP MS/MS also has linear ion trap capabilities, it can be used for metabolite screening and characterization—essentially it combines the capabilities of a triple quadrupole mass spectrometer and a linear ion trap mass spectrometer. 

Our laboratory used the QTRAP MS/MS system for both quantitative analysis and metabolite profiling when assaying plasma samples. We found it useful to use three rules for deciding when to report a possible metabolite ... 

Another recent innovation is the QTrap mass spectrometer. The QTrap MS system combines the capabilities of a triple quadrupole mass spectrometer and a linear ion trap mass spectrometer into one MS system. Initially, the QTrap MS was used primarily as a tool for metabolite identification studies [34, 35, 38]. As reported by Li et al. [138], the QTrap MS can also be used as an excellent system for the quantitative analysis of discovery PK samples. The advantage of the QTrap MS system for quantitative analysis is that it can be used to look for plasma metabolites of the NCE and provide an easy way to monitor them while providing the quantitative data on the NCE. 

C.A. Mueller, W. Weinmann, S. Dresen, A. Sclu eiber, M. Gergov, Development of a multi-target screening analysis for 301 drugs using a QTrap LC-MS-MS system and automated library searching. Rapid Commun. Mass Spectrom., 19 (2005) 1332. 

In addition to the dosed compound, often one can look for common metabolites when assaying plasma samples from a PK study this step is often referred to as metabolite profiling. In our laboratory we have used the QTrap MS/MS system to provide both quantitative analysis and metabolite profiling when assaying plasma samples. The hardware and software tools that are part of the QTrap MS/MS system are well suited to this purpose [110-114], We have found it useful to use three rules for deciding when to report a possible metabolite. The metabolite reporting rules are as follows ... 

In the present system, MS/MS is performed in space where the LIT serves only as a trapping and mass analyzing device. The commercial form of this instrument is named Q Trap and already four different generations have been developed using different quadrupole geometries (Q Trap, 3200 Qtrap, 4000 Qtrap, and 5500 Qtrap). While quadrupole CID spectra are obtained in MS, MS are typical trap CID spectra. 

Prior to P450 reaction phenotyping or inhibition experiments, it is important to determine enzyme kinetic parameters such as Km and Umax for the formation of selected metabolites that are subjected to quantitative analysis by LC-MS. For example, -warfarin is catalyzed by CYP2C9 to a specific metabolite, 7-hydroxy-5 -warfarin (Fig. 15.13). Thus, a CYP2C9 inhibition assay is developed based on the reaction. In the assay, Y-warfarin is incubated with HLM in the presence of a test compound, followed by quantification of 7-hydroxy-5 -warfarin by LC—MS (Zhang et ah, 2001). To set up this assay in our lab, enzyme kinetics for the formation of 7-hydroxy-iS-warfarin in HLM was determined. In this experiment, warfarin was incubated at concentrations from 0 to 250 >M with HLM at optimized conditions. Rates of 7-hydroxy-S -warfarin formation at various substrate concentrations were determined as shown in Figure 15.13a, from which Km and Umax values were calculated. The warfarin assay represented an analytical challenge since the turnover of warfarin in the HLM system was extremely low. To be able to quantitatively determine low concentrations of 7-hydroxy-5 -warfarin in the incubations, a very sensitive LC—MS method that used MRM with a 4000 QTRAP has been developed (Fig. 15.13a). 

Binary solvent system, water with UPLC-QTRAP MS 0.1% formic acid, acetonitrile... 

Figure 4.4 ESI product ion mass spectra of protonated molecules [M+H] of (a) morphine (mol wt = 285), and (b) pethidine (mol wt = 247), recorded on a QTrap 2000 system.

Figure 5.7 ESI product ion mass spectra of the five-fold charged precursor ions [M+5H] of (a) m/z 1162 of Humalog LisPro, (b) m/z 1166 of Novolog Aspart, and (c) m/z 1165 of Glulisine Apidra measured on a QTrap 4000 system.

Figure 5.8 ESI product ion mass spectrum of the aT9 peptide characterizing the a-chain of bovine hemoglobin, measured on a QTrap 4000 system.

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