Trap-triple quadrupole mass spectrometer

A triple-quadrupole mass spectrometer with an electrospray interface is recommended for achieving the best sensitivity and selectivity in the quantitative determination of sulfonylurea herbicides. Ion trap mass spectrometers may also be used, but reduced sensitivity may be observed, in addition to more severe matrix suppression due to the increased need for sample concentration or to the space charge effect. Also, we have observed that two parent to daughter transitions cannot be obtained for some of the sulfonylurea compounds when ion traps are used in the MS/MS mode. Most electrospray LC/MS and LC/MS/MS analyses of sulfonylureas have been done in the positive ion mode with acidic HPLC mobile phases. The formation of (M - - H)+ ions in solution and in the gas phase under these conditions is favorable, and fragmentation or formation of undesirable adducts can easily be minimized. Owing to the acid-base nature of these molecules, negative ionization can also be used, with the formation of (M - H) ions at mobile phase pH values of approximately 5-7, but the sensitivity is often reduced as compared with the positive ion mode. 

Figeys, D. Aebersold, R. High sensitivity identification of proteins by electrospray ionization tandem mass spectrometry inital comparison between an ion trap mass spectrometer and a triple quadrupole mass spectrometer. Electrophoresis 1997,18, 360-368. 

Multiple mass analyzers exist that can perform tandem mass spectrometry. Some use a tandem-in-space configuration, such as the triple quadrupole mass analyzers illustrated (Fig.3.9). Others use a tandem-in-time configuration and include instruments such as ion-traps (ITMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS or FTMS). A triple quadrupole mass spectrometer can only perform the tandem process once for an isolated precursor ion (e.g., MS/MS), but trapping or tandem-in-time instruments can perform repetitive tandem mass spectrometry (MS ), thus adding n 1 degrees of structural characterization and elucidation. When an ion-trap is combined with HPLC and photodiode array detection, the net result is a profiling tool that is a powerful tool for both metabolite profiling and metabolite identification. 

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. 

Quadrupole mass spectrometers [10] or quadrupole ion traps are today the most widely used mass spectrometers. The physical bases were described in the early 1950s by Paul and Steinwedel. For his work Paul received the Nobel Prize in 1989 [11]. Triple quadrupole mass spectrometers have become very popular instruments for qualitative and quantitative analysis. Yost et al. [12] built in 1978 the first instrument and it took four years before this type of instrument was commercialized. The coupling with liquid chromatography or gas chromatography is well established and benchtop ion traps or quadrupoles are nowadays part of the standard equipment of many analytical laboratories. 

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. 

The most common types of MS/MS instruments available to researchers in food chemistry include triple quadrupole mass spectrometers and ion traps. Less common but commercially produced tandem mass spectrometers include magnetic sector instruments, Fourier transform ion cyclotron resonance (FTICR) mass spectrometers, and quadrupole time-of-flight (QTOF) hybrid instruments (Table A.3A.1). Beginning in 2001, TOF-TOF tandem mass spectrometers became available from instrument manufacturers. These instruments have the potential to deliver high-resolution tandem mass spectra with high speed and should be compatible with the chip-based chromatography systems now under development. 

The two-dimensional (2-D) or linear ion trap (LIT) emerged in the 2000s as an effective alternative to the 3-D trap. Before 1995, linear traps were used primarily as ion storage/transfer/ion-molecule reaction devices in combination with FTICR (Senko et al., 1997 Belov et al., 2001), TOF (Collings et al., 2001), 3D ion trap (Cha et al., 2000), and triple-quadrupole (Dolnikowski et al., 1988) mass spectrometers because LITs offer better ion storage efficiencies in comparison to 3D quadrupole ion traps of the same dimensions (Hager, 2002 Schwartz et al., 2002). In 2002, commercial LITs were introduced as either stand-alone mass spectrometers (Schwartz et al., 2002) or as part of a triple quadrupole mass spectrometer (Hager, 2002). 

The LIT introduced as part of a triple-quadrupole mass spectrometer is marketed under the name QTRAP. As shown in Fig. 1.26, the ion path and the differentially pumped region of QTRAP are similar to a triple quadrupole (API 3000, API 4000, and API 5000), except the Q3 is capable of functioning as a linear trap. QTRAP and its capabilities are described in detail in Chapter 3. Table 1.2 compares some of the advantages and limitations of QTRAP and LTQ mass spectrometers. 

Josephs, J. L., and Sanders, M. (2004). Creation and comparison of MS/MS spectral libraries using quadrupole ion trap and triple-quadrupole mass spectrometers. Rapid Commun. Mass Spectrom. 18 743-759. 

For abbreviation of analyte names see Sect. Abbreviations . ACN acetonitrile, APCI atmospheric pressure chemical ionization, dial, microdialysis samples, ESI electrospray ionization, FA formic acid, iso isocratic, IT ion trap, lin range linear range, MeOH methanol, MRM multiple reaction monitoring, MS full scan mass spectrometry, n.s. not specified, OAc acetate, QqQ triple quadrupole mass spectrometer, SIM selected ion monitoring, Solv HPLC solvent, SQ single quadrupole mass spectrometer, T temperature Ratios given as v/v... 

The linear trap with axial ejection was invented by Hager, from MDS Sciex, in 2002 [20], Figure 2.31 displays a scheme of such an ion trap included in the ion path of a triple quadrupole mass spectrometer. 

A second type of MS instrument capable of performing a product ion scanning experiment is the ion trap mass spectrometer. The difference between this instrument and the triple quadrupole mass spectrometer is the ion trap is capable of performing numerous sequential product ion experiments on the same compound. For example, a potential metabolite is dissociated into several characteristic fragment ions in the first stage of MS/MS. Then, one of these fragment ions can be further dissociated into smaller ions. This is a second stage of MS/MS known as MS. This process can continue until the site of meta-... 

A. Low-Resolution CE-MS AND CE-MS/MS Methods Using Triple Quadrupole Mass Spectrometers or Quadrupole Ion Traps... 

M.S. The role of LC/MS/MS Spectral Library Searching for impurity Analysis Using Ion Trap and Triple Quadrupole Mass Spectrometers, in Proceedings of the 46th ASMS Conference on Mass Spectrometry and Allied Topics, Orlando, FL, 1998. 

Many similar applications of quadrupole linear ion trap instruments have been reported [320-322,329,330], As discussed above, the Q-Trap is a triple quadrupole mass spectrometer capable of performing QMF type and 2D ion trapping experiments. This mass spectrometer can be operated exclusively in the QMF mode, as with a conventional QMF, or it can be operated exclusively in the ion trapping mode similar to a conventional 2D ion trap mass spectrometer. Advantages of using a Q-Trap mass spectrometer over a conventional QMF mass spectrometer come into play when one is attempting to perform both quantitative and qualitative metabolite detection/identification experiments from a single injection rather than separate... 

For one study involving the differentiaton of C3H3 isomers, a Finnigan triple quadrupole mass spectrometer was employed. This type of mass spectrometric instrumentation has been described in several publicatons (23-24) and has been applied to a number of problems (25-26) in analytical chemistry. The first quadrupole is used to select an ion of interest, the second, in an rf-only mode, is used as a trap in which the ion undergoes (in our case reactive) collisions with a selected neutral gas, and the third quadrupole is used to analyze the results of those collisions. Work on structure differentiation was carried out on a VG Analy-... 

A triple-quadrupole linear ion trap (QqLIT), which is the most widely used hybrid linear ion trap, is based on the ion path of a triple-quadrupole mass spectrometer with Q3 operated as either a conventional RF/DC quadrupole mass filter or a linear ion trap mass spectrometer. " A QqLIT combines the advantages of a QqQ and a QIT within the same platform without compromising the performance of either mass spectrometer. It retains classical QqQ functions such as MRM, product ion scan, precursor ion scan, and constant neutral loss scan for quantitative and qualitative analysis, and possesses MS" ion accumulation... 

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