Triple-detector instrument

Fig. 11.16. Representation of three tandem mass spectrometry (MS/MS) scan modes illustrated for a triple quadrupole instrument configuration. The top panel shows the attributes of the popular and prevalent product ion CID experiment. The first mass filter is held at a constant m/z value transmitting only ions of a single mlz value into the collision region. Conversion of a portion of translational energy into internal energy in the collision event results in excitation of the mass-selected ions, followed by unimolecular dissociation. The spectrum of product ions is recorded by scanning the second mass filter (commonly referred to as Q3 ). The center panel illustrates the precursor ion CID experiment. Ions of all mlz values are transmitted sequentially into the collision region as the first analyzer (Ql) is scanned. Only dissociation processes that generate product ions of a specific mlz ratio are transmitted by Q3 to the detector. The lower panel shows the constant neutral loss CID experiment. Both mass analyzers are scanned simultaneously, at the same rate, and at a constant mlz offset. The mlz offset is selected on the basis of known neutral elimination products (e.g., H20, NH3, CH3COOH, etc.) that may be particularly diagnostic of one or more compound classes that may be present in a sample mixture. The utility of the two compound class-specific scans (precursor ion and neutral loss) is illustrated in Fig. 11.17.

Due to the problems encountered with SEC-LALLS and SEC-viscometry, a triple-detector SEC technology has been developed, where three on-line detectors are used together in a single SEC system. In addition to the concentration detector, an on-line viscometer and a LALLS instrument are coupled to the SEC... 

W. W. Yau and D. T. Gillespie, Triple-detector TREE instrument for polyolefin research. Waters International GPC Symposium Proceedings, 1998, pp. 252-256 (www.waters.com). 

The triple quadrupole instrument has three quadrupoles in series these are often called Ql, Q2 and Q3. In full scan mode, a broad m/z range of ions passes through all three quadrupoles to the detector giving a mass spectrum. In selected ion monitoring , Ql receives a mixture of all ions but only passes the ion of interest into Q2. Q2 is a collision... 

Nonetheless, compared with its older cousin Tref, Crystaf is still in its early stage of development. Improvements not only in terms of a better theoretical understanding, but also from the viewpoint of instrumentation, might lead to a more efficient fractionation process. For example, the recent development of a triple detector (IR/light scattering/viscometer) for Crystaf, the so-caUed Crystaf 3D, can provide a wealth of information on polymer microstructure at each crystallization temperature. 

Frequently, viscometry and light scattering detection are combined in a single instrument (Mendichi Schieroni, 2001 Wang et al, 2004). This yields direct estimates of the IVD and the MMD, as well as of the Mark-Houwink constants. The root-mean-square radius cannot be obtained from such a Triple SEC or Triple detector system. 

Scattering on the Triple-Axis-Diffractometer [1,2] at the HASYLAB high-energy beamline BW5 is performed in the horizontal plane using an Eulerian cradle as sample stage and a germanium solid-state detector. The beam is monochromatized by a singlecrystal monochromator (e.g. Si 111, FWHM 5.8 ), focused by various slit systems (Huber, Riso) and iron collimators and monitorized by a scintillation counter. The instrument is controlled by a p-VAX computer via CAMAC. 

In tandem MS mode, because the product ions are recorded with the same TOF mass analyzers as in full scan mode, the same high resolution and mass accuracy is obtained. Isolation of the precursor ion can be performed either at unit mass resolution or at 2-3 m/z units for multiply charged ions. Accurate mass measurements of the elemental composition of product ions greatly facilitate spectra interpretation and the main applications are peptide analysis and metabolite identification using electrospray iomzation [68]. In TOF mass analyzers accurate mass determination can be affected by various parameters such as (i) ion intensities, (ii) room temperature or (iii) detector dead time. Interestingly, the mass spectrum can be recalibrated post-acquisition using the mass of a known ion (lock mass). The lock mass can be a cluster ion in full scan mode or the residual precursor ion in the product ion mode. For LC-MS analysis a dual spray (LockSpray) source has been described, which allows the continuous introduction of a reference analyte into the mass spectrometer for improved accurate mass measurements [69]. The versatile precursor ion scan, another specific feature of the triple quadrupole, is maintained in the QqTOF instrument. However, in pre-... 

Figure 6.8 Diagram of instrumental configuration of the LC/MS system used for characterization of crude fermentation extracts. The system consists of the following components (1) HPLC (2) loop injector (3) guard column (4) 5pm C18 HPLC column (4.6mm x 25cm) (5) zero dead volume tee (6) UV detector (7) fraction collector (8) triple quadrupole mass spectrometer equipped with ESI interface (9) ESI power supply and gas manifold and (10) syringe pump. (Reprinted with permission from Ackermann et al., 1996a. Copyright 1996 Elsevier.)...

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