Triple quad instruments

FIA-MS-MS in parent or neutral loss mode on triple quad instruments can also be applied to screen mixtures of unknown compounds quite rapidly, so that compound classes can be recognised. Yet despite the information about molecular weight and the structural information by product ions, MS-data systems in their commercial form up to the mid-1990s provided no structural information for identification purposes in the form of libraries comparable with the NIST-library of El spectra in GC-MS analysis. It can be hoped that troubles arising out of the lack of computer-searchable library data for identification will be overcome with the gradual increase in trap applications in MS-MS mode. The situation in identification is set to change [36]. 

Most methods for determination of these compoimds are based on liquid chromatography or gas chromatography, which require derivatization (Hack and Muir, 2003). Selective MS-MS techniques facilitated by triple quad instruments or ion trap instruments enable the detection of hydrolysis products to the range of pg/mL (Barr et al., 2004 Riches et al., 2005). This concentration is so low that hydrolysis products can be detected in urine up to 1 week after exposure (Riches et al., 2005). Nerve agents bind to proteins such as AChE and butyrylcholinester-ase (BuChE). These proteins are not excreted or metabolized rapidly (typical half-life is 12 days for BuChE) (Hall et al., 1984), which means that adducts to proteins can serve as retrospective biomarkers for exposure to nerve agents (Bidder et al., 2002 van der Schans et al., 2004). The enzymahc measurement of AChE activity, known as the Ellman assay, is the easiest method to determine nerve agent exposure (Ellman et al., 1961 Halbrook et al., 1992). 

Accurate mass assignment of highly resolved ion-intensity signals remains problematic. QITMS is a relatively simple and compact apparatus (benchtop) and an order of magnitude less expensive than the multistage (triple quad or tandem double-focusing) instruments traditionally used for structural determination. 

One way to carry out MS-MS is to link two or more mass analyzers in series to produce an instrument capable of selecting a single ion, and examining how that ion (either a parent or daughter ion) fragments. For instance, three quadrupoles can be linked (a so called triple quad ) to produce a tandem mass spectrometer. In this arrangement, the first quadrupole selects a specific ion for further analysis, the second... 

S uzuki et al. report a hybrid triple quadrupole/linear ion trap MS/MS technique. The triple quad-rupole-linear ion trap LC/MS combines the scan speed and sensitivity of ion trap MS while retaining the selective scanning modes of triple quadrupole MS. The ability to perform both types of MS on a single instrument reduces the time required for analysis while eliminating the chance of errors due to analyzing different samples in multiple MS runs. The method, coupled with LC separation, was demonstrated to be usefuUy applied to the structure elucidation of YTX analogues. ... 

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