Triple quadrupole analyzer

Linked Scanning with Triple Quadrupole Analyzers... 

Scanning techniques are carried out differently with such hybrid instruments as the triple quadrupole analyzer, the Q/TOF (quadrupole and time-of-flight), and double magnetic-sector instruments. 

Q/TOF, used for two mass analyzers (quadrupole and time-of-flight) used in combination QQQ (or QqQ)- a triple quadrupole analyzer (if q is used, it means the central quadrupole is also a collision cell)... 

FIGURE I (A) An ESI source attached to a single quadrupole analyzer. The Instrument can be interfaced to an HPLC, CE or a syringe pump. The ionization is done at atmospheric pressure and the mass analysis in vacuum. This configuration is used for molecular weight determination. (B) An ESI source attached to a triple quadrupole analyzer. In a typical MS - MS experiment the precursor ion (Mp) is selected by the first analyzer (Ql), reacts with an inert gas in Q2 to yield the product ions (MI, M2, M3), and the product ions are analyzed by scanning Q3. This yields the product (fragment) ion spectrum. 

FIG U RE 4.9 A representative chromatogram of microsomal stability profiling of buspirone analyzed by FlashQuant workstation. Samples ( 2pL) are spotted and air-dried on a MALDI plate. Solid samples are irradiated by a focused laser light, and the resulting ions are analyzed under the MRM mode by triple quadrupole analyzer. Ninety-six samples were analyzed in 5 min and 384 samples were analyzed in 20 min. (Courtesy of Applied Biosystem and MDS SCIEX, Foster City, CA.)... 

FIGURE 3.17 Comparison of ion traces from single and triple quadrupole analyzers. 

Recently (Corr 2006) a detailed account of design considerations for, and initial performance characteristics of, a MALDI-MS/MS instrument for high speed quantitative analysis of small molecules has described incorporation of most of the considerations of the preceding paragraph. The use of a triple quadrupole analyzer in MRM mode with a high repetition rate laser avoids the disadvantages associated with use of an o-MALDI-TOF... 

It should also be noted that the RF-only quadrupoles (as well as the related RF-only hexapoles and octapoles) can be operated as ion lenses, often referred to as RF-only ion guides or simply ion guides. RF-only quadrupoles (denoted as lower case q , nonitalicized, to distinguish them from the closely related quadrupole mass filters Q) also act as efficient collision cells for collision induced dissociation in triple quadrupole analyzers (QqQ, Section 6.4.3) and hybrid tandem quadrupole-time of flight instruments (QqTOF, Section 6.4.7). Discussion of these devices must be postponed imtil the principles of all hnear quadrupoles have been considered (Section 6.4.2). 

There are a number of options for analyzing a peptide mixture extracted from a gel by mass spectrometry. The most widely used techniques are MALDI-TOF, preferably with delayed extraction, and ESI with a triple-quadrupole analyzer or a combination of quadrupole and TOF analyzers. The combination of ESI with an ion trap is also of great interest due to its sensitivity and the possibility of performing structural studies by MS". Downsizing of the electrospray capillary such as in the nanospray technique results in another gain in sensitivity and an extension of the measuring time, which is important to optimize fragmentation conditions. 

MS spectra with fragmentation of molecules require collision-activated dissociation (CAD) and triple quadrupole analyzers. In these instruments, the analysis is performed as follows the first quadrupole selects the interesting ion (parent ion), the second produces the fragments from the isolated ion, and the third quadrupole analyzes the fragmentation products (daughter ion spectmm). These steps (ion isolation, fragmentation, and analysis) can be repeated by addition of n quadrupole devices (multisector mass spectrometer) to allow multiple MS/MS experiments (MS") to be performed. 

For optimal selectivity, particularly for quantitation with ion trap or triple quadrupole analyzers, MS/MS scanning techniques can be utilized in GCMS. With these techniques, instruments are operated to perform one of three basic experiments including product ion analysis, precursor ion analysis or neutral loss analysis. Ion traps are normally limited to product ion scans in which a particular ion of interest is isolated in the ion trap, subjected to collisional activation and its fragments are detected. Triple quadrupoles can additionally be operated to detect all precursors that generate a common fragment or the analyzer can be set to detect a specific neutral loss characteristic of an analyte functional group. All these methods add specificity to mass spectral detection. 

Highly resolved selected reaction monitoring, MS/MS target compound scan technique using enhanced mass resolution at Q1 of a triple quadrupole analyzer for increased analyte selectivity. 

The acquisition and study of the spectra of selected precursor ions, or of precursor ions of a selected neutral mass loss. Structure selective target analyte quantitations use SRM/MRM data acquisition methods. MS/MS can be accomplished using beam instruments incorporating more than one analyser (tandem mass spectrometry in space, triple quadrupole analyzer) or in trap instruments (tandem mass spectrometry in time). 

The ionization process in ES-MS is very gentle thus resulting in very few fragment ions and little or no sequence information. To overcome this problem many ES instruments have triple quadrupole analyzers for coUisional activation MS/MS experiments. The first quadrupole is used to select the parent ion, the second is the collision chamber and the third separates the resulting fragment ions. 

The trends in the analysis of biopesticides are aimed at analytic methods that allow the detection of trace amounts of these compounds in a very short time. In this sense, the best-positioned techniques at this moment are as follows (a) SPE (with novel selective tailor-made sorbent materials) and QuE-ChERS (with its variants) for sample preparation and (b) ultra-performance LC coupled to MS with an electrospray source and a triple quadrupole analyzer (UPLC-ESI-QqQ-MS/MS) for identification/quantification. However, more improvements are still needed to allow a full understanding of the fate and behavior of biopesticides in the environment. 

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