Quadrupole ion trap instrument

Example The ESI mass spectrum and the charge-deconvoluted molecular weights (inset) of bovine serum albumine (BSA) as obtained from a quadrupole ion trap instrument are compared below (Fig. 11.19). Ion series A belongs to the noncovalent BSA dimer, series B results from the monomer. [24]... 

A major breakthrough was the eommereial introduetion of dedieated quadrupole ion-trap instruments equipped with an API souree for ESI and APCI, i.e., the LCQ instraments from Thermo Fiimigan, the Esquire from Broker, and the LC-MSD-Trap from Agilent Technologies. 

As an alternative to a triple-quadrupole, ion-trap instruments have been used in some cases. Dne to the limited nnmber of quantitative applications [41], the potential of quadrapole-hnear-ion-trap hybrid (Q-LIT) caimot yet be evalnated. 

Tandcm-in-Time Spectrometers. Tandem-in-iime instruments form the ions in a certain spatial region and then at a later lime expel the unwanted ions and leave the selected ions to be dissociated and mass analyzed in the same spatial region. This process can be repeated many limes over to perform not only MS/MS experiments, but also MS/MS/MS and MS" experiments. Fourier transform ICR and quadrupole ion-trap instruments are well suited lor performing MS" cxperimenls. In principle, tandem-in-time spectrometers can perform M.S/MS experiments much more simply than tandem-in-space instruments because of the dilTiculty in providing different ion focal positions in the latter. Although tandem-in-time spectrometers can readily provide product ion scans, other scans, such as precursor ion scans and neui ral loss scans, are much more difficult to perform than they arc with tandem in space instruments. 

ESI mass spectrum of recombinant human insulin recorded at low mass resolution (M/AM < 1,000) by a quadrupole ion-trap instrument (spraying solution 50/50 methanol/water containing 1% acetic acid, SpL/min). Inset Profile of the multiple-charged ions in the m/z 1160 to 1180 range. 

FIGURE 14.1 Diagram of the first 3D quadrupole ion trap instrument designed for the... 

The following specific applications of the use of quadrupole ion trap instruments demonstrate clearly the power of this analytical tool. Software and hardware improvements have made the set-up and analysis of data extremely easy for users, even when performing different scanning functions in the same analysis. 

The new technology embodied in the quadrupole ion trap instruments of today provides also excellent quantitative data. A calibration curve was prepared for Method 8270 using, as the required low, mid, and high concentration levels, solutions of 5 ppm, 50 ppm, and 150 ppm the solutions were prepared in pure solvent (dichlo-romethane, DCM). A TIC obtained at 5 ppm is shown in Figure 15.34. In addition, these same calibration concentration levels were prepared in DCM containing a mixture of both 2 diesel fuel oil and lOW-30 motor oil at a concentration of 3000 ppm. The corresponding TIC is shown in Figure 15.35. 

In this study, the level of scrambling at different CID fragmentation amplitudes was monitored in the model peptide PI (HHHHHHIIKIIK) with a regioselective deuterium labeling that is a sensitive probe for H/D scrambling (see Section 8.2.3) [43]. In a 3D quadrupole ion trap instrument, the triply charged peptide was subjected to various degrees of RF-induced collisional activation followed by... 

O. A. Silivra, F. Kjeldsen, I. A. Ivonin, and R. A. Zubarev, Electron capture dissociation of polypeptides in a three-dimensional quadrupole ion trap instrumentation and first results, 7. Am. Soc. Mass Spectrom. 16, 22-27 (2005). 

Key among these are quadrupole based instruments, single quadrupoles and triple quadrupoles as well as the closely related quadrupole ion trap instruments (3D and 2D ion traps). Their widespread use in trace quantitative analyses has been facilitated by the fact that these instruments can also be readily coupled to GC and/or LC because of inherent features of the mass analyzer fields, i.e. they operate at or near ground potential. 

A 50 pg LOD for TATP has been reported using single ion monitoring (SIM) of m/z 43,59,75,101, and 222, under conditions where the GC-MS analyses was carried out at an injector temperature of 120°C and El source temperature of 200°C [36]. Linear quadrupole and quadrupole ion trap instrument have been reported to yield 50 and 100 pg LOD based on extracted ions m/z 43, 59, and 75 under optimized conditions of injection... 

Fig. 4.50. Layout of a quadrupole ion trap instrument equipped with an external ESI ion source. The analogy to the ESI-LIT configuration shown in Fig. 4.41 is striking. Reproduced from Ref. [168] by permission. John Wiley Sons, 2000.

The 2008 version of the NIST/EPA/NIH Mass Spectral Database [77,83] contains about 222,000 El spectra of more than 192,000 compounds plus roughly 28,000 replicate spectra. For almost 43,000 compounds there is a conpilation of 293,000 Kovats retention index (KRI) values as determined on nonpolar and polar columns. Since 2005, this database also offers CID spectra, which actually sum up to 14,800 spectra of about 5,300 different ions. The reason for the larger number of spectra over the number of ions is the inclusion of multiple spectra for a given ionic species as obtained by nozzle-skimmer dissociatio and CID on triplequadru-pole or quadrupole ion trap instruments, respectively [84]. The NIST/EPA/NIH Mass Spectral Database is available as a stand-alone version or with - most probably - any commercial mass spectrometer that can be equipped with an El ion source. 

Fig. 4. Illustration of proteomic analysis of the rat synaptic plasma-membrane fraction by combination of SDS-PAGE and gradient reversed-phase LC/ESI-MS/MS (GeLC/MS/MS) on a quadrupole ion-trap instrument [21]. (A) The developed gel is cut into bands and the bands are (i) destained, digested (trypsin), and the sample is desalted for injection into the column. (B) Base-peak chromatogram obtained from the tryptic digest of the 98-120 kDa. Data-dependent acquisition is employed, where in one acquisition cycle (ii) a full-scan mass spectrum is acquired (C), followed by (iii) CID-MS/MS of the most intense ion (m/z 915.5) in this mass spectrum (D). (However, MS/MS is not initiated, when ion intensity in the full-scan mass spectrum is below a preset threshold.) Database search (iv) matches the MS/MS to the protein(s) (Table 1, major sequence ions of the peptide are indicated in chart D).

The different types of analyser for quadrupole rod and quadrupole ion trap instruments function on the same mathematical basis (Paul and Steinwedel, 1953 Paul et al., 1958 and patent specification 1956) and, therefore, show the same resolution properties (Figure 2.183). 

In sections covering the MS/MS scan, we discussed coUisional-activated dissociation (CAD) in a triple quadrupole and in a quadrupole ion traps instruments. Other ion trap CAD schemes have been developed to increase energy deposition and/or the degree of fragmentation. For example, a characteristic of using single-frequency resonance excitation is that when the product ions are formed, they are not activated because they have a... 

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