Scan function

Table 2. Scan Functions for a Triple Quadrupole Mass Spectrometer...

Laser Doppler Vibrometry (LDV) is a sensitive laser optical technique well suited for noncontact dynamic response measurements of microscopic structures. Up to now, this technology has integrated the micro-scanning function for... 

The 28 scan and layer line scan functions are provided as an aid to obtaining better estimates of the unit cell parameters for the substance being studied and in assessing contributions from background scattering and overlapping diffraction maxima. 

Data-dependent acquisition ability has been developed and incorporated into most software packages [MetaboLynx, Xcalibur, and Analyst Information Dependent Acquisition (IDA)]. In data-dependent acquisition mode, a mass spectrometer decides on the fly whether to collect MS/MS or MSn data, remain in full scan MS mode, or conduct other survey scans based upon user-defined criteria. Product ion spectra of potential metabolites can be automatically acquired in a single LC/ MS run. However, false positives may be generated due to highly intense matrix ion signals that may inadvertently trigger MS/MS or MSn scan functions. 

Fig. 11.10. Diagram illustrating the inner surfaces of the primary components of a Paul (3D) quadrupole ion trap. Ions generated by an external source are injected into the trap through an aperture in one of the end caps. Scan functions for isolating ions in the trap, exciting the mass selected ions to induce unimolecular dissociation, and ejecting ions from the trap (for detection) are implemented through the application of DC and RF voltages to the ring electrode.

Fig. 4.45. Complex scan function used for a tandem mass spectrometric study of 2,4,3, 6 -tetrachlorodiphenylether. Reproduced from Ref. [156] by permission. lohn Wiley and Sons, 1997.

Precursor ion and neutral loss scan functions are unique to a triple quadrupole mass spectrometer. These are powerful techniques for targeted detection of compounds and their related impurities that produces a characteristic neutral loss or a fragment ion corresponding to a unique structural feature. Both neutral loss and... 

Now use the Scan function to inspect the rows and columns of your 2D spectrum. Note the number of one of them and use the Slice function to transfer it to 1D WIN-NMR for further inspection. 

Figure 3.12. Mass spectra of BSA digest obtained using a QTRAP with (bottom panel) and without (top panel) EMC scan function. In the bottom spectrum, all the singly charged background ions are removed to enhance the multiply charged ions from the BSA digest.

The tandem-in-time instruments are mostly ion-trapping devices, including ion trap and FT-ICR. They operate in a time sequence in the scan function to yield MS/MS data, mostly product ion spectra. No additional mass analyzer is required. In the case of an ion trap, the scan function begins with the isolation of ions of interest with ejection of all other ions from the ion trap, followed by (a) translational excitation of ions by applying a supplementary RF voltage to the trap and (b) mass analysis of the product ions using resonant ejection. 

A third type of MS/MS instruments is a hybrid of tandem-in-space and tandem-in-time devices, including the Q-trap (QQ-2D-linear trap) [45] and the ion trap-FT-ICR (2D-linear ion trap-FT-ICR) [46]. The Q-trap takes the configuration of triple quadrupole, with the third quadrupole replaced by a 2D-linear ion trap. The uniqueness of this design is that the 2D-linear ion trap component can be used to perform either (a) a normal quadrupole scan function in the RF/DC mode or (b) a trap scan function by applying the RF potential to the quadrupole. It is well-suited for both qualitative and quantitative studies. In the case of ion Trap-FT-ICR, it combines ion accumulation and MS" features of a 2D-linear ion trap with excellent mass analysis capability (mass resolution, mass accuracy, and sensitivity) of FT-ICR. 

The rapid structure identification of metabolites is a powerful complement to previously described quantitative approaches. The utility of an automated metabolite identification approach, using LC/MS/MS with an ion trap mass spectrometer has been demon-strated.f In this study, MS" analysis is automated to provide maximum structural information in combination with predictive strategies for biotransformation. Automated data-dependent scan functions are used to generate full scan, MS/MS, and MS" mass spectra of... 

DDA was applied in a nnmber of studies to indinavir metabolism [36-38]. To study the in vitro metabolism of indinavir by incnbation with rat liver S9 fractions, a DDA procedure of six scan function was applied [36]. Upon detection of an ion with an abundance above the preset threshold in the snrvey scan, a full-spectrum production MS-MS spectrum of the most abundant ion in the MS spectrum was acquired, followed by a product-ion MS experiment on the most abrmdant ion in the MS-MS... 

A relatively new and powerful tool in metabolite identification is the (J-LIT instrument. In this triple-quadrapole instmment, the third quadrupole can be apphed as a scanning quadmpole, but also as a linear ion trap (Ch. 2.4.2). Potential and additional features of a Q-LIT in metabolite identification have been discussed by various groups [44-45]. The advantages of triple-quadrupole MS-MS spectra at ion-trap sensitivity as well as the enhanced sensitivity and speed in DDA experiments with the (J-LIT was demonstrated for the collagenase inhibitor trocade [44]. Various enhanced scan functions of the Q-LlT were applied in the identification of 6-aminobutylphthalide metabolites in rat brains, using microdialysis and LC-MS-MS [45]. Simultaneous quantification of a parent compound and screening for its... 

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