Product ion scanning

A product ion scan. Source ions (mT, f,, . .., fs ) are selected by setting Ql, in this case, to pass only m,. Collisional activation of these ions in Q2 induces dissociation to give fragment ions (f,, fj, f, ), which are detected by scanning Q3. The symbolism for this process is shown. 

Fixed-product ion scans (sector instruments). High-voltage scan or linked scan at constant B /E. Both techniques give a spectrum of all precursor (parent) ions that fragment to yield a preselected product (daughter) ion. 

As with the Q-ToF instrument, only two types of MS-MS experiment are available with the ion-trap, i.e. the product-ion scan and selected-decomposition monitoring, as described in Sections 3.4.2.1 and 3.4.2.4, respectively. 

The ion-trap and Q-ToF instruments are, because of the way that they operate, unable to carry out precursor-ion scans. Computer manipulation of data generated during product-ion scans of the Q-ToF system, however, can yield equivalent data to that produced directly by precursor-ion scans on other instruments and an evaluation of this software-based approach has been carried out [14],... 

In the ion-trap, the precursor is selected by the methodology described in Section 3.4.2.1 above for the product-ion scan. In SDM, however, the product ion scan is confined to only one m/z ratio, namely that of the product ion of interest. 

If SDM (see Section 3.4.2.4 above) is to be used, product-ion scans on ions associated with the analyte must be carried out to determine whether fragmenta-tion(s) occur that are appropriate to monitor. 

MS-MS is a term that covers a number of techniques in which two stages of mass spectrometry are used to investigate the relationship between ions found in a mass spectrum. In particular, the product-ion scan is used to derive structural information from a molecular ion generated by a soft ionization technique such as electrospray and, as such, is an alternative to CVF. The advantage of the product-ion scan over CVF is that it allows a specific ion to be selected and its fragmentation to be studied in isolation, while CVF bring about the fragmentation of all species in the ion source and this may hinder interpretation of the data obtained. 

Figure 5.42 Structures of three monhydroxylated metabolites of Indinavir proposed on the basis of the product-ion scans of their (M - - H)+ ions. Reprinted by permission of Elsevier Science from Identification of in vitro metabolites of Indinavir by Intelligent Automated LC-MS/MS (INTAMS) utilizing triple-quadrupole tandem mass spectrometry , by Yu, X., Cui, D. and Davis, M. R., Journal of the American Society for Mass Spectrometry, Vol. 10, pp. 175-183, Copyright 1999 by the American Society for Mass Spectrometry.

Mass-analysed ion kinetic energy spectrometry (MIKES) A form of MS-MS product-ion scan that may be carried out on a reversed-geometry double-focusing mass spectrometer. 

Product-ion scan An MS-MS scan in which those ions obtained by fragmentation of a given precursor ion are detected. 

Q-ToF The combination of quadrupole and time-of-flight mass analysers. This allows the m/z ratios of ions produced during a product-ion scan to be measured accurately and the elemental composition of these ions to be determined. 

Figure 6.2 Product-ion scan (EI-MS/MS) of M+ 783 (Irganox 3114). After Lattimer [37], Reprinted from Journal of Analytical and Applied Pyrolysis, 26, R. P. Lattimer, 65-92, Copyright (1993), with permission from Elsevier...

While metastable decompositions have been extensively studied for many decades, nowadays the use of tandem MS is almost exclusively limited to the study of decompositions caused by collision. Different kinds of experiments can be carried out by tandem MS the most common is the product ion scan. This is carried out by selecting ions with a given m/z value among all those formed in the source and detecting selectively their product ions formed due to CIDs. It follows that at least two analyzers (the tandem) are required. In... 

Figure 2.14 Tandem mass spectrometry product ion scan experiments in space (a) and in time (b)...

In a subsequent development, a novel, real-time peak detection algorithm known as intelligent automated LC/MS/MS (INTAMS) was developed for the analysis of samples generated by in vitro systems.27 INTAMS also requires two separate chromatographic runs for each sample. It allows the user to detect the two most abundant ions of all components and also any predetermined metabolite precursor ions. In the second chromatographic run, INTAMS conducts automatic product ion scanning of molecular ions of metabolites detected in the first full scan analysis. 

Lau Y.Y. 2007. High throughput simultaneous detection and identification of reactive intermediates using negative precursor ion scans combined with positive product ion scans. Presented at PittCon 2007. 

Production process changes, waste minimization via, 25 884t Product ion scan spectrum, 75 665 Production systems, improvement of, 24 190-191 Productivity... 

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