Multiple ion recording

The ions selected for such recording can be one, two, three, or more (multiple ion recording). In fact, through judicious choice of ions, the method can be so selective that a chosen component can be identified and quantified even though it could not even be observed in the original total-ion-current chromatogram. This very powerful technique is frequently used to examine extremely complex mixtures when the goal is to identify small amounts of a particular substance in a mass... 

Quantitative Determination of Sal-butanol in Plasma, as Either Its Trimethylsilyl or tert-Butyldi-methylsilyl Ether Using a Stable Isotope Multiple Ion Recording Technique... 

Selected-ion monitoring (SIM). Describes the operation of a mass spectrometer in which the ion currents at one (or several) selected m/z values are recorded, rather than the entire mass spectrum. The use of the terms multiple-ion detection (MID), multiple-ion (peak) monitoring (MPM), and mass fragmentography are not recommended. 

Selected Reaction Monitoring (SRM) Data acquired from specific product ions corresponding to m/z selected precursor ions recorded via two or more stages of mass spectrometry. Selected reaction monitoring can be preformed as tandem mass spectrometry in time or tandem mass spectrometry in space. The term multiple reaction monitoring is deprecated [1],... 

Therefore, a C13-AE, a cationic (quaternary ammonium) surfactant (quat), an amphoteric Ci2-alkylamido betaine, and the non-ionic fatty acid diethanol amide (FADA) as presented with their FIA-MS spectra in Fig. 2.5.12(a)-(d) were analysed as pure blends and as mixtures always obtained from two blends in FIA-MS multiple ion detection mode (MID). Mixtures as well as pure blends contained identical concentrations of surfactant homologues. For AE quantitation the mass traces of all A m/z 44 equally spaced homologues (m/z 306-966) of the C13-AE were recorded. The cationic (quaternary ammonium) surfactant, the amphoteric Ci2-alkylamido betaine, and the non-ionic FADA were quantified recording the mass traces at m/z 214 and 228, or 184, 212, 240, 268, 285, 296, 313, 324 and 341, or 232,260, 288, 316 and 344, respectively. 

Fig. 2.5.13. Ion current traces of APCI-FIA-MS(+) examinations of compound interferences performed in multiple ion detection mode applied for quantification of pure AE blend (A AE b,d,f recorded between 0 and 4.0 min), pure quat (B a), betaine (B c) and FADA (B e) blend (cf. B Selected compounds a,c,d recorded between 4.0 and 8.5 min). In mixtures of AE with quat, betaine or FADA, respectively, all constituents were determined by MID (cf. C Mixture AE/quat (a,b), AE/betaine (c,d), and AE/FADA (e,f) (recorded between 8.5 and 14.0 min, respectively). Ions recorded in MID mode for quantification AE (all ions starting at m/z 306 + A 44 and ending at 966), quat m/z 214 and 220, betaine m/z 184, 212, 240, 268, 285, 296, 313, 324 and 341, FADA m/z 232, 260,...

The operation of magnetic sector (Chap. 4.3), linear quadrupole (Chap. 4.4), or quadrupole ion trap (Chap. 4.5) mass spectrometers in the repetitive scanning mode is useful for the identification of the components of a mixture. If quantitation is a major issue (below), selected ion monitoring (SIM) is preferably employed the term multiple ion detection (MID) and some others are also in use. [33] In the SIM mode, the mass analyzer is operated in a way that it alternately acquires only the ionic masses of interest, i.e. it jumps from one m/z value to the next. [34-39] The information obtained from a SIM trace is equivalent to that from a RIC, but no mass spectra are recorded. Thus, the scan time spent on a diagnostically useless m/z range is almost reduced to zero, whereas the detector time for the ions of interest is increased by a factor of 10-100. [40] An analogous improvement in sensitivity (Chap. 5.2.3) is also observed. 

Vinyl chloride Mass fragmentography then GC-MS recording m/e 62 and 64 peaks. Quadrupole m/s equipped with multiple ion detection sub pg L1 [18]... 

Also the derivatization produced electron capturing impurities which occasionally interfered with the tetradecenal peak. Our present method of analysis involves quantitation of TDAL using a capillary column GC/MS technique. The GC/Mass Spectrometer (Finnigan 4021) is used in the multiple ion detection (MID) mode under computer control. Specific ions in both the internal standard (decylbenzene) and the pheromone are recorded. The combination of high resolution capillary gas chromatography and the specificity of the mass spectrometer in the MID mode, makes this technique superior to the oxime method, albeit, a little less sensitive. (EC v-lOO peg MID 500 peg)... 

The technique known variously as multiple ion detection (MID), selected ion recording (SIR), and selected ion monitoring (SIM) employs the mass spectrometer to monitor only a few significant ions. In this way both die sensitivity and selectivity are increased markedly, the former by a factor ap-... 

Using SIFT-MS it is possible to record mass spectra in the full-scan mode (FS) of quadrupole MS or in multiple ion monitoring mode (MIM) when ions are passed thorough the quadrupole with a certain m/z ratio. FS mode allows the full mass spectrum of analytes in a defined range of m/z values to be registered within a specified time period. In the case of MIM, precursor ions and selected ions, formed during reaction of the reagent ion and the analyte, are scanned. 

Patch-clamp—Technique for recording tiny electrical currents flowing through a single or multiple ion channels. 

A QTRAP instrument is capable of a wide variety of scan modes full MS scan (MS), product ion scan (MS and MS ), PI scan, NL scan, MRM, predictive MRM (pMRM), multiple ion monitoring (MIM), enhanced multiply charged (EMC) scan and time-delayed fragmentation (TDF) (Hopfgartner et al., 2004 King and Fernandez-Metzler, 2006). Most of these scan modes can be incorporated into an IDA experiment to achieve metabolite detection and MS/MS spectral recording in a single run. 

Axial TOP analyzers typically record the spectra in the ADC mode, whereas oTOF instruments use TDC or a hybrid ADC/TDC detechon. In the latter case the number of accumulated runs is given by the repetihon rate of the ion pusher of the TOF, rather than the pulse repetihon rate of the laser. Because in the TDC mode multiple ions of given arrival hme must be avoided, the pusher repehtion rate in oTOF instruments is typically a factor of about 10 larger than the laser repetihon frequency. 

LC coupled with detection by mass spectrometry (MS) offers the potential for excellent sensitivity and specificity. Sample preparations suitable for niacin analysis by LC-UV and other methods should also be suitable for LC-MS. However, chromatographic methods developed for LC-UV or LC-fluorescence methods would in most cases have to be modified due to issues such as ion suppression and problems created by non-volatile species in commonly used mobile phases. Niacin has a relatively low molecular mass (123 Da), and thus in selected ion recording (SIR) mode, there may still be significant interference problems. With instruments that allow a multiple reaction monitoring mode (MRM), however, interference problems can potentially be avoided even without optimized chromatography or sample clean-up. 

Table 19.1 Ions monitored for determination of niacin by isotope dilution mass spectrometry using positive electrospray ionization. Both natural and labelled nicotinic acid are protonated in positive ion electrospray ionization, giving quasi-molecular ions at mass-to-charge ratios (m/z) of 124 and 128, respectively, which can be monitored directly in selected ion recording (SIR) experiments and selected as the parent ions in multiple reaction monitoring (MRM) experiments. In MRM experiments protonated nicotinic acid can be induced to produce daughter ions at several other m/z values, but the given transitions are the ones with the highest signal intensity.

Multiple ion detection, the recording of several individual ions m/z values) for increased dwell time and detection sensitivity in contrast to full scan, also SIM. 

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