Single-ion monitoring

A second use of arrays arises in the detection of trace components of material introduced into a mass spectrometer. For such very small quantities, it may well be that, by the time a scan has been carried out by a mass spectrometer with a point ion collector, the tiny amount of substance may have disappeared before the scan has been completed. An array collector overcomes this problem. Often, the problem of detecting trace amounts of a substance using a point ion collector is overcome by measuring not the whole mass spectrum but only one characteristic m/z value (single ion monitoring or single ion detection). However, unlike array detection, this single-ion detection method does not provide the whole spectrum, and an identification based on only one m/z value may well be open to misinterpretation and error. 

SIM. selected (or single) ion monitoring SIMS, secondary ion mass spectrometry SIR. selected (or single) ion recording... 

SIM(-MS) Selected-ion monitoring (single ion monitoring) mass spectrometry... 

Figure 5.19 Formation of amino acids on ice surfaces irradiated in the laboratory (Nature Nature 416, 403-406 (28 March 2002) doi 10.1038/416403a-permission granted). Data were obtained from analysis of the room temperature residue of photoprocessed interstellar medium ice analogue taken after 6 M HCl hydrolysis and derivatization (ECEE derivatives, Varian-Chrompack Chirasil-L-Val capillary column 12 m x 0.25 mm inner diameter, layer thickness 0.12 pirn splitless injection, 1.5 ml min-1 constant flow of He carrier gas oven temperature programmed for 3 min at 70°C, 5°C min-1, and 17.5 min at 180°C detection of total ion current with GC-MSD system Agilent 6890/5973). The inset shows the determination of alanine enantiomers in the above sample (Chirasil-L-Val 25 m, single ion monitoring for Ala-ECEE base peak at 116 a.m.u.). DAP, diaminopentanoic acid DAH, diaminohexanoic acid a.m.u., atomic mass units.

Fig. 3.9. Single-ion monitoring mass chromatogram (m/z 443, dwell time 500 ms) obtained in the positive-ion mode during the sequential step sampling (30 s sampling time) of four separate bands from developed spots (0.4 p each) of differing amounts of rhodamine 6G, namely, 0 (blank solvent), 1.4, 14 and 145 ng. Reprinted with permission from G. J. Van Berkel et al. [88],...

Full scan Ql/single ion monitoring (SIM) Ql Scan/fixed Rf mode... 

By choosing appropriate fragment ions a virtual sensor array based on a mass spectrometer in single ion monitoring mode can be implemented to discriminate the hop varieties (Fig. 15.13) without appreciable interference of the main component myrcene. In contrast to the analyses performed with QMB and MOS sensors, the discrimination obtained with the MS sensor is based on chemical knowledge and not on assumptions. 

Keller S, Jahreis G (2004) Determination of underivatised sterols and bile acid trimethyl silyl ether methyl esters by gas chromatography-mass spectrometry-single ion monitoring in faeces. J Chromatogr Analyt Technol Biomed Life Sci 813 199-207... 

Abbreviations GC/FID, gas chromatography/flame ionization detection GC/MS-SIM, gas chromato-graphy/mass spectrometry with single-ion monitoring... 

Startin, J.R. Gilbert, J. (1984) Single ion monitoring of butadiene in plastics and foods by coupled mass-spectrometry-automatic headspace gas chromatography. J. Chromatogr.. 294, 427-430... 

Choose selective mass traces of labeled and unlabeled compound for subsequent quantification using single ion monitoring (SIM mode). 

Tomlinson, Wang and Caruso [96] used an Alltech Adsorbosphere cation-exchange column for the speciation of vanadium (IV) and (V) with ICP-MS detection. Single ion monitoring at m/z 51 was used and the mobile phase consisted of 7 mM 2,6-pyridine... 

Owen et al. [42] used RPLC-ICP-MS to separate Zn-containing species in an in vitro gastrointestinal digest of chicken meat that had been isocratically labeled with Zn both intrinsically and extrinsically. Single ion monitoring was used for two separate isotopes, 66Zn and 68Zn. Aqueous Zn eluted from C8... 

Selected Ion Monitoring (SIM) The mass analysis process in which only a single m/z value is selected by the mass analyzer and transmitted to the detector. Also referred to as the single ion monitoring. ... 

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