Selected Ion Flow Tube-Mass Spectrometry SIFT-MS

5 Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) 

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Smith D, Spanel P (2005) Selected ion flow tube mass spectrometry (SIFT-MS) for on-line trace gas analysis. Mass Spectrom Rev 24(5) 661-700... 

Selected ion flow tube mass spectrometry (SIFT-MS) is an analytical technique used for direct and quantitative determination of VOCs in mixtures of gases. SIFT-MS was introduced in 1976 by N. G. Adams and D. Smith. The technique can be applied for parallel real-time monitoring of a few substances [126]. A scheme of the SIFT-MS system is presented in Fig. 14.9 [127]. The principle of gas mixture analysis is based on the reaction of reagent ions with molecules of analyte within a specific time (a few milliseconds). In this method, chemical ionization is applied reagent ions are generated in the ion source by a suitable ionization gas (nitrogen, oxygen, or water vapor). Of aU the obtained ions, only cations of the desired m/z... 

Smith, D., Spanel, P. Selected ion flow tube mass spectrometry, SIFT-MS, for on-line trace gas analysis. In Amann, A., Smith, D. (eds.) Breath Analysis for Clinical Diagnosis and Therapeutic Monitoring, pp. 3-34. World Scientific Publishing, Toh Tuck Link, Singapore (2005)... 

A more sophisticated, though less common version of PTR-MS is selected ion flow tube mass spectrometry (SIFT-MS). In this technique, a mixture of reagent ions is generated in a gas discharge ion source and then a Q mass filter is used to select one reagent ion, which is then injected into an inert carrier gas (usually He), for... 

Those are, for instance, known as active chemical ionization mass spectrometry (ACIMS) for atmospheric trace-gas measurements in the chemosphere, proton transfer reaction mass spectrometry (PRT-MS), selected ion flow tube mass spectrometry (SIFT-MS), ion-molectrle reaction mass spectrometry (IMR-MS), ion attachment mass spectrometry (lAMS), and ion mobility spectroscopy (IMS). Those have now become part of the exterrsive resources of experimental techniques dedicated to all the scientific fields, especially such as fundamentals of gas-phase ion kinetics and thermochentistry, physical organic chemistry, atmospheric chemistry, interstellar chemistry, plasma, and combustion chemistry, radiation chemistry, analytical chemistry, and irltimately even medicine and biology. 

Alkali metal ion/molecule association reactions have been exploited in various mass spectrometric methods since the early 1970s. Initial studies were to determine metal ion affinities of simple compounds, with use of Fourier transform ion cyclotron resonance (FTICR) mass spectrometers. Alkali ions offer unique and interesting potential in analytical chemistry and studies of chemical dynamics. Consequently, the use of metal ions as reagents for Cl mass spectrometry has been developed. The major advances in the apphcation of MS as a routine analytical instmment using the complex ion/molecule chemistry came arotmd in the past decades. They include atmospheric pressure chemical ionization (APCI), proton transfer reaction mass spectrometry (PTR-MS), selected ion flow tube mass spectrometry (SIFT-MS), ion attachment mass spectrometry (lAMS) and ion molecrtle reaction mass spectrometry (IMM-MS). 

Huang Y Barringer S A. Monitoring of cocoa volatiles produced during roasting by selected ion flow tube-mass spectrometry (SIFT-MS). J Food Sci. 2011 76 C279-C86. 

However, the desire to reduce or even eliminate the required sample preparation has led to the development of newer techniques, such as proton-transfer-reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry coupled with ion mobility spectrometry (MS-SIFT IMS). These techniques allow real-time measurements within a single second. This enables analysis of gas composition during technological processes, monitoring of indoor air, and investigation of VOCs emitted by living organisms. 

SIFT-MS selected ion flow tube mass spectrometry... 

By combining the principles of PICI with an apparatus derived from selected-ion flow tube (SIFT) experiments, the technique of proton transfer reaction mass spectrometry (PTR-MS) has been developed as a dedicated tool for the analysis of volatile organic compounds (VOCs) at parts-per-trillion by volume (pptv) level in air [51,52]. PTR-MS is highly useful as a fast and quantitative method for the determination of VOCs as proven by numerous applications in food control, envi-... 

We start with a description of what is currently the single most important and widely used technique for VOC gas analysis, gas chromatography. We will then turn our attention to techniques that typically show a much faster response, starting with ion mobility spectrometry and its variants. Flowing afterglow and selected ion flow tube studies of ion-molecule reactions are then considered, since these set the scene for the two main direct mass spectrometry techniques for quantifying gaseous VOCs, PTR-MS and SHT-MS. The chapter closes with an introductory account of both PTR-MS and a comparison of PTR-MS with SIFT-MS. 

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