Ambient ionization mass spectrometry

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

Z. Takats, J. M. Wiseman and R. G. Cooks, Ambient mass spectrometry using desorption electrospray ionization (DESI) instmmentation, mechanisms and applications in forensics, chemistry, and biology, J. Mass Spectrom., 40, 1261 1275 (2005). 

Recent innovations in ionization techniques have allowed the development of ambient mass spectrometry. Mass spectra can be determined for samples in their native environment without sample preparation. Although the ambient mass spectrometry technique is still in its infancy, its potential for serving as a tool of choice for high-throughput bioanalysis is very encouraging. 

Z. Takats, I. Cotte-Rodrfguez, N. Talaty, H. Chen, and R. G. Cooks. Direct, Trace Level Detection of Explosives on Ambient Surfaces by Desorption Electrospray Ionization Mass Spectrometry. Chem. Commun., no. 15 (2005) 1950-1952. 

J. Shiea, M.-Z. Huang, H.-J. HSu, C.-Y. Lee, C.-H. Yuan, I. Beech, and J. Sunner. Electrospray-Assisted Laser Desorption/Ionization Mass Spectrometry for Direct Ambient Analysis of Solids. Rapid Commun. Mass Spectrom., 19(2005) 3701-3704. 

G.A. Eiceman, J.H. Kremer, A.P. Snyder and J.K. TofFeri, Quantitative assessment of a corona discharge ion source in atmospheric pressure ionization-mass spectrometry for ambient air monitoring. International Journal of Environmental Analayrical Chemistry 33 (1988) 161—183. 

R. G. Ambient mass spectrometry using desorption electrospray ionization (DESI) instrumentation, mechanisms and applications in forensics, chemistry, and biology. 

Electrospray (ESI) is an atmospheric pressure ionization source in which the sample is ionized at an ambient pressure and then transferred into the MS. It was first developed by John Fenn in the late 1980s [1] and rapidly became one of the most widely used ionization techniques in mass spectrometry due to its high sensitivity and versatility. It is a soft ionization technique for analytes present in solution therefore, it can easily be coupled with separation methods such as LC and capillary electrophoresis (CE). The development of ESI has a wide field of applications, from small polar molecules to high molecular weight compounds such as protein and nucleotides. In 2002, the Nobel Prize was awarded to John Fenn following his studies on electrospray, for the development of soft desorption ionization methods for mass spectrometric analyses of biological macromolecules. ... 

Mass spectrometiy. Several instruments based on chemical ionization mass spectrometry (CIMS) have been developed and applied to ambient air (Huey et al., 1998 Mauldin et al., 1998). Figure 11.32 shows two such instruments that have undergone an informal intercomparison study between themselves and a filter pack (nylon) method (Fehsenfeld et al., 1998). 

Another approach combines the mass spectrometric derivatization approach with chemical amplification (Reiner et al., 1997, 1998). In this instrument, H02 and R02 are converted to OH through the reactions in the chemical amplifier approach discussed below, and the OH is then converted to H2S04 by reaction with S02 and measured by chemical ionization mass spectrometry using NO, (HN03) clusters as described earlier. In this case, the use of isotopically labeled S02 is not necessary, since the ambient H2S04 concentration is much smaller than that of the peroxy radicals. 

As seen in Chapter 9.C.2, a very wide variety of organics are found in particles in ambient air and in laboratory model systems. The most common means of identification and measurement of these species is mass spectrometiy (MS), combined with either thermal separation or solvent extraction and gas chromatographic separation combined with mass spectrometry and/or flame ionization detection. For larger, low-volatility organics, high-performance liquid chromatography (HPLC) is used, combined with various detectors such as absorption, fluorescence, and mass spectrometry. For applications of HPLC to the separation, detection, and measurement of polycyclic aromatic hydrocarbons, see Wingen et al. (1998) and references therein. 

Takats, Z., J.M. Wiseman, B. Gologan, and R.G. Cooks. 2004. Mass spectrometry sampling under ambient conditions with desorption electrospray ionization. Science 306 471-473. 

Dwivedi P, Hill HH Jr (2008) A rapid analytical method for hair analysis using ambient pressure ion mobility mass spectrometry with electrospray ionization (ESI-IMMS). Int J Ion Mobil Spec 11 61-69... 

Ifa D, Wiseman J, Song Q, Cooks G (2007) Development of capabilities for imaging mass spectrometry under ambient conditions with desorption electrospray ionization (DESI). Int J Mass Spectrom 259 8-15. doi 10.106/j.ijms.2006.08.003... 

Nemes P, Barton A, Li Y, Vertes A (2008) Ambient molecular imaging and depth profiling of live tissue by infrared laser ablation electrospray ionization mass spectrometry. Anal Chem 80 4575 1582. doi 10.1021/ac8004082... 

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