Compiling Mass Reference Lists

A reference list may be compiled once the mass spectrum of a calibration standard is known and the elemental composition of the ions that are to be included in the mass reference list are estabhshed by an independent measuremeait. For this purpose, the listed reference masses should be calculated using six decimal digits. Otherwise, one runs a chance of obtaining erroneous reference values, especially when masses of ion series are calculated by multiplication of a subunit. This can easily be done using conventional spreadsheet applications. 

Example Cesium iodide is frequently used for mass calibration in fast atom bombardment (FAB) mass spectrometry (Chap. 10) because it yields cluster ions of the general formula [Cs(CsI)J in positive-ion and [I(CsI)J in negative-ion mode. For the [Cs(CsI)io] cluster ion, m/z 2730.9 is calculated instead of the correct value tn/z 2731.00405 by applying only one decimal digit rather than the exact values Mines = 132.905447 and Mijn - 126.904468. The error of 0.104 u is acceptable for LR work, but definitely unacceptable if accurate mass measurements are needed. 

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The interpretation of mass spectra is based on the chemistry of gaseous ions these can now be formed by a wide variety of methods, and can be mass-analyzed and detected with a wide variety of instrumentation. Of necessity this book gives a limited discussion of these complete details are available in the excellent books listed at the end of this chapter. Compilations of references to the mass-spectrometry literature are also available from Chemical Abstracts and The Mass Spectrometry Bulletin of the Royal Society of Chemistry. 

The mass absorption coefficient is a constant for a given element at a given wavelength and is independent of both the chemical and physical state of the element. An updated compilation of mass absorption coefficients can be found online at the NIST website http //www.nist.gov/pml/ data/xraycoef/index.cfm (J.H. Hubbell and S.M. Seltzer) or in the text by Bertin or handbooks listed in the bibliography or references in the literature. 

The upper display is its reaction pyrogram at 420 °C, followed by the peak assignment table for the pyrogram together with MW, RI, and relative peak intensity data. As the footnote, the related references in which the concerned pyrolysis information is reported were listed. At the right hand page, its selected mass spectra for up to 12 major peaks are compiled. 

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