Major Reference Masses in the Spectrum

Reference Compounds under Electron Impact Conditions in Mass Spectrometry Major Reference Masses in the Spectrum of Heptacosafluorotributylamine (Perfluorotributylamine)... 

MAJOR REFERENCE MASSES IN THE SPECTRUM OF HEPTACOSAFLUOROTRIBUTYLAMINE (PERFLUOROTRIBUTYLAMINE)... 

See the table Major Reference Masses in the Spectrum ofHeptacosafluorotributylamine (Perfluorotributylamine) in this section for additional details. 

The following list tabulates the major reference masses (with their relative intensities and formulas) of the mass spectrum of heptacosafluorotributylamine.1 This is one of the most widely used reference compounds in mass spectrometry. 

An example of the spectrum/substructure determination process is illustrated for the reference compound di-n-octylphthalate. Daughter spectra were acquired for every major ion (above 1 relative intensity) that appeared in the conventional mass spectrum (Figure 2) of the reference compound. All the daughter spectra were then matched against the reference daughter spectra of the same parent mass (but from different compounds) in the data base. The results of some of the matches are described below. 

On the other hand, the intensity of the peaks is also dependent on the amount of substance introduced into the ion source. Hence, it is necessary to subject the spectrum obtained to additional treatment, which consists of relating all the peak intensities to that of a reference one. The most intense, or major, peak of the spectrum is commonly taken as the reference. The relative intensity is independent of the amount of substance, and all of the peaks can be expressed in one scale. The peak intensities may be also expressed in per cent of the total intensity of all the peaks of the mass spectrum this form is preferred when the mass spectra of several related compounds are to be compared, because the total peak intensity of the mass spectra of related compounds varies insignificantly, whereas the intensity of the major peak may, in this case, change very strongly. 

Reproducibility of the relative intensities in El mass spectra is a concern, despite the fact that spectra are recorded under standardized conditions. Different mass spectrometers produce spectra with, sometimes, large spreads in the relative intensities. An impression of the possible variation is given in Table 2. In this table, the relative intensities of major fragments in the El mass spectra of three nerve agents, taken from three different sources, are presented. It is clear that there exist no reference mass spectra of these Schedule 1 chemicals, which can be considered as true physical constants. A compilation of more than one spectrum of the same compound in the OPCW Analytical Database gives an indication of the possible spread. 

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