Isotopomer spectral analysis

S 0 0)2 isotopomer (mass spectral analysis of the parent ion can not distinguish the two possibilities, vida infra). For the scrambling", or O-atom addition case, two possibilities exist. The first is that oxygenation of the first sulfur is by molecular addition and the subsequent formation of 3... 

MS can measure the ratio between molar fractions of mass isotopomers. The ratio between two mass isotopomer pools of masses nti and m2 is defined in the present work as intensity ratio Jmi/m2- K identical with a mass spectral intensity ratio. If more than two mass isotopomer pools are assessed, their relative ratios, normalized to the sum, are named mass isotopomer distribution. The mass distribution of a compound can be thus obtained from the analysis of ions, which contain the intact carbon skeleton of the analyte. In the area of me-tabohc flux analysis, mass distributions of various metaboHtes have been assessed by MS. The major method used is GC/MS, whereby the analytes are deriva-tized into forms with desired physico-chemical properties such as increased volatihty, thermal stabiHty and suitable MS properties [62]. The mass of the formed derivate must be sufficiently high (usually above 175 apparent mass units) to avoid background interference [48]. To obtain the mass distribution of a compound, ions with the entire carbon skeleton of the analyte have to be present. For accurate quantification of the mass distribution of such ions, they should occur in high abundance and preferably be unique species, thus being formed by only one fragmentation pathway. 

The combination of laser- and mass-spectrometry has brought a wealth of new information on the structure and dynamics of molecules [494]. If, for instance a mixture of different isotopomers of a molecular species (these are molecules with different atomic isotopes) is present, the absorption spectra of the different isotopomers might overlap which impedes the analysis of the spectrum. Therefore the separation of these isotopomers by a mass spectrometer will facilitate the unambiguous analysis. The isotope shift of spectral lines gives additional information on the molecular structure. 

---