Analysis thermospray spectra

A large number of LC-MS systems are equipped with a thermospray interface, which can accept LC flow rates up to ImL/min and is especially useful for the analysis of polar and nonvolatile molecules (18). The major disadvantage of this interface is the mass spectrum produced. The "classical" thermospray system only provides spectra with a single molecular ion and little structural information. Only when used with an additional element like a fragmentor electrode is it possible to obtain detailed information regarding the chemical structure of the molecule (19). 

Metabolite M4 was analyzed by thermospray LC/MS (Fig. 5a) and produced a protonated molecular ion at m/z 497, 499 (confirmed by fast atom bombardment mass spectral analysis). This mass spectrum, as well as proton NMR analysis (not shown) was consistent with the acyl carnitine conjugate of the parent. Fragmentation occurred via loss of the carnitine moiety to give m/z 371, 373 the fragment ion at m/z 455, 457 could correspond to an... 

Despite outstanding FD measurements in laboratories at Mainz and a few other places, analysis of glucuronic acid conjugates by FAB is generally more reliable than FD analyses. However, FAB is also not completely reliable. We have worked with some glucuronic acid conjugates which provided neither an anion or cation spectrum from a variety of FAB matrices. In one of these cases the analysis has been obtained successfully by thermospray. 

Thermospray is a gentle mode of ionization. The spectrum contains mostly the intact molecular ion and its adduct with buffer components. Because fragmentation of the molecular ion species is relatively sparse, stmctural information is usually absent. Several classes of compounds, snch as peptides, dinucleotides, prostaglandins, diquatemary ammonium salts, pesticides, drugs, dyes, and environmental pollutants, are accessible to thermospray analysis. Also, it is an effective interface for LC/MS applications. Conventional colnmns with flow rates up to 2 mLmin can be coupled to this interface. 

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