Infrared laser desorption mass spectra

FIGURE 6.9 Infrared laser desorption mass spectrum of the molecular-ion region of digitonin and the reference compound, phosphazine. (Reprinted with permission finom reference 9). 

This paper describes the further physical and chemical characterization of these two new forms of molecular carbon." Our results include the high-yield production (14%) of soluble material under optimized conditions, consisting of only C o and C70 in measurable quantity. These have been separated in analytical amounts by column chromatography and have been characterized in pure or mixed forms by a combination of electron impact, fast atom bombardment (FAB), and laser desorption mass spectrometry. Spectroscopic characterization is reported including the C NMR spectrum and the infrared absorption spectrum for the crude... 

FIGURE 6.13 Infrared laser desorption (IRLD) mass spectrum of maltotetraose in KCI. (Reprinted with permission from reference 50). 

The initial observation is that PMMA is essentially completely degraded to monomer by heating to 375°C in a sealed tube while heating a mixture of red phosphorus and PMMA under identical conditions yields a solid, non-deqraded, product as well as a lower yield of monomer. One may observe, by 3C NMR spectroscopy, that the methoxy resonance is greatly decreased in intensity and methyl, methoxy phosphonium ions are observed by 31P NMR. Additional carbonyl resonances are also seen in the carbon spectrum, this correlates with a new carbonyl vibration near 1800 cm 1 in the infrared spectrum and may be assigned to the formation of anhydride. The formation of anhydride was also confirmed by assignment of mass spectra obtained by laser desorption Fourier transform mass spectroscopy, LD-FT-MS. 

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