Approach for obtaining mass spectra of involatile and thermally unstable natural products has been performed by two strategies. One is a optimization of sample vaporization, which contains rapid sample heating followed by thermal desorption and ionization under CI condition, that is Emitter CIMS. Another is a direct ionization of sample from a surface. Although several techniques have been discussed for this purpose, we adopt Molecular SIMS, which does not essentially require heating of sample for ionization and desorption. Emitter CI mass spectra of kanamycin A, B and C showed unequivocally protonated molecular ions (MH^+) in all the cases. The principal fragmentation pattern and m/z value of the characteristic sequence ions (a-е) are summarized in Fig.3. These ions are formed by the reproducible fragmentation process at the glycosidic bonds. Moreover, the shifting technique using ND_3 as the reagent gas was succesfully employed. Secondary ion mass spectra of kanamycins are presented. MH^+, [M+Na]^+ and [M+Ag]^+ were observed as molecular ion species in all the cases. The co-existing NaCl increased the relative abundance of [M+Na]^+ in the spectra. Furthermore, SI mass spectra of other aminoglycoside antibiotics and oligosaccharides could be succesfully measured.
