Laser desorption mass spectrometry and matrix-assisted laser desorption
mass spectrometry (MALDI-MS) have been investigated for the analysis of a
set of synthetic compounds containing one, two, five, eight or nine
porphyrins. Intact singly ionized molecule ions were observed for each
compound and the spectra were readily interpretable. The use of a matrix of
4-hydroxy-α-cyano-cinnamic acid greatly diminished the extent of
fragmentation. Examination of the resulting mass spectra provides insight
into aspects of the MALDI process. The present results show that high
molecular weight photochemically active materials that absorb strongly at
the wavelength of laser illumination can be analysed effectively and that
MALDI-MS is a powerful analytical tool for synthetic chemistry of
porphyrin-based molecules with dimensions ranging to 10 nm. The strong
molecule ions observed for the largest compounds investigated ( Zn
8-octamer, Zn 9-nonamer)
indicates that this method should be applicable to even larger porphyrin
arrays.