Elemental sulfur as a matrix for mass spectrometry of photosynthetic pigments and fullerenes

Abstract

Elemental sulfur works well as a matrix for laser desorption time-of-flight mass spectrometry of bacteriochlorophylls and carotenoids, the major pigments in photosynthetic bacteria. Because sulfur lacks protons, pigment ionization probably involves electron, rather than proton, transfer. Fragmentation of chlorophylls that are esters of allylic alcohols occurs, but is partially suppressed when sulfur is used as a matrix. Mass spectrometry on sulfur itself shows that the most abundant positive ion is S5 +, while the most abundant negative ion is S3 −, indicating that light absorption causes photodissociation of S8 rings into these products. A similar pattern was observed with red selenium, which also occurs as 8-membered rings. Molecular masses of other hydrophobic analytes, such as fullerene compounds, can also be determined using elemental sulfur as the matrix. Copyright © 1999 John Wiley & Sons, Ltd.