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

Elemental sulfur works well as a matrix for laser desorption time-of-flight mass spectrometry of bacteriochlorophylls and carotenoids, the major pigme nts in photosynthetic bacteria. Because sulfur lacks protons, pigment ioniz ation probably involves electron, rather than proton, transfer. Fragmentati on of chlorophylls that are esters of allylic alcohols occurs, but is parti ally suppressed when sulfur is used as a matrix. Mass spectrometry on sulfu r itself shows that the most abundant positive ion Is S-5(+), while the mos t abundant negative ion is S-3(-), indicating that light absorption causes photodissociation of S-8 rings into these products. A similar pattern was o bserved with red selenium, which also occurs as 8-membered rings. Molecular masses of other hydrophobic analytes, such as fullerene compounds, can als o be determined using elemental sulfur as the matrix. Copyright (C) 1999 Jo hn Wiley & Sons, Ltd.