Infrared laser desorption/vacuum ultraviolet photoionization mass spectrometry of petroleum saturates: a new experimental approach for the analysis of heavy oils.

A novel method combining infrared (IR) laser desorption with tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (LD/VUV PIMS) is applied to characterize a number of petroleum saturates samples from Lungu atmospheric residue (LGAR) under different treatment procedures. The mass spectra of these saturates are well resolved with even masses as the dominant ions and are clearly sample-dependent. In order to assess the ability of IR LD/VUV PIMS to determine the average molecular weight of heavy oils, the dependence of the measured molecular weight distributions on the VUV ionization photon energies is also discussed.