Characterization of petroporphyrins in Gudao residue by ultraviolet–visible spectrophotometry and laser desorption ionization-time of flight mass spectrometry

A porphyrin-containing fraction isolated from the >500 °C residue of Chinese Gudao heavy oil was analyzed using laser desorption ionization-time of flight mass spectrometry (LDI-TOF-MS) for the first time. LDI-TOF-MS was revealed to be suitable for the characterization of petroporphyrins mixture. LDI-TOF mass analysis, combined with UV–vis measurement, indicated that the nickel porphyrins in Gudao residue are a mixture of ETIO homologues (C25–C34) maximizing at C30 and DPEP homologues (C28–C37) maximizing at C31. The ΣDPEP/ΣETIO ratio is about 1.04, suggesting Gudao oil is in the stage of becoming mature.