Petroleum samples are complicated hydrocarbon mixtures containing paraffins, cyclic paraffins (naphthenes), multi-ring aromatics, and various heteroatomic hydrocarbons (most commonly O, S, and N). Virgin petroleum crude oils contain molecules of a wide boiling point range from highly volatile C4 hydrocarbons to nonvolatile asphaltenes. Analysis of petroleum composition of various boiling ranges is valuable for improving the operation of many subsequent processes.
According to at least some conventional definitions, a vacuum gas oil (VGO) is a crude oil fraction that boils between about 343° C. (about 650° F.) to 538° C. (about 1000° F.). A vacuum residuum (VR) is a residuum obtained by vacuum distillation of a crude oil and boils above a temperature about 538° C.
U.S. Pat. No. 6,275,775 describes methods for correlating properties determined by conventional methods with measurements made using a chromatography technique. The described methods start by determining properties for a set of sample compounds using a conventional method, such as using an ASTM method for determining cetane. The reference set of compounds are then characterized using chromatography combined with another spectroscopic technique to characterize the compounds relative to boiling point. The two measurements for the reference compounds are then used to build a model. An unknown sample is then measured using the chromatography and spectroscopic technique, and the model is used to determine the correlated property value for the unknown sample in relation to a predicted boiling point profile for the unknown sample.
An article in the Journal of the American Society for Mass Spectrometry by Chen et al (pg 1186-1192, vol. 12, issue 11, November 2001) describes using matrix assisted laser desorption ionization for generation of ions of polyethylene waxes for detection using mass spectrometry. The article describes use of a copper or cobalt matrix with a silver nitrate solution for forming ions of the wax.