The invention provides a method of analysing a complex
hydrocarbon-containing mixture, the method comprising the steps of:
obtaining a liquid sample of the complex hydrocarbon-containing mixture;
injecting the sample into a liquid carrier flowing to a mass
spectrometer, wherein the mass spectrometer is set so as to ionise
molecules in the sample without causing fragmentation thereof; recording
a mass spectrum for ions obtained from the sample; and using the mass
spectrum to obtain fingerprint of the mixture. {dot over (a)}In one
embodiment, two or more mass spectra are recorded and are combined to
obtain a fingerprint of the mixture.