Derivative UV-Vis Spectroscopy of Crude Oil and Asphaltene Solutions for Composition Determination

The determination of the first and second derivatives in the UV spectra of crude oil and asphaltene solutions allows the identification of signals attributed to compounds in the crude oil that cannot be seen in the normal spectrum. This processing of the crude oil UV-Vis spectrum to determine first and second derivatives allowed the identification of five maxima. The maxima observed in the first derivative spectrum can be related to different types of compounds in crude oil: ~230 nm for benzene compounds, 259 nm for naphthalene compounds and their derivatives, 295 nm for pure phenanthrene, 328 nm for aromatic chromophores with three or four aromatic rings, and 401 nm for the Soret electronic absorption band of vanadyl porphyrins. The shape of the spectra was analyzed to predict the presence of colloids or particles in the solutions.