Characterization of Petroleum Crude Oils using Laser Induced Fluorescence

The use of laser induced fluorescence (LIF) spectroscopy to characterize crude oil has privileges compared to conventional techniques in terms of reducing the size of sample, rapidity of measurements, high sensitivity and simplicity of sample handling and possibility of in situ measurements. The fluorescence radiation emitted from crude oil is the result of the interaction between the aromatic compounds and the electromagnetic radiation. The fluorescence spectra and their intensities are directly affected by the chemical composition and physical properties of the investigated samples. Important fluorescent information might be lost with the use of a single excitation wavelength, but might be obtained using other excitation wavelengths and thus enhancing the technique’s discrimination capability between different crude oil samples. For this reason, fluorescence spectra in the present work were obtained using four types of CW lasers as excitation sources. Five dry crude oil samples with American Petroleum Institute (API) gravities between 18 and 44 were diluted to 5 mg/l using chlorinated solvent. The excitation of the samples was performed using diode pumped solid state lasers (DPSS) emitting at 266 nm, 405 nm, 532 nm and an argon ion laser at 488 nm. The present work introduces for the first time the usage of laser induced fluorescence spectroscopy in the characterization of Egyptian crude oils. The results revealed the dependence of the emitted fluorescence on the physical and chemical properties of the oil samples including the API gravity, viscosity, sulphur and asphaltene contents. Thus, it is feasible to make use of LIF as a simple and fast spectrochemical analytical technique in differentiating between different types of crude oil. Characterization of Petroleum Crude Oils using Laser Induced Fluorescence