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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:21 |
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Conference: Bucharest University Faculty of Physics 2015 Meeting
Section: Biophysics; Medical Physics
Title:
Asphaltene quantification using Fluorescence Spectroscopy
Authors:
Roua G. POPESCU(1), Gheorghe STOIAN(1)
Affiliation:
1) University of Bucharest, Faculty of Biology , Department of Biochemistry and Molecular Biology, Bucharest, Romania
E-mail
roua.g.popescu@gmail.com
Keywords:
crude oil, Fluorescence spectroscopy, paraffin oil, asphaltenes
Abstract:
Petroleum oils are complex mixtures of aliphatic, aromatic, and high molecular weight organic compounds that can be separated into maltenes (saturates, aromatics, resins) and asphaltenes, using different volatile solvents.
Given the complexity of asphaltenes that lead to the formation of supramolecular aggregates, which has the effect of disrupting the linearity of Lamber Beer law, in the case of UV-Vis analysis, the aim of our research was to analyze different asphaltene fractions from crude oils and polluted soils using a nonvolatile solvent, paraffin oil, to quantify asphaltenes from different samples.
The samples were collected from an oil-producing source in Suplacu de Barcău and processed by specific chemical means. Asphaltenes have been separated from the maltene fraction by selective extraction (0.1 v/v in n-hexane) followed by their solubilization in paraffin oil (from 0.05 0.005 %) in order to enable their fluorescence analysis. The emission spectra were obtained by exciting the samples at 350 nm, 450 nm and 532 nm, because paraffin oil is a solvent that has no signal at these bands. The emission spectra of asphaltenes (200-700) nm have been recorded at different concentrations of crude oil samples.
Our results show that, in the (0.05-0.005) % domain, the fluorescence intensity is linear with concentration of asphaltenes at λex = 532 nm (R2 = 0.9865), and λex = 450 nm (R2 = 0.9965) and as compared with crude oil intensity of fluorescence spectra represent 46 %. Linearity was not obtained at λex = 350 nm. Also, it was possible to determine the asphaltene content in soils polluted by crude oil, 2.29 ± 0.1 % soil sample.
This study represents an effective means to rapidly obtain the distribution of crude oil concentration. When the oil concentration increase occurs, a displacement in the fluorescence wavelength is noticed, possible due to the higher oil concentration, that is dependent only on the net concentration of asphaltenes (450 ± 10) mg/L, and not on that of other crude oil constituents.
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