Fingerprinting of crude oils and their products. A review on the applicability of some analytical techniques

A review of recent studies on the applicability of some analytical techniques for fingerprinting the oil types are reported. A broad range of analytical techniques were carried out on the oils using digestion and enrichment of trace metals, coordination, ion-exchange and adsorption chromatography followed by measurement of physical properties such as ultraviolet absorption spectrophotometry; infrared spectrophotometry, proton nuclear magnetic resonance spectrometry, X-ray fluorescence spectrometry and gas chromatography. Some of the oil parameters evaluated as potential fingerprint indices are trace metal indices, aromatic/aliphatic infrared absorbance ratios, ratios of the adjacent peak heights on the gas chromatogram, average molecular structure parameters calculated from the proton nuclear magnetic resonance of the aromatic fraction and the specific absorptivity ratios [i.e. K p /(K m +K d )] of the polyaromatic hydrocarbon fractions at the maximum wavelength (λ max .). On the basis of the criteria used in these studies for judging the appropriateness of an analytical technique for fingerprinting oils, a rating scheme was proposed which enabled an objective critical comparison of the techniques.