Eighteen crude oils and condensates have been investigated by means of infrared (IR) and
near-infrared spectroscopy (NIR) and high-performance liquid chromatography (HPLC). By means
of HPLC the samples have been separated into four chemical group classes, namely saturates,
aromatics, resins, and asphaltenes, the so-called SARA fractions. Using multivariate analysis
techniques such as principal component analysis (PCA) and partial least-squares analysis (PLS),
the predictive ability of the spectroscopic techniques with regard to the SARA components have
been explored. The results show that the SARA distribution of crude oils and related materials
can be determined both from infrared and near-infrared spectroscopy. The uncertainties in the
prediction models based on IR spectroscopy have been found to be 2.5, 2.2, 1.4, and 1.3 wt % for
the saturate, aromatic, resin, and asphaltene fraction, respectively. For NIR the equivalent
uncertainties are 2.8, 2.4, 1.4, and 1.0 wt %. These values are in the same range as the reported
uncertainty in the direct determination by HPLC. Spectroscopic determination of SARA values,
especially using NIR, offers the possibility of rapid SARA determinations of these values. The
determinations could be done at high pressure and temperature.
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