Determination of some physicochemical properties in Brazilian crude oil by 1H NMR spectroscopy associated to chemometric approach

• API gravity, carbon residue, wax appearance temperature and basic organic nitrogen in crude oil were determined.
• 1H NMR spectroscopy associated to partial least squares regression to determine such properties were used.
• A previous study involving pattern recognition to better known of sample set was performed.
• Principal component analysis was used as pattern recognition method.
• Accuracy, confidence intervals, systematic and tendency errors were evaluated in each models fitted.

An alternative method for establishing crude oil properties, using 1H nuclear magnetic resonance (1H NMR) associated with partial least squares regression is proposed. It can be used for determination of API gravity, carbon residue (CR), wax appearance temperature (WAT) and basic organic nitrogen (BON). At a 95% confidence level, the main results obtained for API gravity, CR, WAT and BON models provide determination coefficients for prediction (R2p) and root mean square error for prediction (RMSEP) equal to 0.945, 0.802, 0.857 and 0.789; and 0.8, 0.598% w/w, 3.8 °C, 0.009% w/w, respectively. The residuals of each fitted model were evaluated taking into account systematic and random errors and all results were considered acceptable. The determination of these physicochemical properties in Brazilian crude oil was successfully achieved using a chemometric approach in association with 1H NMR.

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