Spectra of regular and premium gasoline comparing the olefin concentrations.  The main olefin peaks are observed in the 1640 to 1680 cm-1region, and the regular gasoline has more olefin (12.6%) compared to the premium (0.8%).

Typical online PLSanalysis of the percent olefin concentration. The plot shows Raman predicted values vs. the measured laboratory values.  The standard error of prediction for the PLS model with outliers removed was 0.48%.

A histogram of the distribution of differences between the laboratory and Raman predictions for an independent validation set of spectra that are not included in the PLS model.  The standard error of prediction for the validation set (939 samples) with 4 outliers removed was 0.60.