Assessment of Different Measurement Methods Using 1H-NMR Data for the Analysis of the Transesterification of Vegetable Oils

In the present work we make assessments of the correlation of equations based on H-1-NMR data for the analysis of FAME in 45 transesterification products with methanol from several vegetable oils (soybean, corn, sunflower, canola, linseed, cottonseed and jatropha). The products employed in this study were of high and low yield. A comprehensive approach to the applicability, advantages and limitations of employing NMR expressions is described. A new expression to determine the degree of unsaturation of combined and free fatty acids was found to be satisfactory when compared with the classic expression. Estimates of uncertainties for classic equations, which have been used to determine yield and degree of unsaturation, were proposed in the present work. The results show that either one or both of the expressions for estimating yields could not be satisfactorily used for products from linseed oil, and also indicate the possibility that products from cottonseed oil may also be exceptions. Both the equations were found to be satisfactory for the products obtained from the other oils (soybean, corn, sunflower, canola and jatropha), considering the uncertainties proposed in the present work.