Determinação do teor de monoésteres em biodiesel: um estudo comparativo por cromatografia líquida de alta eficácia e ressonância magnética nuclear de hidrogênio

Abstract

In this study the use of techniques 1H NMR spectroscopy and high performance liquid chromatography are compared for evaluating the content of methyl and ethyl esters formed by transesterification of soybean oil. For that, equations reported in the literature were used and that has been developed for the quantitation of methyl and ethyl esters of soybean by H1 NMR. Several samples were obtained by transesterification in order to obtain models exhibiting different ester concentrations. The signals of H1 NMR spectra of the soybean oil, methyl and ethyl esters of soybean oil with total and partial conversion were assigned.The NMR technique, despite being regarded as a qualitative and quantitative technique, was not effective for determination of methyl and ethyl esters due to the overlap of the signals used for calculating the areas. By comparing the results obtained using both techniques, we obtained differences of ~ 15% and ~ 20% for methyl esters and ethyl esters, respectively.