Determination of the content of fatty acid methyl esters (FAME) in biodiesel samples obtained by esterification using 1H-NMR spectroscopy.
Three different calibration curves based on (1)H-NMR spectroscopy (300 MHz) were used for quantifying the reaction yield during biodiesel synthesis by esterification of fatty acids mixtures and methanol. For this purpose, the integrated intensities of the hydrogens of the ester methoxy group (3.67 ppm) were correlated with the areas related to the various protons of the alkyl chain (olefinic hydrogens: 5.30-5.46 ppm; aliphatic: 2.67-2.78 ppm, 2.30 ppm, 1.96-2.12 ppm, 1.56-1.68 ppm, 1.22-1.42 ppm, 0.98 ppm, and 0.84-0.92 ppm). The first curve was obtained using the peaks relating the olefinic hydrogens, a second with the parafinic protons and the third curve using the integrated intensities of all the hydrogens. A total of 35 samples were examined: 25 samples to build the three different calibration curves and ten samples to serve as external validation samples. The results showed no statistical differences among the three methods, and all presented prediction errors less than 2.45% with a co-efficient of variation (CV) of 4.66%.
Mello
Vinicius M
VM
Laboratório de Materiais e Combustíveis, Instituto de Química, Universidade de Brasília, C.P.04478, 70919-970, Brasília, DF, Brazil.
Oliveira
Flavia C C
FC
Fraga
William G
WG
do Nascimento
Claudia J
CJ
Suarez
Paulo A Z
PA
D002138:Calibration; D004736:Energy-Generating Resources; D004951:Esterification; D005227:Fatty Acids / Q000032:analysis*; D005742:Gasoline; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards*; D010938:Plant Oils; D011522:Protons
D005227:Fatty Acids; D005742:Gasoline; D010938:Plant Oils; D011522:Protons