Three different biodiesel sources (cotton, castor and palm) were adulterated with raw soybean oil at concentrations ranging from 1-40% (m/m). These samples were analyzed by infrared spectrometry (MIR) and their spectra were studied at three different spectral ranges: full spectrum (4000-665 cm-1), and the spectral ranges of 1800-1700 cm-1 and 1800-1000 cm-1. To determine the source of biodiesel used in the adulterated system, the data were analyzed by PCA (principal components analysis) spectral analysis tool and the best segregation of the sources was obtained at the range of 4000-665 cm-1. The explained variance was of 99% for the first three components. To quantify the raw soybean oil partial least squares (PLS) tool was applied. The best results were obtained for the spectral range of 1800-1000 cm-1, with values of RMSEP (root mean square error of prediction) varying from 1.10 to 1.47% (m/m).
biodiesel adulteration; multivariate calibration; ATR-FTIR
