Abstract
bDepartment of Chemistry, ICE, Federal University of Amazonas - UFAM , Manaus, AM - Brazil Near-infrared spectroscopy (FT-IR) is an useful tool for the study of biological molecules. The application of this technique is continually expanding mainly for the characterization of proteins and lipids. Quantitative analysis relies on a calibration model which can be semi-quantitative by multiple linear regression analysis. The advantage of this technique is that substances are analysed without chemical treatment, avoiding secondary reactions. In addition, all compounds are measured simultaneously, speeding analysis. Accordingly, two techniques were tested: i) FT-IR , based on rapid determination of trans geometric isomers isolated in fats and oils at ATR (Attenuated Total Reflection) by infrared spectroscopy (Method Cd 14d- 99, AOCS ), ii) Gas Chromatography Coupled with Mass Spectrometry, which analysis were made in Fourier Transform Infrared Spectrometer (FT-IR). A calibration curve was constructed using a B100 biodiesel, to estimate the percentage of ester in the samples. The area was obtained by integration of the absorption region at 1750 cm -1 and the slope and intercept determined in the linear fit. The FT-IR analysis indicated the major structural features of the product, the estimate ester percentage in the samples and the percentage of reactions conversion. The identification of the ethyl ester was confirmed by gas chromatography with mass detector. The samples obtained by different methods of methyl and ethyl transesterification reaction in situ yielded 75.1 % and 93.4 % of ester, respectively, while the transesterification reaction of the extracted oil yielded 95.5 L% of esters. The spectras of the crude oil and biomass were also obtained for comparison and identification of the compounds. Besides the identification of the components and the estimation of esters in the sample, the use of FT-IR as a primary or auxiliary technique can contribute to the process control quickly with good response. However, this technique requires a validation for the construction of a mathematical model using a chemometrics method for making it reliable and effective.
