Determination of the Hydroxyl Value of Soybean Polyol by Attenuated Total Reflectance/Fourier Transform Infrared Spectroscopy |
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Authors: | Simone C Godoy Marco Flôres Ferrão Annelise E Gerbase |
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Affiliation: | (1) Instituto de Química, Universidade Federal do Rio Grande do Sul, CP 15003, 91501-970 Porto Alegre, RS, Brazil;(2) Departamento de Química e Física, Universidade de Santa Cruz do Sul, Santa Cruz do Sul, RS, Brazil |
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Abstract: | A rapid method for the quantitative determination of the hydroxyl value (OHV) of hydroxylated soybean oils by HATR/FTIR spectroscopy
is described. Calibration standards were prepared by the formic acid/hydrogen peroxide method and OH values were determined
by the official method of AOCS Tx 1a-66, covering an analytical range of 3.5–125 mg of KOH/g of sample. A partial least squares
(PLS) calibration model for the prediction of the hydroxyl value (OHV) was developed based on eight different spectral subregions
between 3,150 and 990 cm−1 and combinations of them. On average, 36 samples were used for the modeling and 17 were used for external validation. The
resulting calibration was linear over the analytical range and had a standard deviation of 2.334. Validation of the method
was carried out by comparing the OHV of a series of hydroxylated soybean oils predicted by the PLS model to the values obtained
by the AOCS standard method. A correlation coefficient of R
2 = 0.9843 and RMSEC and RMSEP values of, respectively, 3.393 and 3.643 were obtained. After the calibration of the spectrometer,
the OHV could be obtained in 2–3 min per sample, a major improvement over conventional wet chemical methods. The advantages
of these methodologies are that they do not destroy the sample, have a lower cost, expedite the analysis and do not produce
residues. Therefore, they may yield excellent results when used to quantify OHV of soybean polyols obtained by hydroxylation
reaction. |
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Keywords: | Hydroxyl value Hydroxylated soybean oil Partial least squares regression Attenuated total reflectance Infrared spectroscopy Chemometrics Multivariate analysis |
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