| Fatty acids of different chain lengths are chemically similar to one another. This similarity is quite evident when comparing their vibrational spectra. The common belief is that it is easy to identify or quantify materials when they have distinct chemical features, but difficult when the materials of a mixture have similar structural moieties.
Diffuse reflectance Fourier transform near-infrared (FT-NIR) spectroscopy was investigated as a tool to quantify the concentrations of a model quaternary mixture of stearic acid, palmitic acid, mystiric acid and lauric acid. This study demonstrates the feasibility of this application as well as the advantage of the Fourier transform technique. It has been the belief better resolution and superior wavelength repeatability allow better quantification. This was demonstrated in this study by comparing results with data collected on an Antaris FT-NIR Analyzer at 4,8,16 and 32 cm-1 optical resolution.
Calibration models using blends of these fatty acids were developed and tested using a cross-validation procedure. Errors for these predictions are good, suggesting that FT-NIR can be used as a convenient, spectroscopic measurement tool for this application.
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