Abstract

Infrared spectra of five samples of sunflower seed oil and five samples of cold-pressed olive oil of different brands are recorded in the range of 650–3800 сm^–1. The structural models of eight fatty acids (oleic, linoleic, palmitic, stearic, α-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic), as well as of triglycerides of the first four of these acids, are constructed using B3LYP/6-31G(d) methods. The vibrational wavenumbers and intensities in the IR spectra are calculated. The IR spectra of olive and sunflower seed oils are simulated using the supermolecular approach. The dependence of the intensity of vibrational bands at ν_exp = 914 and 3009 сm^–1 on the concentration of triglycerides of oleic and linoleic acids in oils, as well as on the saturation degree of fatty acids, are studied. Experimental and empirical dependences are plotted to estimate the relative concentrations of triglycerides of oleic and linoleic acids in mixtures of olive and sunflower seed oils. The applicability of the density functional theory in combination with IR spectroscopy for characterization of vegetable oils is discussed.

中文翻译：

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红外光谱和密度泛函理论用于估计橄榄油和葵花籽油混合物中油酸和亚油酸甘油三酸酯的相对浓度

摘要

在650–3800сm ^–1的范围内，记录了五种不同品牌的葵花籽油和五种冷榨橄榄油的红外光谱。使用B3LYP / 6-31G（ d）方法。计算红外光谱中的振动波数和强度。使用超分子方法模拟了橄榄油和葵花籽油的红外光谱。振动带的强度中的ν依赖性_EXP  = 914和3009сm ^-1研究了油中油酸和亚油酸甘油三酯的浓度以及脂肪酸的饱和度。绘制了实验和经验相关性，以估计橄榄油和葵花籽油混合物中油酸和亚油酸甘油三酸酯的相对浓度。讨论了密度泛函理论与红外光谱技术结合用于植物油表征的适用性。