The Use of Raman Spectroscopy and Methods of Quantum Chemistry for Assessing the Relative Concentration of Triglycerides of Oleic and Linoleic Acids in a Mixture of Olive Oil and Sunflower Seed Oil

The Raman spectra of five samples of sunflower seed oil and five samples of cold-pressed olive oil of various brands are recorded in the range of 500–2000 cm^–1. Within the framework of the B3LYP/6-31G(d)/6-31G(d,p)/6-31+G(d,p)/6-311G(d)/6-311G(d, p)/6-311+G(d,p) methods, the structural models of eight fatty acids (oleic, linoleic, palmitic, stearic, α-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic) are constructed, and also within the framework of the B3LYP/6-31G(d) method, the structural models of triglycerides of the first four of the above acids are obtained. The vibrational wavenumbers and intensities in the IR and Raman spectra are calculated. The Raman spectra of olive oil and sunflower seed oil were simulated by using the supermolecular approach. We investigated the dependence of the relative intensity of the vibrational bands ν_exp = 1660 and 1445 cm^–1 on the concentration of triglycerides in oils of oleic and linoleic acids and the dependence of the intensity of these bands on the degree of saturation of fatty acids. Experimental and empirical dependences are constructed to estimate the relative concentration of triglycerides of oleic and linoleic acids in a mixture of olive oil and sunflower seed oil. The applicability of the density functional theory together with the vibrational spectroscopy for the identification of mixtures of vegetable oils is discussed.     

The Use of IR Spectroscopy and Density Functional Theory for Estimating the Relative Concentration of Triglycerides of Oleic and Linoleic Acids in a Mixture of Olive and Sunflower Seed Oils

Optics and Spectroscopy - 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...     

The experimental vibrational infrared spectrum of lemon peel and simulation of spectral properties of the plant cell wall

The experimental vibrational IR spectra of the outer part of lemon peel are recorded in the range of 3800–650 cm^–1. The effect of artificial and natural dehydration of the peel on its vibrational spectrum is studied. It is shown that the colored outer layer of lemon peel does not have a noticeable effect on the vibrational spectrum. Upon 28-day storage of a lemon under natural laboratory conditions, only sequential dehydration processes are reflected in the vibrational spectrum of the peel. Within the framework of the theoretical DFT/B3LYP/6-31G(d) method, a model of a plant cell wall is developed consisting of a number of polymeric molecules of dietary fibers like cellulose, hemicellulose, pectin, lignin, some polyphenolic compounds (hesperetin glycoside-flavonoid), and a free water cluster. Using a supermolecular approach, the spectral properties of the wall of a lemon peel cell was simulated, and a detailed theoretical interpretation of the recorded vibrational spectrum is given.

     

Structural Parameters and Thermodynamics of the Formation of Molecular Water Clusters

The formation of molecular water clusters is simulated using the theoretical density functional theory/ B3LYP/6-311+G(d,p) method. The spatial configurations of 29 clusters with 2 to 28 water molecules are calculated. The dipole moments, the complete complex-formation enthalpy, and the enthalpy of the successive joining of water molecules are determined with the basis-set superposition error taken into account. The features of the geometric structure and the hydrogen-bond strength of water clusters are analyzed on the basis of the obtained theoretical data. The complex-formation enthalpy is revealed to depend periodically on the number of water molecules in a cluster. It is found that clusters with molecules whose number is a multiple of four are energetically most advantageous. When a molecular cluster is built starting with 17 molecules, the cluster structure is changed, resulting in that one end of the complex rolls up into a prismatic configuration.     

Algorithm for solving the inverse vibronic problem on the basis of SVL fluorescence spectra

Computer methods whereby the inverse vibronic problem is solved on the basis of resonance fluorescence spectra with the use of modern quantum-mechanical methods for constructing structuraldynamic models of polyatomic molecules are discussed. An algorithm is proposed for solving the inverse vibronic problem according to resonance fluorescence spectra under laser excitation, and the corresponding calculation programs are constructed. The initial program data are acquired by means of an original software package which implements the scaling of quantum-mechanical force fields in two electronic states. The Duschinsky matrix and the initial matrix of shifts in normal coordinates caused by electron excitation are calculated in the Cartesian and natural vibrational coordinates. The program data are taken from quantum-molecular models based on calculations performed via ab initio modern quantum-mechanical methods and density functional theory. The algorithm is tested through the calculation of a model molecular system.     

Optical Clearing of Human Skin Using Some Monosaccharides in vivo

Optics and Spectroscopy - We present the results of in vivo optical immersion clearing of human skin by aqueous solutions of some immersion agents (ribose, glucose, and fructose monosaccharides and...     

Application of IR Spectroscopy for the Estimation of the Relative Content of Unsaturated Fats in Vegetable Oils

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - The IR spectra of five samples of sunflower seed oils and five samples of cold-pressed olive oil of various brands are...