Qualitative analysis of desi ghee,edible oils,and spreads using Raman spectroscopy

Keeping in view the importance of dietary fats in modulating disease risk, a study was planned to compare edible oils, spreads, and desi ghee based on fatty acid composition through Raman spectroscopy. The double bonds in unsaturated oils tend to react more with oxygen causing oxidative stress in living cells; therefore, the excessive use of processed vegetable oils may pose risk for human health. In the spectral analysis, Raman peaks at 1063 and 1127 cm⁻¹ represent out‐of‐phase and in‐phase aliphatic C C stretch for saturated fatty acids. The peak at 1300 cm⁻¹, labeled for alkane, decreases with increase in the double bond contents (unsaturation). Further, the Raman peak at 1655 cm⁻¹ showed a monotonic increase as a function of unsaturation. The double bond contents in the Raman spectra from 1650–1657 cm⁻¹ represent unsaturated fatty acids that changes during the synthesis of spreads and banaspati ghee. Desi ghee, extracted from cow and buffalo milk, showed distinctive Raman peaks at 1650 and 1655 cm⁻¹, which originates because of isomers of conjugated linoleic acid. These Raman shifts differentiated desi ghee from other artificially produced banaspati ghee, spreads, and oils. Conjugated linoleic acid has proved to be anti‐carcinogenic, anti‐inflammatory, and anti‐allergic properties; therefore, the limited use of desi ghee may reduce the risk of cardiac diseases. Principal component analysis has been applied on the Raman spectra that clearly differentiated desi ghee, mono‐unsaturated extra virgin olive oil, and extra virgin olive oil spread from other oils, oil mixtures, spreads, and ghee. In addition, principal component analysis has been blindly applied successfully on 13 unknown samples to classify them with reference to the known ghee sample. Copyright © 2016 John Wiley & Sons, Ltd.     

Depth profiling of horse fat tissue using mid-infrared and confocal Raman microscope

Attenuated total reflection Fourier transform infrared (ATR FT-IR) and confocal Raman microscopes were used to record horse fat depth profiles. The dependence of the unsaturation level and the iodine value on the distance from the skin were studied for tissue of the plane 10?×?10?mm and thickness of 30?mm. The degree of unsaturation was determined as well as the content of carotenoids and retinoids in horse fat were analyzed using the same spectroscopic methods. Clear and characteristic changes of the studied material parameters depending on the distance from the skin were described.     

Spectrum of OH-stretching vibrations of water in a “floating” water bridge

The axial distribution (over the cross section) of the spectra of the OH-stretching band of water in a water bridge is investigated using the Raman scattering method. It is found that the axial structure of the bridge is inhomogeneous: the core at the center of the bridge contains a larger amount of water with an ??icelike?? structure and a presumably larger number of H⁺ ions, while the outer layer probably consists of water with a larger number of OH^? ions.     

Comparison of connective tissue invaded by Lewis lung carcinoma to healthy connective tissue by means of micro‐Raman spectroscopy

We have measured the micro‐Raman spectra of mouse tissues invaded by Lewis lung carcinoma (LLC). We have also carried out categorical principal component analysis (CATPCA) on the acquired spectra. The results indicate that the tumor tissues can be well discriminated from normal tissues by the first two principal components extracted from the spectra. Furthermore, we have found that the concentrations of nucleic acids and lipids/fatty acids in the tumor are considerably higher than those in the normal tissue, whereas the collagen concentration is lower. These differences can be detected and characterized by Raman images using the 788 cm⁻¹ DNA/RNA band and the 1301 cm⁻¹ lipid/fatty acid band. Copyright © 2009 John Wiley & Sons, Ltd.     

Infrared and Raman spectroscopic studies of the charge localization in one‐dimensional organic metals (DMtTTF)2X (X = ReO4, ClO4) with regular organic stacks

A novel selective synthesis of the unsymmetrically substituted tetrathiafulvalene dimethyltrimethylene‐tetrathiafulvalene (DMtTTF) is described together with its electrocrystallization to the known conducting mixed‐valence ClO₄^– and ReO₄^– salts. Infrared (IR) and Raman spectra of the two isostructural quasi‐one‐dimensional cation radical salts (DMtTTF)₂X (X = ReO₄^–, ClO₄^–) are investigated as a function of temperature (T = 5–300 K). At ambient temperature, these salts show metallic‐like properties and below T_ρ = 100–150 K, they undergo a smeared transition to semiconducting state. To study this charge localization, we measured temperature dependence of polarized IR reflectance spectra (700–16 000 cm^–1) and Raman spectra (150–3500 cm^–1, excitation λ = 632.8 nm) of single crystals. For both compounds, the Raman data and especially the bands related to the C=C stretching vibration of the DMtTTF molecule show that the charge distribution on molecules is uniform down to the lowest temperatures. Similarly, IR data confirm that down to the lowest temperatures, there is neither charge ordering nor important modification of the electronic structure. However, the temperature dependence of Raman spectra of both salts reveals a regime change at about 150 K. Additionally, using Density Functional Theory (DFT) methods, the normal vibrational modes of the neutral DMtTTF⁰ and cationic DMtTTF⁺ species and also their theoretical IR and Raman spectra were calculated. The theoretical data were compared with the experimental IR and Raman spectra of neutral DMtTTF⁰ molecule. Copyright © 2013 John Wiley & Sons, Ltd.     

Vibrational spectra of p-chlorobenzaldehyde and its deuterated derivatives

The vibrational modes of parachlorobenzaldehyde are assigned using infrared and Raman spectra, valence force field calculations of normal coordinates, and deuteration effects. Low temperature and isotopic studies show that the band at 310 cm^?1 previously observed as a single band is a closely spaced doublet. One component is assigned as the out-of-plane CCl wagging mode, the other as a mixed CClCHO in-plane bending deformation. A feature of the spectra in all the isotopic parachlorobenzaldehydes is an intense doublet in the 1700 cm^?1 region interpreted as Fermi resonance between a combination band and the carbonyl stretching mode.     

High‐resolution Raman imaging reveals spatial location of heme oxidation sites in single red blood cells of dried smears

Raman confocal microscopy with 488 nm excitation wavelength supported with atomic force microscopy (AFM), scanning near‐field optical microscopy (SNOM) and UV–Vis spectrometry was used to investigate air‐dried erythrocytes (red blood cells, RBCs) in whole human blood smears. The central internal part of the cell was dominated by the laser‐induced O₂ dissociated oxyHb form as evidenced by the Fe²⁺ marker band appearing at 1356 cm⁻¹. The existence of a thin outer layer of hemoglobin in the periphery of RBCs was assigned to hemichrome. Evidence for hemichrome includes the oxidation state marker band appearing at 1376 cm⁻¹, the absence of FeO₂ band at 570 cm⁻¹ and a UV–Vis spectrum consistent with hemichrome. This is the first time that distributions of Fe²⁺/Fe³⁺ hemes inside the single RBC have been reported. The outer layer formation of hemichrome was additionally studied when RBCs were in contact with leucocytes and carotenoids of blood plasma. Copyright © 2014 John Wiley & Sons, Ltd.     

Involvement of weak C?H···X hydrogen bonds in metal‐to‐semiconductor regime change in one‐dimensional organic conductors (o‐DMTTF)2X (X = Cl,Br, and I): combined IR and Raman studies

We report on the infrared (IR) and Raman studies of the three isostructural quasi‐one‐dimensional cation radical salts of 3,4‐dimethyl‐tetrathiafulvalene (o‐DMTTF)₂X (X = Cl, Br, and I), which all exhibit metallic properties at room temperature and undergo transitions to a semiconducting state in two steps: a soft metal‐to‐semiconductor regime change in the temperature region T_ρ = 5–200 K and then a sharp phase transition at about T_MI = 50 K. Polarized IR reflectance spectra (700–16 000 cm⁻¹) and Raman spectra (50–3500 cm⁻¹, excitation λ = 632.8 nm) of single crystals were measured as a function of temperature (T = 5–300 K) to assess the eventual formation of a charge‐ordered state below 50 K. Additionally, the temperature dependence of the IR absorption spectra of powdered crystals in KBr discs was also studied. The Raman spectra and especially the bands related to the CC stretching vibration of o‐DMTTF provide unambiguous evidence of uniform charge distribution on o‐DMTTF down to the lowest temperatures, without any modification below 50 K. However, the temperature dependence of Raman spectra indicates a regime change below about 200 K. Temperature dependence of both electronic dispersion and vibrational features observed in the IR spectra also clearly confirms the regime change below about 200 K and shows the involvement of C H···X hydrogen bonds in the electronic localization; some spectral changes can be also related with the phase transition at 50 K. Additionally, using density functional theory methods, the normal vibrational modes of the neutral o‐DMTTF⁰ and cationic o‐DMTTF⁺ species, as well as their theoretical IR and Raman spectra, were calculated. The theoretical data were compared with the experimental IR and Raman spectra of neutral o‐DMTTF molecule. Copyright © 2011 John Wiley & Sons, Ltd.     

FTIR and Raman spectroscopic study of Fenugreek (<Emphasis Type="Italic">Trigonella foenum graecum L.</Emphasis>) seeds

The composition of Fenugreek seeds in the form of powder, ash, and oil is investigated through FTIR and FT Raman spectra measurements. The results indicate that Fenugreek seeds (powder) are rich in proteins. Fats (lipids) and starch are present in small amounts in the seeds. The FTIR absorption bands of seed powder appeared at: 3365 cm^–1 assigned as N-H stretching vibrations (amide A of protein), 1657 cm^–1 (C=O, amide I), 1540 cm^–1 (N-H bending vibration, amide II), and 1240 cm^–1 (N-H bending, amide III). In the FT Raman spectra the band at 1661 cm^–1 is ascribed to amide I (C=O) of proteins while the band at 1080 cm^–1 indicates the starch. The fenugreek oil Fourier transform infrared absorbance ratios A(3009 cm^–1)/A(2924 cm^–1), A(3009 cm^–1)/A(2854 cm^–1), and A(3009 cm^–1)/A(1740 cm^–1) were considered for measuring the iodine values. These ratios (0.3609, 0.4916, and 0.4129) revealed that the iodine value of fenugreek oil is higher than that of other oils. On the other hand, the ash of fenugreek is very rich in phosphate compounds. The spectra showed absorption bands at frequencies 1082, 1000, 618, and 566 cm^–1, and the FT Raman spectrum showed a strong absorbance band at 793 cm^–1, which is due to phosphate compounds. It could be concluded that the inorganic part of fenugreek consists mainly of phosphate compounds. The Fenugreek seed contains proteins, fat, fiber, and ash, which is in complete harmony with AACC, 1980.__________Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 106–110, January–February, 2005.     

Raman identification of lonsdaleite in Popigai impactites

Micro‐Raman spectroscopy and X‐ray diffraction method (XRD) were used to characterize impact carbonaceous rocks excavated from the Popigai crater (Siberia). The deconvolution of the first‐order Raman spectra of the rocks containing different amounts of carbon phases (diamond, lonsdaleite and graphite) allowed the identification of lonsdaleite spectrum. The most intensive band at 1292–1303 cm⁻¹ was ascribed to A_1g vibration mode of lonsdaleite, whereas the less intense band at 1219–1244 cm⁻¹ was attributed, in agreement with previously reported ab initio calculations, to E_2g vibration mode. The established correlation between the intensities of Raman and XRD peaks permits a rough estimation of lonsdaleite/diamond phase ratio in the impact rocks using micro‐Raman measurements. The second‐order Raman spectra of lonsdaleite–diamond rocks were recorded. Copyright © 2014 John Wiley & Sons, Ltd.     

Raman study on electrochemical lithium insertion into multiwalled carbon nanotubes

We have carried out in situ Raman studies during the electrochemical insertion of lithium ions (Li⁺) into pristine and thermally treated multiwalled carbon nanotubes (MWNTs). We found an improved structural integrity as well as the removal of defects in the thermally treated tubes. The different Li⁺ insertion behaviors above 0.5 V in as‐grown and thermally treated tubes could be explained by the presence of defects on the outer surface of the tubes. No change of Raman spectra from 2.8 to 0.8 V is characterized by the coverage of Li⁺ on the outer surface of tubes, whereas the upshift of G band and the absence of a separated G band below 0.75 V indicate the formation of diluted graphite intercalation below the stage‐2 phase (LiC₁₂). Copyright © 2008 John Wiley & Sons, Ltd.     

Characterization of Ir(ppy)3 and [Ir(ppy)2 bpy]+ by infrared,Raman spectra and surface‐enhanced Raman scattering

The Raman and infrared spectra of fac ‐tris(2‐phenylpyridinato‐N,C2′)iridium(III), Ir(ppy)₃ and surface‐enhanced resonance Raman spectra of bis(2‐phenyl pyridinato‐) (2,2′bipyridine) iridium (III), [Ir(ppy)₂ (bpy)]⁺ cation were recorded in the wavenumber range 150–1700 cm⁻¹, and complete vibrational analyses of Ir(ppy)₃ and [Ir(ppy)₂ (bpy)]⁺ were performed. Most of the vibrational wavenumbers were calculated with density‐functional theory agree with experimental data. On the basis of the results of calculation and comparison of the spectra of both complexes and their analogue [Ru(bpy)₃]²⁺, we assign the vibrational wavenumbers for metal–ligand modes; metal–ligand stretching wavenumbers are 277/307 and 261/236 cm⁻¹ for Ir(ppy)₃, and 311/324, 257/270, 199/245 cm⁻¹ for [Ir(ppy)₂ bpy]⁺. Surface‐enhanced Raman scattering spectra of [Ir(ppy)₂ bpy]²⁺ were measured at two wavelengths on the red and blue edges of the low‐energy metal‐to‐ligand charge‐transfer band. According to the enhanced Raman intensities for the vibrational modes of both ligands ppy and bpy, the unresolved charge‐transfer band is deduced to consist of charge‐transfer transitions from the triplet metal to both ligands ppy and bpy. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopic evaluation of the influence of Pseudomonas bacteria on aflatoxin B1 in the BioArena complex bioautographic system

The mechanism of the antibacterial‐toxic effect of aflatoxin B1 (AFB1) was investigated in the BioArena complex bioautographic system that consists of planar liquid chromatographic development and biological detection. In this system, the killing‐inhibiting activity of AFB1 against Pseudomonas savastanoi (Psm) bacterial cells was visualised. The role of formaldehyde (HCHO) was suggested in the antibacterial‐toxic action of AFB1. Raman spectroscopy (RS) was used to investigate whether the excess HCHO found earlier in the AFB1 spot (comparing with background) originated partly from the demethylation of the toxin, or only from the enhanced demethylation of the normal cell ingredients because of the stress situation. Fourier transform (FT) Raman and surface‐enhanced FT‐Raman spectra were obtained in situ about the AFB1 chromatographic and background spots in bacteria‐free and inoculated thin layer chromatography (TLC) layers, and ex situ about their dried methanolic extract. The reduction of the δ CH₃ band of AFB1 (1386 cm⁻¹) in the presence of Psm can indicate the demethylation of aflatoxin at its methoxy‐group in BioArena. It seems from the Raman spectra that, apart from demethylation, aflatoxin does not suffer other structural changes. However, Psm can reduce the Raman activity of νCO bond of the pyran ring of AFB1, causing lower intensity and a broader band (1747 and 1754 cm⁻¹). Psm can also disrupt the strong interactions between the AFB1 and the adsorbent layer through the νCO bond of the cyclopentene ring causing a blue‐shift (1667 → 1686 cm⁻¹). The very reactive HCHO that originated from exogenous sources, e.g. from the demethylation of AFB1, has no determined biochemical pathway, so it means higher risk. Copyright © 2008 John Wiley & Sons, Ltd.     

Crystal → nematic phase transition in the liquid crystalline system 1‐isothiocyanato‐4‐(trans‐4‐propylcyclohexyl) benzene (3CHBT) probed by temperature‐dependent micro‐Raman study and DFT calculations

Raman spectra of 3CHBT in unoriented form were recorded at 14 different temperature measurements in the range 25–55 °C, which covers the crystal → nematic (N) phase transition, and the Raman signatures of the phase transition were identified. The wavenumber shifts and linewidth changes of Raman marker bands with varying temperature were determined. The assignments of important vibrational modes of 3CHBT were also made using the experimentally observed Raman and infrared spectra, calculated wavenumbers, and potential energy distribution. The DFT calculations using the B3LYP method employing 6‐31G functional were performed for geometry optimization and vibrational spectra of monomer and dimer of 3CHBT. The analysis of the vibrational bands, especially the variation of their peak position as a function of temperature in two different spectral regions, 1150–1275 cm⁻¹ and 1950–2300 cm⁻¹, is discussed in detail. Both the linewidth and peak position of the ( C H ) in‐plane bending and ν(NCS) modes, which give Raman signatures of the crystal → N phase transition, are discussed in detail. The molecular dynamics of this transition has also been discussed. We propose the co‐existence of two types of dimers, one in parallel and the other in antiparallel arrangement, while going to the nematic phase. The structure of the nematic phase in bulk has also been proposed in terms of these dimers. The red shift of the ν(NCS) band and blue shift of almost all other ring modes show increased intermolecular interaction between the aromatic rings and decreased intermolecular interaction between two  NCS groups in the nematic phase. Copyright © 2009 John Wiley & Sons, Ltd.     

Near‐infrared Raman spectroscopy for gastric precancer diagnosis

Raman spectroscopy is a molecular vibrational spectroscopic technique that is capable of optically probing the biomolecular changes associated with neoplastic transformation. The purpose of this study was to apply near‐infrared (NIR) Raman spectroscopy for differentiating dysplasia from normal gastric mucosa tissue. A total of 65 gastric mucosa tissues (44 normal and 21 dysplasia) were obtained from 35 patients who underwent endoscopy investigation or gastrectomy operation for this study. A rapid NIR Raman system was utilized for tissue Raman spectroscopic measurements at 785‐nm laser excitation. High‐quality Raman spectra in the range of 800–1800 cm⁻¹ can be acquired from gastric mucosa tissue within 5 s. Raman spectra showed significant differences between normal and dysplastic tissue, particularly in the spectral ranges of 850–1150, 1200–1500 and 1600–1750 cm⁻¹, which contained signals related to proteins, nucleic acids and lipids. The diagnostic decision algorithm based on the combination of Raman peak intensity ratios of I₈₇₅/I₁₄₅₀ and I₁₂₀₈/I₁₆₅₅ and the logistic regression analysis yielded a diagnostic sensitivity of 90.5% and specificity of 90.9% for identification of gastric dysplasia tissue. This work demonstrates that NIR Raman spectroscopy in conjunction with intensity ratio algorithms has the potential for the noninvasive diagnosis and detection of precancer in the stomach at the molecular level. Copyright © 2009 John Wiley & Sons, Ltd.     

拉曼光谱法测定天然脂肪球脂质成分

天然脂肪球主要由甘油三酯构成,以不同大小的球状形式分泌而得。不同大小的脂肪球的球体和膜组成成分不同,从而影响了脂肪在乳中的存在形式和最终的乳品功能特性。然而,不同大小的脂肪球成分的差异尚未完全阐明。利用拉曼光谱测定特定大小脂肪球及膜的脂质和脂肪酸组成。拉曼光谱能够从单个脂肪球获得特定拉曼信号,并且在不破坏天然脂肪球构型的情况下进行测定。结果显示,小脂肪球在2 885/2 850 cm-1处条带信号较高,表明小脂肪球趋于形成结晶态的脂肪球膜包裹流动态的甘油三酯内核的结构。此外,小脂肪球与大脂肪球相比,1 655/1 443 cm-1的条带信号较低,表明小脂肪球的脂肪酸不饱和程度较高。总之,从本实验结果可以推断,用特定的小脂肪球分离而得的稀奶油在熔化时较大脂肪球难熔化,搅拌耗时更多,但能形成更柔软的黄油。     

Raman Intensity of the v C=O Band in Hydrogen Bonded Complexes Involving Ethylformate and Phenol Derivatives

The hydrogen bonded complexes between carbonyl bases and hydroxylic derivatives have been extensively studied by infrared spectrometry; by comparison very little Raman data have been reported in the literature. Some qualitative measurements on the v _C=O band of acetone dissolved in water-tetrachloride mixtures have been performed by Singurel¹. Quantitative data on the absolute Raman intensity have been obtained for complexes involving cyclohexanone², acetone, acetophenone³ and methylacetate⁴. For these systems, hydrogen bond formation brings about a moderate intensity enhancement of the v _C=O band. In this work the Raman intensity of the v _C=O band of ethylformate (EtFo) complexed with phenol derivatives is investigated.     

Orientation of sp2 carbon nanoclusters in ion‐implanted polymethylmethacrylate as revealed by polarized Raman spectroscopy

Raman spectroscopy is widely used for the characterization of bonding type in carbon‐based materials, including carbonized surface layer in ion‐implanted polymers. Studies of the polarization properties of Raman scattering from amorphous carbonaceous materials, however, are very scarce. In this paper, we investigate the polarized Raman spectra of polymethylmethacrylate (PMMA) implanted with 50‐keV Si⁺ ions at fluences in the range 3.2 × 10¹⁴–1.0 × 10¹⁷ ions/cm² and for different visible excitation wavelengths. The spectra of the implanted samples are dominated by the D‐ and G‐bands of sp² carbon, which evidence strong carbonization of the ion‐modified layer. The multiwavelength excitation allowed us to resonantly probe the depolarization ratios for sp² clusters of different sizes. We established that the depolarization ratio ρ_G of the G‐band correlates with the sp² cluster size approaching the random orientation limit of 0.75 for the smallest clusters and a limiting value of 0.41 for the largest clusters. The experimental findings give evidence for a preferable orientation of the larger size clusters with their hexagonal planes perpendicular to the surface of the sample. A plausible explanation for such an arrangement is that the sp² clusters form tile‐like arrangements along the ion tracks. This finding may give clues for understanding of the strong transconductance of the ion‐modified layer, and open prospects for the application of polarized Raman spectroscopy as a characterization tool for surface morphology in ion‐implanted materials. Copyright © 2010 John Wiley & Sons, Ltd.     

Structure comparison of Orpiment and Realgar by Raman spectroscopy

Raman spectroscopy was used to characterize and differentiate the two minerals, Orpiment and Realgar, and the bands related to the mineral structure. The Raman spectra of these two minerals are divided into three sections: (a) 100–250?cm^?1 region attributed to the sulfur–arsenic–sulfur bending vibrational modes; (b) 250–450?cm^?1 region due to the arsenic–sulfur stretching vibration; and (c) 450–850?cm^?1 region assigned to overtone and combination bands. A total of 14 Raman bands for the spectrum in the 1600–100?cm^?1 region were observed. The significant differences between the minerals Orpiment and Realgar are observed by Raman spectroscopy. Realgar shows the typical bands observed at 340, 268, 228, and 218?cm^?1, and the special bands at 379, 289, 200, 176, and 102?cm^?1 for Orpiment are observed. The additional bands in 850–450?cm^?1 region are only observed for the mineral Orpiment, which may be attributed to overtone and combination bands in the Raman spectrum. The variation in band positions is dependent upon the structural symmetry, arsenic–sulfur bond distances, and angles. Moreover, another cause for the difference is the effect of the intermolecular forces and to the strong coupling between close lying external and internal modes. The difference of these two minerals structure induce tremendous diversity on Raman spectra, so Raman spectroscopy offers the information on the molecular structure of the minerals Orpiment and Realgar.     

Nondestructive analysis of single rapeseeds by means of Raman spectroscopy

The value of different vegetable oils can be correlated with the content of polyunsaturated fatty acids, especially omega‐3‐fatty acids such as linolenic acid, because of their contribution to healthy nutrition. One expression for the degree of unsaturation is the iodine value normally measured with gas chromatography. The use of Raman spectroscopy allows a rapid calculation of the iodine value and, in addition, only in a minimal sample volume. Therefore, this method can be used in single rapeseeds in order to predict the iodine value before harvesting. Additionally, the method can also be used for breeding investigations. Here, the lipid content and composition of a plant can be predicted by measuring the seedling without destruction. Copyright © 2006 John Wiley & Sons, Ltd.