Infrared spectrophotometric procedure for determining azelaaldehydic acid derivatives

A convenient and accurate infrared procedure was developed for determining the conversion of azelaaldehydic esters to acetals by measuring disappearance of the aldehydic C−H stretching vibration at 2720 cm⁻¹ (3.68μ). No. Utiliz. Res. Dev. Div., ARS, USDA.     

Stability determination of soy lecithin-based emulsions by Fourier transform infrared spectroscopy

The stability of soy lecithin-stabilized emulsions was determined by Fourier transform infrared spectroscopy. Oilin-water (o/w) emulsions were prepared with 6% (vol/vol) medium-chain triglycerides (MCT), 94% (vol/vol) water, and 4% (wt/vol) Lecigran and Lecimulthin soy lecithin. There were little or no differences between the 4% Lecigran and 4% Lecimulthin emulsions for all vibrational regions studied (OH at 3348 cm⁻¹, C=O at 1741 cm⁻¹, PO and C−O−C at 1157 cm⁻¹, and P−O−C at 1101 cm⁻¹), but the control emulsion, without emulsifier, had increased vibrations as the emulsion separated. The weaker vibrations of the more stable emulsions were probably due to reduced molecular interaction at the interface. However, added magnesium or calcium chloride enhanced the vibration of these groups, probably by disrupting the lecithin interaction at the emulsion interface.     

Differentiation of 1- and 2-Monoglycerides by near-infrared absorption spectroscopy

1- and 2-monoglycerides can be differentiated and mixtures analyzed by investigating the overtone of the OH stretching vibration, which occurs in the near-infrared spectral region close to 1.4 microns. The results are compared with data obtainable in the fundamental rock-salt region. Presented at the 53rd fall meeting, American Oil Chemists’ Society, New York, October 17–19, 1960. Eastern Utilization Research and Development Division, Agricultural Research Service, United States Department of Agriculture.     

Structure of hydroperoxides obtained from autoxidized methyl linoleate

Summary A sample of debromination methyl linoleate has been autoxidized to a peroxide value of 671 m.e./kg. at approximately 0°C. in the dark. An essentially pure concentrate of methyl octadecadienoate monohy-droperoxide was quantitatively separated; infrared and ultraviolet spectral studies were made on the peroxide concentrate and on the corresponding hydroxyl derivative obtained by reducing the peroxides with stannous chloride. The infrared data showed no conjugated peroxides having geometric configurations other than cis, trans; the same data also showed that the peroxide concentrate contained at least 90% conjugated cis,trans forms. Calculations based on ultraviolet spectrophotometric methods also indicated that the peroxides were at least 90% conjugated. The remaining 10% of the sample is most likely nonconjugated diene hydroperoxide. Since analogous cis, cis conjugated dienes have not been isolated and their infrared and ultraviolet properties are unknown, their presence here in small amounts is possible. Ultraviolet and infrared spectra of the reduced compounds conform closely to those of the peroxides except for reduction in the intensity of the OH bond at 2.88 μ. The infrared absorption spectra of the C−H structure and carbonyl groups of an essentially pure conjugated cis, trans methyl octadecadienoate monohydroperoxide were recorded, using a LiF prism. The infrared absorption spectra of the C−H strucfraction isolated from methyl linoleate autoxidized in the dark at 24°C. indicated that appreciable amounts of conjugated trans, trans hydroperoxides were present, in addition to those of the cis, trans type. It is possible that the conjugated cis, trans isomers were formed originally but were labile at the higher temperature and in the presence of catalysts (e.g., peroxides) were transformed to the thermodynamically more stable conjugated trans, trans isomer. This work was supported in part by a contract between the Office of Naval Research, Department of the Navy, and the University of Minnesota. Hormel Institute publication No. 81, and paper No. 133, Journal Series, General Mills Research Laboratories.     

Application of a Handheld Portable Mid-Infrared Sensor for Monitoring Oil Oxidative Stability

This study evaluated the capabilities of a handheld mid-infrared (MIR) spectrometer combined with multivariate analysis to characterize oils, monitor chemical processes occurring during oxidation, and to determine fatty acid composition. Vegetable oils (corn, peanut, sunflower, safflower, cottonseed, and canola) were stored at 65 °C for 30 days to accelerate oxidation reactions. Aliquots were drawn at 5 day intervals and analyzed by benchtop and portable handheld mid-infrared devices (4,000–700 cm⁻¹) and reference methods (IUPAC 2301 [1], 2302 [1]; AOCS Cd 8-58 [2]; and Shipe 1979 [3]). PLSR and soft independent modeling of class analogy (SIMCA) models were developed for oil classification and estimation of oil stability parameters. Models developed from MIR spectra obtained with a benchtop spectrometer equipped with a 3-bounce ATR device resulted in superior discriminative performances for classifying oils as compared to those obtained from handheld spectra (single-bounce ATR). Models developed from reference tests and handheld spectra showed prediction errors (SECV) of 1 meq/kg for peroxide value, 0.09% for acid value and 2% for determination of unsaturated fatty acids in different oils. Spectral regions ~3,012–2,850 cm⁻¹ (C–H stretching bands/shoulders of fatty acids), ~1,740 cm⁻¹ (C=O stretching of esters), and ~1,114 cm⁻¹ (–C–O stretching) were found to be important for prediction. Handheld-FTIR instruments combined with multivariate-analysis showed promise for determination of oil quality parameters. Portability and ease-of-use makes the handheld device a great alternative to traditional methods.     

IR spectra of long chain vinyl derivatives

Differences in their IR spectra are used to identify and analyze compounds containing a monosubstituted ethylenic (vinyl) group. Variations in location, shape and intensity of the various bands due to this structure were studied. Although previous work was briefly reviewed, emphasis was on new information obtained from IR spectra of long chain vinyl compounds related to vegetable oils, including 1-alkenes, acrylic esters, allyl esters and ethers, vinyl esters, vinyl ethers and vinyl ketones. In IR spectra of long chain (C₁₀−C₁₈) vinyl compounds bands caused by the vinyl structure show clearly and, usually, without interference. These bands consist of stretching vibrations of the vinyl olefinic bond and the three vinylic C−H bonds, and of in-plane and out-of-plane deformations of the C−H linkages. Since the vinyl group and neighboring groups influence one another, the interactions of vinyl groups with carbonyl groups and single C−O bonds, as in esters and ethers, were investigated. Presented at the AOCS Meeting, New York, October 1968. No. Market. Nutr. Res. Div., ARS, USDA.     

Ricinelaidic acid and methyl ricinelaidate. Their preparation and determination by infrared spectroscopy

Summary Improved methods for the preparation of ricinelaidic acid and methyl ricinelaidate are described. The methods depend upon the elaidinization of methyl ricinoleate with a relatively small quantity of a nitrite-nitric acid solution, fractional crystallization of the methyl ricinelaidate, and its subsequent hydrolysis to ricinelaidic acid. The infrared spectra of these two compounds are presented, and bands arising from a deformation of the C−H about thetrans C=C group are discussed. Absorptivity values for this band in chlorform and in carbon disulfide solutions are given as additional criteria of purity of ricinelaidic acid and its methyl ester. The infrared absorption procedure for the quantitative determination of isolatedtrans ethylenic bond was applied to the determination of both ricinelaidic acid and methyl ricinelaidate. Details of specific procedures for the determination of each compound are given with the equations necessary for their calculation. Use of these methods is illustrated with the analysis of elaidinization mixtures. The repeatability and accuracy obtaineble are given. A value is reported for the methyl ricinoleate—methyl ricinelaidate equilibrium and the mechanism of the reaction is discussed briefly. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Direct determination oftrans unsaturation in triglycerides by infrared spectrophotometry

A differential infrared spectrophotometric method is described for the determination oftrans unsaturation in fats. The method utilizes absorption at 965 cm⁻¹, due to the C−H out-of-plane deformation vibrations oftrans unsaturated compounds. The method is rapid, accurate, and directly applicable to the determination oftrans unsaturation in triglycerides. It is applicable to samples which contain low concentrations oftrans acids (down to 2%) and also to samples with fatty acids of mixed chain length.     

Mid-IR real-time monitoring of the carbocationic polymerization of isobutylene and styrene

The in-situ monitoring of the living carbocationic polymerization of isobutylene (IB) and styrene (St) with a fiber optic Attenuated Total Reflection (ATR) probe in the mid-IR "fingerprint" range is reported here for the first time. Monomer consumption was followed by the disappearance of the C=C stretching for both IB and St, and the C−H bending of the CH₃-group in IB. The formation of polyisobutylene (PIB) was also monitored by tracing the asymmetrical doublet characteristic of C−H bending of the t-butyl groups of the PIB. Conversion measurements by conventional off-line gravimetry correlated well with the new technique. Received: 27 August 1997/Revised version: 2 November 1997/Accepted: 20 November 1997     

Characterization of edible oils,butters and margarines by Fourier transform infrared spectroscopy with attenuated total reflectance

The combination of attenuated total reflectance (ATR) and mid-infrared spectroscopy (MIRS) with statistical multidimensional techniques made it possible to extract relevant information from MIR spectra of lipid-rich food products. Wavenumber assignments for typical functional groups in fatty acids were made for standard fatty acids: Absorption bands around 1745 cm⁻¹, 2853 cm⁻¹, 2954 cm⁻¹, 3005 cm⁻¹, 966 cm⁻¹, 3450 cm⁻¹ and 1640 cm⁻¹ are due to absorption of the carbonyl group, C−H stretch, =CH double bonds of lipids and O−H of lipids, respectively. In lipid-rich food products, some bands are modified. Water strongly absorbs in the region of 3600–3000 cm⁻¹ and at 1650 cm⁻¹ in butters and margarines, allowing one to rapidly differentiate the foods as function of their water content. Principal component analysis was used to emphasize the differences between spectra and to rapidly classify 27 commercial samples of oils, butters and margarines. As the MIR spectra contain information about carbonyl groups and double bonds, the foods were classified with ATR-MIR, in agreement with their degree of esterification and their degree of unsaturation as determined from gas-liquid chromatography analysis. However, it was difficult to differentiate the studied food products in terms of their average chainlength.     

Polarized infrared spectra of some crystalline fatty acids

Summary Polarized infrared spectra of thin films of representative samples of form C′, B′, and A′ n-alkyl monocarboxylic acids have been observed. The data obtained on C′ heptadecanoic acid confirm that the type C and type C′ structures are very similar and that the major difference is in the packing of the CH₃ end-groups. The results on type B′ and A′ acids indicate that meaningful polarization data can be obtained on triclinic crystals of n-alkyl carboxylic acids, provided that careful consideration is given to the sample orientation and to the symmetry characteristics of certain portions of the molecules. The P₁ space structure of these crystals and the orthorhombic substructure of the B′ configuration as well as the triclinic substructure of the A′ configuration were confirmed. Some strong infrared bands of the highly irregular triclinic A′ structure did not seem to be appreciably polarized. The data on group-frequency bands which did show clear-cut polarization were in agreement with prediction. The spectra of form A′, B′, and C′ crystals did not coineide with data obtained on KBr pellets. It is concluded that in these pellets fatty acids exist in a form which is not easy to duplicate under more conventional conditions. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

In situ fourier‐transform infrared spectra analysis of hydrogen bond in polypropylene/chlorinated polypropylene/polyaniline composite

The previous studies suggest that hydrogen bond between chlorinated polypropylene (CPP) and polyaniline (PANI) plays a prominent role in the decision of polypropylene/CPP/PANI composites' electric property. In situ Fourier‐transform infrared spectra were employed to detect and identify the relationship between the hydrogen bond and the temperature. Two kinds of hydrogen bond were carefully studied in the nitrogen–hydrogen bond (N? H) stretching, sulfur–oxygen double bond (S?O) stretching, and carbon–chlorine bond (C? Cl) stretching regions, using an iterative least‐squares computer program to obtain the best fit of spectra. The ratio of absorptivity coefficients and the mole fraction of the “free” and two kinds of H‐bonded N? H were calculated. There exists an apparent turning point in the curves of the relationship between the fraction of two kinds of H‐bonded N? H and temperature. This phenomenon also exists in the S?O stretching region, and the turning point is at about 60°C. The mole fraction of H‐bonded C? Cl decreases, and that of “free” C? Cl increases with increasing temperature. The enthalpy gap between the H‐bonded N? H…O?S and the H‐bonded N? H…Cl?C dissociation was also obtained as 23.2 KJ/mol. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Differentiation of Lard From Other Edible Fats and Oils by Means of Fourier Transform Infrared Spectroscopy and Chemometrics

Fourier transform infrared (FTIR) spectra at mid infrared regions (4,000–650 cm⁻¹) of lard and 16 edible fats and oils were compared and differentiated. The chemometrics of principal component analysis and cluster analysis (CA) was used for such differentiation using FTIR spectra intensities of evaluated fats and oils. With PCA, an “eigenvalue” of about 90% was achieved using four principal components (PCs) of variables (FTIR spectra absorbances at the selected frequency regions). PC1 accounted for 44.1% of the variation, while PC2 described 30.2% of the variation. The main frequency regions that influence the separation of lard from other evaluated fats and oils based on PC1 are 2,852.8 followed by 2,922 and 1,464.7 cm⁻¹. Furthermore, CA can classify lard into its group based on Euclidean distance.     

The infrared spectra of saturated fatty acids with even number of carbon atoms from caproic,C6 (Hexanoic), to stearic,C18 (Octadecanoic), and of their methyl and ethyl esters

Summary Infrared spectra from 1 to 12 microns have been obtained for 7 of the homologous series of monobasic, straight-chain, saturated fatty acids of even carbon atom content from C₆ to C₁₈ and of their methyl and ethyl esters. Infrared data are presented as plots of the percentage transmission against the wavelength in microns on a linear wavelength scale for each compound, and the exact wavelength positions of maxima of the 11 most prominent bands are tabulated. Correlations of each of these bands with molecular structure are given. Methods for distinguishing the acids from the esters and of differentiating an ethyl ester from a methyl ester by observation of infrared spectra are described. An explanation, supported by earlier work with deuterium-substituted compounds, is given to account for the nonappearance, in the spectra of the fatty acids of any absorption attributable to either the free O—H group or the bonded O—H... O group. Evidence has been accumulated which indicates an association of some sort of the esters and that this association probably involves the carbonyl and the methyl groups. Data are presented to show which of the bands in the infrared spectra do and which do not follow Beer’s law. Presented before the 1950 Fall Meeting of the American Oil Chemists’ Society, San Francisco, California. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Air oxidation of Beypazari lignite at 50°C, 100°C and 150°C

Structural changes occurred in Beypazari lignite while oxidizing at 50°C, 100°C and 150°C in a dynamic air atmosphere was detected by infrared spectroscopy. Relative changes in the amount of various oxygenated functional groups with respect to time were determined by curve resolution procedures. Investigation of the spectra of the samples at different oxidation conditions reveal that as the duration and temperature of the oxidation reactions increased the absorption in the aliphatic C–H stretching region decreased, while the absorption in the C=O stretching region presented a significant increase.     

Synthesis and spectroscopic properties of long-chain aza,aziridine and azetidine fatty esters

Reaction of 1-mesyloxynonane with methyl 8-aminooctanoate gives methyl 9-azastearate (I, 20%); treatment of methyl 9(10),10(9)-azidohydroxyoctadecanoate and methyl 10-azido-12-hydroxyoctadecanoate with triphenylphosphine furnishes the corresponding aziridine derivative (II, 75%) and two geometric azetidine isomers (IIIa and IIIb, 37%), respectively. The aza function in compound I, the aziridine nucleus in compound II and the azetidine system in compounds IIIa, IIIb were characterized by¹H nuclear magnetic resonance (NMR) and¹³C NMR spectral analysis. The infrared spectral analyses of compounds (I), (II) and (IIIa,IIIb) showed characteristic absorption bands at 3200–3300 cm⁻¹ for the N-H stretching vibration.     

Cottonseed oil pigments: Fractionation by means of molecular sieves,countercurrent distribution,and low-temperature crystallization

Crude cottonseed oils were shown to have spectra of two types, those exhibiting a single maximum at about 360 mμ and those exhibiting a double maxima at about 375 and 400 mμ. Gossypol and cottonseed oil pigments which absorb below about 375 mμ are trapped by molecular sieve No. 13X, appear in the hydrophilic phase in countercurrent distribution of the oil between 95% ethanol and isooctane, and are found in the liquid fraction on crystallization of oil from acetone at −63°C. Those pigments not admitted by molecular sieve No. 13X are found in the hydrophobic phase in countercurrent distribution and in the solid fraction from low-temperature crystallization. Only countercurrent distribution achieved separation of both types of pigments from the triglycerides. Insufficient quantities of pigments were isolated for any extensive characterization. Use of large-scale apparatus would appear to make it possible to separate the pigments for characterization and evaluation of their relation to the refining properties of oils. Presented at the Annual Meeting, American Oil Chemists' Society, Dallas, Tex., April 4–6, 1960. National Cottonseed Products Association Fellow. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Tocopherol concentrates by the fractional crystallization of cottonseed oil from solvents

Summary 1. Tocopherol concentrates equivalent in tocopherol content and antioxygenic activity to molecularly distilled concentrates, have been obtained from cottonseed oil by hydrogenating the oil and removing the bulk of the glycerides and sterols by low temperature crystallization from acetone. 2. High-tocopherol concentrates can be obtained only from hydrogenated oils. Completely hydrogenated oils are the best source of concentrates at crystallization temperatures down to −60° C.; below this temperature partially hydrogenated oils are equally as good. 3. A solvent-oil ratio of 8:1 by weight appears to be about the optimum. At this ratio, crystallization from acetone at the temperature of Dry Ice (−78° C.) yields a concentrate containing 34 percent tocopherols from an oil originally containing 0.05 percent tocopherols. 4. The direct addition of Dry Ice to the solvent and oil is to be avoided, since this lowers the recovery of tocopherols. 5. Petroleum naphtha and methyl ethyl ketone are less suitable solvents than acetone, because of their greater capacity for dissolving glycerides at low temperatures. Presented before the American Oil Chemists’ Society Meeting, New Orleans, Louisiana, May 10 to 12, 1944. This is one of four regional research laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Glyceride structure of vegetable oils by countercurrent distribution. VI. Corn oil

Corn oil has been fractionated in a 200-tube countereurrent distribution apparatus. Although this technique gives no information about the positional isomers of the glycerides, the fatty acid composition of the fractions and the amounts of the more unsaturated triglycerides are in agreement with an essentially random pattern. Presented at fall meeting. American Oil Chemists’ Society, New York, N.Y,, October 17–19, 1960. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.