Quantitation of estolides by Fourier transform infrared spectroscopy

Estolides were produced from meadowfoam oil fatty acids, oleic, linoleic, petroselinic, andcis-5,cis-13 docosadienoic acids. Estolide reaction mixtures were quantitated by Fourier transform infrared spectroscopy and compared to the area percentages determined by high-performance liquid chromatography. The absorbance frequency of estolide carbonyl (1737 cm⁻¹) is different than the lactone carbonyl (1790 cm⁻¹) and the acid carbonyl (1712 cm⁻¹). Estolide standards were obtained by wiped-film molecular-still distillations and column chromatography.     

Fourier transform Raman and Fourier transform infrared spectroscopy studies of silk fibroin

The chemical and conformational structures of Bombyx mori silk were studied with the complementary techniques of Fourier transform Raman spectroscopy and Fourier transform infrared spectroscopy. The Fourier transform Raman spectrum of silk showed strong bands for the photosensitive aromatic amino acids tyrosine, tryptophan, and phenylalanine. Intensive UV/ozone irradiation reduced the Raman intensities of the amide III band and the tyrosine signals due to peptide chain scission of the silk polymer and the photochemical changes in the tyrosine residues on the silk molecules. However, the Raman spectroscopy changes for tryptophan were less clearly defined because of peak overlapping with other amino acid signals and the low concentration of tryptophan. The Fourier transform infrared (attenuated total reflectance) technique, coupled with second‐derivative spectroscopy analysis, demonstrated a decrease in the crystallinity degree and tyrosine content of UV/ozone‐irradiated silk, as indicated by changes in the Fourier transform infrared bands of amide III doublet and tyrosine signals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1999–2004, 2005     

Monitoring peroxide value in oxidized emulsions by Fourier transform infrared spectroscopy

Soybean oil (SBO) was blended with 10–40% palm kernel olein (PKO) to obtain SBO:PKO blends with different degrees of unsaturation. Oil‐in‐water (O/W) emulsions were then prepared with 70 wt‐% of SBO or SBO:PKO blends and monitored for their chemical destabilization after an accelerated oxidation process up to 12 days at 60 °C. The formation rate of hydroperoxides, as demonstrated by peroxide value (PV) evolution, throughout the oxidation period was relatively high for a fully SBO‐based emulsion as compared to those with PKO incorporation. Fourier transform infrared (FTIR) spectroscopic method was also performed in parallel with PV determination, providing further information on structural changes of the functional groups due to lipid oxidation in the emulsions. By using a partial least square chemometric method, a developed calibration model that was based on the spectral region between 1800 and 1480 cm^?1 was shown to be able to predict the PV in oxidized emulsions over the range of 4–45 meq/kg. With a ‘leave‐one‐out’ cross‐validation optimization procedure, the calibration model provides a good coefficient of determination of 0.98 and a root mean standard error of cross‐validation of 2.09. In general, FTIR spectroscopy is a suitable technique to monitor PV in oxidized emulsions.     

Characterization and microstructure study of low‐density polyethylene by Fourier transform infrared spectroscopy and temperature rising elution fractionation

Infrared spectroscopy is a powerful technique for studying the microstructure and determining the short‐chain branch distribution of polyethylene. In this work, the types and amounts of short‐chain branches in low‐density polyethylene were investigated with Fourier transform infrared spectroscopy, and a new and simple method for the determination of butyl short branches was discovered. The amount of each unsaturated species in low‐density polyethylene was also determined with Fourier transform infrared after the bromination of samples. Furthermore, the resin was fractionated by preparative temperature rising elution fractionation, and the branch distribution and melting endotherm of each fraction were analyzed with attenuated total reflectance/Fourier transform infrared and differential scanning calorimetry. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characterization of cellulose aldehyde using Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy has been used to study cellulose aldehyde groups in bleached cotton, unbleached cotton, and in periodate oxidized cotton. Second derivative spectroscopy could reproducibly identify aldehyde bonds in oxidized cotton only if the samples were predried at 110°C for 24 h; the aldehyde band appeared at 1732–1734 cm^?1. Diffuse reflectance spectroscopy in the Environmental Chamber readily detected the above aldehyde absorbances at temperatures above 100°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1195–1202, 2001     

Theory and practice in using Fourier transform infrared spectroscopy to detect hydrocarbons in emissions from gas turbine engines

This paper describes the procedures used to detect hydrocarbons in emissions from gas turbine engines using non-intrusive Fourier Transform Infrared (FTIR) spectroscopy. The basic theory of FTIR is described together with the spectroscopic concepts necessary to be able to perform observations of hydrocarbons (HC). The processes of identification and quantification of the compounds present in combustion gases from infrared spectra are described and these techniques are applied to laboratory experiments using kerosene fuel burners. The results of field trials where exhausts from commercial aircraft were studied and unburnt hydrocarbons features in the C-H stretch region were measured are discussed. Quantitative measurements of HC were performed using the hexane equivalent concentration technique.     

Characterization of semisolid fats and edible oils by Fourier transform infrared photoacoustic spectroscopy

The potential of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) for the analysis of semisolid fat and edible oil was demonstrated with butter, soybean oil, and lard as representative materials. Results of Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy analysis was compared with FTIR-PAS results. The PAS technique is simple and requires no sample preparation unlike ATR. Optimal PAS instrumental parameters for obtaining quality spectra are a scanning speed of 5 kHz, number of scans of 256 scans/sample, and a resolution of 4 cm⁻¹. The PAS spectra of soybean oil and lard are similar because they have similar functional groups. Results for soybean oil compare well with those available in the literature. The ATR spectra of butter were better than those from its PAS counterpart. Functional groups corresponding to vibration mode and intensity are provided for soybean oil and lard.     

Evaluating cell wall structure and composition of developing cotton fibers using Fourier transform infrared spectroscopy and thermogravimetric analysis

Universal attenuated total reflectance Fourier transform infrared (UATR‐FTIR) spectroscopy and thermogravimetric analysis (TGA) were used to investigate the structural changes of cotton (Gossypium hirsutum L.) fibers as a function of developmental programming. The presence of noncellulosic compounds (wax, protein, hemicelluloses, pectic substances, amino acids, etc.) was evident from FTIR spectra of fibers at 10, 14, 17, and 20 dpa (day postanthesis). The vibration corresponding to the noncellulosic compounds disappeared at 36 dpa. Furthermore, independent TGA analysis supported the results obtained with FTIR, showing that the transition from primary cell wall synthesis to secondary cell wall synthesis occurs at or around 20 dpa. This study is the first to report on the use of the UATR‐FTIR and TGA to elucidate structural changes during cotton fiber development. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characterization by Fourier transform infrared spectroscopy of hydroxyapatite co-doped with zinc and fluoride

Pure and Zn²⁺ and/or F⁻ doped hydroxyapatite (HA) were synthesized by the precipitation method and detection of ion incorporations into the HA structure was investigated by a non invasive Fourier transform infrared (FTIR) spectroscopic technique. The synthesized materials were sintered at 1100 °C for 1 h. The Zn²⁺ addition amount was kept constant at 2 mol% whereas F⁻ amount was changed. The weight fractions of the HA and CaO were calculated by Rietveld analysis by using GSAS. Co-doping of Zn²⁺ and F⁻ ions increased the stability of HA. A detailed analysis of FTIR spectroscopy was performed to observe whether HA structure was formed or not. The bands corresponding to the (PO₄³⁻) functional group and (OH⁻) functional group were observed. Moreover, the ion incorporation into the HA structure and the amount of the ions were analyzed by FTIR spectroscopy. The OH…F bands were observed at 711 cm⁻¹ and 3543 cm⁻¹. The Zn–O stretching band was observed at 3403 cm⁻¹ and 433 cm⁻¹. The area calculation under the OH…F bands and (OH⁻) stretching and librational modes of the bands revealed that as the F⁻ amount increased, the area under the bands at 711 cm⁻¹ and 3543 cm⁻¹ increased whereas the area under the (OH⁻) stretching and librational modes of the bands decreased due to the fact that F⁻ ion replaced with (OH⁻) ion in HA structure. All these results showed that Zn²⁺ and F⁻ ions were successfully incorporated into the HA structure. Moreover, the amount of F⁻ ions in the HA structure was successfully confirmed by determination of the area under the F⁻ and (OH⁻) related bands.     

Rapid method for determining moisture content in crude palm oil by Fourier transform infrared spectroscopy

A simple, rapid, and direct Fourier transform infrared (FTIR) spectroscopic method was developed for the determination of moisture content of crude palm oil (CPO). The calibration set was prepared by adding double-distilled water to dried CPO in ratios (w/w) between 0 and 13% moisture. A partial least squares (PLS) regression technique was employed to construct a calibration model followed by cross-validation step. The accuracy of this method was comparable to the accuracy of the American Oil Chemists' Society's vacuum oven method, which is used for determination of moisture and volatile matter, with mean difference (MD_a) of 0.0105, a coefficient of determination (R ²) and a standard error of calibration (SEC) of 0.9781 and 0.91, respectively. It is also comparable to the accuracy of the International Union of Pure and Applied Chemistry's distillation method with MD_a, R ², and SEC of 0.0695, 0.9701, and 0.65, respectively. The study showed that midband FTIR spectroscopy combined with the PLS regression calibration technique is rapid and accurate for determination of moisture content of CPO samples with a total analysis time of less than 2 min and less than 2 mL of sample.     

Characterization by Fourier transform infrared spectroscopy of polyethylene adipate/cholesteryl palmitate blends

FT‐IR spectroscopy has been employed to study compatibility, melting, and crystallization of the polyethylene adipate (PEA)/cholesteryl palmitate (CP) blends. The changes in FT‐IR spectra were followed by controlled rate of heating and cooling. The bands corresponding to the crystalline structure have been assigned. The accuracy of the transition temperature determination has been improved by fitting the curve of the integral absorbance dependence on temperature with a Boltzmann function. From dependence of the transition temperatures on the composition of the blend, it has been established that for each mixing ratio a certain mass fraction of CP should be dissolved in the PEA matrix. The PEA/CP blends behave as a phase‐separated system with partial miscibility. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1156–1163, 2004     

Monitoring peroxide value in fatliquor manufacture by Fourier transform infrared spectroscopy

A Fourier transform infrared (FTIR) spectrometer equipped with an attenuated total reflectance (ATR) sample handling accessory was used to rapidly monitor the peroxide value (PV) of oils undergoing catalytic oxidation to produce sulfonated fatliquors used in the leather industry. PV quantitation was based on the stoichiometric reaction of triphenylphosphosphine (TPP) with hydroperoxides to produce triphenylphosphine oxide (TPPO). By using a germanium ATR accessory that has a very short effective pathlength, the spectral contributions of the base oil could be subtracted out, eliminating any oil-dependent intereferences as well as providing a facile means of observing the spectral changes associated with the TPP/TPPO reaction. A calibration was devised by adding a constant amount of TPP-saturated chloroform to oils containing varying amounts of tert-butyl hydroperoxide (TBHP) to produce TPPO that had a measurable band at 1118 cm⁻¹. this band was linearly related to TBHP concentration and the calibration devised had an SD of ∼3.4 PV over the range of 0–250 PV. The ATR-PV method was standardized and the spectrometer programmed using Visual Basic to automate the analysis. the automated FTIR-ATR method was found to be a convenient means of tracking PV of oils undergoing oxidation, and the results correlated well with the PV values obtained using the AOAC iodometric method (r=0.94). The FTIR-ATR PV methodology provides a simple means of monitoring the PV of oils undergoing rapid oxidation and could serve as a quality-control tool in the production of sulfonated oils for the leather industry.     

Cure-reaction kinetics of amine-blocked polyisocyanates with alcohol using hot-stage Fourier transform infrared spectroscopy

Cure reaction between a series of N-methylaniline-blocked polyisocyanates, based on 4,4′-methylenebis(phenyl isocyanate), poly(tetrahydrofuran) and several substituted N-methylanilines, and n-decanol has been studied. The solid-state isothermal cure reaction was carried out using hot-stage FTIR spectroscopy, in the temperature range of 125–145°C. The urea carbonyl absorption band of blocked polyisocyanate moiety was used to monitor the conversion of blocked polyisocyanate into polyurethane. Kinetic and thermodynamic parameters were calculated using normalized conversion curves. The overall order of cure reaction, for each of the blocked polyisocyanates was found to be first order. Based on the results of kinetics and reaction conditions used in this study, the elimination-addition (S_N¹) mechanism was suggested for the cure reaction between N-methylaniline-blocked polyisocyanates and n-decanol. The effect of substituents present in the blocking agents on the cure reaction of N-methylaniline-blocked polyisocyanates was investigated and found that the cure reaction of N-methylaniline-blocked polyisocyanates was retarded by electron-donating substituents and facilitated by electron withdrawing substituents. The observed high negative entropy of activation value supports the formation of a four-centered, intramolecularly hydrogen-bonded ring structure during transition state of the cure reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The determination of peroxide value by fourier transform infrared spectroscopy

A rapid method for the quantitative determination of peroxide value (PV) of vegetable oils by Fourier transform infrared (FTIR) transmission spectroscopy is described. Calibration standards were prepared by the addition oft-butyl hydroperoxide to a series of vegetable oils, along with random amounts of oleic acid and water. Additional standards were derived through the addition of mono- and diglyceride spectral contributions, as well as zero PV spectra obtained from deuterated oils. A partial least squares (PLS) calibration model for the prediction of PV was developed based on the spectral range 3750–3150 cm⁻¹. Validation of the method was carried out by comparing the PV of a series of vegetable oils predicted by the PLS model to the values obtained by the American Oil Chemists Society iodometric method. The reproducibility of the FTIR method [coefficient of variation (CV)=5%)] was found to be better than that of the chemical method (CV =9%), although its accuracy was limited by the reproducibility of the chemical method. The method, as structured, makes use of a 1-mm CaF₂ flow cell to allow rapid sample handling by aspiration. The spectrometer was preprogrammed in Visual Basic to guide the operator in performing the analysis so that no knowledge of FTIR spectroscopy is required to implement the method. The method would be suitable for PV determinations in the edible oil industry and takes an average of three minutes per sample.     

Characterization of copper-silica catalysts by means ofin Situ diffuse reflectance infrared Fourier transform spectroscopy

Copper silica catalyst precursors have been characterized by diffuse reflectance infrared Fourier transform spectroscopy. The measurements were performed both under atmospheric conditions and under controlled gasatmospheres at elevated temperatures. Two reflection bands at 3615 and 690 cm^–1 have been attributed to hydroxyl vibrations associated with the presence of copper ions highly dispersed over the silica surface. Calcination of a catalyst precursor at 800 K led to the disappearance of the copper-related surface hydroxyl groups.     

A study of hydrogel thermal-dynamics using Fourier transform infrared spectrometer

A rapid and reliable method was presented for studying hydrogel dynamics/kinetics. Two temperature-sensitive hydrogels, poly-N-isopropylacrylamide (poly(NIPAAm)) and the copolymer of N,N-diethylacrylamide and sodium methacrylate (molar ratio=97:3, poly(NDEAAm-co-MAA)) were synthesized. The thermal-behaviors of the gels were studied through the absorbance intensities of both swollen water and gel frame components, and the peak positions of amide band along heating/cooling pathways under dynamic Fourier transform infrared (FTIR) probing. The results showed that the lower critical solution temperature (LCST) of poly(NIPAAm) is about 33-35 °C, which is consistent with reported value of ∼34 °C. Compared to poly(NIPAAm), poly(NDEAAm-co-MAA) has relatively continuous volume phase transition, starting at ∼35 °C and a better thermal-reversibility with similar swelling and deswelling profiles over a larger temperature range (10-80 °C for poly(NDEAAm-co-MAA) vs. 10-33 °C for poly(NIPAAm)). The H-bonding water along phase transition was also studied, showing a less reversibility of poly(NIPAAm) compared to poly(NDEAAm-co-MAA). In addition, FTIR spectrometer was also used to study the volume changes of poly(NDEAAm-co-MAA) under variations in environmental salinity.     

傅里叶变换红外光谱法测定B–GAP羟值

为解决支化聚叠氮缩水甘油醚(B–GAP)羟值测试不稳定的问题,选用异氰酸苯酯对B–GAP进行衍生处理使羟基转化成酯基,采用傅里叶变换红外光谱法测定产物中酯基的吸光度以间接得到B–GAP羟值;研究了衍生时间、异氰酸苯酯用量等对测定结果的影响。结果表明,B–GAP羟值与衍生后分子链中酯基的红外特征峰吸收峰强度之间可进行定量关联,用该方法测定羟值,具有较好的重复性和较高的准确度。     

Fourier transform infrared spectroscopy studies on thermal decomposition of tetrakis-dimethyl-amido zirconium for chemical vapor deposition of ZrN

The decomposition behavior of tetrakis (dimethylamido) zirconium (TDMAZ) under various ambient gases was studied by using in-situ Fourier transform infrared spectroscopy (FTIR) aimed at understanding the gas phase reactions and also at selecting the appropriate process conditions for ZrN chemical vapor deposition (CVD). The infrared absorbance of the stretching vibration at 933.37 cm-1 was employed to monitor the degree of dissociation of the gaseous TDMAZ. In the case of argon and nitrogen atmospheres, TDMAZ starts to decompose at above 300 °C, while in a hydrogen atmosphere it starts to decompose at above 350 °C. To evaluate the effect of the decomposition behavior of the precursor on CVD ZrN, the ZrN films were grown at 150–375 °C under Ar, N₂, and H₂. A clear difference in transition temperature of controlling from surface reaction to gas phase mass transfer was observed: The ZrN growth rate decreased rapidly at above 300 °C under Ar or N₂ atmospheres, and increased continuously with increase of the deposition temperature under an H₂ atmosphere.