Polarization modulation Fourier transform infrared spectroscopy

Polarization modulation Fourier transform infrared spectroscopy can be measured by either double modulation FTIR or interferometric modulation FTIR techniques. The principles of both techniques are presented with examples of representative measurements. The relative advantages and disadvantages of each method are compared.     

Sexing of turkey poults by Fourier transform infrared spectroscopy

Fourier transform infrared (FT-IR) spectroscopy was used to probe the molecular composition of germinal cells and to identify the gender of turkey poults. Germinal cells obtained from a feather pulp were characterized by FT-IR micro spectroscopy. The sample set consisted of growing contour feathers from 23 male and 23 female turkey poults. Significant spectral variations were observed in the range between 1,000 and 1,250 cm⁻¹. The spectra of male turkey poults exhibit a significantly higher content of RNA than those of female turkeys. Spectral classification was performed by a non-supervised method based on the principal component analysis. An evaluation of the first and third PCs led to a classification of female and male poults with an accuracy of more than 95%.     

Characterization of chemically modified silica gels by DRIFT spectroscopy

Chemically modified silica gels are investigated with respect to identity, purity and degree of surface coverage using diffuse reflectance FTIR (DRIFT) Spectroscopy. We report the results for two bonded HPLC phases, pyrene butyric acid propylamido- and octadecyl-groups grafted on irregular porous silica gel. For quantitative determination calibration standards are prepared by adsorbing structurally similar ligand compounds onto the surface of the silica gel; these coated materials give linear calibration curves up to a concentration of 1 mmol/g modified silica gel.     

Conformational study of 2-phenylethylamine by molecular-beam Fourier transform microwave spectroscopy

The conformational preferences of the simplest amine neurotransmitter 2-phenylethylamine have been investigated using molecular beam Fourier transform microwave (MB-FTMW) spectroscopy. Two new conformers have been observed together with the two previously reported by Godfrey et al. [J. Am. Chem. Soc., 1995, 117, 8204]. The (14)N nuclear quadrupole hyperfine structure has been resolved for all four conformers. Comparison of the experimental rotational and quadrupole coupling constants with those calculated theoretically provides a conclusive test for the identification of all conformers. The two most stable conformers present a gauche (folded) disposition of the alkyl-amine chain and are stabilised by a weak NH...pi interaction between the amino group and the aromatic ring. The other two conformers show an anti (extended) arrangement of the alkyl-amine chain. Tunnelling splittings have been observed in the spectrum of one of the anti conformers. The post expansion relative abundances in the supersonic jet have been also investigated and related to the conformer energies.     

Preparation of dimethoxyborane and analysis by Fourier transform infrared spectroscopy

Dimethoxyborane was prepared by the reaction of trimethoxyboroxine, sodium borohydride and trimethyl borate in diethylene glycol dimethyl ether solvent at 70°C under atmospheric pressure followed by distillation to increase the purity and analyzed in liquid phase by FT-IR. The concentration of dimethoxyborane was identified by hydrolysis with water, which yields boric acid, methanol and hydrogen, whereas the generated hydrogen was analyzed by the mass detector of a volumetric flow apparatus. The FT-IR absorbance peak area showed a linear dependence on dimethoxyborane concentration in the wavenumber range 873 to 950 cm⁻¹ for samples with dimethoxyborane concentrations 0 to 6.2 wt% in trimethyl borate. Data fitting using the least square method gave an R ² value of 97%.     

Fourier transform infrared photoacoustic spectroscopy of dental calculus

The mid and far FTIR spectra of supragingival and subgingival calculus were measured, respectively. From the subtraction spectra of the two types of calculus, the protein components of calculus have been obtained. The results of photoacoustic spectroscopy indicated the presence of protein layer on the surface of early calculus.     

Characterization of modified silica powders by fourier transform infrared spectroscopy and cross-polarization magic angle spinning NMR

Silica gel and Cab-O-Sil were chemically modified (silylated) with 3-aminopropyltriethoxysilane and 3-methacryloxypropyltrimethoxysilane under carefully controlled conditions. Subsequently the products were investigated by elemental analysis, Fourier transform IR spectroscopy, and ¹³C and ²⁹Si cross-polarization magic angle spinning NMR (CP-MAS NMR). The influence of the reaction conditions of the silylation and the effect of subsequent heat treatment and water addition were studied. The resulting differences shed new light on the combined effects of reaction conditions and silica surface structures on the course of the reactions. Some assignments of ²⁹Si NMR signals to specific structures were confirmed, while in one case a reassignment was proposed.     

Dynamic Fourier transform infrared spectroscopy in polymer research

The rapid-scanning capability of FTIR instrumentation has revitalized the field of vibrational spectroscopy in polymer research and will be discussed with reference to the study of polyurethane kinetics, the temperature dependence of hydrogen bonding in polyamide 6 and strain-induced crystallization in a polydimethylsiloxane elastomer.     

Instrumental barriers in biological Fourier transform infrared spectroscopy

Biological applications of infrared spectroscopy have pressed for ever greater instrumental capabilities in terms of spectral sensitivity and quantitative exactness. Improved instrumentation has provided measurement of many vibrational modes in biological samples that previously were lost in noise. With highly optimized sampling conditions, useful measurements have been made with a peak-to-peak noise level less than 5 microabsorbance (5×10^–6 absorbance), at 0.5 cm^–1 resolution. However, optical and instrumental instabilities often result in sine waves that are not totally removed by the ratio of sample to reference. These often limit effective spectral sensitivity to 50 or 100 microabsorbance, peak-to-peak, and constitute a non-random noise. Non-atmospheric absorptions, especially one at 1959 cm^–1 with 0.8 cm^–1 band width (FWHM) are reported. The latter is due to a trace impurity in the KBr beam splitter substrate and compensator plate. Improvements in instrumentation and sampling conditions are expected to yield measurements of absorption bands as small as 50 microabsorbance with excellent signal/noise.     

Study of tissue engineered bone nodules by Fourier transform infrared spectroscopy

The key criteria for assessing the success of bone tissue engineering are the quality and quantity of the produced minerals within the cultured constructs. The accumulation of calcium ions and inorganic phosphates in culture medium serves as nucleating agents for the formation of hydroxyapatite, which is the main inorganic component of bone. Bone nodule formation is one of the hallmarks of mineralization in such cell cultures. In this study, we developed a new two-step procedure to accelerate bone formation in which mouse bone cell aggregates were produced first on various chemically treated non-adhesive substrates. After this step, the bone cells' growth and mineralization were followed in conventional culture plates. The number and size of cell aggregates were studied with light microscopy. The minerals' formation in the form of nodules produced by the cell aggregates and the bone crystal quality were studied with Fourier Transform Infrared (FTIR) spectroscopy. The FTIR spectra of the ash specimens (mineral phase only) from thermal gravimetric analysis (TGA) provided valuable information of the quality of the minerals. The υ(4) PO(4) region (550-650 cm(-1)), which reveals apatitic and non-apatitic HPO(4) or PO(4) environments, and phosphate region (910-1180 cm(-1)) were examined for the minerals produced in the form of nodules. The peak position and intensity of the spectra demonstrate that the quality of the bone produced by cell aggregates, especially from the bigger ones, which were formed on Plunoric treated substrates, exhibit a composition more similar to that of native bone. This work establishes a new protocol for high quality bone formation and characterization, with the potential to be applied to bone tissue engineering.     

Monitoring of the smoking process by multicommutation Fourier transform infrared spectroscopy

Nicotine was selected as the target molecule for monitoring of the smoking process by multicommutation Fourier Transform Infrared spectroscopy (FTIR). The method involved the use of CHCl₃ for on-line extraction of nicotine from tobacco, cigarette filters and tobacco ash from NH₄OH alkalinized samples, and absorbance measurement of the characteristic band at 1316 cm⁻¹ in the stopped-flow mode, by obtaining the peak area in the range between 1334 and 1300 cm⁻¹. Under the best operational conditions, the procedure developed provided a detection limit of 0.05 mg mL⁻¹ nicotine, corresponding to 0.5 mg g⁻¹ in the solid sample, a relative standard deviation less than 2.5%, and a sampling frequency of 12 determinations h⁻¹. It can be concluded that nicotine migrates in the smoke mainstream towards the filter during the smoking process. The smoking of cigarettes and cigars is different. Nicotine is retained weakly by both tobacco and filter in the case of cigarettes, and strongly by the unburned tobacco in cigars. The incomplete smoking of cigars and cigarettes reduces nicotine intake and thus reduces the additive effect.     

Detection of weathering in stockpiled coals by Fourier transform infrared spectroscopy

The process of natural oxidation of two low-rank coals exposed to the atmosphere for 11 months has been studied by Fourier transform infrared (FT-IR) spectroscopy. The study was carried out on samples taken at different time intervals and additionally from zones where signs of high oxidation and self-ignition were detected. The aliphatic hydrogen (3000-2800 cm⁻¹) and oxygen-containing structures (1800-1500 cm⁻¹) regions of the spectra were examined by curve-fitting analysis and a series of structural parameters based on ratios of integrated absorbance areas of curve-fitted bands were established. The aliphatic hydrogen content of samples tended to decrease with increasing time of storage and carboxyl groups only increased slightly under conditions of low pile activity. When oxidation and self-ignition processes took place, the structural changes were more significant. Aliphatic structures decreased drastically and net production of oxygen-containing structures was observed. Aliphatic hydrogen content evaluated from integrated absorbance measurements of normalized spectra and the CO/aliphatic hydrogen ratio seemed to be very sensitive in detecting signs of weathering even at very low levels of activity.     

Surface hydration of aqueous calcium minerals as studied by Fourier transform Raman and infrared spectroscopy

Rapid hydration reactions of several calcium minerals are studied using Fourier transform (FT) Raman and infrared (IR) spectroscopy. Oleate adsorption over aqueous synthetic fluorite, calcite and gypsum (pH 9) is investigated and adsorption mechanisms are discussed.     

Fourier transform raman spectroscopy using a bench-top fourier transform infrared spectrometer

The use of a bench top FTIR spectrometer for near infrared Fourier transform Raman spectroscopy is demonstrated. The use of near infrared excitation results in fluorescence free Raman spectra allowing previously difficult samples to be measured.     

Fourier transform infrared spectroscopy study of nanostructured nickel oxide

Nanostructured nickel oxide having different average particle sizes ranging from 3 to 16 nm were synthesized and Fourier transform infrared (FTIR) spectra of the samples were recorded in the far infrared (IR) region. The spectra were found to be dominated by surface mode absorptions with no distinct absorption corresponding to the bulk transverse optical mode. IR absorption coefficient, alpha, for the nanostructured NiO samples were calculated as a function of frequency using a macroscopic approach devised by Fuchs. The effects of crystalline geometry, numerical values of optical constants, filling factor and increased damping on the spectral features of the samples were analyzed. Though the simulations approximately reproduced the occurrence of a shoulder in the experimental spectra, the most intense peak in the simulated spectra was found to be about 50 cm(-1) above the corresponding experimentally observed peak. It was shown that the experimentally observed absorption maximum of all the samples were in close agreement with that determined using a microscopic theory based on the rigid ion model. The weak absorption peaks in the frequency region 60-100 cm(-1) appearing in the spectra of all the samples were identified as surface induced transverse acoustical modes, omegaTA, which became IR active due to the breakdown of translational symmetry in the nanocrystallites.     

Rapid discrimination of Eurycoma longifolia extracts by Fourier transform infrared spectroscopy and two dimensional correlation infrared spectroscopy

Eurycoma longifolia is a herbal medicinal plant of South-East Asian origin, popularly recognized as ‘Tongkat Ali’. The root extracts have been used in indigenous traditional medicines for its unique antimalarial, anti-pyretic, antiulcer, cytotoxic and aphrodisiac properties. It is an important task that fast and effective analysis methods monitor the inherent qualities of traditional herbal medicines and its corresponding extracts products as a complicated mixture system. Owing to the unique fingerprint character and extensive applicability to test sample, infrared spectral method have been used in many research fields. In this paper, we use FT-IR, second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR) step by step to analyze E. longifolia and its different extracts (extracted by hexane, ethyl acetate, dichloromethane and methanol in turn). The findings indicated that FT-IR and 2D-IR can provide many holistic variation rules of chemical constituents. The structural information of the samples indicated that E. longifolia and its extracts contain a large amount of quassinoids, since some characteristic absorption peaks of quassinoids, such as ∼1700 cm⁻¹, ∼1670 cm⁻¹, ∼1600 cm⁻¹,∼1500 cm⁻¹, and ∼1270 cm⁻¹ can be detected. This method, having its high resolution and excellent macroscopic fingerprint features, can not only supply lots of structural information of main components in the complicated system, but also can differentiate the tiny differences between the similar systems according to the macro-fringerprint characters. This method is highly rapid, effective, accurate and well repetitive for pharmaceutical research.     

A modified diffuse reflectance infrared Fourier transform spectroscopy cell for depth profiling of ceramic fibers

A modified diffused reflectance infrared Fourier transformed spectroscopy (DRIFTS) accessory was used to analyze the surface properties of alumino-silicate fibers. The modifications are simple and involve a different way of performing depth-profiling from traditional DRIFTS by removing approximately 2 mm of salt from a full cup prior to placing the sample in for depth profiling. This method proved successful in elucidating the effects of quenching alumino-silicate fibers in mineral oil versus quenching in an air stream.     

Determination of total sterols in brown algae by Fourier transform infrared spectroscopy

A procedure is proposed for the determination of the total amount of sterols in brown algae Bifurcaria bifurcata, Cladostephus hirsitus, Dictyota dichotoma and Cystoseira sedoides, globally determined as fucosterol, which is the major sterol contained in these algae. The method involves the use of cholesterol as reference standard and a correction factor of 1.259 ± 0.003, which represents the ratio between the slopes of calibration lines obtained from fucosterol and cholesterol. The method provides precise and accurate results for the IR analysis of real samples.