Fourier transform infrared INDEX

In situ Fourier transform infrared and in situ infrared reflection spectroscopies have been used to study the electrical double layer structure and adsorption of various species at low-index single-crystal faces of Au, Pt, and other electrodes.206"210 It has been shown that if the ions in the solution have vibrational bands, it is possible to relate their excess density to the experimentally observed surface. 

Prior to solving the structure for SSZ-31, the catalytic conversion of hydrocarbons provided information about the pore structure such as the constraint index that was determined to be between 0.9 and 1.0 (45, 46). Additionally, the conversion of m-xylene over SSZ-31 resulted in a para/ortho selectivity of <1 consistent with a ID channel-type zeolite (47). The acidic NCL-1 has also been found to catalyze the Fries rearrangement of phenyl acetate (48). The nature of the acid sites has recently been evaluated using pyridine and ammonia adsorption (49). Both Br0nsted and Lewis acid sites are observed where Fourier transform-infrared (FT IR) spectra show the hydroxyl groups associated with the Brpnsted acid sites are at 3628 and 3598 cm-1. The SSZ-31 structure has also been modified with platinum metal and found to be a good reforming catalyst. 

X-ray photoelectron spectroscopy (XPS) was used for elemental analysis of plasma-deposited polymer films. The photoelectron spectrometer (Physical Electronics, Model 548) was used with an X-ray source of Mg Ka (1253.6 eV). Fourier transform infrared (FTIR) spectra of plasma polymers deposited on the steel substrate were recorded on a Perkin-Elmer Model 1750 spectrophotometer using the attenuated total reflection (ATR) technique. The silane plasma-deposited steel sample was cut to match precisely the surface of the reflection element, which was a high refractive index KRS-5 crystal. 

SOM, soil organic matter HS, humic substances DH, degree of humification HAC, humic acid C FAC, fulvic acid C TEC, total extractable C HR, humification rate HI, humification index NHC, nonhumified C TOC, total organic C HA, humic acid FA, fulvic acids UV-Vis, ultraviolet-visible FT-IR, Fourier transform infrared NMR, nuclear magnetic resonance ESR, electron spin resonance EEM, excitation-emission matrix. 

Fourier transform infrared microscopes are equipped with a reflection capability that can be used under these circumstances. External reflection spectroscopy (ERS) requires a flat, reflective surface, and the results are sensitive to the polarization of the incident beam as well as the angle of incidence. Additionally, the orientations of the electric dipoles in the films are important to the selection rules and the intensities of the reflected beam. In reflectance measurements, the spectra are a function of the dispersion in the refractive index and the spectra obtained are completely different from that obtained through a transmission measurement that is strongly influenced by the absorption index, k. However, a complex refractive index, n + ik can be determined through a well-known mathematical route, namely, the Kramers-Kronig analysis. 

M.T. Soderstrom, R.A. Ketola and O. Kostiainen, Identification of nerve agents and their homo-logues and dialkyl methylphosphonates by gas chromatography/Fourier transform infrared spectrometry (GC-FT1R), Part II Spectral search with help of retention indexes, Fresenius J. Anal. Chem., 352, 550-556 (1995). 

A technique which has proven useful for our studies is that of cylindrical internal reflectance (CIR), coupled with a Fourier transform infrared spectrometer. In this study, an IBM-85 FTIR equipped with either a DTGS (deuterated triglycine sulfate) or MCT (mercury-cadmium-tellurium) detector was used. The infrared radiation is focused by concave mirrors onto the 45° conical ends of a transmitting crystal (Figure 1). The crystal may be made of any material which is optically transparent, has a high mechanical strength and high index of refraction, and is resistant to thermal shock and chemical attack. Suitable materials include ZnS, ZnSe,... 

ATR-FTIR spectroscopy (attenuated total reflectance Fourier transform infrared spectroscopy)—IR spectroscopy uses the absorption of infrared radiation to probe the vibrational frequency of molecular motions. Attenuated total reflectance method uses a crystal of high refractive index to channel the infrared light (using total internal reflectance) into the crystal and causes only a thin layer of a sample in contact with the exterior of the crystal to be sensitively detected. 

Infrared-based techniques are used to identify molecules on the surface. IR radiation is used to excite vibrational modes in molecules in the gas phase or adsorbed on a surface. The transmitted or reflected IR spectrum can be analyzed in a spectrometer. Considerable improvement in the sensitivity can be achieved by use of Fourier transform infrared (FTIR) spectroscopy. Attenuated total reflection (the ATR-FTIR method) inside a crystal (germanium) of high refractive index can be used to further enhance the surface sensitivity (using the evanescent field). 

High-performance liquid chromatography (HPLC) may be used for the simultaneous separation of ethanol and other wine constituents such as carbohydrates, glucose, fructose, and saccharose, coupled with either refractive index or Fourier transform infrared (Fl lR) detection. Ethanol may also be codetermined with other volatile compounds in wine by gas chromatography with flame ionization detection. It is important to note that chromatographic methods for the analysis of ethanol are not suitable where accurate determinations are required. 

LC provides good reproducibility and high-quality results the cost is reasonable for routine applications and it is fairly easy to operate the equipment. UV-visible detectors are most commonly used for routine impurity determinations by LC. Other detectors that are useful for the identification of impurities or for specialized purposes are refractive index, fluorescence, electrothermal detectors, polarimeters, Fourier transform infrared spectrometers, and mass spectrometers. 

In one study. X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy and refractive index measurements were utilized to characterize the state of molecular orientation in one-way and two-way (bi-axially) drawn isotactic polypropylene (iPP) films [6]. It was shown that the use of all three techniques leads to much greater confidence in the orientation averages deduced than can be obtained by using any two of the techniques. It was observed that, with one-way drawing, the chain axes of both crystalline and amorphous regions orient towards the direction of drawing. The crystalline chains are more highly oriented than the amorphous chains and tend to orient towards the plane of the... 

Modern interfaces joining LC and Fourier transform infrared spectroscopy (FTIR) function in two ways The first technique is based on a flow cell ( on-line ), in which sensitivity is limited by the dilution of the analyte in the mobile phase. In the second technique the mobile phase is evaporated, leaving the analyte as a small spot that is scanned ( off-line ) by FTIR. The advantage of this approach is a significant enhancement in sensitivity. Compared to the refractive index detector the IR detector has a lower sensitivity but theoretically offers the possibility of gradient runs. 

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