Fourier transform infrared reference spectra

Gurka DF, Umana M, Pellizzari ED, et al. 1985. The measurement of on-the-fly Fourier transform infrared reference spectra of environmentally important compounds. AppI Spectrosc 39 297-303. 

For infrared spectroscopy, 20-50 mg of the cobalt-exchanged zeolite was pressed into a self-supporting wafer and placed into an infrared cell similar to that described by Joly et al. [21], Spectra were recorded on a Digilab FTS-50 Fourier-transform infrared spectrometer at a resolution of 4 cm-i. Typically, 64 or 256 scans were coadded to obtain a good signal-to-noise ratio. A reference spectrum of Co-ZSM-5 in He taken at the same temperature was subtracted from each spectrum. 

Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy ( ll NMR) have become standards for verifying the chemistry of polyanhydrides. The reader is referred to the synthesis literature in the previous section for spectra of specific polymers. The FTIR spectrum for PSA is shown in Fig. 2. In FTIR the absorption... 

C. Refer to the Fourier transform infrared spectrum in Figure 20-29. 

Fourier transform infrared spectroscopy FT-IR. The measurement of individual degradation products with FT-IR is very simple, quick and precise. A reference sample spectrum of new oil is required to subtract electronically from the oil sample spectrum. The spectra of the fresh oil and the used oil sample are obtained individually in the same cell. The results - both spectra and the "differential" spectrum are stored in the computer in absorbance format, a form that varies linearly with concentration. 

The details of the electrohydrodimerization of dimethyl maleate in methanol has been studied using Fourier transform infrared (FTIR) spectroscopy [339]. Spectra were recorded as a function of time at a constant applied potential (—1.5 V versus Ag/AgCl) with the reference spectrum being obtained at OV. The result is shown in Fig. 49(a) as plots of dR/R versus the wavenumber (cm" ), where R is the reference spectrum and dR is the sample spectrum minus the reference spectrum. Thus, positive dR/R values indicate loss of chromophore, while negative dR/R values indicate gain of chromophore. The analysis of the spectral data showed that the formation of the hydrodimer, 1,2,3,4-butane tetracarboxylic acid, is accompanied by isomerization of dimethyl maleate (the cis isomer) to dimethyl fumarate (the trans isomer). This is nicely illustrated by Fig. 49(b), from which it is seen that the loss of chromophore at 1390 cm" (cis isomer) proceeds more rapidly than the gain in chronomophore at 1288 cm" (trans isomer). 

The properties of the dual-film electrode were characterized by in situ Fourier transform infrared (FTIR) reflection absorption spectroscopy [3]. The FTIR spectrometer used was a Shimadzu FTIR-8100M equipped with a wide-band mercury cadmium teluride (MCT) detector cooled with liquid nitrogen. In situ FTIR measurements were carried out in a spectroelectro-chemical cell in which the dual-film electrode was pushed against an IR transparent silicon window to form a thin layer of solution. A total of 100 interferometric scans was accumulated with the electrode polarized at a given potential. The potential was then shifted to the cathodic side, and a new spectrum with the same number of scans was assembled. The reference electrode used in this experiment was an Ag I AgCl I saturated KCl electrode. The IR spectra are represented as AR/R in the normalized form, where AR=R-R(E ), and R and R(E ) are the reflected intensity measured at a desired potential and a base potential, respectively. 

On the other hand, successful identification of bacterial spores has been demonstrated by using Fourier transform infrared photoacoustic and transmission spectroscopy " in conjunction with principal component analysis (PCA) statistical methods. In general, PCA methods are used to reduce and decompose the spectral data into orthogonal components, or factors, which represent the most coimnon variations in all the data. As such, each spectrum in a reference library has an associated score for each factor. These scores can then be used to show clustering of spectra that have common variations, thus forming a basis for group member classification and identification. 

Fourier transform infrared spectroscopy The Fourier transform refers to mathematical procedures, which are needed to convert the basic data, the actual quantities measured, back to the familiar data of absorption spectroscopy. Properly adjusted and understood, it is possible to find the spectrum of what is adsorbed on the electrode and how it varies with potential. 

Fourier transform infrared spectroscopy (FTIR) is a common identification test. Chapter 11 also discusses FTIR applications supporting stability. The Fourier transform enhances sensitivity and greatly reduces the time of the spectroscopic measurement. FTIR is commonly used as an identification test, but has been used qualitatively (e.g., dimethicone). Spectra are compared with a reference spectrum for identification purposes. As an identification test, FTIR is used as a release test rather than a stability test. Additional testing information can be found in USP/NF, General Chapter <851 >. 

A Fourier-transform infrared (FT-IR) spectrometer in transmission mode under dry nitrogen flow (10 cubic centimeters per minute, cepm) was used to test the physicochemical interactions between PPy and Fc203 nanoparticles. The dried PPy powder was mixed with powdered KBr, ground and compressed into a pellet. Its spectrum was recorded as a reference for comparison with that of the Fe203/PPy nanocomposites. 

In many studies, particularly those related to materials and forensic science, it is frequently necessary to measure a mid-infrared spectrum from a trace amount of a sample or a sample of small size. In some circumstances, this may be accomplished by using a beam-condenser accessory within the conventional sample compartment of a Fourier-transform infrared (FT-IR) spectrometer. Perhaps today though, it is more convenient to use infrared microspectrometry (often commonly referred to as infrared microspectroscopy or even infrared microscopy). Based on an optical microscope (or infrared microscope) coupled to an FT-IR spectrometer, it is one of the most useful methods for structural analysis of such samples and can often be undertaken in a non-destructive manner [1, 2]. 

The Michelson interferometer does not measure the infrared spectrum directly. Rather, an interfero-gram is measured, and converted to a single-beam spectrum via Fourier transformation. Because of the critical role of this transformation, the method is generally referred to as Fourier-transform infrared spectroscopy, or FT-IR . Instruments using this... 

Multidimentional nonlinear infrared spectroscopy is used for identification of dynamic structures in liquids and conformational dynamics of molecules, peptides and, in principle, small proteins in solution (Asplund et al., 2000 and references herein). This spectroscopy incorporates the ability to control the responses of particular vibrational transitions depending on their couplings to one another. Two and three-pulse IR photon echo techniques were used to eliminate the inhomogeneous broadening in the IR spectrum. In the third-order IR echo methods, three phase-locked IR pulses with wave vectors kb k2, and k3 are focused on the sample at time intervals. The IR photon echo eventually emitted and the complex 2D IR spectrum is obtained with the use of Fourier transformation. The method was applied to the examination of vibrational properties of N-methyl acetamid and a dipeptide, acyl-proline-NH2.in D20. The 2D IR spectrum showed peaks at 1,610 and 1, 670 cm 1, the two frequencies ofthe acyl-proline dipeptide. Geometry and time-ordering of the incoming pulse sequence in fifth-order 2D spectroscopy is shown in Fig. 1.3. 

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