FTIR Methods

In the transmission mode, spatial resolution was found to be 40 p m [183]. For an aperture corresponding to a sample size of 8 pm, the diameter of the sample actually viewed is about six times larger [239]. Curve 2 in Fig. 4.35 shows the transmission spectrum of a 0.1-pm-thick film of an epoxy resin taken from a sampling area 8x8 pm [218]. For comparison, the transmission spectrum of a larger sample area is also shown (Fig. 4.35, curve 1). One can see that this film can be identified even when the sampling area approaches the theoretical diffraction limit. Sampling areas of 100-200 pm have been reported in Refs. [239-241]. 

Spatial resolution can be inaeased by introducing a dual aperturing (Redundant, Spectra-Tech). In this case, two apertures of identical size are placed at the source and sample images. This technique reduces the stray light by a factor of 3 [183] by reducing the illuminated spot at the sample. 

Better resolution but stiU controlled by diffraction can be obtained with a synchrotron IR source in a confocal arrangement. The intrinsically brighter synchrotron IR source allows areas as small as 3-4 p,m to be probed [248-252, 266], which is very important for improving the quality of maps (vide infra). An additional advantage of synchrotron sources in orientational measurements is that the probing radiation is 100% polarized in the plane of the storage ring. 

MAPPING, IMAGING, AND PHOTON SCANNING TUNNELING MICROSCOPY 

The mapping of a single cell from a wheat cross section (aleurine cell from a row of cells between the endosperm and seed coat) was achieved as early as 1993 [263]. With the use of a synchrotron source of IR radiation, maps of an aleurine cell and a cell wall with a spatial resolution of 5-6 p,m [264, 265] and maps of a hair cross section with a spatial resolution of 3-4 p,m [266] were obtained. The distribution of certain species such as proteins, lipids, and nucleic acids inside single living cells (some of which are mitotically active) [267, 268] was investigated 

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The ability of SFE-FTIR to perform a variety of extraction methods is a definite advantage, especially for the study of complex mixtures containing analytes of varying solubility. For analytes which are readily solubilised in C02, direct dynamic and direct static-dynamic SFE-FTIR methods are quite successful. Elimination of the trapping process reduces both analysis time and potential analyte loss arising from... 

ESRI is a nondestructive method for the study of degradation, which is an important advantage, especially for crystalline polymers. The major advantage of ESRI compared with FTIR methods is its sensitivity to early events in the aging process. Further developments of ESRI methods are expected to be of help in the ultimate goal accurate predictions of lifetimes for polymeric materials and a better understanding of the environmental factors. 

The most discriminating technique for proving the identity and purity of analyte peak of a chromatogram, especially for analyzing biological samples and natural products, is by using online LC-UV/MS or GC-MS/FTIR methods [15]. Alternatively, one could use a combination of TLC and MS, where direct determination on the TLC plates is made by matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) [16]. 

The final step in obtaining the spectrum by the FTIR method is turning back the data obtained as a result of the repetitive interference action of the moving mirror into an intensity wavelength line. It is here that Fourier Transform mathematics is utilized. It is the signal intensity that is stored in a digital representation of the Interferogram. This information is then Fourier transformed by the computer into the frequency spectrum. 

ES yA3 dictates the selected databases and sample-tracking mechanism that are based on the decisions of ES 2. For example, data obtained using a direct FTIR method as suggested in the decisions of ES 1 and 2 would be put into the FTIR database under D conditions. However, a sample examined with the GC-FTIR configuration would be entered into the GC-FTIR database with... 

B. Yan, Chapter 3 Solid-Phase Reaction Optimisation Using FTIR Methods, in Analytical Methods in Combinatorial Chemistry, Technomic, Pennsylvania,... 

In this experiment, cyclopentylacetic acid, 2-norbornaneacetic acid, and 1-adman-taneacetic acid reacted, respectively, with the alcohol resins (1) (Scheme 12.2) of three sizes. These resins have different diameter ranges, namely, 35-75, 160-200, and 500-560 pm. The relative conversion of the starting material to the product was determined by single bead FTIR method. Fig. 12.6 shows IR spectra taken at... 

It is a commonplace that FTIR-based analyzers are the predominant technology for mid-infrared applications. This arises from a unique tie-in between the inherent advantages of the FTIR method and serious limitations in the mid-infrared range. The most serious problem for mid-infrared spectroscopy is the very low emissivity of mid-infrared sources combined with the low detectivity of mid-infrared thermal detectors. 

Despite considerable effort to understand the chemical nature of the organic and inorganic portions of coal, and substantial advances in instrumentation and methodologies, much of coal s chemical nature remains intractable. This paper reviews methods and their limitations for the determination of specific minerals in coal, and presents results of efforts at Consolidation Coal Company to develop FTIR methods for routine coal mineralogy. 

Mineral matter characterization in coal has received considerable attention. Given and Yarzab (1) discussed the problems posed by mineral matter in various coal analyses. Furthermore, mineral matter complicates the chemical treatment of coal. It also has many adverse effects on commercial coal utilization. Coal consumers pay to ship mineral matter, to accommodate its impact on capital equipment and operations, and to dispose of the resultant ash. The impact of coal minerals on utilization motivated Consol s initial interest in mineralogy (2). The results reported here are from a second phase of the FTIR method development, in which extensive improvements were made to the methods. 

TG-FT-IR, Pyrolysis analyses were performed on the preliquefaction solids using thermogravimetric (TG) analysis with on-line analysis of the evolved products (including an infrared spectrum of the condensables) by FT-IR. The TG-FTIR method has been described previously (23-25). The Bomem TG/plus instrument was employed. A sample is continuously weighed while it is heated. A flow of helium sweeps the products into a multi-pass cell for FT-IR analysis. Quantitative analysis of up to 20 gas species is performed on line. Quantitation of the tar species is performed by comparison with the balance reading. 

We have applied the FTIR method to investigate the surface properties of NiO/Ni(100) films by following the adsorption of CO. A comparison of FTIR spectra of CO on various surfaces is shown in Figure 3. Figure 3a is a typical CO chemisorption spectrum on a clean Ni(lOO) surface at 300 K. The CO coverage of this surface is about 0.5 ML with all CO molecules occupying the terminal sites on clean Ni(lOO). The vibrational feature observed at 2032 cm-i can be easily assigned to the... 

Li et al. [278] have studied adsorption of L-phenylalanine at Au(lll) electrodes using electrochemical and subtractively normalized interfacial FTIR methods. It has been found that the adsorbed molecules change their orientation with the electrode potential. At a negatively charged surface, the compound was predominantly adsorbed in the neutral form of the amino acid. At potentials positive with respect to pzc, L-phenylalanine was adsorbed predominantly as zwitterion with —GOO ... 

The FTIR method, which has significantly altered traditional methods of obtaining IR spectra, has several advantages ... 

Su et al. first reported experimental evidence for the HOO + HCHO reaction by the FTIR method in the Cl-atom initiated oxidation of HCHO [67,68]. 

Alkenes. The available kinetic and mechanistic data show that under atmospheric conditions the reaction of HO radicals with alkenes proceeds predominantly via addition of the HO radical to the carbon-carbon double bond(s) [30]. The energized HO-adducts which result are rapidly thermalized to yield HO-substituted alkyl radicals which, in turn, undergo subsequent free-radical reactions leading to the formation of molecular products. Thus, the possible reactions in the HO-inidated oxidation are, in many respects, analogous to those of alkyl radicals described in the preceding section. Product studies on these reactions have mainly been made by the FTIR method [109-112]. 

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