Spectroscopy multiple attenuated total

J.W. Hail, A. Pollard Near-infrared spectroscopic determination of serum total proteins, albumin, globulins and urea. Clin. Biochem. 26, 483 (1993) Y. Mendelson, A.C. Clermont, R.A. Peura, B.-C. Lin Blood glucose measurement by multiple attenuated total reflection and infrared absorption spectroscopy. lEEB Tkans. Biomed. Eng. 37, 458 (1990)... 

The existence of hybridisation effect in polycyanurate-polyurethane semi-IPNs via chemical interaction between cyanate and urethane groups was confirmed later by the method of multiple attenuated total reflection (ATR) infrared spectroscopy [29]. The ATR infrared spectra for some of the samples studied are given in Figure 14. The disappearance of the 2240-2270 cm" doublet in the spectra of properly prepared samples was accompanied by characteristic spectral changes depending on the polyurethane (PUR) content of the sample. These changes refer especially to appearance and enhancement of the 1560 and 1360 cm" bands of C=N and to absorption of polyurethane at 1700-1740 cm". ... 

The existence of hybridization effects via cyanate-urethane chemical interaction was evidenced in polyurethane/polycyanurate semi-IPNs by multiple attenuated total reflection (ATR) infrared spectroscopy [40]. It was calculated that at least 10-30% of the cyanate groups participate in the reaction with TPU at a 20 to 60% TPU content in the composition. It is noteworthy that the above estimates are in good agreement with FTIR/HPLC experiments performed on a low-molecular model cyanate/urethane blend [63] it was shown that, in addition to polycyclotrimerization, ca. 20-30% of the cyanate groups formed co-products with the urethane. 

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

There is substantial history regarding the application of conventional vibrational spectroscopy methods to study the intact surface of skin, the extracted stratum corneum and the ceramide-cholesterol-fatty acid mixtures that constitute the primary lipid components of the barrier. The complexity of the barrier and the multiple phases formed by the interactions of the barrier components have begun to reveal the role of each of these substances in barrier structure and stability. The use of bulk phase IR to monitor lipid phase behavior and protein secondary structures in the epidermis, as well as in stratum corneum models, is also well established 24-28 In addition, in vivo and ex vivo attenuated total reflectance (ATR) techniques have examined the outer layers of skin to probe hydration levels, drug delivery and percutaneous absorption at a macroscopic level.29-32 Both mid-IR and near-IR spectroscopy have been used to differentiate pathological skin samples.33,34 The above studies, and many others too numerous to mention, lend confidence to the fact that the extension to IR imaging will produce useful results. 

IR spectroscopy is a common analytical technique in the textile industry. IR is capable of identifying fibers and their additives, as well as showing quantitative blend ratios and additive contents. The ATR (attenuated total reflection) technique, especially in its multiple form, MIR (multiple internal reflection) is of special importance in this field. The sample preparation is simple and fast the cut out swatches with appropriate surface areas are placed against each side of the MIR crystal, ensuring sufficient and uniform contact across the crystal surface. The internal reflection methods are non-destructive, so that the sample may be saved for other types of analysis, they are, further, methods of surface analysis. This is advantageous in all cases where the finish resides primarily on the fiber surface. In this case, a very strong spectrum of the finish is obtained, with minimal interference from the base fiber (Hannah et al., 1975). 

Another approach, internal reflection spectroscopy (IRS) or attenuated total reflectance (ATR) spectroscopy, takes advantage of the total reflection observed when a light beam is directed to the back of the OTE at an angle greater than the critical angle. Since the reflection takes place at the electrode-solution interface, the light beam is attenuated only by molecules close to the electrode surface. The penetration depth is about 1000 A in a typical experiment. Because of this very small effective cell length, the electrode is most frequently used in a multiple reflection mode [Fig. 44(b)]. 

A nonelectrochemical method also sensitive to the presence of water is infrared spectroscopy with multiple internal reflection, applied by Nguyen and coworkers to study the swelKng of an organic coating at the metal-polymer interface in situ [58]. The integration of the stretching vibration of water was used as a measure of the water uptake at the interface. Stratmarm and coworkers measured the increase of the water concentration at the Fe-alkyd-polymer interface by means of single attenuated total infrared reflection spectroscopy (ATIRS) [59]. An ultrathin Fe film was evaporated onto a ZnSe crystal and coated with an alkyd primer. The authors concluded that no separate water film is... 

Good results in the IR spectroscopy of aqueous samples are given by the ATR technique (attenuated total reflection) and a further development of this, the MIR technique (multiple internal reflection) a prerequisite is that the sample space of the IR spectrophotometer is sufficiently large to accommodate the supplementary MIR device. The MIR technique likewise involves measurement of the absorption spectrum of the substance. All of the same molecule-specific and analytical conclusions can therefore be drawn as with an IR spectrum in the transmission of the same substance, even though the two spectra are physically not quite identical. 

Internal reflection spectroscopy, also known as attenuated total reflectance (ATR) or multiple internal reflectance (MIR), is a versatile, nondestructive technique for obtaining the infrared spectrum of the surface of a material or the spectrum of materials either too thick or too strongly absorbing to be analyzed by standard transmission spectroscopy. 

Sampling systems based on the multiple internal reflection (MIR) technique, also called attenuated total reflectance (ATR) spectroscopy [916], are very useful for the study of polymer surface degradation [476,1437]. 

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