Attenuated Total Reflection Infrared Spectrometry ATR

Infrared internal reflection spectroscopy was used by Brash and Lyman to study the adsorption of the plasma proteins, albumin, y-glcbu-lin, and fibrinogen, on a variety of hydrophobic polymer surfaces. The results indicated that all the proteins investigated behaved rather similarly on a variety of hydrophobic surfaces. Under static conditions the proteins appeared to be rapidly adsorbed as monomolecular layers from solutions varying in concentration from a few milligram percent to the concentration levels of normal plasma. They deduced these monolayers to be closely packed arrays in which the protein molecules appeared to retain their native globular form. 

Infrared studies of the amide I band of transferred films of jS-lacto-globulin B spread on 0.5 M KCl were obtained via the multiple internal reflection (MIR) technique by Loeb. The spectra were recorded following transfer of films maintained at different surface pressures. At a high 

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The two additives have heen identified hy matrix assisted laser desorption ionisation mass spectrometry (MALDI-MS) and attenuated total reflection infrared spectroscopy (ATR). 

Evaluation of the meaningfulness of results from less sensitive and less selective methods needs additional attention (e.g. attenuated total reflectance infrared (ATR-IR) or solid-state NMR spectrometry) [2]. Indirect insights from functional studies include support for transmembrane orientation (Fig. 11.13b) from parabolic dependence of the activity of synthetic ion channel or pore on bilayer thickness (Section 11.3.7) [56] and other readouts in support of operational hydrophobic matching. Flippase activity may provide some support for interfacial location (Section 11.3.7, Fig. 11.13d) [61, 62]. 

The aim of this work is the determination of several nutritional parameters, such as Energetic Value, Protein, Fat, and Carbohydrates content, in commercially available yoghurt samples by using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FT-IR) spectrometry and a partial least square approach. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

Heinen M, Jusys Z, Behm RJ. 2009. Reaction pathways analysis and reaction intermediate detection via simultaneous differential electrochemical mass spectrometry (DBMS) and attenuated total reflection Bourier transform infrared spectroscopy (ATR-BTIRS). In Vielstich W, Gasteiger HA, Yokokawa H, eds. Handbook of Buel Cells. Volume 5 Advances in Electrocatalysis. Chichester John Wiley Sons, Ltd., in press. 

To shed light on the mechanism of formation of silsesquioxane a7b3, to identify the species formed during the process, and to try to explain the high selectivity towards structure a7b3 of the optimised synthetic method described above (64% yield in 18 h), the synthesis of cyclopentyl silsesquioxane a7b3 was monitored by electrospray ionisation mass spectrometry (ESI MS) [50-52] and in situ attenuated total reflection Fourier-transform infrared (ATR FTIR) spectroscopy [53, 54]. Spectroscopic data from the latter were analysed using chemometric methods to identify the pure component spectra and relative concentration profiles. 

Parallel to the synthesis of library compounds on solid supports, the direct analysis (i.e. on-bead ) is an attractive concept. Leaving aside the methods of on-bead-infrared-spec-troscopy [41] using attenuated total reflection (ATR) and gel-phase NMR-techniques [42, 43], we wish to consider the use of on-bead analysis in mass spectrometry. The requirements of the ionization process restrict on-bead analysis to the MALD1 technique. However, also for MALDI-analysis, in so-called direct monitoring studies [44-46], the compounds are cleaved from the bead before the actual ionization. True on-bead analysis under MALDI conditions is only possible with photolytically cleavable linkers, and this technique has been dealt with in several publications [28,29] in which the compounds are both cleaved and ionized simultaneously within the MALDI source with a single laser shot. The wavelength of the MALDI-laser must however correspond with the wavelength required to cleave the compounds from the resin. Therefore, on-bead analysis represents a method for special analytical problems which is limited to MALDI. 

An example of blending was when phenylcarbomylated or azido phenylcarbo-mylated p-CD was successfully blended with polymethyl methacrylate (PMMA) and electrospun into nanofibrous membranes for organic waste treatment and water purification (Kaur et al. 2006). The presence of the p-CD derivatives on the surface of the nanofibers was confirmed by attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR) and x-ray photoelectron spectroscopy (XPS). A solution containing phenolphthalein (PHP) was used to determine the ability of the functionalized membranes to capture small organic molecules. The results showed... 

Among these, some of the most frequently used are attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SSIMS), energy dispersive X-ray spectroscopy (EDS), optical microscopy, laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM), enviromnental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), contact angle measurement, and some evaluation methods for the biocompatibility of membrane surfaces. 

In principle, all kinds of spectroscopic techniques lend themselves to on-line measurements. Only a very few are practical. Although low-field NMR has been used to measure various material properties by applying empirical relationships, NMR is still not a realistic proposition for on-line measurements. Ironically, ETIR spectroscopy suffers from too much sensitivity. Typically, good spectra can be obtained only from very thin polymeric films (or solutions). Attenuated total reflection (ATR) probes, in which only a fraction of the IR light penetrates a very short distance into the sample, reduce the problem of excessive sensitivity. However, they aggravate the problems of variations in the baseline and nonlinear response. The latter problem also obstructs the use of UV spectrometry for monitoring polymerization reactions. Of the remaining options, near-infrared (NIR) and Raman spectroscopy are the most attractive. 

Attenuated total reflection (ATR) spectrometry is becoming an increasingly important sampling technique for infrared microspectrometry using both single-element and array detectors. This topic is covered in Chapter 15. 

Attenuated total reflection (ATR) has grown into the most widely practiced technique in infrared spectrometry. The reasons for this are fairly straightforward the technique requires little or no sample preparation, and consistent results can be obtained with relatively little care or expertise. The technique is not foolproof, but it can be very forgiving. ATR spectrometry is known by a number of alternative names, for example, multiple internal reflection (MIR), which is not to be confused with mid-infrared, frustrated multiple internal reflection (FMIR), evanescent wave spectrometry (EWS), frustrated total internal reflection (FTIR), which is not the same as Fourier transform infrared (FT-IR) spectrometry, and internal reflection spectrometry (IRS), but IRS is better known, at least in the United States, as the Internal Revenue Service. 

If a material could be made extremely thin, for example, to the level of a single layer of molecules, this thin layer would transmit almost all of the infrared radiation, so that its infrared transmission spectrum could be measured. In fact, it is possible to measure a mid-infrared transmission spectrum from a thin soap film. It is usually practically difficult, however, to maintain such a thin film without it being supported by a substrate. For a thin film supported on a substrate, its infrared spectmm is often obtained by utilizing a reflection geometry. Two reflection methods are available for measuring infrared spectra from substrate-supported thin films, depending on the dielectric properties of the substrates used. External-reflection (ER) spectrometry, which is the subject of this chapter, is a technique for extracting useful information from thin films on dielectric (or nonmetallic) substrates, while reflection-absorption (RA) spectrometry, described in Chapter 10, is effective for thin films on metallic substrates [1]. In addition to these two reflection methods, attenuated total-reflection (ATR) spectrometry, described in Chapter 13 and emission spectroscopy, described in Chapter 15 may also be useful in some specific cases. 

This time-resolved measurement method can be applicable to relatively slow transient phenomena, as its time-resolved measurements are undertaken while the movable mirror is at rest. The number of applications of step-scan FT-IR spectrometry to time-resolved measurements currently is more than that by any other method, and it has been applied to various studies in many fields such as studies of biomolecules, liquid crystals, polymers, photochemical reactions in zeolites, oxidation-reduction reactions on electrode surfaces, and excited electronic states of inorganic complexes. Further, this method has been applied to time-resolved measurements in combination with attenuated total reflection (ATR) (see Chapter 13), surface-enhanced infrared absorption (see Section 13.2.2) [10, 11], infrared microscopic measurements (see Chapter 16) [12], and infrared spectroscopic imaging (see Chapter 17) [13]. 

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