Spectroscopy combined techniques

When considering the application of chromatography-IR spectroscopy combination techniques, three questions should be answered (i) is the problem the analysis of a composite sample (ii) can the sample be separated by a chromatographic method (iii) is there a chance that the IR spectrum of the components will help identification If the answer is yes to these questions, a chromatography-IR spectroscopy combination is a promising approach to the analytical problem. 

ICP/AES. inductively coupled plasma and atomic-emission spectroscopy used as a combined technique... 

Electrochemical techniques have been developed into very powerful tools for research and technology. However, decades ago, researchers started to understand that even more insight could be obtained if electrochemical techniques were combined with additional spectroscopic tools. Among these it is sufficient to mention infrared spectroscopy, Raman spectroscopy, luminescence techniques, electroreflection or ellipsometry. 

Electrochemical processes are always heterogeneous and confined to the electrochemical interface between a solid electrode and a liquid electrolyte (in this chapter always aqueous). The knowledge of the actual composition of the electrode surface, of its electronic and geometric structure, is of particular importance when interpreting electrochemical experiments. This information cannot be obtained by classical electrochemical techniques. Monitoring the surface composition before, during and after electrochemical reactions will support the mechanism derived for the process. This is of course true for any surface sensitive spectroscopy. Each technique, however, has its own spectrum of information and only a combination of different surface spectroscopies and electrochemical experiments will come up with an almost complete picture of the electrochemical interface. XPS is just one of these techniques. 

IR dichroism has also been particularly helpful in this regard. Of predominant interest is the orientation factor S=( 1/2)(3—1) (see Chapter 8), which can be obtained experimentally from the ratio of absorbances of a chosen peak parallel and perpendicular to the direction in which an elastomer is stretched [5,249]. One representation of such results is the effect of network chain length on the reduced orientation factor [S]=S/(72—2 1), where X is the elongation. A comparison is made among typical theoretical results in which the affine model assumes the chain dimensions to change linearly with the imposed macroscopic strain, and the phantom model allows for junction fluctuations that make the relationship nonlinear. The experimental results were found to be close to the phantom relationship. Combined techniques, such as Fourier-transform infrared (FTIR) spectroscopy combined with rheometry (see Chapter 8), are also of increasing interest [250]. 

Microporous nanoparticles with ordered zeolitic structure such as Ti-Beta are used for incorporation into walls or deposition into pores of mesoporous materials to form the micro/mesoporous composite materials [1-3], Microporous particles need to be small enough to be successfully incorporated in the composite structure. This means that the zeolite synthesis has to be stopped as soon as the particles exhibit ordered zeolitic structure. To study the growth of Ti-Beta particles we used 29Si solid-state and liquid-state NMR spectroscopy combined with x-ray powder diffraction (XRPD) and high-resolution transmission electron microscopy (HRTEM). With these techniques we monitored zeolite formation from the initial precursor gel to the final Ti-Beta product. 

Another technique that has been employed for studying certain types of changes in solids is infrared spectroscopy, in which the sample is contained in a cell that can be heated. By monitoring the infrared spectrum at several temperatures, it is possible to follow changes in bonding modes as the sample is heated. This technique is useful for observing phase transitions and isomerizations. When used in combination, techniques such as TGA, DSC, and variable-temperature spectroscopy make it possible to learn a great deal about dynamic processes in solids. 

We now extend the work to in situ measurements on metal ions adsorbed at the metal oxide/aqueous solution interface. In this report, our previous results are combined with new measurements to yield specific information on the chemical structure of adsorbed species at the solid/aqueous solution interface. Here, we describe the principles of emission Mossbauer spectroscopy, experimental techniques, and some results on divalent Co-57 and pentavalent Sb-119 ions adsorbed at the interface between hematite (a-Fe203) and aqueous solutions. 

Apart from the above techniques, the electromodulated reflectance spectroscopy combined with cyclic voltammetry has been utilized by Gaigalas et al. [14] in the investigations of electron transfer between the 2Fe-2S protein putidaredoxin and either bare or bekanamycin-modified Ag electrode. Of the two models considered, the free diffusion model, as compared to the adsorbed layer model, exhibited better concordance with the experimental data. After modification of the Ag electrode with bekanamycin, it exhibited only a small increase in the observed redox reaction... 

Spectroelectrochemistry [3] is the field in which electrochemistry is combined with spectroscopy. Spectroelectrochemical techniques are useful in studying the electrochemical phenomena that occur both in solutions and at electrode surfaces. Here, only the phenomena in solutions are considered. 

Apart from the many advantages of X-ray diffraction and X-ray absorption spectroscopy, each method, as discussed in Sections II and IV, is also characterized by some important limitations in the investigation of catalysts. These limitations to a large extent are complementary, and they can therefore be overcome by using a combination of both techniques. The various approaches for performing experiments with the combined techniques are described in Section V, and some examples are given in Section VI. 

Subsequently, fluorescent MIPs for cGMP were fabricated [46 18, 66, 67]. For that, 1,3-diphenyl-6-vinyl-1 //-pyrazolo 3.4-/ quinoline (PAQ) was introduced as the fluorescent indicator to interact with cGMP in a thin-layer fluorescent MIP chemosensor. Both steady-state (Fig. 1) and time-resolved fluorescence spectroscopy were used as two independent analytical techniques for investigation of the chemosensor properties in the presence of cGMP. Steady-state fluorescence spectroscopy is a common technique applied to MIP sensing. Nevertheless, the use of time-resolved fluorescence spectroscopy combined with microscopy was a new approach to MIP sensing. 

The vast identification potential of micro-Raman spectroscopy combined with the aforementioned sophisticated chemometric analysis methods is corroborated within various works In one study a total of 2257 Raman spectra of single cells were used to differentiate among 20 strains belonging to 9 different species. Here, a recognition rate of 89.2% for strains using the SVM technique could be achieved, albeit these bacteria were grown under different conditions (cultivation time medium, and temperature). [45]... 

FTIR spectroscopy has become a standard technique for investigating Idle structure and level of orientational order of ultrathin films, that is, films in the submicron range (2.5 to 500 nm) (9). By combining transmission spectroscopy with infrared reflection-absorption spectroscopy (this technique is also referred to as grazing incidence reflection), the orientation of the functional groups of the molecules in the film can be investigated. These measurements are nondestructive to the film and can be conducted at a range of temperatures and pressures. 

The book has been written as an introductory text rather than as an exhaustive review. It is meant for students at the start of their Ph.D. projects, and also for anyone else who needs a concise introduction to catalyst characterization. Each chapter describes the physical background and principles of a technique, a few recent applications to illustrate the type of information that can be obtained, and an evaluation of possibilities and limitations. Chapter 9 contains case studies which highlight a few important catalyst systems and illustrates the power of combining techniques. The Appendix, which incorporates the surface theory of metals and details of chemical bonding at surfaces, is included to provide a better insight into the results of photoemission, vibrational spectroscopy, and thermal desorption. 

The thermal characterisation of elastomers has recently been reviewed by Sircar [28] from which it appears that DSC followed by TG/DTG are the most popular thermal analysis techniques for elastomer applications. The TG/differential thermal gravimetry (DTG) method remains the method of choice for compositional analysis of uncured and cured elastomer compounds. Sircar s comprehensive review [28] was based on single thermal methods (TG, DSC, differential thermal analysis (DTA), thermomechanical analysis (TMA), DMA) and excluded combined (TG-DSC, TG-DTA) and simultaneous (TG-fourier transform infrared (TG-FTIR), TG-mass spectroscopy (TG-MS)) techniques. In this chapter the emphasis is on those multiple and hyphenated thermogravimetric analysis techniques which have had an impact on the characterisation of elastomers. The review is based mainly on Chemical Abstracts records corresponding to the keywords elastomers, thermogravimetry, differential scanning calorimetry, differential thermal analysis, infrared and mass spectrometry over the period 1979-1999. Table 1.1 contains the references to the various combined techniques. 

As we saw in Chapter 13, infrared (IR) spectroscopy can be used to determine which functional group is present in a compound. This chapter discusses proton and carbon-13 nuclear magnetic resonance (NMR) spectroscopy. These techniques complement IR spectroscopy because they provide information about the hydrocarbon part of the molecule. The combination of IR and NMR spectroscopy often provides enough data to determine the structure of an unknown compound. 

While XAFS spectroscopy is a powerful catalyst characterization method it is clear that XAFS spectroscopy combined with other complementary techniques offers the possibility of providing a more complete understanding of catalyst structure. The designs of cells that allow both XAFS and XRD data to be collected have already been described (above). More recently, the combination of two, or even three, other complementary techniques to XAFS spectroscopy has now been successfully demonstrated. Beale et al. (2005) briefly described a design combining UV-vis... 

Although the experiments referred to here demonstrate the wealth of kinetics and structural data that can be obtained from TR-XAFS data, application of XAFS spectroscopy combined with complementary techniques provides unique and even more detailed information. This statement refers to the most elegant way of using XAFS spectroscopy simultaneously with other methods (e.g., XRD Clausen, 1998 Clausen et al., 1993 Dent et al., 1995 Thomas et al., 1995), and it also refers to XAFS experiments complemented by experiments carried out under similar experimental conditions (e.g., laboratory techniques such as XRD, Raman spectroscopy, TG/DTA). More often than not, a detailed XAFS analysis is possible only when all additional data (characterizing phases, metal valences, and structure) representing the catalyst are available. Furthermore, the analysis of TR-XAFS data should aim at extracting as much information from the XANES part and the EXAFS part of a XAFS spectrum as possible. 

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