Infrared spectroscopy practical aspects

As several researchers have shown empirically, the use of —log(reflectance) can provide, analogous to a transmittance measurement, a linear relationship between the transformed reflectance and concentration, if the matrix is not strongly absorbing as can be found for many samples studied by near-infrared spectroscopy. This issue is presented in detail below. A different approach based on a physical model was considered for UV/VIS measurements and later also applied within the mid-infrared. A theory was derived by Kubelka and Munk for a simple, onedimensional, two-flux model, although it must be noted that Arthur Schuster (1905) had already come up with a reflectance function for isotropic scattering. A detailed description of theoretical and practical aspects was given by Korttim. The optical absorption... 

A complete characterization of liquid crystalline polymers should include at least two aspects the characterization of the molecular structure and that of the condensed state structure. Since the first characterization is nothing more than what is practiced for non-liquid-crystalline polymers, we will restrict the discussion to only a short introduction of methods mostly used in the characterization of the presence and the main types of polymeric liquid crystal phases. The methods include the mostly used polarizing optical microscopy (POM, Section 4.1), differential scanning calorimetry (DSC, Section 4.2) and X-ray diffraction (Section 4.3). The less frequently used methods such as miscibility studies, infrared spectroscopy and NMR spectroscopy will also be discussed briefly (Section 4.4). 

Many universities now offer short courses in practical infrared spectroscopy and/or interpretation. Some instrument manufacturers also hold regular tutorials on aspects of data collection or interpretation. 

One of the most important practical aspects of infrared spectroscopy is that it may be applied to almost any type of sample in any physical state, form, or modification. In this section, sampling will be discussed in terms of physical state and/or physical nature of the sample. One point that will be emphasized throughout is the importance of documentation of all experimental procedures, sampling methods and conditions, and any abnormalities observed during the sample preparation procedure. 

C. Pasquini. Near Infrared Spectroscopy Fundamentals, Practical Aspects and Analytical Applications. J Braz ChemSoc 14(2) 198-219, 2003. 

Beckman Bibliography of Infrared Applications, Several issues of a bibliography of infrared applications compiled by W. F. Ulrich of Beckman Instruments, Inc., Fullerton, California, are available from that firm. The practical aspects of infrared spectroscopy are emphasized and the service is by no means a complete abstract of the literature. 

Infrared spectroscopy is a useful tool for molecular structural studies, identification, and quantitative analyses of materials. The advantage of this technique lies in its wide applicability to various problems in both the condensed phase and gaseous state. As described in the later chapters of this book, infrared spectroscopy is used in chemical, environmental, life, materials, pharmaceutical, and surface sciences, as well as in many technological applications. The purpose of this book is to provide readers with a practical guide to the experimental aspects of this versatile method. 

This book is divided into two parts, including the theoretical basis of linear-dichroic infrared (IR-LD) spectroscopy (Chapter 1), the orientation method as colloid suspension in nematic hosts (Chapter 2), and practical aspects (Chapters 3 through 6) associated with the use of the method for the characterization of inorganic chemicals and glasses as well as various classes of organic compounds. In all of the examples, the scope and limitation of the method are discussed and summarized. Therefore, this text can serve as a useful source of information not only for specialists in IR spectroscopy but also for other scientists as well as Ph.D. students working in the field of structural analysis. It can also be successfully used by B.Sc. and M.Sc. students who attend courses for advanced physical methods of analysis. 

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