Application areas examples spectroscopy

Raman spectroscopy was discovered over 75 years ago but has only been a viable process tool for 10-15 years. However, there has been an astounding increase in process Raman spectroscopy examples in the last five years. The United States Food and Drag Administration s (US FDA) endorsement of process analytical technology clearly set off an explosion of activity. Problems that sometimes sidelined Raman in the past, such as fluorescence or highly variable quantitative predictions from samples that were too small to be representative, are being re-examined and leading to new technology. In turn, that helps open, or perhaps reopen, new application areas. The availabihty of easy to use Raman instrumentation at many prices also helps with that. 

I venture to say that the majority of practical chemometrics applications in analytical chemistry are in the area of instrument specialization. The need to improve specificity of an analyzer depends on both the analytical technology and the application. For example, chemometrics is often applied to near-infrared (NIR) spectroscopy, due to the fact that the information in NIR spectra is generally non-specific for most applications. Chemometrics may not be critical for most ICP atomic emission or mass spectrometry applications because these techniques provide sufficient selectivity for most applications. On the other hand, there are some NIR applications that do not require chemometrics (e.g. many water analysis applications), and some ICP and mass spectrometry applications are likely where chemometrics is needed to provide sufficient selectivity. 

This chapter gives a brief overview of IR and Raman spectroscopy, with examples from a number of application areas, demonstrating the usefulness of both techniques in the pharmaceutical laboratory. In general, these examples will be grouped by application, rather than by technique, since the two should ideally be used together, in conjunction with other analytical techniques, in a problem-driven manner. 

The applications of NIR spectroscopy to process analysis and control are far too numerous to comprehensively cover in a text of this type. A regular review of literature in this area is given in NIR News [10]. Examples in Tab. 17.1 illustrate the breadth of NIR applications to process analysis. Table 17.2 summarises the use of NIR in process analysis. 

The major areas of application of reflectance spectroscopy have been the elucidation of reaction mechanisms, double layer studies, investigations of underpotential deposition (UPD), and studies of the electroreflectance effect (ER). This range is too large for an in depth discussion to be given here. Instead, two examples of the type of information that can be obtained will be described (a third system, hydrogen adsorption on platinum, has been discussed in Chapter 7). Those readers interested in more details are referred to a recent review [1], and the literature cited therein. 

Chapters 4 and 5 introduce the concepts of group theory, which makes symmetry indispensible for understanding many areas of chemistry. This book concentrates on applications in vibrational spectroscopy and molecular orbital theory and so illustrative examples are drawn from these areas. 

NMR spectroscopy is one of the most widely used analytical tools for the study of molecular structure and dynamics. Spin relaxation and diffusion have been used to characterize protein dynamics [1, 2], polymer systems[3, 4], porous media [5-8], and heterogeneous fluids such as crude oils [9-12]. There has been a growing body of work to extend NMR to other areas of applications, such as material science [13] and the petroleum industry [11, 14—16]. NMR and MRI have been used extensively for research in food science and in production quality control [17-20]. For example, NMR is used to determine moisture content and solid fat fraction [20]. Multi-component analysis techniques, such as chemometrics as used by Brown et al. [21], are often employed to distinguish the components, e.g., oil and water. 

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