Solutions to Practice Problems

Solutions to practical problems rarely depend upon a single technique or a single approach. The following example of an impurity identification in a pharmaceutical product illustrates the key role that LC-MS can play in such an investigation, but also illustrates the limitations of the technique. The identification of this impurity has been published elsewhere in complete detail [75]. The problem and solution is summarized here. The impurity, designated as H3, was observed at 0.15% in a bulk lot of the drug substance in the structure below. The impurity required identification before the bulk lot could be released for use in further studies. 

We hope the book has conveyed a compelling picture of the vast potential of Raman spectroscopy which recent applications and instrumentation advances have unlocked. Many areas within these specialist biomedical and pharmaceutical fields are rapidly progressing from academic research environments to implementation as solutions to practical problems. In the pharmaceutical industry this process is well advanced. The march into the biomedical area is underway and further penetration into clinical applications appears imminent. 

Appropriate methods for the study of the materials surface have been treated by the keyword Surface Analytical Methods. Especially XPS is a powerful tool even for practical corrosion problems and other problems which may occur at surfaces or surface layers. In many cases one may give solutions to practical problems caused by contaminations, wrong treatment of the surfaces and unexpected surface attack due to changes in the environment. This method has been applied to many practical problems in the macroscopic and microscopic environments ranging from large metal constructions to the micro- and nanoworlds of electronics. 

The conversion of NO(g) to N20(g) plus NOiig) is spontaneous under standard conditions. The forward reaction under these conditions is scarcely observed because its rate is so slow. Nonetheless, its equilibrium constant can be calculated Such calculations often have enormous impact in evaluating proposed solutions to practical problems. For example, the calculation shows that this reaction could be used to reduce the amount of NO in cooled exhaust gases from automobiles. The fundamental reaction tendency is there, but successful application requires finding a route to increasing the reaction rate at standard conditions. Had the equilibrium constant calculated from thermodynamics been small, this proposed application would be doomed at the outset and investment in it would not be justified. 

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