Quantitative polarimetry

It is worth noting that quantitative data on the rate of enolization could be obtained by polarimetry measurements since optically active thiazoline-5-ones are now available. 

Polarimetry is defined as the quantitative measurement of a change in the direction of the vibration of plane-polarized light during its passage through an optically anisotropic substance or its solution33. 

The quantitative analysis of Chincona bark by the classical methods of titrimetry, gravimetry, and polarimetry has been performed for many years in order to ascertain its commercial value. These compounds have been analyzed by GC, GC-MS, TLC, and mainly HPLC (353-361) with UV or electrochemical detection. Ion-pair HPLC was also used with UV or fluorescence detection by Jeuring et al. (357). Photoreactions of Qn in aqueous citric acid solution have been studied by Laurie et al. (358). After isolation of the components by HPLC and TLC, different spectroscopic techniques (MS, NMR, IR) were used to identify the photoproducts. 

While rheological measurements are wonderfully quantitative, they are usually poor qualitative probes of fluid structure. This is because in rheological experiments, the structural changes responsible for the measured relaxation behavior remain hidden. Thus, rheometry is often most useful when supplemented by other experimental methods that characterize fluid structure and flow-induced structural changes. Some of the most useful methods are microscopy, light, x-ray, and neutron scattering, and polarimetry. 

However, inherent in these methods are the assumptions that no chro-mogenic substances, other than adrenaline, are present and that the rotatory power of the solutions is due solely to /-adrenaline which precludes their use for routine testing of samples in which the nature of the other materials present is unknown. For such samples Welsh has produced a method in which the adrenaline is converted quantitatively to the triacetyl derivative which may be determined qualitatively as well as quantitatively by polarimetry, and this method has been adopted by the U.S.P, for Epinephrine Solution, Inhalation, Injection, and Sterile Suspension and Epinephrine Bitartrate Ophthalmic Ointment. It is described in detail under Solution of Adrenaline. 

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