Abbe refractometry

Fig. 12.4 Continuous dilution differential refractometric data for the C6H12/C6D12 isotopomer pair at 298.15 K. (a) through (d) are interferograms observed at 650, 559, 520 and 470 nm, respectively. (e) shows refractive index differences derived from the interferograms left to right 650, 559, 520 and 470 nm) and (f) is a dispersion plot of the data. In (f) the interferometric data are compared with the result at 589.3 nm obtained by Abbe refractometry, which nicely illustrates the better precision of CDDR (Reprinted from Wieczorek, S. A., Urbanczyk, A. and Van Hook. W. A., J Chem. Thermodyn. 28, 1009 (1996) copyright 1996 with permission from Elsevier)...

These are properties, such as the pH of an aqueous solution, melting point/range, and refractive index. The procedures used for the measurement of these properties are usually unique and do not need much elaboration, for example, capillary melting point and Abbe refractometry. The tests performed in this category should be determined by the physical nature of the new drug substance and its intended use. 

Refractometry can be used to determine the composition of a copolymer. In addition, differential refractometry has been used to study micellization in dilute block copolymer solutions (Tfizar and Kratochvfl 1972). The refractive index (n) is obtained in an Abbe refractometer via measurements of the critical angle for external reflection. The refractive index increment dn/dc, where c is the polymer concentration, can be related to the molecular weight of particles in solution. Further details of the method are provided by Pepper and Samuels (1989). 

One of the most important requirements for reproducible lipoprotein analysis is the accurate manipulation and monitoring of solvent densities. Since the lipoprotein fractionation utilized here involves the use of the monovalent salts NaCl and NaBr, the ability to control accurately and measure conveniently these salt-solution densities is essential. It is recommended, therefore, that both an absolute and relative method for density measurement, utilizing pycnometry (6) and precision refractometry (7, 8), respectively, be employed, A precision Abb sugar refractometer (Bausch and Lomb, Rochester, N.Y.), with a range of n from 1.203 to 1.508 operated above room temperature and temperature-controlled to 0.05°C, is extremely well suited for this latter work. 

An Abbe refractometer with a rotable polarizer was used. For the liquid-crystalline blend solutions, the ordinary refractive index ( <,) and the extraordinary refractive index rig) were observed. Birefringence in this study was defined as the difference between n and rig. Further details of the refractometry have been described elsewhere [52]. 

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