Repeated separation path

With capillary electrophoresis (CE), another modern primarily analytically oriented separation methodology has recently found its way into routine and research laboratories of the pharmaceutical industries. As the most beneficial characteristics over HPLC separations the extremely high efficiency leading to enhanced peak capacities and often better detectability of minor impurities, complementary selectivity profiles to HPLC due to a different separation mechanism as well as the capability to perform separations faster than by HPLC are frequently encountered as the most prominent advantages. On the negative side, there have to be mentioned detection sensitivity limitations due to the short path length of on-capillary UV detection, less robust methods, and occasionally problems with run-to-run repeatability. Nevertheless, CE assays have now been adopted by industrial labs as well and this holds in particular for enantiomer separations of chiral pharmaceuticals. While native cyclodextrins and their derivatives, respectively, are commonly employed as chiral additives to the BGEs to create mobility differences for the distinct enantiomers in the electric field, it could be demonstrated that cinchona alkaloids [128-130] and in particular their derivatives are applicable selectors for CE enantiomer separation of chiral acids [19,66,119,131-136]. 

The material is placed on the top of an inclined plane containing a series of holes. Prisms in the path of the stream fraction the powder some falls into the holes and is discarded while the rest carries onto the next set of prisms and holes and the process is repeated. The powder that remains at the bottom of the plane is the sample. The initial feed must be uniformly distributed and after each separation must be a complete mix because of the errors occurring. There is a very low accuracy with this technique. ... 

Figure 10 (a) The origin of Bragg s law. The X-ray waves of wavelength A are reflected at an angle 0 from successive planes of equivalent atoms, separated by a lattice repeat d. (b) For constructive interference to take place between the waves reflected the path length difference AB + BC needs to be a multiple of the wavelength. This is true when 2d sin 6=nX. 

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