Capillary electrophoresis is a new analytical technique that has seen a great upswing in recent years, because this adaptation of electrophoresis may be automated and simple, direct quantification is possible. As in conventional electrophoresis, samples with a large range of molecular weights, from inorganic ions to biopolymers such as DNA and proteins, can be separated. Uncharged molecules can also be separated when micelle-forming detergents are added to the buffer; the distribution mechanism that then comes into play increases the separation efficiency of this micellar electrokinetic chromatography. Chiral additives such as cyclodextrins make the separation of enantiomers possible. The rapid increase in the popularity of capillary electrophoresis is reflected in instrument sales and the growing number of scientific publications dealing with the method, and it seems that the future of this technique is assured.
Reaction of glycine methyl ester (19) with imidate 18 under carefully optimized conditions allowed preparation of the rather unstable imidazolinone 11 in ca. 90% yield. Reaction of 11 with POCl(3)/DMF followed by aqueous workup gave aldehyde 2, a key intermediate for the synthesis of the angiotensin II antagonist Losartan, in ca. 55% yield. Structural identification of intermediates and byproducts formed during both the reaction to prepare 11 and the reaction of 11 with POCl(3)/DMF allowed development of several closely related syntheses of aldehyde 2.
Abstract. With uncoated fused silica capillaries, the electroosmotic flow and its contribution to solute migration are in part responsible for problems with the reproducibility of migration time due to hysteresis effects. In transferring coating procedures from silica to capillary surfaces, it has been possible to prepare stable polymeric coatings where hysteresis effects are negligible. Acrylamide coatings reduce the electroosmotic flow. A pH independent flow could be achieved with bonded cation exchange groups. With bonded anion exchangers, reversal of electroosmotic flow is possible.
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