Microionization constants: novel approach for the determination of the zwitterionic equilibrium of hydroxyphenylalkylamines by photometric titration

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• 作者：Peinhardt ; Gü ; nter ; Wiese ; Michael
• 关键词：Etilefrine ; Isoxsuprine ; Oxedrine ; Pholedrine ; Tyramine
• 刊名：International Journal of Pharmaceutics
• 出版年：2001
• 出版时间：March 14, 2001
• 年：2001
• 卷：215
• 期：1-2
• 页码：83-89
• 全文大小：113 K

文摘

The record of the formation of the phenolate and the zwitterionic form in the course of titration by photometry makes it possible to estimate the tautomeric equilibrium, K_Z, between the zwitterionic and the uncharged form of an ampholyte, provided that (1) the absorptivity of the phenolate and the zwitterionic form are identical and (2) the absorptivities of both forms are distinct from the absorptivities of the protonated and the uncharged form. The relation between the absorbance and K_Z, the degree of titration and the degree of overlapping of the basic and the acid ioinization constant is given.