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本文研究在两种质子化状态存在时奎宁的电极行为与特点,证明在不同pH溶液中变价态奎宁电极电位不能直接用能斯脱公式或Nicolsky-Eisenman公式表出。提出了变价态电极的S-δ经验式,并依据此式,用奎宁选择性电极测出20℃下I=0.5 Mc Ilvaine缓冲液中双质子化奎宁、辛可宁、硫胺的K_(al)分别为(8.37±0.96)×10~(-5),(8.00±0.92)×10~(-5)。(8.37±0.96)×10~(-6)。指出:同系列溶剂介电常数增大,液膜电极斜率增大,存在S-1/ε线性关系。电极可用于奎宁的电位滴定法或直接电位法测定。
In this paper, the electrode behavior and characteristics of quinine in the presence of two protonated states are investigated. It is shown that the quinine electrode potential in variable pH solutions can not be directly expressed by the Nernst equation or the Nicolsky-Eisenman equation. In this paper, the S-δ empirical formula of the variable-value electrode was proposed. Based on this formula, the K_ (al) of di-protonated quinine, cinchonine and thiamine in I = 0.5 Mc Ilvaine buffer solution at 20 ℃ was measured with quinine selective electrode ) Were (8.37 ± 0.96) × 10 -5 and (8.00 ± 0.92) × 10 -5, respectively. (8.37 ± 0.96) × 10 ~ (-6). It is pointed out that the dielectric constant of the same series of solvents increases and the slope of the liquid film electrode increases with the linear relationship of S-1 / ε. The electrode can be used for the quinine potentiometric titration or direct potentiometry.