固定pH滴定法测定弱酸弱碱性药物

Fixed pH Titration Method for Weakly Acidic and Basic Drugs

报道一种水溶液中测定弱酸弱碱性药物的新型滴定分析方法——固定ｐＨ滴定法。其理论基础是弱酸弱碱在水溶液中各种存在形式的分布系数在ｐＨ值固定时为常数。对甲硝唑、盐酸美西律等离解常数在１０－８至１０－１１范围内的７种弱酸弱碱性药物进行测定，结果与药典法吻合，回收率在９９．４％～１００．６％。方法简便、快速、准确，制剂中的赋形剂及有色物不影响测定。

A novel titration method in aqueous solution,fixed pH titration,for weakly acidic and basic drugs is presented .It is based on the fact that the distribution coefficients of various species of weak acid or base are constant at a fixed pH value.It is not necessary to ascertain the equivalent point of titration and to know the concentration of the titrant.The method has been used to determin metronidazole,cimetidine,and five hydrochlorides of mexiletine,amitriptyline,chlorpromazine,levamisole and diphenhydramine with very satisfactory results.The acid or base dissociation constants of these drugs range from 10 -8 to 10 -11