固定pH滴定法测定弱酸性药物盐酸普鲁卡因

Determination of Procainum Hydrochloride by pH－fzxed Titration

本文报道了一种水溶液中测定弱酸性药物的固定ｐＨ滴定法．它以弱酸在水溶液中各 种存在形式的分布系数与ｐＨ值的关系为理论依据，不要求滴定反应定量完成，是利用滴定到一定 ｐＨ值时滴定剂消耗体积与弱酸物质的量之间的正比关系进行定量分析，应用该法测定弱酸性药 物盐酸普鲁卡因，结果与药典一致，回收率在９９.６ ％～１００．３％，试液低至 ５×１０－４ｍｏＶＬ，也可用该 法准确测定．本法操作简便、快速、制剂中的赋形剂及有色物无干扰．

A simple, rapid and accurate titration method in aqueous sotutuin for weak acidic and drugs,pH-fixed titration, is reported. It is based on the fact that the distribution coefficients of various species of a weak acid or base in aqueous sotution are constants at a fixed pH value. During the titration, the volume of the titrant consumed to reach a certain pH value is proportional to the amount of the weak acid or base in the solution. It is not necessary to ascertain the equivalent point and to know the concentration of the titrant. The method has been used to determine procainum hydrochloride with rery satisfactory results .The acid dissociation constant of the drug determined is 2 X 10-9.