Golabi S M, Showkati-Shishevan M
Electroanalytical Chemistry Laboratory, Faculty of Chemistry, University of Tabriz, Tabriz,Iran.
Talanta. 1991 Nov;38(11):1253-6. doi: 10.1016/0039-9140(91)80101-5.
The potentiometric titration of some phenothiazine drugs in chloroform is described. A standard solution of bromine in chloroform was used as titrant and the end-points were detected with a small platinum indicator electrode, and an Ag/AgCl electrode in 0.01M Et(4)NCl in chloroform as reference. A fast redox reaction occurs during the titrations and the phenothiazine ring is oxidized to the phenothiazonium free radical (P(+)). The low dielectric constant of the medium favours the formation of (P(+)Br(-)) ion-pairs or (P(+)Br(-)(3)) ion-pairs on further addition of bromine, which has no influence on the position of the first end-point. The method was used for the determination of promethazine, chlorpromazine, trifluoperazine and thioridazine in pharmaceutical preparations after extraction into chloroform. The relative standard deviation for the determination of 5 mg of all these phenothazines was about 1%.
描述了一些吩噻嗪类药物在氯仿中的电位滴定法。以氯仿中的溴标准溶液作为滴定剂，用一个小的铂指示电极和一个置于0.01M四乙基氯化铵的氯仿溶液中的Ag/AgCl电极作为参比电极来检测终点。滴定过程中发生快速氧化还原反应，吩噻嗪环被氧化为吩噻嗪鎓自由基（P(+)）。介质的低介电常数有利于在进一步加入溴时形成（P(+)Br(-)）离子对或（P(+)Br(-)₃）离子对，这对第一个终点的位置没有影响。该方法用于在将药物制剂萃取到氯仿中后测定其中的异丙嗪、氯丙嗪、三氟拉嗪和硫利达嗪。测定5mg所有这些吩噻嗪类药物的相对标准偏差约为1%。
