Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria.
Acta Pharm. 2009 Dec;59(4):407-19. doi: 10.2478/v10007-009-0039-2.
A new approach to the spectrophotometric determination of metronidazole (MZ) and tinidazole (TZ) has been developed. The procedure involves coupling of diazotized nitroimidazoles with p-dimethylaminobenzaldehyde (DMAB) to form a greenish-yellow solution. Optimal temperature and time were 0 degrees C (iced) and 3 minutes for diazotization and 30 degrees C and 2 minutes for coupling for both MZ and TZ. Coloured adducts of MZ and TZ showed shoulders at 406 nm and 404 nm, respectively, which were selected as analytical wavelengths. The reaction with p-DMAB occurred in a 1:1 mole ratio. Beer's law was obeyed within the 4.8-76.8 microg mL(-1) concentration range with low limits of detection. The azo adducts were stable for over a week. Molar absorptivities were 1.10 x 10(3) (MZ) and 1.30 x 10(3) L mol(-1) cm(-1) (TZ). Overall recoveries of MZ and TZ from quality control samples were 103.2 + or - 1.3 and 101.9 + or - 1.3% over three days. There was no interference from commonly utilized tablet excipients. No significant difference was obtained between the results of the new method and the BP titrimetric procedures. The azo approach using the p-dimethylaminobenzaldehyde procedure described in this paper is simple, fast, accurate and precise. It is the first application of DMAB as a coupling component in the diazo coupling reaction.
已开发出一种测定甲硝唑（MZ）和替硝唑（TZ）的分光光度新方法。该方法涉及将亚硝化硝基咪唑与对二甲氨基苯甲醛（DMAB）偶联，形成黄绿色溶液。最佳温度和时间分别为 0°C（冰浴）和 3 分钟用于亚硝化，30°C 和 2 分钟用于 MZ 和 TZ 的偶联。MZ 和 TZ 的有色加合物在 406nm 和 404nm 处分别显示肩峰，分别选择为分析波长。与 p-DMAB 的反应以 1:1 的摩尔比发生。在 4.8-76.8μgmL(-1)浓度范围内，遵守比尔定律，检测限低。偶氮加合物在一周以上的时间内稳定。MZ 的摩尔吸光系数为 1.10×10(3)（MZ）和 1.30×10(3)Lmol(-1)cm(-1)（TZ）。MZ 和 TZ 从质控样品中的总回收率在三天内分别为 103.2±1.3%和 101.9±1.3%。常用片剂赋形剂无干扰。新方法与 BP 滴定法的结果无显著差异。本文描述的使用对二甲氨基苯甲醛的偶氮方法简单、快速、准确、精密。这是 DMAB 首次作为偶联反应中的偶联成分。
