Youssef Nadia Fayek, Taha Elham Anwer
National Organization for Drug Control and Research NODCAR, Cairo, Egypt.
Chem Pharm Bull (Tokyo). 2007 Apr;55(4):541-5. doi: 10.1248/cpb.55.541.
Three reliable, rapid and selective methods have been developed and validated for the determination of lamotrigine in the presence of its impurity, 2,3-dichlorobenzoic acid. The first method is spectrophotometric method using p-chloranilic acid forming a colored product with lambda(max) 519+/-2 nm. All variables affecting the reaction have been investigated and the conditions were optimized. Beer's law was obeyed over a concentration range of 10-200 microg ml(-1) with mean accuracy 100.13+/-0.44%. The molar ratio of the formed ion-association complex is found to be 1 : 1 as deduced by Job's method. The conditional stability constant (K(f)), standard free energy (DeltaG), molar absorptivity(epsilon), and sensitivity index were evaluated. The second method is based on TLC separation of the cited drug (Rf=0.75+/-0.01) from its impurity (Rf=0.23+/-0.01) followed by densitometric measurement of the intact drug spots at 275 nm. The separation was carried on silica gel plates using ethyl acetate : methanol : ammonia 35% (17 : 2 : 1 v/v/v) as a mobile phase. The linearity range was 0.5-10 microg/spot with mean accuracy 99.99+/-1.33%. The third method is accurate and sensitive stability-indicating HPLC method based on separation of lamotrigine from its impurity on a reversed phase C(18) column, using a mobile phase of acetonitrile : methanol : 0.01 M potassium orthophosphate (pH 6.7+/-0.1) (30 : 20 : 50 v/v/v) at ambient temperature 25+/-5 degrees C and UV detection at 275 nm in an overall analysis time of about 6 min., based on peak area. The injection repeatability, intraday and interday repeatability were calculated. The procedure provided a linear response over the concentration range 1-12 microg ml(-1) with mean accuracy of 99.50+/-1.30%. The proposed methods were successfully applied for the determination of lamotrigine in bulk powder, in dosage form and in presence of its impurity. The results obtained were analyzed by ANOVA to assess that no significant difference between each of the three methods and the reported one. The validation was performed according to USP guidelines.
已开发并验证了三种可靠、快速且具选择性的方法，用于在其杂质2,3 - 二氯苯甲酸存在的情况下测定拉莫三嗪。第一种方法是分光光度法，使用对氯苯醌与拉莫三嗪形成λ(max)为519±2 nm的有色产物。研究了影响该反应的所有变量并优化了条件。在10 - 200 μg ml⁻¹的浓度范围内符合比尔定律，平均准确度为100.13±0.44%。通过乔布法推导得出所形成的离子缔合络合物的摩尔比为1 : 1。评估了条件稳定常数(K(f))、标准自由能(ΔG)、摩尔吸光系数(ε)和灵敏度指数。第二种方法基于薄层层析，将所述药物(Rf = 0.75±0.01)与其杂质(Rf = 0.23±0.01)分离，然后在275 nm处对完整药物斑点进行光密度测定。分离在硅胶板上进行，使用乙酸乙酯:甲醇:35%氨水(17 : 2 : 1 v/v/v)作为流动相。线性范围为0.5 - 10 μg/斑点，平均准确度为99.99±1.33%。第三种方法是一种准确且灵敏的稳定性指示高效液相色谱法，基于在反相C₁₈柱上分离拉莫三嗪及其杂质，使用乙腈:甲醇:0.01 M磷酸氢二钾(pH 6.7±0.1)(30 : 20 : 50 v/v/v)作为流动相，在25±5℃的环境温度下，于275 nm处进行紫外检测，基于峰面积，总分析时间约为6分钟。计算了进样重复性、日内和日间重复性。该方法在1 - 12 μg ml⁻¹的浓度范围内提供线性响应，平均准确度为99.50±1.30%。所提出的方法已成功应用于原料药粉末、剂型以及存在其杂质情况下拉莫三嗪的测定。对所得结果进行方差分析以评估三种方法中的每一种与已报道方法之间无显著差异。根据美国药典指南进行了验证。
