Central composite design based RP-HPLC method optimization for the synchronized analysis of Efonidipine Hydrochloride Ethanolate (EFE) and Chlorthalidone (CHL) in tablet. The effective separation was performed using Inertsil ODS C18 column (250 × 4.6 mm, 5 μm), PDA detector with 0.05 M KH2PO4 Buffer (pH 4.5): Acetonitrile (40:60%v/v) mobile phase. Independent variables were investigated include the concentration of KH2PO4 (X1) and flow rate of mobile phase (X2). Based on responses obtained (retention time, resolution and tailing factor), the optimum condition selected was X1 = 40% and X2 = 1 ml/min. Optimized HPLC condition was validated by assessing validation parameters and it meets the acceptance criteria set by ICH. The linear calibration curve was found to be in the quantity range 6.25–18.75 and 20–60 μg/ml Assay of drugs was 100.94 and 100.06% for CHL and EFE. The validated RP-HPLC-PDA method can be used for routine analysis of EFE and CHL in tablet.

中文翻译：

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中心复合设计专家支持的 RP-HPLC 优化和片剂中盐酸依福地平乙醇盐和氯噻酮的定量评价

基于中心复合设计的 RP-HPLC 方法优化，用于同步分析片剂中盐酸依福地平乙醇盐 (EFE) 和氯噻酮 (CHL)。使用 Inertsil ODS C18 柱 (250 × 4.6 mm, 5 μm)、PDA 检测器和 0.05 M KH2PO4 缓冲液 (pH 4.5): 乙腈 (40:60%v/v) 流动相进行有效分离。研究的自变量包括 KH2PO4 浓度 (X1) 和流动相流速 (X2)。根据获得的响应（保留时间、分辨率和拖尾因子），选择的最佳条件是 X1 = 40% 和 X2 = 1 ml/min。通过评估验证参数对优化的 HPLC 条件进行了验证，它符合 ICH 设定的验收标准。发现线性校准曲线的数量范围为 6.25–18.75 和 20–60 μg/ml。CHL 和 EFE 的药物含量分别为 100.94 和 100.06%。经过验证的 RP-HPLC-PDA 方法可用于片剂中 EFE 和 CHL 的常规分析。