Laboratory of Analytical Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, University of Liege, Liège, Belgium.
J Pharm Biomed Anal. 2011 Mar 25;54(4):687-93. doi: 10.1016/j.jpba.2010.10.020. Epub 2010 Oct 30.
Ropivacaine is the first enantiomerically pure long-acting local anaesthetic used for surgical anaesthesia and post-operative pain relief. A liquid chromatographic (LC) method using acetonitrile as the main solvent and cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica as chiral stationary phase was successfully developed and applied for the enantiomeric purity determination of S-ropivacaine in a pharmaceutical formulation (Naropin(®)). The key role played by the acidic additive (trifluoroacetic acid or formic acid) in the enantioseparation of basic drugs in these LC systems was demonstrated by the reversal of ropivacaine enantiomers elution order observed when both acids were compared. In order to elute the enantiomeric impurity (R-ropivacaine) before S-ropivacaine, formic acid (FA) was selected. The temperature and the percentages of acidic additive and hexane in the mobile phase were found to significantly influence the retention and resolution of these enantiomers. The optimized mobile phase consisted of ACN/0.1% DEA/0.2% FA/5% hexane (v/v/v/v). The temperature was set at 35°C to avoid the interference from a peak system related to the presence of water in the sample on ropivacaine enantiomers. The LC method was then fully validated applying the strategy based on total measurement error and accuracy profiles. The accuracy profile obtained by linear regression after square root transformation was selected, the acceptance limits being settled at ±10% for the intended use of this analytical method. The relative bias was lower than 1.5%, while the RSD values for repeatability and intermediate precision were both below 1.0%. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be about 0.2 and 1.0 μg/mL, respectively, corresponding to 0.02 and 0.1% of the enantiomeric impurity in S-ropivacaine.
罗哌卡因是第一种用于手术麻醉和术后止痛的手性纯长效局部麻醉剂。本文建立了一种使用乙腈为主要溶剂、纤维素三（4-氯-3-甲基苯基碳酸酯）涂覆在硅胶上作为手性固定相的高效液相色谱（LC）方法，并成功地应用于测定一种药物制剂（Naropin（®））中 S-罗哌卡因的对映体纯度。研究结果表明，在这些 LC 系统中，酸性添加剂（三氟乙酸或甲酸）在手性药物对映体拆分中起着关键作用，通过比较两种酸，可以观察到罗哌卡因对映体洗脱顺序的反转。为了在 S-罗哌卡因之前洗脱对映体杂质（R-罗哌卡因），选择了甲酸（FA）。结果发现，温度、流动相中酸性添加剂和正己烷的百分比显著影响这些对映体的保留和分离。优化的流动相由 ACN/0.1%DEA/0.2%FA/5%正己烷（v/v/v/v）组成。为了避免样品中水分对罗哌卡因对映体的干扰，将温度设定在 35°C。然后，根据总测量误差和准确度轮廓图，对 LC 方法进行了全面验证。选择了经过平方根变换后的线性回归得到的准确度轮廓图，接受限设定为±10%，以满足该分析方法的预期用途。相对偏差低于 1.5%，重复性和中间精密度的 RSD 值均低于 1.0%。检测限（LOD）和定量限（LOQ）分别约为 0.2 和 1.0 μg/mL，相当于 S-罗哌卡因中对映体杂质的 0.02%和 0.1%。
