Hitit University, Faculty of Science and Arts, Dept. of Chemistry, Corum, Turkey.
J Pharm Biomed Anal. 2012 Jul;66:116-25. doi: 10.1016/j.jpba.2012.03.025. Epub 2012 Mar 23.
The detailed electrooxidative behavior of benidipine (BEN) has been studied by using glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Using cyclic voltammetry, depending on the pH values and the working electrodes, BEN showed one or two sharp and irreversible oxidation responses. The voltammetric experiments on some model compounds allowed elucidation of the oxidation mechanism of BEN. Highly sensitive, selective, rapid, and fully validated voltammetric methods for the determination of BEN in tablet dosage form were also presented. Under optimized conditions, the peak current showed a linear dependence with concentration in the range between 3.25 μg mL(-1) and 54.20 μg mL(-1) for GC and 1.08 μg mL(-1) and 54.20 μg mL(-1) for BDD electrodes by using differential pulse (DPV) and square wave (SWV) voltammetric techniques. In this study, acid dissociation constant (pK(a)) value of BEN was determined by using the dependence of the retention factor on the pH of the mobile phase using reverse phase-liquid chromatographic (RP-LC) method. The effect of the composition of the mobile phase on the ionization constant was studied by measuring the pK(a) at different acetonitrile-water mixtures, ranging between 50 and 65% (v/v). Also simple, accurate, precise and fully validated RP-LC method for the assay of BEN in dosage form has been developed. XTerra RP-18 column at 25 °C with the mobile phase of acetonitrile:water 55:45 (v/v) adjusted to pH 3.0 with 15 mM o-phosphoric acid was used. Isocratic elution was performed in less than 5.0 min with a flow rate of 1.0 mL min(-1). The RP-LC method allowed quantitation over the 0.25-15.00 μg mL(-1) range for BEN. The proposed voltammetric and RP-LC methods allow a number of cost and time saving benefits. BEN was also exposed to thermal, photolytic, oxidative stress, acid-base catalyzed hydrolyses, and the stressed samples were detected by the proposed RP-LC method.
本文使用玻碳电极和掺硼金刚石电极研究了比尼地平（BEN）的详细电氧化行为。通过循环伏安法，根据 pH 值和工作电极，BEN 显示出一个或两个尖锐且不可逆的氧化响应。对一些模型化合物的伏安实验阐明了 BEN 的氧化机制。还提出了用于测定片剂中 BEN 的高度灵敏、选择性、快速和完全验证的伏安方法。在优化条件下，峰电流在 GC 和 BDD 电极上，对于 DP 和 SW 伏安技术，在 3.25μg mL(-1)至 54.20μg mL(-1)之间和 1.08μg mL(-1)至 54.20μg mL(-1)之间，与浓度呈线性关系。在这项研究中，使用反相液相色谱 (RP-LC) 法，通过保留因子随流动相 pH 的变化来确定 BEN 的酸离解常数 (pK(a)) 值。通过测量不同乙腈-水混合物（50%至 65%，v/v）的离解常数来研究流动相组成对离解常数的影响。还开发了用于测定制剂中 BEN 的简单、准确、精密和完全验证的 RP-LC 方法。在 25°C 下，使用 XTerra RP-18 柱，流动相为乙腈：水 55:45（v/v），用 15 mM 邻磷酸调至 pH 3.0。以 1.0 mL min(-1)的流速进行等度洗脱，不到 5.0 min 即可完成。RP-LC 法允许 BEN 在 0.25-15.00μg mL(-1)范围内进行定量。所提出的伏安法和 RP-LC 法可节省大量成本和时间。还通过所提出的 RP-LC 方法检测了 BEN 暴露于热、光解、氧化应激、酸碱催化水解后的样品。
