Application of redox reactions for the determination of valganciclovir hydrochloride in pharmaceuticals

Two simple, selective and sensitive spectrophotometric methods were developed and validated for the determination of valganciclovir hydrochloride (VLGH) in pure drug and tablets. The first method was based on the reduction of iron(III) to iron(II) by VLGH and subsequent formation of iron(III)-ferricyanide complex (Prussian blue) in acid medium which was measured at 730 nm (method A). In the second method (method B), permanganate was reduced by VLGH to bluish green manganate in alkaline medium and the absorbance was measured at 610 nm. The absorbance measured in each case was related to VLGH concentration. The experimental conditions were carefully studied and optimized. Beer’s law was obeyed over the concentration ranges of 2.5-20.0 and 2.0-40.0 µg mL-1 for method A and method B, respectively, with corresponding molar absorptivity values of 1.28×104 and 6.88×103 L mol-1 cm-1. The limits of detection (LOD) and quantification (LOQ) were 0.11 and 0.33 µg mL-1 (method A) and 0.21 and 0.64 µg mL-1 (method B). Within-day and between-day relative standard deviations (%RSD) at three different concentrations levels were < 2.4%, and the respective relative errors (%RE) were ≤ 3%. The proposed methods were successfully applied to the determination of VLGH in tablets, and the results confirmed that the proposed methods were equally precise and accurate as the official method.

本研究建立并验证了两种简便、选择性佳且灵敏度高的分光光度法，用于测定原料药与片剂中的盐酸缬更昔洛韦（valganciclovir hydrochloride, VLGH）。第一种方法（方法A）基于盐酸缬更昔洛韦将三价铁还原为二价铁，随后在酸性介质中形成三价铁-铁氰化物络合物（普鲁士蓝，Prussian blue），于730 nm波长处测定其吸光度；第二种方法（方法B）则利用盐酸缬更昔洛韦在碱性介质中将高锰酸盐还原为蓝绿色锰酸盐，于610 nm波长处测定吸光度。两种方法的吸光度值均与盐酸缬更昔洛韦浓度呈线性相关。研究人员对实验条件进行了系统优化与细致考察。方法A与方法B的比尔定律（Beer’s law）线性范围分别为2.5~20.0 μg·mL⁻¹与2.0~40.0 μg·mL⁻¹，对应的摩尔吸光系数分别为1.28×10⁴与6.88×10³ L·mol⁻¹·cm⁻¹。方法A的检测限（LOD）与定量限（LOQ）分别为0.11 μg·mL⁻¹与0.33 μg·mL⁻¹，方法B则分别为0.21 μg·mL⁻¹与0.64 μg·mL⁻¹。在三个不同浓度水平下，方法的日内与日间相对标准偏差（%RSD）均小于2.4%，对应的相对误差（%RE）均不超过3%。所建立的两种方法已成功应用于片剂中盐酸缬更昔洛韦的含量测定，结果表明本方法与官方药典方法相比，具有相当的精密度与准确度。