Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt.
Pharmaceutical Chemistry Department, National Organization for Drug Control and Research (NODCAR), Giza, Egypt.
Luminescence. 2020 Aug;35(5):728-737. doi: 10.1002/bio.3778. Epub 2020 Jan 28.
A novel approach on fluorescence quenching of tyrosine and l-tryptophan is presented for spectrofluorimetric determination of aniracetam in drug substances and products. The quenching mechanism was investigated using Stern-Volmer plots and ultraviolet spectra figures of quencher-fluorophore mixtures. Binding constant and stoichiometry were calculated using double-log plots. The spectrofluorimetric method was optimized for the experimental conditions affecting fluorescence quenching including fluorophore concentration, diluent, and reaction time. Moreover, the pH-rate profile of aniracetam was studied using simple kinetics and found to be stable within the pH range 5-8. Fluorescence quenching of tyrosine and l-tryptophan were observed on addition of aniracetam in aqueous medium at pH 5.5-6.5. Aniracetam quenched the fluorescence of tyrosine and l-tryptophan in the concentration range 1-20 μg/ml and 0.3-20 μg/ml, respectively, with binomial relationships between quenching values (ΔF) and aniracetam concentration. Limits of detection were found to be 0.10 μg/ml for tyrosine-aniracetam and 0.14 μg/ml for l-tryptophan-aniracetam. Method validation was performed as per ICH guidelines and demonstrated that the developed spectrofluorimetric method was accurate, precise, specific, and suitable for analysis of aniracetam in routine quality control laboratories. All experimental materials and solvents used are eco-friendly, indicating that the cited spectrofluorimetric procedure is an excellent green method.
一种新颖的酪氨酸和 l-色氨酸荧光猝灭方法被提出，用于在原料药和制剂中测定安理申。通过 Stern-Volmer 图和猝灭剂-荧光团混合物的紫外光谱图研究了猝灭机制。使用双对数图计算了结合常数和化学计量比。优化了荧光猝灭实验条件下的光谱荧光法，包括荧光团浓度、稀释剂和反应时间。此外，还使用简单动力学研究了安理申的 pH-速率曲线，并发现其在 pH 5-8 范围内稳定。在 pH 5.5-6.5 的水介质中加入安理申时，观察到酪氨酸和 l-色氨酸的荧光猝灭。安理申在 1-20 μg/ml 和 0.3-20 μg/ml 的浓度范围内猝灭酪氨酸和 l-色氨酸的荧光，猝灭值（ΔF）与安理申浓度之间存在二项式关系。对于酪氨酸-安理申，检测限为 0.10 μg/ml，对于 l-色氨酸-安理申，检测限为 0.14 μg/ml。方法验证符合 ICH 指南，表明所开发的光谱荧光法准确、精密、特异，适用于常规质量控制实验室中安理申的分析。所用的实验材料和溶剂均为环保型，表明所引用的光谱荧光法是一种极好的绿色方法。
