Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta University, 31111, Egypt; Australian Centre for Research on Separation Science (ACROSS), School of Chemistry, University of Tasmania, Private Bag 75, 7001 Tasmania, Australia.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Jan 5;188:626-632. doi: 10.1016/j.saa.2017.07.066. Epub 2017 Jul 31.
A new innovative spectrophotometric method is developed to determine the concentration ratios in binary mixtures by determining the zero crossing point in the first derivative of the gross curve. This relationship can be applied if the part of the UV spectrum of substance Y, that intersects with the overlaid spectra of substance X is straight. By plotting the intersection wavelength against the concentration ratio (CC), a straight line was obtained with a co-efficient of determination equals 0.9999. As an application, simultaneous determination of sofosbuvir and ledipasvir in their binary mixtures was performed using two methods; a direct UV spectrophotometric method for determination of ledipasvir at 333nm, and the new "wavelength-intersection ratio" method for determination of sofosbuvir. In the wavelength-intersection ratio method, different mixtures of sofosbuvir and ledipasvir containing different concentration ratios were prepared; the zero crossing point of the first derivative curve in the range 285 to 295nm were determined for each mixture. An absorbance shift in the intersection was obtained with the change in the concentration ratio (sofosbuvir/ledipasvir). When the concentration ratio was plotted against the intersection wavelength, a straight line was obtained with a coefficient of determination of 0.9992. The direct method was linear in the range 3 to 18μg/mL while the wavelength-intersection ratio method was linear in the range 11-110μg/mL. The limits of detection were determined and found to be 0.5 and 3μg/mL for ledipasvir and sofosbuvir, respectively. The accuracy and repeatability of the two methods were tested. The mean %recovery was found to be 100.19% and 100.75% for ledipasvir and sofosbuvir, respectively. The relative standard deviation was 0.57 for ledipasvir and 1.79 for sofosbuvir. The intermediate precision was also checked, the coefficients of variation for sofosbuvir and ledipasvir measurements between days did not exceed 1.88%.
一种新的创新分光光度法是通过确定总曲线一阶导数的过零点来确定二元混合物中浓度比的。如果物质 Y 的紫外光谱的一部分与物质 X 的重叠光谱相交是直线，则可以应用这种关系。通过绘制交点波长与浓度比（CC）的关系，得到一条直线，其决定系数等于 0.9999。作为应用，使用两种方法同时测定其二元混合物中的索非布韦和雷迪帕韦；一种直接紫外分光光度法用于测定 333nm 处的雷迪帕韦，以及新的“波长交点比”法用于测定索非布韦。在波长交点比法中，制备了含有不同浓度比的不同索非布韦和雷迪帕韦的混合物；确定了每个混合物在 285 至 295nm 范围内一阶导数曲线的零交点。随着浓度比（索非布韦/雷迪帕韦）的变化，在交点处获得了吸光度偏移。当浓度比与交点波长作图时，得到一条决定系数为 0.9992 的直线。直接法在 3 至 18μg/mL 范围内呈线性，而波长交点比法在 11 至 110μg/mL 范围内呈线性。确定了检测限，发现雷迪帕韦和索非布韦的检测限分别为 0.5 和 3μg/mL。测试了两种方法的准确性和重复性。雷迪帕韦和索非布韦的平均回收率分别为 100.19%和 100.75%。雷迪帕韦的相对标准偏差为 0.57，索非布韦的为 1.79。还检查了中间精密度，索非布韦和雷迪帕韦测量值之间的日内变异系数不超过 1.88%。
