Analytical Chemistry Department, Faculty of Pharmacy, Al-Azhar University (Girls), Cairo, Egypt; Pharmaceutical Chemistry Department, Faculty of Pharmacy, Badr University in Cairo (BUC), Badr City, Cairo, Egypt.
Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Kafrelsheikh University, Kafrelsheikh City, Egypt.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Oct 5;203:112-117. doi: 10.1016/j.saa.2018.05.064. Epub 2018 May 16.
The limited linear range of UV-Visible spectrophotometry may be insufficient to occupy multiple components with wide variations in their concentrations or absorptivities that will hinder the simultaneous spectrophotometric determination and may require spiking or measurements in subsequent dilution steps. The current work introduces the absorptivity target concentration (ATC) values, a simple way for the proper choice of the working spectral region to execute accurate and linear spectrophotometric measurements. Simultaneous spectrophotometric determination of linagliptin (LNG) and metformin (MET) that are present in a ratio of 1:400 was carried out using traditional spectrophotometric techniques such as third derivative and derivative ratio as well as recently developed techniques such as ratio difference and factorized dual wavelength. The proposed methods were able to determine MET in the concentration range of 50-1200 μg mL. On the other hand, LNG was successfully determined from its zero-order absorption UV-spectrum at λ (296 nm) in the concentration range 2.5-25 μg mL. The mentioned methods were successfully applied for the determination of the LNG and MET in their combined dosage form. The methods were validated according to the ICH guidelines. The proposed ATC value can be employed as a novel concept for the proper choice of the working spectral region where spectrophotometric measurements can be deployed accurately and precisely.
紫外可见分光光度法的线性范围有限，可能不足以同时测定浓度或吸光度差异较大的多个成分，这将阻碍同时分光光度法的测定，可能需要进行加标或后续稀释步骤的测量。本工作引入了吸光度目标浓度（ATC）值，这是一种选择适当工作光谱区域进行准确和线性分光光度测量的简单方法。采用传统分光光度技术，如三阶导数和导数比，以及最近开发的技术，如比值差和双波长因子化，对 1:400 比例存在的利格列汀（LNG）和二甲双胍（MET）进行同时分光光度测定。所提出的方法能够在 50-1200μg/mL 的浓度范围内测定 MET。另一方面，LNG 可以在 2.5-25μg/mL 的浓度范围内通过其零阶吸收 UV 光谱在 λ（296nm）处成功测定。所提到的方法成功地应用于其组合剂型中 LNG 和 MET 的测定。该方法根据 ICH 指南进行了验证。所提出的 ATC 值可用作选择适当工作光谱区域的新概念，在该区域可以准确和精确地进行分光光度测量。
