Direct determination of linagliptin (LIN) using fluorimetry has been limited because LIN releases a very weak fluorescence signal. Accordingly, it should be derivatized first with a fluorogenic reagent to enhance its fluorescence and consequentially the sensitivity required for its bioanalysis. This is the first description of a spectrofluorimetric method for LIN quantification in human plasma. The suggested method exploits the nucleophilic nature of its amino group to react with 4‐chloro‐7‐nitrobenzofurazan (NBD‐Cl) in borate buffer at pH 8.5 to yield a strong fluorescent product with excitation and emission wavelengths of 459 and 529 nm, respectively. Experimental variables concerning the conditions of reaction and fluorescence intensity were carefully investigated and optimized. The linearity range was from 1.0–100 ng ml⁻¹ with a lower detection limit and a lower quantification limit of 0.60 ng ml⁻¹ and 1.82 ng ml⁻¹, respectively. Validation of the suggested method has been accomplished and the application to LIN analysis in commercial tablets as well as in human plasma resulted in a mean per cent recovery of 100.12 ± 1.57 and 99.65 ± 1.22, respectively. The developed method was proven to be a promising, simple and fast alternative bioanalytical method for LIN quantification in clinical and bioequivalence research.

中文翻译：

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利用其与4-氯-7-硝基苯并呋喃酮的相互作用，对生物液体中的利格列汀进行了新的荧光光谱定量分析。

由于LIN释放出非常弱的荧光信号，因此使用荧光法直接测定linagliptin（LIN）受到了限制。因此，应先用荧光试剂将其衍生化，以增强其荧光性，从而增强其生物分析所需的灵敏度。这是对人血浆中LIN定量的荧光光谱法的首次描述。建议的方法利用其氨基的亲核性质与pH 8.5的硼酸盐缓冲液中的4-氯-7-硝基苯并呋喃（NBD-Cl）反应生成强烈的荧光产物，其激发和发射波长分别为459和529 nm 。仔细研究和优化了有关反应条件和荧光强度的实验变量。线性范围为1.0–100 ng ml^-1的检测下限和定量下限分别为0.60 ng ml ^-1和1.82 ng ml ^-1。所提出方法的验证已经完成，将其应用于商业片剂和人血浆中的LIN分析中，平均回收率分别为100.12±1.57和99.65±1.22。实践证明，所开发的方法是一种在临床和生物等效性研究中用于LIN定量分析的有前途的，简单且快速的替代生物分析方法。