Novel spectrofluorimetric quantification of linagliptin in biological fluids exploiting its interaction with...

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.