A sensitive and green spectrofluorimetric method for determination of guanfacine hydrochloride based on NBD-Cl derivatization

Abstract

A sensitive and environmentally friendly spectrofluorimetric method was developed for the determination of guanfacine in pharmaceutical formulations. The method is based on derivatization of guanfacine with 4-chloro-7-nitrobenzofurazan in alkaline medium to yield a highly fluorescent product measured at 535 nm after excitation at 466 nm. Experimental conditions affecting the reaction were systematically optimized to achieve maximum fluorescence intensity. The method exhibited excellent linearity over the concentration range of 50–500 ng/mL with a correlation coefficient of 0.9994. The limits of detection and quantitation were found to be 13.80 and 41.82 ng/mL, respectively, indicating high sensitivity. The method was validated in accordance with ICH guidelines and demonstrated satisfactory accuracy, precision, robustness, and selectivity. It was successfully applied to the analysis of guanfacine in commercial tablet formulations without interference from excipients. Greenness assessment using Analytical Eco-scale and AGREE tools confirmed the environmentally benign nature of the method, achieving a high Eco-scale score of 89 and an AGREE score of 0.68. Compared with a reported method, the proposed approach offers improved sensitivity and superior environmental benignity, making it suitable for routine quality control analysis.