A New Fluorescence Probe for the Quantification of Acetylcysteine and Carbocisteine in Bulk and Spiked Urine: Greenness Appraisal by Exploiting Different GAC‐Metric Strategies

Herein, a novel spectrofluorometric sensor is proposed for the sensitive analysis of two nonfluorescent mucolytic drugs, namely, acetylcysteine (ACT) and carbocisteine (CST), utilizing the newly synthesized 2-[(2-hydroxyethyl)-(2,8,10-trimethylpyrido[2',3':3,4]pyrazolo[1,5-a]pyrimidin-4-yl)-amino]-ethanol as a fluorescence probe (Flu. Probe). This fluorophore exhibits fluorescence emission at 445 nm upon excitation at 275 nm. The addition of increasing concentrations of each drug resulted in quantitative quenching of the Flu. Probe's fluorescence. Investigation into the quenching mechanism revealed that static quenching is the primary contributing factor for both drugs. The spectroscopic characteristics of the Flu. Probe in the presence of ACT and CST were analyzed using DFT and TD-B3LYP calculations, revealing typical π → π* transitions, attributed to stable hydrogen-bonding structures. The developed method was validated in accordance with ICH Q2(R1) guidelines. Linear responses for ACT and CST were observed over concentration ranges 0.125-2.25 and 0.125-3.0 μg/mL, respectively, with detection limits (LODs) 31.97 and 37.14 ng/mL. The proposed spectrofluorometric platform was successfully applied to the analysis of ACT and CST in pharmaceutical dosage forms and spiked urine, within concentration ranges 0.25-2.25 and 0.25-2.50 μg/mL and LODs = 80.21 and 71.48 ng/mL, respectively. Finally, the greenness of the proposed protocol was evaluated employing GAPI, hexagon, and AGREE approaches.