Novel Green Spectrofluorimetric‐Derived Quenching Assay for the Efficient Determination of 3‐Chlorotyrosine Marker of Myeloperoxidase‐Catalyzed Protein Oxidation in Pure Form and Biological Fluids

3-Chlorotyrosine (Cl-Tyr) serves as a distinct biomarker of myeloperoxidase (MPO)-induced protein oxidation. For the first time, this work developed a spectrofluorimetric assay for Cl-Tyr using a 2-naphthol-mediated, slightly alkaline micelle-fluorescent platform that is quantitatively quenched upon addition of Cl-Tyr. At λex 243 nm, the fluorescence emission peak of 2-naphth (λem 420 nm), in the presence of sodium hydroxide (2 mM) and 1.54-mM cetyl tetraammonium bromide (CTAB), is decreased linearly by the addition of Cl-Tyr in the range from 0.1 to 15 μg/mL with a correlation coefficient of 0.9988, and the detection limit was 0.044-μg/mL Cl-Tyr. The intraday and interday percent recoveries ranged from 95.392% to 99.280%, with a percent relative standard deviation (%RSD) of 0.332%-2.128%, indicating that the developed method is both accurate and precise for the determination of Cl-Tyr. Moreover, the proposed method was successfully applied to determine Cl-Tyr in human serum samples, with recovery percentages ranging from 94.842% to 101.192%, confirming its reliability and applicability to biological matrices. Accordingly, the 2-naphtholate/CTAB fluorescent platform offers an inexpensive, accessible, and environmentally considerate alternative to other sophisticated and time-consuming technicalities utilized for routine Cl-Tyr monitoring.