β‐Casein‐Based Synchronous Fluorescence Method for Sensitive Detection of Levofloxacin in Pharmaceutical Products

Abstract To ensure accurate dosing, therapeutic efficacy, patient safety, and quality control in production and storage, detecting pharmaceutical product concentrations is essential. This study describes a β‐Casein‐based synchronous fluorescence technique for the sensitive, accurate, and straightforward quantitative measurement of levofloxacin in various pharmaceutical items. Synchronous scanning fluorescence was employed to investigate the fluorescence spectrum behavior of β‐casein in the 220–320 nm region at varied wavelengths, with a Δ λ of 60 nm, using 10 nm excitation and emission windows, thereby revealing the intrinsic fluorescence signals. Levofloxacin reacts with β‐Casein and forms a stable ion‐associated complex. Levofloxacin subsequently inhibits the intrinsic fluorescence signals of β‐Casein in a Britton–Robinson buffer solution (pH 7.0). Levofloxacin concentrations were found to range from 0.3 to 4.0 µg/mL, with 0.074 µg/mL being the lowest detectable quantity. The concentration of levofloxacin showed a strong linear relationship ( R 2 = 0.9985) with the quenching fluorescence intensity (Δ F ). This method demonstrated no interference from common pharmaceutical excipients. The results were validated by comparison with a conventional high‐performance liquid chromatography (HPLC) technique, showcasing remarkable consistency in accuracy and precision. Synchronous fluorescence offers a reliable method for assessing levofloxacin in pharmaceutical quality control.