An L-Tryptophan Fluorescence Quenching Approach for Sensitive Determination of Levofloxacin in Pharmaceutical Formulations and Biological Samples.

This study developed and validated a simple, sensitive spectrofluorimetric method for quantifying levofloxacin in pure form, pharmaceutical formulations, and biological samples. The method is based on fluorescence quenching of L-tryptophan upon interaction with levofloxacin in borate buffer (pH 10.5), forming a stable complex. Following excitation at 286 nm, fluorescence emission was recorded at 362 nm, and the quenching induced decrease in emission intensity was quantitatively monitored. Key experimental parameters, including buffer pH and volume, L-tryptophan concentration and volume, were systematically optimized to enhance complex formation. Across a concentration range of 0.2-1.0 μg mL-1, a linear calibration curve with excellent correlation coefficient (R2 = 0.9997) was obtained. The method exhibited detection and quantification limits of 0.0043 and 0.014 μg mL-1, respectively. No interference from common pharmaceutical excipients was observed. Levofloxacin was successfully determined in standard solutions, commercial formulations, and biological samples. Validation according to ICH guidelines confirmed excellent precision, accuracy, and sensitivity. The method is reliable, cost effective, and suitable for routine analysis, with strong sustainability demonstrated by AGERR and BAGI assessments.