Determination of danofloxacin and its photodegradation products by HPLC-DAD. Kinetic evaluation of the degradation process and identification of photoproducts by mass spectrometry

Abstract

A HPLC method was developed for determination of danofloxacin (DAN) in the presence of its photodegradation products. Chromatography was performed on a Gemini-NX C18 110A, 150 mm × 4.60 mm, 3 μm particle size column with 0.025 M phosphate buffer (pH = 5.00)–acetonitrile–methanol (95 : 10 : 30 v/v/v) as the mobile phase at a flow rate of 1.2 mL min⁻¹. UV detection was performed at 280 nm. The column was thermostatted at 25 °C. The elaborated method meets the acceptance criteria for specificity, linearity, sensitivity, accuracy, and precision. The linear regression analysis for the calibration curve showed a good linear correlation over the concentration range 0.20–0.80 mg mL⁻¹, with determination coefficient, R², exceeding 0.9966. The method was shown to have good and intermediate precision, as reflected by the relative standard deviation values, lower than 2.21% and characterized by a recovery rate at three concentration levels from 98.0% to 101.70%. The limits of detection and quantification were respectively 0.0055 and 0.0167 mg mL⁻¹. The photodegradation process of DAN followed kinetics of the first order reaction for the substrate. Ten products of photodegradation were identified by UPLC/MS/MS.