Data fusion applied to the photodegradation study of ciprofloxacin using hyphenated detection systems (UV–Vis and fluorescence) and multivariate curve resolution

Abstract

In this article, a new method was developed based on a flow system with hyphenated UV and fluorescence detection to study the photodegradation of ciprofloxacin. The photodegradation was investigated at both pH 7.0 and 9.0 (Britton-Robinson buffer), i.e. the conditions normally found in hospital wastewaters (HWWs) and urban wastewaters (UWWs). The flow system included a reactor (12 m in length and 0.5 mm internal diameter) coiled on a germicide UV lamp (λmax 254 nm, 15 W). Ciprofloxacin solution was pumped through the system at the optimal conditions (0.1 mL min−1 flow rate), with a maximal time of residence in the photoreactor of 18.8 min. Both UV and fluorescence spectra were taken every 4 s. The UV spectra were recorded from 210 to 400 nm (Δλ = 2.0 nm), while the fluorescence spectra were recorded from 372 to 620 nm (Δλ = 1.7 nm). A data fusion strategy was carried out to analyze the obtained spectroscopic signals and the Hard and Soft Multivariate Curve Resolution (HS-MCR) was applied to obtain the pure spectra and concentration profiles related to ciprofloxacin and its main degradation products, as well as the corresponding kinetic rate constants. Previously, photodegradation pathways were proposed, taking into account the concentration profiles recovered by pure soft modeling analysis. The rate constants for ciprofloxacin obtained after HS-MCR analysis were 0.0302 s−1 and 0.0322 s−1 for pH 7.0 and 9.0, respectively. The reaction pathway and the kinetic rate constants were in close agreement with the ones reported in the bibliography and with the HPLC analysis previously performed. The proposed method is simple, rapid, and represents a greener and cheaper alternative to HPLC for studying photodegradation processes.