Development of an analytical method for eight fluoroquinolones using solid-phase extraction and liquid chromatography with fluorescence detection

In this study, a practicable and effective analytical method based on solid-phase-extraction and reversed-phase liquid chromatography with fluorescence detection (SPE-LC-FLD) was developed and partially validated for routine analysis of eight FQs in wastewater at the trace level. Different SPE materials, pH conditions and eluents were modified to find an economic and effective SPE conditions. In our work, it is the first time that well-known commercially available SPE sorbent are compared to 'generic' cheap SPE sorbent. Aqueous samples (pH 2-3) were extracted using Anpel^TM MEP cartridges where they were subsequently eluted by 6 mL of 2% formic acid in MeOH. The aqueous extracts were analysed by gradient elution LC-FLD, whose initial mobile phase was composed of ACN and 10 mmol L ¹ tetrabutyl ammonium bromide (4/96, v/v, pH 3). The LODs and LOQs of the wastewater were as low as 0.32-2.12ng L¹ and 1.07-7.07ng L¹, respectively. The precisions of the overall method (RSD, n=3) using wastewater were below 10%. The method was used to quantify FQs in influents and effluents of several typical sewage treatment plants (STPs) in Shanghai. The extraction recoveries of 100mL influent, 500mL effluent and 500mL of river water samples were between 88.6 and 102.6%, 79.2 and 109.2%, 80.0 and 105.5% and 87.4 and 99.4%, respectively. FQs of interest except sarafloxacin were identified in the influents, effluents and river waters with concentrations varying from 0.012-1.163μgL¹, 0.003-0.291μgL¹, and 0.002-0.040μg L¹, respectively. The method can serve as a tool to obtain detailed information on occurrence, behaviour and fate of FQs in the aquatic environment. Occurrence of FQs detected in summer is higher than in spring at STPs, and those detected in the suburban area are less than those in the urban area. Complete removal of FQs is not achieved from the STPs, indicating domestic wastewater and STP discharge is the source of FQs in the surface water.