On-site extraction using a 3D printed device coated with Zn/Co-ZIF-derived carbon followed by an on-line SIA-HPLC-FL system for fluoroquinolones determination in wastewater.

A 3D printed device covered with Zn/Co-ZIF-derived carbon allows the on-site extraction of fluoroquinolones (FQs) from wastewater, avoiding the sample transportation to the laboratory, and the subsequent elution, separation and determination using an on-line flow system based on sequential injection analysis (SIA) coupled to HPLC-FL. Several parameters that affect the extraction efficiency and desorption were optimized including the sorption phase immobilization technique on the 3D device, extraction time, pH effect, sample volume as well as the type of eluent, eluent volume, and flow rate. Under optimum conditions, detection limits of 3-9 ng L-1 were achieved for norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin and difloxacin. The precision expressed as relative standard deviation (%RSD, n = 3), showed intraday and interday ranges of 1.5-5.3% and 2.8-5.7%, respectively, demonstrating a good precision of the proposed methodology. To assess matrix effects and accuracy of the proposed method in real samples, recovery studies were performed without and with FQs spiked at different concentrations (0.5-10 μg L-1 ) to wastewater samples, showing good recoveries in the range of 91-104%. The results allow to confirm the applicability of MOF-derived carbons as adsorbents for on-site extraction, and the satisfactory separation and quantification of FQs by a SIA-HPLC-FL on-line system after their desorption with small eluent volumes.