Automatic solid-phase extraction by programmable flow injection coupled to chromatographic fluorimetric determination of fluoroquinolones

摘要

Fluoroquinolones are broad-spectrum bactericidal agents applied for the treatment of human and veterinary diseases. Their common use and their incorrect disposal foster environmental contamination, namely in water resources, increasing the risk of antimicrobial resistance. Hence, a method based on automatic solid-phase extraction coupled to liquid chromatography and fluorimetric detection is proposed for the determination of fluoroquinolones in environmental waters. For the solid-phase extraction procedure, a commercially available molecularly imprinted polymer targeting fluoroquinolones was trapped inside a flow-through extraction column, integrated into a programmable flow injection system using multisyringe flow injection analysis, where all steps concerning sorbent conditioning, sample loading, matrix removal, and analyte elution were performed under computer control. The eluate resulting from the sample preparation was collected and transferred at-line to chromatographic analysis using a reversed-phase monolithic column coupled to a fluorimetric detector, and isocratic elution with methanol-phosphoric acid (pH 3.0; 5.0 mM) (17.5:82.5, v/v) at a flow rate of 3.5 mL min(-1). Sample treatment and chromatographic analysis were performed in tandem, with sample throughput limited by the sample treatment step. Calibration curves based on fluorescence intensity vs. analyte mass were obtained in the range of 10 to 1000 pg for norfloxacin, ciprofloxacin, and enrofloxacin with LOD values of 6-19 ng L-1 for a sample volume of 100 mL, and RSD 11% at 0.7 g L-1. The method was successfully applied to estuarine river water analysis.