Facile and fast preparation of low-cost silica-supported graphitic carbon nitride for solid-phase extraction of fluoroquinolone drugs from environmental waters

The analytical application of silica-supported graphitic carbon nitride (g-C3N4) for solid-phase extraction (SPE) of fluoroquinolone (FQ) pollutants from water is presented for the first time. g-C3N4 was easily and quickly prepared by one-pot thermal condensation of dicyandiamide and characterized by powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and surface area measurements. The novel composite was applied as sorbent for SPE of FQs from water prior high-performance liquid chromatography with fluorescence detection. The extraction efficiency of g-C3N4 was tested in tap and surface waters at actual concentrations (10-100 ng L-1). Quantitative adsorption was achieved using 100 mg sorbent (20 wt% g-C3N4) for pre-concentration of 50-500 mL sample, at the native pH (~ 7.5-8). Elution was performed with 25 mM H3PO4 aqueous solution acetonitrile (80:20), obtaining recoveries in the range 70-101%, enrichment factors up to 500 and inter-day RSDs 12 %. The batch-to-batch reproducibility was assessed on 3 independently synthesized g-C3N4@silica preparations (RSD < 6-12 %). g-C3N4 supported on silica microparticles proved to be of easy preparation, costless, reusable for at least 4 extractions of raw surface waters and suitable for determination in real matrices.