Diffusive gradients in thin films based on MOF-derived porous carbon binding gel for in-situ measurement of antibiotics in waters

Abstract

Diffusive gradients in thin films (DGT) can achieve the time-weighted-average (TWA) concentrations of analytes in the period of deployment. Here we developed an approach based on DGT with a novel binding gel using porous carbon material (PCM) derived from metal-organic framework (MOF) for in-situ measurement of antibiotics in water samples. The diffusion coefficients of 20 antibiotics (nine sulfonamides, ten fluoroquinolones, and trimethoprim) in agarose diffusive gel were 1.41 × 10−6 cm2/s to 4.75 × 10−6 cm2/s at 25 °C. The capacity of PCM binding gel toward the antibiotics was ~100 μg per gel disc. The masses of the antibiotics accumulated by PCM-based DGT increased linearly with time, and they were almost independent of pH (4.2–8.4) and ionic strength (1–500 mM). The performance of the novel DGT was evaluated using freshwater and synthetic seawater spiked with the antibiotics in laboratory. The results showed good agreement with the theoretical predications except sulfacetamide. The detection limits achieved by the DGT with three devices together for deploying up to seven days were 1.0–18.0 ng/L. Field deployment in municipal wastewater treatment plant effluent and seawater showed that the TWA concentrations of antibiotics were 3.8–1342.5 ng/L and 5.6–43.3 ng/L, respectively, which were comparable to those measured by grab sampling. The proposed DGT was an efficient tool for the measurement of antibiotics in environmental waters.