Harnessing an amide‐based covalent organic framework in solid‐phase extraction for chlorophenol analysis in industrial wastewaters

An amide-based covalent organic framework (COF) was successfully synthesized using the reaction between 1,3,5-trimesoyl chloride and ethylenediamine. The structure and morphology of the COF were characterized using Fourier-transform infrared spectra, nuclear magnetic resonance spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface area analysis. The COF was employed as a solid-phase extraction adsorbent for the sampling and preconcentration of chlorophenols from industrial wastewater samples prior to high-performance liquid chromatography with ultraviolet detection. The experimental parameters influencing the extraction efficiency including type and volume of eluent solvent, sample solution volume, salt concentration, sample flow rate, and sample solution pH were investigated and optimized using a response surface methodology employing Box-Behnken-design. Under optimized conditions, calibration curves exhibited good linearities over the range of 0.003-10 µg/mL with determination coefficients (R²) ranging from 0.9982 to 0.9999. The method's limits of detection ranged from 0.001 to 0.01 µg/mL. Good repeatability was achieved with relative standard deviations below 4.7%. The developed procedure utilizing the COF adsorbent was successfully applied to determine chlorophenols accurately and precisely in various industrial wastewater samples.