Controllable synthesis of reticulated covalent organic polymers for the rapid extraction of triazine herbicides in vegetables prior to analysis by high-performance liquid chromatography.

Covalent organic polymers (COPs) with different morphologies were synthesized using 2,5-dimethoxyterephthalaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine as building blocks. The COPs with reticular porous structure showed higher adsorption efficiency (> 99%) for triazine herbicides (simazine, ametryn, and prometryn) than that of the spherical COPs (42%-92%) due to the larger specific surface areas, pore volume and more adsorption sites. The reticulated structure enabled the fast diffusion and rapid extraction of three triazine herbicides within 5 min. The adsorption capacities of COP for simazine, ametryn, and prometryn were 4.11 mg g⁻¹, 4.52 mg g⁻¹, and 5.20 mg g⁻¹, respectively, facilitated by π-π interactions, hydrogen bonding, and electrostatic interactions. The reticulated COPs based solid-phase extraction enabled the high-efficiency extraction of triazine herbicides in tomato and celery samples with complex matrix prior to the analysis by HPLC-UV. The linear range of the analytical method ranged from 1 to 200 ng mL⁻¹, and detection limits ranged from 0.5 to 1.1 ng mL⁻¹, with intra- and inter-day precisions below 8.8%. This work not only provides a high-efficiency sorbent for sample preparation, but also sheds some lights on improving the sorption performance by morphological control.