Quaternary ammonium salt based magnetic microporous organic network: An efficient extractant for plant growth...

A novel cationic quaternary ammonium salt-based magnetic microporous organic network named MMON-DBB-2 was ingeniously designed for the efficient magnetic solid-phase extraction (MSPE) of plant growth regulators (PGRs) from vegetable samples. MMON-DBB-2 exhibited exceptional stability, rapid magnetic responsiveness, high surface area, and abundant positive charged binding sites, making it an ideal adsorbent for the enrichment of polar and acidic PGRs in complex matrices. Factors affecting MSPE were systematically optimized, involving pH, ionic strength, eluent type and volume, desorption time, adsorbent dosage, and extraction time. Under optimal conditions (desorption solvent: 1 % NH₃·H₂O + MeOH; eluent volume: 0.6 mL; desorption time: 6 min; pH: 5; adsorbent dosage: 3 mg; extraction time: 4 min), a MSPE-HPLC method with low detection limit (1.0-3.6 μg kg^-1), wide linear range (4.0-400.0 μg kg^-1), large enrichment factor (98.8-99.2), less adsorbent dosage, and short extraction time was developed. The determination of trace PGRs in cucumber, carrot and tomato samples was also realized with the recoveries of 80.0-108.2 %. The possible extraction mechanisms (electrostatic, ion exchange, and π-π interactions) were elucidated. This work highlights the potential of quaternary ammonium salt based MON in MSPE and paves the way for the rational design of advanced cationic MONs for sample pretreatment..