Sulfonate-bonded covalent organic polymer as mixed-mode sorbent for on-line solid-phase extraction of ß2-receptor agonists.

A novel sulfonate-bonded covalent organic polymer (COPTPBA-BPDA@SA) with mixed-mode interactions of hydrophobic and cation-exchange was synthesized and exploited as sorbent for on-line solid-phase extraction (on-line SPE) of ß2-receptor agonists. The successful synthesis of COPTPBA-BPDA@SA was confirmed by the characterization of SEM, XPS and FT-IR. Due to the excellent mixed-mode extraction ability towards the positively charged ß2-receptor agonists and the good anti-interference performance, COPTPBA-BPDA@SA was introduced into on-line SPE-HPLC system for selective extraction of ß2-receptor agonists in pork and pork liver. Via the optimization of the extraction condition, including formic acid percentage and ACN percentage in the sampling solution, the mixed-mode extraction mechanism of COPTPBA-BPDA@SA was investigated. The elution condition, such as the pH value, formic acid percentage and ACN percentage of the eluent was also optimized for the desired SPE performance. Under the optimized condition, COPTPBA-BPDA@SA revealed better purification performance than COPTPBA-BPDA without sulfonating. The LODs for ß2-receptor agonists were in the range of 0.08-0.22 μg/kg, and the recoveries in different samples at three spiked levels (0.4, 4.0, 8.0 μg/kg) were ranged from 83.2% to 98.5% with RSDs less than 5.2%, which indicated the satisfactory mixed-mode extraction ability of COPTPBA-BPDA@SA as well as the good applicability of the developed method.