Multi-functional porous organic polymers for highly-efficient solid-phase extraction of β-agonists and β-blockers in milk.

A simple, accurate, and highly sensitive analytical method was developed in this study for the determination of ten β-agonists and five β-blockers in milk. In this method, new adsorbent phosphonic acid-functionalized porous organic polymers were synthesized through a direct knitting method. The synthesis procedure of the materials and the extraction conditions (such as the composition of loading buffer and eluent) were optimized. Benefitting from the high surface area (545-804 m 2 g -1 ), multiple functional framework and good porosity, the phosphonic acid-functionalized porous organic polymers showed a high adsorption rate and high adsorption capacity for β-agonists (224 mg g -1 and 171 mg g -1 for clenbuterol and ractopamine, respectively). The analytes were quantified by ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry. It showed a good linearity (with R 2 ranging from 0.9950 to 0.9991 in the linear range of 3-5 orders of magnitude), with low limits of quantification ranging from 0.05 to 0.25 ng g -1 . The limits of detection of the method for the analytes were measured to be in the range of 0.02 to 0.1 ng g -1 . The recoveries of target analytes from real samples on the material were in the range of 62.4-119.4% with relative standard deviations of 0.6-12.1% ( n = 4). Moreover, good reproducibility of the method was obtained with the interday RSD being lower than 11.7% ( n = 5) and intraday RSD lower than 12.2% ( n = 4). The proposed method was accurate, reliable and convenient for the simultaneous analysis of multiple β-agonists and β-blockers. Finally, the method was successfully applied for the analysis of such compounds in milk samples.