Fabrication of a molecularly imprinted polymer immobilized membrane with nanopores and its application in determination of β2-agonists in pork samples

In this paper, a method for the synthesis of ractopamine molecularly imprinted polymers (MIPs) nanotube membranes on anodic alumina oxide (AAO) nanopore surface by atom transfer radical polymerization (ATRP) was presented, in which methacrylic acid (MAA) was selected as functional monomer with a polymerization rate of 1:6 between ractopamine and MAA by the computational investigations. The morphology of MIPs nanotube membranes characterized by scanning electron microscope (SEM) suggested a well growth in the AAO nanopore surface. A series of adsorption experiments revealed that the MIPs nanotube membranes showed better extraction capacity and good selectivity for ractopamine and its analogues than that of non-imprinted polymers (NIPs) nanotube membranes. In order to evaluate the usability of the MIPs nanotube membranes, a methodology by combining MIPs nanotube membranes extraction couple with high performance liquid chromatography (HPLC) detection for the determination of β2-agonists in complex samples was developed. The linear ranges were 10-1000 μg/L for ractopamine, 100-1000 μg/L for clenbuterol, epinephrine and dopamine, and 200-1000 μg/L for terbutaline. The detection limits were within the range of 0.074-0.25 μg/L and the RSDs (n = 3) were from 2.8% to 4.3%. The method was successfully applied to the analysis of β2-agonists in spiked real samples, The recoveries of all the β2-agonists at the two concentration levels were found to be within the range of 86.3-97.0% and 82.8-95.7%, respectively. The RSDs were within 2.7-5.7%. The results demonstrated that the proposed method is very suitable for the determination of β2-agonists in pork samples.