Synthesis of molecularly imprinted co-polymers for recognition of ephedrine

Abstract

In the present work, an improved approach for the preparation of molecularly imprinted polymers (MIPs) was proposed. The MIPs were prepared based on terpolymer copolymerization under acidic environmental conditions at room temperature and with a solvent eluting template, using ephedrine as the template, and melamine–urea–formaldehyde (MUF) as the terpolymer and also as a functional monomer. In this preparation protocol, the cross-linker was not added. Gas chromatography and mass spectrometry (GC/MS) were used to evaluate the adsorption properties and recognition mechanism of the ephedrine molecularly imprinted co-polymer (EMIP). The recognition property of EMIPs for ephedrine was investigated in depth with both static and dynamic methods using pseudo-ephedrine, another enantiomer of ephedrine, as the comparison compound. The EMIP's ability to bind ephedrine and pseudo-ephedrine was examined. Results showed that the EMIP had good recognition selectivity and binding affinity towards ephedrine, whereas its ability to bind pseudo-ephedrine was poor. The selectivity coefficient of EMIP for ephedrine with respect to pseudo-ephedrine is over seven. It indicated that it had a separation ability at the molecular configuration level. The solid-phase extraction (SPE) experiment showed that the EMIP was able to rebind and enrich ephedrine from the herb ephedra when used as the solid sorbent. The extraction results were compared with those of the liquid–liquid extraction (LLE), showing that the EMIP had a specific adsorption capacity for ephedrine. The amount of ephedrine extracted using SPE was 1.3 times higher than that using LLE.