Photoresponsive molecularly imprinted polymers based on 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid for the determination of sulfamethazine.

Core-shell structured photoresponsive molecularly imprinted polymers were developed for the determination of sulfamethazine in milk samples. The photoresponsive imprinted polymers were prepared with polymethyl methacrylate containing a mass of ester groups as core, sulfamethazine as template molecules, self-synthesized water-soluble 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid as a photoresponsive monomer, and ethylene dimethacrylate as cross-linker. Interestingly, the imprinted polymer can specifically adsorb sulfamethazine under dark and 440 nm irradiation, and release it at 365 nm. A series of adsorption experiments showed that the maximum adsorption capacity reached 12.5 mg⋅g , and the adsorption equilibrium was achieved within 80 min. Moreover, the imprinted polymers display excellent reusability, with almost no performance loss after four times photo-controlled adsorption-release cycles, and the imprinted polymers have excellent selectively for sulfamethazine (imprinting factor  = 3.01). In the end, the imprinted polymers realized effective separation and enrichment of sulfamethazine in milk, with a recovery rate of over 97.5%. The material can be used as a solid-phase extractant in the process of enrichment and separation for the quantitative detection of sulfamethazine in milk samples.