Enzyme-linked immunoassay based on imprinted microspheres for the detection of sulfamethazine residue

This study attempts to develop an enzyme-linked immunoassay (ELISA) using a molecularly imprinted polymer (MIP) as an artificial recognition element. The MIP microspheres were prepared using precipitation polymerization with SM₂ as the template molecule, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. After the microspheres were coated in microtiter plate wells, the molecular imprinting ELISA (MI-ELISA) method was established based on the direct competition between free SM₂ and horseradish peroxidase (HRP)-labelled SM₂ in heterogeneous mode. The linear regression analysis data for the calibration curve showed a good linear relationship with a regression coefficient of 0.999 in the concentration range of 100μgL^-1-3200μgL^-1. Furthermore, following the selective solid-phase extraction (SPE) with bulk SM₂ MIPs as the sorbent and MI-ELISA detection, the limits of detection and quantification were 6.8μgkg^-1 and 20.4μgkg^-1, respectively, for SM₂ in swine muscle. For the first time, MI-ELISA combined with molecular imprinting SPE was developed to determine trace SM₂ in real samples, and the results show that it can be a useful analytical tool for quick detection in residue analysis.