A free elution immunoassay for chloramphenicol in chicken and egg after magnetic ZIF-8 adsorption separation

Abstract

The excellent adsorption and rapid separation capabilities of magnetic MOFs make them desirable pretreatment materials for solid substrates. In this study, magnetic ZIF-8 (mZIF-8) was synthesized in situ by a one-step method in the aqueous solution of magnetic beads. Isothermal adsorption verified that the maximum adsorption capacity of (011) crystal-exposed rhombic dodecahedral ZIF-8 for chloramphenicol was up to 128.31 mg/g (mZIF-8 = 67.18 mg/g). Kinetic adsorption revealed that the type of ZIF-8/mZIF-8 adsorption on chloramphenicol belongs to the pseudo-secondary adsorption kinetics of chemical monomolecular layers. Characterization by FTIR, XPS, and XRD revealed that mZIF-8 interacts with chloramphenicol mainly by π-π electron stacking, electrostatic attraction, and hydrogen bonding interaction. ELISA confirmed that chloramphenicol remained antigenically active after adsorption by mZIF-8. The adsorption and separation of chloramphenicol residues in chicken and egg were completed by mZIF-8 within 20 min. mZIF-8 can be used directly for elution-free ELISA after the adsorption of chloramphenicol. The limits of detection (IC10) of the mZIF-8 + ELISA in chicken and eggs were 1.18 ng/mL and 0.64 ng/mL, respectively. mZIF-8 is expected to be used as a magnetic solid-phase extraction material for the rapid pretreatment of antibiotic residues in other complex solid matrices.