Preparation and evaluation of a novel molecularly imprinted hybrid composite monolithic column for online solid-phase extraction coupled with HPLC to detect trace fluoroquinolone residues in milk

A novel molecularly imprinted organic-inorganic hybrid composite monolithic column (MIP-HCMC) was prepared in a stainless-steel chromatographic column for the determination of fluoroquinolone residues in milk by on-line solid-phase extraction coupled with HPLC. The MIP-HCMC was prepared using enrofloxacin as the template, methacrylic acid and 2-hydroxyethyl methacrylate as functional monomers, tetraethoxysilane as inorganic precursor and methacryloxypropyltrimethoxysilane as coupling agent, toluene and polyethylene glycol as porogenic solvents, and ethylene glycol dimethacrylate as the cross-linking agent. The synthetic conditions were optimized. The chemical group, morphology, thermal stability, dynamic adsorption characteristic and swelling of the monolithic column were characterized by IR, SEM, TG, dynamic binding tests and swelling tests, respectively. An enrichment factor (EF) of 18.5 along with a good sample clean-up effect was obtained under the optimized conditions when the method was applied to milk sample analysis only after centrifugation. The average recoveries of four fluoroquinolones from milk spiked at 0.05, 0.1 and 0.25 mg kg(-1) were in the range of 89.1-99.2% with the precision of 3.55-4.32%. The limits of detection and quantification of the proposed method were 1.69 and 5.63 mu g kg(-1) for ofloxacin, 1.63 and 5.43 mu g kg(-1) for lomefloxacin, 3.74 and 12.5 mu g kg(-1) for ciprofloxacin, 1.37 and 4.56 mu g kg(-1) for enrofloxacin, respectively. The proposed method was successfully applied to on-line extraction and determination of fluoroquinolone antibiotics in milk.