Determination of Tetracyclines Residues in Egg, Milk, and Milk Powder by Online Coupling of A Precolumn Packed with Molecular Imprinted Hybrid Composite Materials to RP-HPLC-UV

A rapid, specific, and sensitive method was developed for determination of tetracyclines (TCs) in egg, milk, and milk powder samples by online molecularly imprinted solid-phase extraction (MISPE) coupled to a reversed-phase high-performance liquid chromatography (HPLC). A molecularly imprinted polymer hybrid composite material (MIP-HCM) was prepared using TC as the template, methacrylic acid as the functional monomer, tetraethoxysilane as inorganic precursor, and methacryloxypropyltrimethoxysilane as the coupling agent. A new technique of online solid-phase extraction (SPE) coupled with HPLC was established. The conditions of online SPE were optimized. Under the optimal conditions, three TCs residues in egg, milk, and milk powder were separated and detected by the proposed method with better clean-up and recoveries. The recoveries of TCs ranged from 85.3% to 98.3%. The limits of detection and quantitation of the proposed method were in the range of 0.76-1.13 mu g/kg and 2.53-3.77 mu g/kg, respectively. The MIP-HCM was first used as online SPE packing and the hyphenated technique is promising as a general strategy for direct determination of veterinary drug residues in milk and other biological samples.