Preparation and application of a restricted access material with hybrid poly(glycerol mono-methacrylate) and cross-linked bovine serum albumin as hydrophilic out layers for directly on-line high performance liquid chromatography analysis of enrofloxacin and gatifloxacin in milk samples.

A novel restricted access material (RAM) was prepared through combination of hydrophilic polymer poly(glycerol mono-methacrylate) and cross-linking bovine serum albumin (BSA) for direct biological analysis. In the material preparation, the poly(styrene-co-divinylbenzene) and poly(glycerol mono-methacrylate) were grafted on silica successively by atom transfer radical polymerization. Then the BSA was adsorbed on the material and cross-linked through an in-column process. The BSA recoveries of the resulted RAM were higher than 99.3%. Small molecules such as alkylbenzene and quinolone antibiotics could be retained with a reversed phase mechanism. The column packed with RAM had good long term stability and could last at least five months without significantly changed in its efficiencies. An on-line SPE/HPLC method for the analysis of enrofloxacin and gatifloxacin in milk samples was established by using the resulted RAM as the solid-phase extraction material. The detection and quantitation limits of two antibiotics were 8.22 and 27.4 ng mL-1 , respectively. In the method validation, least recovery 88.5% with relative standard deviation of less than 3.9% was obtained. It demonstrated that the method is reliable and the material can be used for the direct analysis of veterinary drug residues in biological samples.