On-line coupling of hydrophilic ionic liquids-based polymer monolith microextraction to capillary liquid chromatography with amperometric detection: An ultrasensitive residue analysis method for glycopeptide antibiotics

A hydrophilic ionic liquids based polymer monolith microextraction (PMME) column (poly(ionic liquid-co-hydroxyethyl methacrylate-co-ethylene dimethacrylate); poly(IL-co-HEMA-co-EDMA)) was prepared for the first time in a capillary and utilized in PMME for the enrichment of glycopeptide antibiotics (GAs), followed by the online coupling analysis of capillary liquid chromatography with amperometric detection (cLC-AD). The prepared monolith exhibited large through pores and good storage stability, as well as a selective extraction machanism for GAs that was attributed to the hydrogen bonding, hydrophilic, electrostatic and π-π interactions between GAs and the imidazolium cations or hydroxyl groups on the surface of absorbent. Several experimental parameters, such as sample flow rate, composition of eluent and solvent desorption conditions, were examined to improve the extraction efficiency of PMME. Under the optimal conditions, the proposed PMME-cLC-AD method provides detection limits (S/N = 3) of 1.0-8.0 μg L−1 for three GAs, which are 1000-fold lower than those obtained by cLC-AD, with a wide linear range of 10.0-12000.0 μg L−1. It was successfully applied for the analysis of GAs residues in feed samples with good recoveries (80.3-119.1%) and satisfied intra-day/inter-day precision (<10%). Compared with LC-3Q-MS method, the proposed online approach has the merits of simple, low cost, smaller matrix interference and environmental friendly, which is demonstrated to be a feasible tool for residue analysis of peptide antibiotics in food safety application.