Analysis of trace residues of tetracyclines in dark-colored honeys by high-performance liquid chromatography using polymeric cartridge and metal chelate affinity chromatography.

An efficient clean-up procedure was developed for the trace residue determination of tetracyclines (TCs) in dark-colored honeys. TCs were extracted from samples with McIlvaine buffer (pH 4.0) containing 0.01 mol/L Na(2)EDTA. The extracts were treated with both a polymeric cartridge (GL-Pak PLS-2) and a metal chelate affinity column (MCAC) preloaded with copper(II). TCs were eluted and analyzed by high-performance liquid chromatography (HPLC) using fluorescence detection. The method was evaluated for the determination of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in buckwheat honey, because its color is the darkest. The mean recoveries of OTC, TC and CTC from spiked samples, at three fortification levels, were >70%, and the relative standard deviations (RSDs) were <10%. Limits of quantitation (LOQs) of OTC, TC, and CTC were estimated to be 0.015 mg/kg, 0.019 mg/kg, and 0.024 mg/kg, respectively.