Identification of Residual Tetracyclines in Honey by TLC/FABMS

Abstract

In order to reliably identify residual tetracycline antibiotics (TCs), oxytetracycline, tetracycline, chlortetracycline, and doxycycline, in honey, a confirmation method using thin-layer chromatography/mass spectrometry (TLC/FABMS) with the following characteristics has been established. Use of thioglycerol as a matrix enabled us to measure the FAB mass spectra of TCs without interfering ions due to the matrix and honey. Reversed-phase C8 TLC conditions gave reliable separation with good reproducibility, and the location of TCs extracted from honey could be readily estimated on the basis of the location of neighboring visualized spots of TCs. The condensation technique improved the detection limits 50-fold with good reproducibility. The clean-up procedure using a combination of C18 and COOH (weak cation exchange) cartridges proved to be effective for the identification of residual TCs by TLC/FABMS. The method can reliably identify TCs fortified at concentrations of 0.1ppm in honey, and has been successfully applied to the identification of residual chlortetracycline in a commercial honey previously found positive by high performance liquid chromatography.