Postcolumn zirconium chelation and fluorescence detection for the liquid-chromatographic determination of tetracyclines

A novel highly sensitive liquid chromatographic method for the determination of some tetracycline antibiotics has been developed. It is based upon the measurement of fluorescence induced by complexation of tetracyclines with the zirconium cation, which is added post-column to the liquid chromatographic eluate. The zirconium reagent concentration and post-column configuration were optimized. The effect of time upon the stability of the chelates was studied. The fluorescence intensity was linear in a concentration range of 0.01-10 mu g ml(-1) tetracycline. The proposed method has already been applied to the residue analysis for tetracycline, oxytetracycline and chlortetracycline in bovine milk. The most striking advantages of the method over the reported methods in the literature are the higher sensitivity and specificity achieved. The detection limits of the assay (signal-to-noise ratio = 4:1) were 1 ng ml(-1), 2 ng ml(-1) and 4 ng ml(-1) for oxytetracycline, tetracycline and chlortetracycline, respectively