Fluorimetric assay of tetracycline mixtures

A simple and precise fluorimetric method is described for the simultaneous assay in plasma of a mixture containing chlortetracycline, demethylchlortetracycline and tetracycline. Assay within the therapeutic ranges of 0-5 mg litre(-1) is achieved by formation of strongly fluorescent aluminum/tetracycline complexes, without prior extraction or separation of the individual antibiotics. This is performed by determinations at the peak excitation and fluorescence emission wavelengths of each tetracycline chelate. The method can be similarly applied to the assay of oxytetracycline, rolitetracycline and minocycline.