IMPROVEMENT OF CHEMICAL-ANALYSIS OF ANTIBIOTICS .22. IDENTIFICATION OF RESIDUAL TETRACYCLINES IN HONEY BY FRIT FAB LC/MS USING A VOLATILE MOBILE-PHASE/

A reliable identification method for residual tetracycline antibiotics (TCs), oxytetracycline, tetracycline, chlortetracycline, and doxycycl ine in honey, has been established using frit FAB/LC/MS with a volatil e mobile phase. The TCs were recovered from a Cls solid phase extracti on cartridge and separated on an end-capped phenyl-bonded silica gel c olumn synthesized from 99.99% pure silica gel (5 mu m, 250 x 2.1 mm i. d.) using a mobile phase consisting of methanol-acetonitrile-0.005 M t rifluoroacetic acid (2:2:11) containing 1.0% thioglycerol. The column effluent was introduced into the frit FAB ion source after splitting a t a ratio of 1:20. TCs in honey were reliably identified by their FAB/ MS at 0.2 ppm. Detection limits of protonated molecules are 0.1 ppm in honey. This method is one of the first applications of LC/MS technolo gy to the identification of residual TCs in foods using a volatile mob ile phase without reduction of peak resolution and clogging problems a t the interface.