Determination of veterinary penicillin antibiotics by fast high-resolution liquid chromatography and luminescence detection

A chromatographic method based on the use of a fused-core column and luminescence detection is described for the determination of six penicillin antibiotics used in veterinary practice, namely amoxicillin, ampicillin, penicillin G, oxacillin, cloxacillin and nafcillin. The use of this column provides the separation of these antibiotics with retention times lower than 4.5 min. The tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)32+] – Ce(IV) system has been used as post-column derivatization reagent, obtaining a luminescence signal (λem 610 nm) proportional to the analyte concentration when the system is excited at 450 nm. The dynamic ranges of the calibration graphs are 100–10,000 ng mL−1 for all the antibiotics assayed and the limits of detection are in the range of 44–51 ng mL−1. The precision, established at two concentration levels of each analyte and expressed as the percentage of the relative standard deviation is in the range of 6.9–9.8%. The method has been satisfactorily applied to the analysis of water and pharmaceutical samples, with recoveries ranging from 88.6% to 108.5%.