RAPID-DETERMINATION OF TETRACYCLINE ANTIBIOTICS IN SERUM BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

A rapid and accurate determination of tetracycline antibiotics in huma n serum by reversed-phase high-performance liquid chromatography with fluorescence detection has been developed, based on protein precipitat ion in serum. Various reagents for precipitation were investigated, an d 24% trichloroacetic acid in methanolic solution gave the maximum rec overy (at least 94.3%) and interference-free chromatograms of differen t three tetracyclines. At a concentration of 0.5 mug/ml, the precision (relative standard deviation) ranged from 1.12 to 1.94%. In the range 0.04-10.0 mug/ml for oxytetracycline and chlorotetracycline and 0.01- 10.0 mug/ml for tetracycline, linear responses were observed. The dete ction limits of this method were 10-35 ng/ml for all three antibiotics . The proposed method was applied to the determination of serum concen trations in subjects receiving tetracycline antibiotics.