Reversed-phase high-performance liquid chromatographic determination of tetracyclines in urine and plasma

The high-performance liquid chromatographic separation and quantitative analysis of oxytetracycline, tetracycline, and chlortetracycline from urine and plasma were effected on an octadecylsilane reversed-phase packing. The calcium complexes of the tetracyclines were extracted from urine and plasma with ethylacetate and then reextracted into hydrochloric acid. Following the injection of the hydrochloric acid extracts onto the column, the individual tetracyclines were eluted isocratically and quantitated spectrophotometrically. Concentrations of less than 1 microng/ml in urine and 1.5 microng/ml in plasms were quantitatively determined with a relative standard deviation of less than 5%.