Quantitation of antibiotics using high-pressure liquid chromatography: tetracycline

A method for quantitative determination of tetracycline in serum, using high-pressure liquid chromatography, is reported. After extraction of the drug from serum, using methanol-trichloroacetic acid solution, tetracycline was separated by reverse-phase chromatography. Quantitation of tetracycline was based on a linear relationship between peak heights in the chromatograms and known concentrations of the drug in the original serum samples. Serum tetracycline concentrations as low as 0.3 mug/ml could be accurately measured. Serum samples obtained after a single intravenous injection of tetracycline to three human volunteers and six dogs were assayed by microbiological and chemical assays. Correlation coefficients of 0.95 and 0.97, respectively, were found. This chemical method is rapid (less than 30 min), accurate, sensitive, and reproducible, and it seems feasible for routine clinical use.