Quantitation of serum tobramycin concentration using high-pressure liquid chromatography

A high-pressure liquid chromatography method for the quantitative determination of tobramycin in serum is described. The antibiotic was separated from serum by chromatography on a silica gel column. The adsorbed antibiotic was derivatized with o-phthalaldehyde, and then eluted with isopropanol. The derivatized tobramycin was separated by reverse-phase chromatography and quantitated by fluorometry. Serum concentrations as low as 0.5 microgram/ml could be accurately measured. A linear response for serum samples containing tobramycin ranging from 0 to 20 microgram/ml was obtained. Other antibiotics, including various aminoglycosides, did not interfere with the tobramycin assay. Comparison with a standard microbiologic assay gave a correlation coefficient of 0.99. This chemical assay is sensitive, precise, specific, and can be performed in 30 minutes.