Serum gentamicin assay by high-performance liquid chromatography

Abstract

The antibiotic was separated from serum by passage through a silicic acid column, derivatized with o-phthalaldehyde, and eluted with ethanol. The derivatized gentamicin was then separated into all three of its major components by reversed-phase chromatography and quantified by fluorometry. Concentrations in serum as low as 0,5 mg of gentamicin per liter could be accurately determined. A standard curve showed a linear response for serum containing gentamicin at concentrations ranging from 0 to 20 mg/liter. Tobramycin,amikacin,ampicillin, penicillin G, methicillin,carbenicillin,chloramphenicol, clindamycin,and cephalothin did not interfere with the gentamicin assay. Comparison with an accepted microbiological assay yielded a correlation coefficient of 0.99. This chemical assay is rapid (less than 30 min.), sensitive, accurate, specific, and appears to be applicabele to other aminoglycosides.