Determination of antibacterial agents in microbiological cultures by high-performance liquid chromatography.

A general high-performance liquid chromatographic (HPLC) procedure is described which allows the assay of several antibacterial drugs in combination in a matrix of bacterial cell cultures. The drugs assayed were dibromopropamidine, trimethoprim, sulphadiazine and sulphamerazine. It is also shown that p-aminobenzoic acid, which is an essential metabolite of many micro-organisms, does not interfere and can itself be quantified. The method uses solid-phase extraction on a cyclohexyl-bonded silica with subsequent separation of the analytes by reversed-phase HPLC. Tetrabutylammonium is used in order to reduce the retention of trimethoprim and dibromopropamidine and quantification is by ultraviolet detection at 254 nm. The analytical characteristics of the proposed method are shown for certain drug combinations.