Rapid assay for procaine penicillin G in pharmaceutical dosages by spectrofluorimetry

A method for the spectrofluorimetric determination of procaine penicillin G is proposed (lambda(ex) = 294 nm, lambda(em) = 348 nm) for concentrations between 0.10 and 1.0 ppm. The method was performed in ethanol/water medium (60% V/V), at apparent pH 9.9 provided by adding ammonium/ammonia buffer solution with pH = 10.0. The effect of other penicillins on the determination of procaine penicillin G was examined over a wide range of concentrations, interferences were not observed in the range of studied concentrations. The method was successfully applied to assay all Spanish commercialized injections containing procaine penicillin G, penicillin G and/or benzathine penicillin G.