Determination of a ternary mixture of penicillin-G sodium salt, penicillin-G procain salt and dihydrostreptomycin sulphate, by third-derivative spectrophotometry.
Ternary mixtures of antibiotics, i.e. penicillin-G sodium salt, penicillin-G procain salt and dihydrostreptomycin sulphate salt, are assayed by 'zero-crossing' third-derivative spectrophotometry. Calibration plots follows Beer's law up to 40 mug/ml of penicillin-G sodium at 222.5 nm (r = 0.9997), 46 mug/ml of penicillin-G procain at 217 nm (r = 0.9999) and 36 mug/ml of dihydrostreptomycin sulphate at 211.5 nm (r = 0.9999), in the presence of one another. Detection limits at p = 0.05 level of significance were calculated to be, respectively, 0.66, 0.41 and 0.25 mug/ml. The procedure is rapid, simple, nondestructive and does not require solution of equations. The method was successfully applied for determining laboratory mixtures and commercial injections.
Morelli
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B
Universita' degli Studi, Bari, Dipartimento di Chimica, Campus Universitario, Via E. Orabona, 4 70126-Bari, Italy.