PubMed1986
Mercurimetric determination of penicillins includes direct titration with a solution of mercury (II) perchlorate in the medium of pyridine solvent or acetate buffer, which determines the content of decomposition products, and titration after alkaline hydrolysis, which indicates the total amount of penicillin. The determination which is indicated potentiometrically with continuous addition of the titrant, provides real and reproducible results in the titration rate of 0.6 ml/min with the initial concentration of penicillin 170 mg/30 ml and temperature 25 degrees C. Benzathine and procaine salts of benzylpenicillin and benzathine salt of phenoxymethylpenicillin were dissolved in dimethylformamide (DMF) before the titration in acetate buffer. Titrations of ampicillin, amoxycillin and azlocillin were performed in the mixture of acetate buffer and formamide which ensured real results. Hydrolysis of the lactam ring of azlocillin, mezlocillin, ticarcillin and piperacillin is quantitative in 10 min of action of NaOH (1 mol/l) which was confirmed by comparing with the enzymatic cleavage. Relative standard deviation for all penicillins was less than 1%. The accuracy of the method for the determination of penicillins was proved by comparing with the microbiological and iodometric determination. The mercurimetric determination of penicillins and their decomposition products in acetate buffer was applied to injections, tablets, capsules and dry sirup.