Potentiometric and atomic absorption spectrometric determination of sulfonamides in pharmaceutic preparations.

Potentiometric and atomic absorption spectrometric (AAS) methods are described for the determination of various sulfonamides in tablets, suspensions, and injections, based on reactions with silver and copper ions. The methods involve direct titration at pH 8, using either a graphite electrode in which silver and copper sulfides have been precipitated, or ion selective electrodes to monitor the potential change. AAS measurements of the excess metal ions after metal-sulfonamide reaction are also reported. Results compare favorably with those obtained using USP XIX procedures. The methods described are selective, simple and precise.

Determination of chloramphenicol in pharmaceutical preparations by the cadmium ion-selective electrode, spectrophotometry and atomic-absorption spectrometry.

New simple methods are described for the determination of chloramphenicol and its esters in pure powders, suppositories, injections, eye-drops, capsules and oral suspensions. These are based on reduction with cadmium metal whereby 6 equivalents of cadmium ions per mole and the corresponding amino-derivative are released. Four portions of the reduction products are used for (i) measurement of the cadmium ions by atomic-absorption spectrometry at 228.8 nm; (ii) potentiometric titration with EDTA, with use of the cadmium ion-selective electrode; (iii) visual titration with EDTA, with Eriochrome Black T as indicator, (iv) diazotization and coupling with N-(1-naphthyl)ethylenediamine and measuring the resultant colour at 550 nm. The results obtained by these procedures are in good agreement, and compare favourably with those of the official methods.

Determination of vitamin B1 in pharmaceutical preparations using a lead ion selective electrode and atomic absorption spectroscopy.

Simple, rapid, and accurate methods have been developed for determining vitamin B1 in pharmaceutical preparations without prior separation of the vitamin. The methods are based on the desulfurization reaction with potassium plumbite and measurement of the unreacted lead(II) ions at 217 nm using atomic absorption spectroscopy (AAS), or by titration with EDTA at pH 4.5 with the lead ion selective electrode and Gran's plot. The results compare favorably with those obtained using the USP fluorometric method. Recoveries of pure vitamin B1 averaged 99.1%, with a standard deviation of 0.8%, and 99.0%, with a standard deviation of 0.7%, for the AAS and ion selective electrode procedures, respectively.

Determination of penicillins by desulphurization with lead and edta titration.

A new, simple, accurate and rapid method is described for the determination of total penicillins in pharmaceutical preparations. The method is based on desulphurization with potassium plumbite whereby one mole of lead sulphide is formed per mole of penicillin. The excess of lead ions is titrated with EDTA at pH 4.5, with use of the lead ion-selective electrode. Results are reproducible within +/- 0.5% and compare favourably with those obtained by the procedures of the United States and British Pharmacopoeias.