György Horvai

The application of electroanalytical detectors in continuous flow analysis

Abstract A survey is given of the different fields of application of flow-through techniques employing electroanalytical detectors. Emphasis is placed on recently developed titration techniques.

A polarographic and spectrophotometric routine analyzer for assaying content uniformity in pharmaceutical quality control

Abstract A serial analyzer with polarographic and spectrophotometric detection has been designed to speed up content uniformity tests in pharmaceutical quality control laboratories. The advantages of flow and discrete analysis are combined to provide the required speed and precision. Pharmaceutical preparations of diazepam, nitrazepam, spironolactone and pyridinolcarbamate have been tested satisfactorily. The system is easily constructed from commercially available hardware and a few home-made units. The problem of sample deaeration before polarographic measurements in flow systems is solved succesfully in a very simple way.

Continuous flow determination of sulphate with a lead-selective electrode

A continuous flow system was constructed for the determination of sulphate in the concentration range 10–5–10–3M. The reagent stream, containing lead(II) ion, ionic-strength adjuster and pH-adjustment buffer in methanol, was mixed with a sample sulphate stream and the free lead(II) concentration was monitored with a lead ion-selective electrode. The calibration graph is not linear owing to the titrimetric character of the determination and the curvature is explained by the solubility equilibrium that exists between lead and sulphate. The relative error was within ±10%. Interference from hydrogen carbonate was observed even in the presence of acidic buffer.

Ion exchange at neutral carrier ion-selective electrode membranes

SummaryRadiotracer experiments proved that neutral carrier (valinomycin) containing plasticized PVC membranes behave as cation exchangers. The exchange capacity may be due to lipophilic salt additives, but there is also a native exchange capacity that may be due to hydrophilic salt contaminations trapped in the membrane.