Continuous flow determination of sulphate with a lead-selective electrode

Abstract

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.