Separation of niobium and tantalum oxalate complexes by paper electrophoresis

Abstract

The study of the electrophoretic behaviour of niobium and tantalum oxalate complexes with citric acid-ammonium citrate solutions as buffers has led to the establishment of suitable conditions for their separation. The oxalate concentration and the pH of the sample solution, in addition to the citrate concentration and the pH of the buffer, have been determined. A developing solution containing an excess of pyrogallol and oxalic acid in ethyl acetate is used to detect the metal bands that appear after heating under an infrared lamp. Niobium and tantalum oxalate complexes in a 0·2 to 0·4 M ammonium hydrogen oxalate solution of pH 1·8 to 2·4 can be separated in a 30-minute electrophoresis run, giving two well defined bands, which are lilac and yellow, respectively, when a 0·05 M ammonium hydrogen citrate solution, pH 3·0, is used as buffer, with a potential gradient of about 16 V cm^–1. Down to 0·3 µg of tantalum or niobium can be detected after separation from up to 13 µg of niobium or 50 µg of tantalum on a 1·5 × 20-cm Schleicher & Schüll paper strip.