Liquid Chromatographic Determination of Uranium in Seawater with Coulometric Detection

Abstract

A method of the separation with anion-exchange chromatography and of the coulometric detectionof uranium in seawater was investigated. The size of the separation column used was 9mmin inside diameter and 100mm in length, and strong basic anion-exchange resin (Hitachi No.2632) of carbonate form was packed in the column. A concentrator with two mini-columns in whichthe same resin was packed was applied for the preconcentration of uranium in seawater containing20g of potassium thiocyanate and10ml of hydrochloric acid per liter. Good result was obtainedwhen a mixed solution of sodium carbonate (0.12mol/l), sodium bicarbonate (0.08mol/l), sodiumbisulfite (0.03mol/l) and sodium chloride (0.5mol/l) was used as an eluent for the separation ofuranium from vanadium. Sodium bisulfite was of use for dropping the background current basedon an electrochemical reduction of dissolved oxygen. Sodium bicarbonate acted as an eliminatorof an unknown peak by its bufferise effect. The optimum working electrode potential for the detectionwas-1.45V vs. ferri-ferrocyanide. The detection limit was3.2×10^-10mol (80ngU). Thecoefficient of variation at3.0ppb was about 4%(n=5) for seawater analysis. And the analysis time was approximately 1.5 hours.