APPLICATION OF ION-EXCHANGER PHASE SPECTROFLUOROMETRY TO THE DETERMINATION OF MICRO-AMOUNTS OF SOME RARE-EARTH ELEMENTS BY FLOW-ANALYSIS

The fluorescence bands originating from d --> f electron transitions, which can be used to determine europium, terbium, dysprosium or samarium selectively, were enhanced only if these elements were sorbed in a weak-acid cation-exchange gel, i.e., CM-Sephadex. After a sample solution had been introduced into a fused-silica tube (1.5 mm i.d.) packed with 1 mg of CM-Sephadex, the fluorescence intensity increase, resulting from the rare earth elements sorbed in the ion-exchange gel, could be measured directly with good precision. For europium, the detection limit was 22 ng with an 8.3 cm3 sample solution. The sensitivity of the proposed method depended on the sample volume introduced. The cell could be used repeatedly after desorbing the target element with a solution of nitric acid.