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 cm 3 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.