Rapid 90Sr/90Y determination in water samples using a sequential injection method

We have developed a semiautomatic procedure based on a sequential injection method for 90Sr/90Y determination that allows their radiochemical separation in about 30 min. The method has been tested using 90Sr/90Y solutions with activities lower than 12 Bq. The source is eluted in a pH = 6.5 medium through a MnO2-impregnated cotton filter, where 90Y is preconcentrated in preference by adsorption. 90Y is extracted from the column with hydroxylamine, some 90Sr in the leached solution has also been found. After the radiochemical separation, the total β-activity of the leached solution has been determined using a low background α–β proportional counter and, assuming the presence of 90Sr and 90Y at t = 0, the solution of the Bateman equations allows the initial concentration of both isotopes to be obtained. We have verified that the addition of some ions usually found in water samples (Cl−, HCO3−, NO3−, SO42−, Ca2+, Mg2+) does not interfere with the yield of the radiochemical process, (90 ± 10)%. The method has been applied to 90Sr/90Y determination in mineral waters, and even in thermal waters, where the salt concentration can be about 3500 mg/l, the radiochemical yield remains greater than 80%.