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

We have developed a semiautomatic procedure based on a sequential injection method for Sr-90/Y-90 determination that allows their radiochemical separa tion in about 30 min. The method has been tested using 90Sr/90Y solutions w ith activities lower than 12 Bq. The source is eluted in a pH = 6.5 medium through a MnO2-impregnated cotton filter, where Y-90 is preconcentrated in preference by adsorption. 90Y is extracted from the column with hydroxylami ne, some Sr-90 in the leached solution has also been found. After the radio chemical separation, the total beta-activity of the leached solution has be en determined using a low background alpha-beta proportional counter and. a ssuming the presence of Sr-90 and Y-90 at t = 0, the solution of the Batema n equations allows the initial concentration of both isotopes to be obtaine d. We have verified that the addition of some ions usually found in water s amples (Cl-, HCO3-, NO3-, SO42-, Ca2+, Mg2+) does not interfere with the yi eld of the radiochemical process, (90 +/- 10)%. The method has been applied to Sr-90/Y-90 determination in mineral waters, and even in thermal waters, where the salt concentration can be about 3500 mg/l, the radiochemical yie ld remains greater than 80%. (C) 2000 Elsevier Science Ltd. All rights rese rved.