The use of alumina “SepPaks®” as a simple method for the removal and determination of tungsten-188 breakthrough from tungsten-188/rhenium-188 generators

Abstract A simple method using an alumina SepPak ® has been developed to determine the breakthrough levels of 188 W from 188 W/ 188 Re generator systems. Detection of low levels of 188 W in the presence of high levels of 188 Re (155 keV, 15%) by traditional counting techniques is not possible because the 188 W parent emits gamma photons of only very low intensity at 227 keV (0.22%) and 290 keV (0.40%). In order to remove and quantitate levels of 188 W in “real time” without having to wait several days for decay of the 188 Re caughter, the use of an alumina SepPak ® in tandem with the alumina generator is an effective technique to trap the 188 W breakthrough. The efficiency of this technique was demonstrated by doping 2 mCi of 188 Re with 2 μCi of 188 W. This doped sample provided a control which would correspond to a very high breakthrough value (0.1%), which is 10 3 times greater than the usual breakthrough of the alumina system ( −4 %). Even these very high levels of 188 W could not be detected by gamma-ray spectroscopy in the presence of the 188 Re. When the eluant was subsequently passed through an acid-washed alumina SepPak ® followed by thorough washing (20 mL) with 0.9% NaCl, however, the 227 and 290 keV gamma lines were clearly detected, which facilitated quantification of the 188 W breakthrough levels. Breakthrough levels 1000 times lower could still be detected by this method, making it a useful quality control tool in assessing 188 W/ 188 Re generator performance.