THE USE OF ALUMINA SEPPAKS AS A SIMPLE METHOD FOR THE REMOVAL AND DETERMINATION OF TUNGSTEN-188 BREAKTHROUGH FROM TUNGSTEN-188 RE-188 GENERATORS

A simple method using an alumina SepPak(R) has been developed to determine the breakthrough levels of W-188 from W-188/Re-188 generator systems. Detection of low levels of W-188 in the presence of high levels of Re-188 (155 keV, 15%) by traditional counting techniques is not possible because the W-188 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 W-188 in "real time" without having to wait several days for decay of the Re-188 daughter, the use of an alumina SepPak(R) in tandem with the alumina generator is an effective technique to trap the W-188 breakthrough. The efficiency of this technique was demonstrated by doping 2 mCi of Re-188 with 2-mu-Ci of W-188. 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 (< 10(-4)%). Even these very high levels of W-188 could not be detected by gamma-ray spectroscopy in the presence of the Re-188. When the eluant was subsequently passed through an acid-washed alumina SepPak(R) 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 W-188 breakthrough levels. Breakthrough levels 1000 times lower could still be detected by this method, making it a useful quality control tool in assessing W-188/Re-188 generator performance.