COLLOID FILTRATION AS A PREPARATIVE METHOD FOR RADIOCHEMICAL ANALYSIS OF BIOLOGICAL SAMPLES

A simple, reliable, rapid and efficient method for the radiochemical analysis of polyvalent nuclides in biological samples is described. The method consists of homogenizing, prefiltering at pH 1 and separating the nuclide as the hydrogen phosphate by filtering through a 0.3 μ membrane filter paper at pH 5.0. Optimum conditions were established with respect to pH, carrier concentration, filter paper pore size, and the elimination of chelating agents such as EDTA. The particulate matter filtered was of colloidal size (diameter 0.1 μ). Chemical analysis and isotope dilution studies established that for Y the particulate matter was Y2(HPO4)3. Radiometric yield for 91Y in dog urine was 97 ± 1.0%. Yields for 144Ce(IV), 155Eu(III) and 147Pm(III) were about 97%. Contamination of Y particulate matter by both Ca and Sr was about 1% at pH 5.0 and about 35% at pH 8.0. This procedure eliminates tedious wet ashing steps, yields thin counting samples and minimizes radiochemical and counting errors. It is an excellent procedure for weak beta emitters such as 147Pm. Since it is fast and simple, this method is well suited for routine analysis of large numbers of radiobiological samples. © 1969 Health Physics Society.