To determine the concentrations of elements of atomic number higher than about 60, the KX-ray fluorescence technique employing a 3.7 GBq137Cs gamma-ray source with a pure germanium semiconductor detector is examined. Due to the fairly high energy of the KX-rays this technique is capable of determining the element concentration in a considerably large sample volume with little effects of matrix elements and vessel wall. A narrow gammaray beam and large scattering angle geometry is chosen to discriminate between the KX-rays and the scattered radiations in the measurement. A 300 second measurement allows a relative precision of less than 3% for samples of aqueous solution, mixing powder and alloy containing more than 1-3 wt% high atomic number elements such as W, Pb or U.
The adsorption of67Ga to the inner surface of stainless steel, polyethylene and silicone tubings was studied. The three tubings remarkably adsorbed67Ga in order of stainless steel, silicone and polyethylene tubing. Sodium citrate inhibited the adsorption of67Ga in a dosedependent manner. These phenomena were also observed in blood sampling via the catheter inserted into the external jugular vein. These results show that constant concentration of sodium citrate is necessary for the in vitro study of67Ga in order to prevent the adsorption to the surface of experimental materials.