MULTIELEMENTAL NEUTRON ACTIVATION ANALYSIS OF AN APOLLO-17 LUNAR MARE BASALT SAMPLE USING INSTRUMENTAL AND RADIOCHEMICAL METHODS

By means of instrumental and radiochemical methods, 36 elements are determined in an Apollo-17 lunar mare basalt sample. Total amount of the sample is only 62.10 mg. By using instrumental neutron activation analysis, 19 elements (Al, V, Ti, Ca, Dy, Mo, Eu, Na, Sm, La, Ho, Lu, Yb, Tb, Hf, Cr, Fe, Co, and Sc) are determined for one part of the sample (20.00mg). The other part of the sample (42.10 mg) is irradiated at a thermal flux of 2×1013 n/cm2. s for 40 h. After 12 h cooling, radiochemical separation is preformed and 17 more elements (Pr, Er, Gd, Nd, Ce, Tm, Cs, Rb, Sb, Zn, Zr, Sr, Ba, Ga, Ta, U and Th) are determined. The separation procedure consist of ion exchange, solvent extraction and reverse phase chromatography, resulting in the separation of 36 elements into 12 groups. A CANBERRA SCORPIO-3000 system is used for γ-ray spectrum measurements and data processing. The system includes a Ge (Li) detector with an energetic resolution of 1.9 keV and a relative efficiency of 30% and a computerized data acquisition and reduction system. For each element determined, two or more comparative standards are independently prepared to ensure the reliability of the standards. Accuracy of the results is verified by parallel analysis of USGS SRM W-1 sample. Most of the experimental results including ' 14 rare earth elements agree quite well with those reported in the literature for Apollo-17 lunar mare basalt samples.