Determination of trace zinc, selenium, cadmiyun, indium and tellurium in meteorites by Naa.

Five trace chalcophile elements, Zn, Se, Cd, In and Te in chondritic meteorites were determined by radiochemical neutron activation analysis. Powdered samples of 50 ~ 100 mg, along with standard samples prepared from reagents, were sealed individually in quartz tubes and irradiated in the JRR -4 reactor of the JAERI at a flux of 5.5 × 10¹³ n cm^-2 s^-1 for 12 h. After cooling for 3 ~ 4 d, meteorite samples were fused with sodium peroxide and sodium hydroxide in zirconium. crucibles in which the appropriate amounts of carrier solutions of the above elements had been taken and dried. After the fusion cakes were dissolved in water, sodium sulfide was added. Mixtures of hydroxide and sulfide precipitates involving Zn, Cd, In, and a part of Te were separated by centrifugation. Precipitates were then dissolved in nitric acid. Being converted to the chloride form, the elements separated as precipitates were loaded onto anion exchange resin to be separated successively from each other. Selenium and remainders of tellurium were precipitated as metallic forms by saturating with sulfur dioxide gas. Selenium and tellurium were separated by passing through anion exchange columns. Each element recovered was radiochemically purified and precipitated in an appropriate form to determine the chemical yield gravimetrically. The detection limits of the present method were deduced to be 70 ppb for Zn, 0.61 ppb for Se, 17 ppb for Cd, 3.3 ppb for In and 68 ppb for Te under the current conditions. Analytical precision and accuracy were estimated based on data from the Allende meteorite which was analyzed several times repeatedly.