The determination of molybdenum in geological samples by neutron activation analysis

A metal-silicate extraction technique combined with neutron activation analysis was developed to determine molybdenum in geological samples. The samples are equilibrated with Fe-metal powder at high temperatures. Molybdenum is completely extracted into the metal phase because of very reducing conditions in the furnace. The metal spherule is separated from the silicates, irradiated and dissolved in an acid solution. The molybdenum is precipitated as a sulfide and the precipitate is dissolved in aqua regia and counted on a Ge(Li)-detector. The radiochemical yield is obtained by irradiation of the solution. The method avoids production of sup(99)Mo from induced fission of sup(235)U by performing the metal-silicate separation before irradiation. The precipitation step may be necessary to remove the high background from the decay of sup(59)Fe. Mo concentrations down to 15 ng/g were obtained using this method. (author)