Abstract
A minute amount of copper can be accurately determined by mass spectrometry using a single rhenium filament as a surface ionization device, on which copper compound spiked with 65Cu is loaded. Measurements of 63Cu+ and 65Cu+ ion beam intensity allow to determine the copper amount at(10-110-3)μg level. Add 4μg of 65Cu spike to the samples acidified with hydrochloric acid. Let a pair of spiked samples stand for 3 days and another pair for 4 months. Extract copper as dithizonate in chloroform and evaporate it together with nitric and perchloric acids and finally with sulfuric acid. Dissolve the residue in 0.1 g of redistilled water. An aliquot of the solution is loaded onto the ionization filament, silica gel and phosphoric acid being added as stabilizing agents. The detection limit of Hitachi mass spectrometer is 10-19 A for Cu+ion beam. The ion beam from spiked 65Cu usually gets 10-15 A level of the intensity which is maintained stable for hours. 63Cu+/65Cu+ value is recorded with the coefficient of variation of 0.5%. Copper concentration in sea water determined from the 3-days standing pair samples is (0.38±0.02) ppb and that from another pair is (0.42±0.02) ppb.
