A 14'La tracer has been used to ldentlfy the sources of cross-contamination when conventlonai hlgh-performance liquid chromatography was used to collect metal ion fractlons for subsequent analysls by a spectrometry or mass spectrometry. Major sources of memory effects ldentlfled were normal band broadenlng, sorptlon onto metal surfaces, and retentlon wlthln sample valves; secondary sorptlon effects wlthln the column and Isotopic exchange wlth sorbed metal Ions were not Important sources of memory effects. On the bask of these results a recommended procedure was developed that gives cross-contamlnatlon levels of 10.006 %. Sample preparation technlques for the a spectrometric and mass spectrometrlc analyses of the collected fractions are discussed, and some examples are given of appllcatlons to anaiytlcal problems In geochemlstry and the nuclear Industry. Good sample recoveries were obtained for the sample range studled (0.1-500 ng).USGS BCR-1 sample (0.5 g) was dissolved in HF and "OB,
A thermal ionization mass spectrometric procedure was developed for determination of 240/239 ratios in subpicogram quantities of plutonium (Pu), and was applied to Pu extracted from Lake Ontario sediment. The detection limit was ∼ 4 fg of Pu and the precision of 240/239 ratio measurement was ∼ 7% in the 0.07-0.42 pg range. Results of sediment analyses at various depths showed in all cases 240/239 ratios near the mean global fallout value of 0.176 ± 0.014. The lack of variability of the ratios with depth negated the use of Pu, present in excess in the near-surface samples due to leakage from a nearby reprocessing plant, as a geochronological meter. The 240/239 ratio of the leakage Pu appeared to be very similar to that of fallout Pu.
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