Thermal ionization mass spectrometry of uranium with electrodeposition as a loading technique

Uranium samples are elecroplated on degassed zone-refined rhenium filaments and overplated with rhenium to permit accurate isotopic analyses at nanogram levels. The method provides an ionization efficiency of 1.5 X 10-4 for 10 ng at a temperature of 1620 +/- 10 0C. Isobaric interferences are less than or equal to dark current of the measuring system, 0.05 counts/s. Accuracies achieved on 10 ng of NBS U-500, a 1/1 235/238 uranium isotopic standard, are 0.05% tsigma at the 95% confidence level. The effects of counting system dead time and chemical bank are discussed