Accurate Isotopic Analysis Research Articles

Advanced mass spectrometers for hydrogen isotope analyses

Two advanced mass spectrometers for accurate hydrogen isotope analyses were evaluated at the Savannah River Laboratory. One is a double-focusing instrument with a resolution of 2,000 at mass 4. The second is a stigmatic-focusing instrument with exceptionally high ion intensities for high signal-to-noise ratios. Both instruments are computer controlled. A containment facility permits testing with tritium mixtures. A recovery system prevents the release of tritium to the environment. The performance of the mass spectrometers was essentially equal under simulated process control conditions. Precision and accuracy for the D/T ratio was <0.5% (rel 2σ limits).

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/sup -4/ for 10 ng at a temperature of 1620 +/- 10 /sup 0/C. 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.

Accurate analysis of stable isotopes 68Zn, 70Zn, and 58Fe in human feces with neutron activation analysis

Accurate isotopic analysis of human fecal samples is discussed in relation to mineral bioavailability studies of human subjects. It is shown that for bioavail-ability investigations of Zn and Fe, the method of neutron activation analysis is suitable for routine application to clinical experiments; and the human fecal samples resulting from diet suitably enriched in isotopes 70Zn and 58Fe can be routinely analyzed with relative precisions of about 1% for the isotopes 68Zn, 70Zn and 58Fe.