Application of mass spectrometric isotope dilution methodology for super(90)Sr age-dating with measurements by thermal-ionization and inductively coupled-plasma mass spectrometry

Application of an isotope-dilution method for determining super(90)Zr and super(90)Sr in a super(90)Sr source material spiked with super(86)Sr and super(92)Zr is described. A miniature gas pressurized extraction chromatography (GPEC) system with a column containing Eichrom Sr Resin(TM) was used for separating the elements so isobaric isotopes could be measured by mass spectrometry. Zirconium was rinsed through the column with 3 M HNO sub(3)/trace HF and strontium was eluted with 1% acetic acid. Two mass spectrometric techniques, inductively coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS), were used for measuring isotope ratios. Data were obtained with super(90)Sr from a blood-irradiator source. Results from the TIMS measurements gave a decay time of 45.16 plus or minus 0.26 years, and those from the ICP-MS gave 45.24 plus or minus 0.20 years (uncertainties are expanded uncertainty, k= 2). Quadrupole ICP-MS is preferable to TIMS in this application if the ICP-MS data are suitably corrected for non-linearity and mass discrimination.