Method development for thermal ionization mass spectrometry in the frame of a biokinetic tracer study with enriched stable isotopes of zirconium

Abstract

Isotope dilution in thermal ionization mass spectrometry (ID-TIMS) is a precise method for quantification of isotope ratios in geological samples, or for trace elements analysis in geological and environmental samples. This work presents an optimized ID-TIMS method for application in the field of life sciences, more precisely in the frame of a human biokinetic study on zirconium with oral and intravenous administration of two stable isotope tracers. The method allows analyzing simultaneously different stable zirconium isotopes (two isotopically enriched artificial tracers and the natural background) in human blood plasma and urine. By optimization, tracer detection limits below 1 ng ml −1 could be achieved. The biological samples were prepared by microwave-assisted acidic pressure digestion followed by extraction chromatography. The purified zirconium from the samples was measured on carbon-coated rhenium single filaments. Multiple channel electron multipliers were used as detectors. Interferences were observed from molybdenum isotopes and were corrected for based on the 95Mo count rate. Isotope ratios of zirconium were determined in ranges of 0.016–2.84 ( 91Zr/ 90Zr), 0.020–2.46 ( 92Zr/ 90Zr), 0.115–10.93 ( 94Zr/ 90Zr), and 0.004–5.70 ( 96Zr/ 90Zr). The respective relative uncertainties lay in the range of 0.03–4.2%. Typical relative uncertainties of tracer concentrations were 4%.