MEASUREMENT OF NATURAL MAGNESIUM ISOTOPE EFFECTS IN HUMAN URINE BY GRAVIMETRIC SPIKING-ISOTOPE DILUTION ANALYSIS

Abstract

Subtle variations in the isotopic composition of elements carry unique information about processes in nature and are now exploited in diverse areas of research. Overcoming instrument mass bias effects is one of the biggest challenges in inorganic mass spectrometry. The conventional mass bias correction technique could only be applied to elements with four or more isotopes. We developed the novel Gravimetric Spiking-Isotope Dilution Analysis (GS-IDA) technique for the correction of instrument mass bias for elements with three or more isotopes to include magnesium. Optimization of the parameters was done using Monte Carlo Simulations. We became the first group to study magnesium isotope effects in human urine using the Multi-Collector Thermal Ionization Mass Spectrometer. Our final study involving twenty healthy Chinese males showed that magnesium isotope effects varied with age. The inter-individual differences may be associated with the reabsorption process in the kidney, which is the primary organ for magnesium homeostasis.