APPLICATION OF THERMAL IONIZATION MASS-SPECTROMETRY TO INVESTIGATIONSOF MOLYBDENUM ABSORPTION IN HUMANS

Thermal ionization mass spectrometry (TIMS) has been developed for the detection of Mo in biological samples in order to enable investigatio ns on absorption and biokinetics in humans. A double rhenium filament technique is employed for sample evaporation and ionization, coupled w ith a quadrupole filter. The negative MoO3- ions that are produced are then collected on a secondary electron multiplier and isotopic ratios are measured. A correction must be performed to take into account the isotopic composition of oxygen. The technique has been optimized for the determination of Mo down to 10 ng loaded on the evaporation filame nt. Preliminary tests were applied to aqueous solutions. Subsequently, measurements were performed on human urine samples, and finally the t echnique was applied to investigations on the intestinal absorption of Mo in humans. The technique proves to be quite simple and reliable in application, and enables widely ranging studies on molybdenum metabol ism and biokinetics in humans to be performed without employing radioa ctive tracers.