THERMAL IONIZATION AND INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY -POTENTIAL FOR APPLICATION TO STUDIES ON THE BIOKINETICS OF MOLYBDENUMIN HUMANS

The use of stable isotopes as tracers in biokinetic investigations pro vides a means to obtain important metabolic data directly in humans wi thout exposing the subjects to undue risks. In this work, three types of mass spectrometers are compared with regard to the determination of the abundances of stable isotopes of molybdenum in natural and enrich ed aqueous samples. The data show a good response of thermal ionizatio n mass spectrometry (TIMS) and of high-resolution inductively coupled plasma mass spectrometry (ICPMS) to the isotopic enrichment of the sam ples, whereas conventional quadrupole ICPMS shows an unsatisfactory re producibility of the results. Moreover, only TIMS can achieve an accur acy of better than 1% for the obtained isotopic ratios. Although a ted ious procedure for the preparation of the biological samples is requir ed and less sensitivity is achieved as compared to ICPMS, TIMS still s eems to be method of choice for the accurate assessment of isotope rat ios as required in multitracer studies on human biokinetics of trace m etals.