摘要：An enriched stable isotope is recognized as a label because of its high abundance relative to the corresponding endogenous natural abundance isotope in hosts, and hence is a relative label. Here, lowering the corresponding endogenous natural abundance element, multiple enriched stable isotopes were used as absolute labels for each. Thus, host animals were depleted of natural abundance stable isotopes by feeding a single enriched isotope, followed by administration of multiple precursors labeled with different homo-elemental stable isotopes. Metabolites of each labeled precursor were traced and speciated simultaneously by HPLC-inductively coupled argon plasma-mass spectrometry without interference from endogenous natural abundance isotopes. In the present experiments, rats with a single stable isotope (82Se) were administered with 76Se-selenite and 77Se-selenomethionine simultaneously. The metabolites of 76Se and 77Se were speciated simultaneously as absolute labels, and independently from the endogenous selenium. The advantages of multiple absolute labeling coupled with simultaneous speciation, and general applications to metallomics of biometals and other wider applications, are proposed and discussed.
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