Portal de Periódicos da CAPES

Application of ICP-MS to accurate isotopic analysis for human metabolic studies

1987; Elsevier BV; Volume: 42; Issue: 1-2 Linguagem: Inglês

10.1016/0584-8547(87)80046-0

1873-3565

Bill T. G. Ting, Morteza Janghorbani,

Groundwater and Isotope Geochemistry

The method of inductively coupled plasma mass spectrometry (ICP-MS) is applied to accurate measurement of selected stable isotopes of iron, copper and zinc in human fecal matter. Background peaks are observed at m/z 54, 57 and 58. However, relative to the expected intensity of corresponding isotopes of iron, the background intensities are acceptably small. Of the potential isobaric interferences, viz. 54Cr and 58Ni for iron, and 70Ge for Zn, only 58Ni is of major concern in the fecal matrix. Chemical separation procedures are described and evaluated in specific reference to this application. The relevant isobaric interferences are removed to the required extent by the application of these procedures. Achievable measurement precision in the relevant isotope ratios is at 1% or better which is consistent with the requirements of human metabolic studies. The measured isotope ratios (MR) are converted to true ratios expressed on the mass scale (Mass Isotope Ratio, MIR) by the use of appropriate stable isotope calibration standards. The method of isotope dilution analysis (IDA) is applied to the accurate measurement of absolute isotope contents. The precision and accuracy of IDA is tested on subsamples of human fecal matter and the Standard Reference Material Bovine Liver (SRM 1577a). The coefficient of variation for multiplicate measurements of absolute isotope content is better than 2 % for both fecal matter and the SRM 1577a. The measured isotopic concentration (μgg) of SRM 1577a, expressed in terms of natural element for Fe, Cu and Zn is (mean ± 1SD): 192 ± 2,156 ± 2 and 120 ± 1, respectively. These compare with the corresponding certified values of 194 ± 20, 158 ± 7 and 123 ± 8.