ABSTRACT
Pharmacokinetic studies using stable isotopes of magnesium as tracers need to determine the isotopic abundance in biological media by means of mass spectrometry. Of mass spectrometric techniques, electronic impact-mass spectrometry (EI-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) can be used. We have measured the isotopic abundance in plasma and urinary samples and compared the precision and accuracy of these two methods. Graphical representations showed that mean differences were close to 0, there was no obvious relationship between the difference and the mean, and no systematic bias was evidenced at low or high isotopic abundance. This was shown for isotopic abundance of either 25 Mg and 26 Mg. EI-MS is able to measure magnesium isotopic abundance with an intra-day precision between 0.14 and 0.45 per cent and with an inter-day precision between 0.20 and 1.23 per cent. ICP-MS exhibited an intra-day precision between 0.01 and 0.06 per cent and an inter-day precision between 0.01 and 0.15 per cent. Our results showed that, despite the similar isotopic abundances in biological samples obtained with the two methods, a large difference in precision clearly favours ICP-MS in studies of magnesium behaviour using stable isotopes.
Subject(s)
Magnesium/pharmacokinetics , Mass Spectrometry/methods , Biological Availability , Feces/chemistry , Humans , Injections, Intravenous , Isotopes , Magnesium/blood , Magnesium/urine , Reproducibility of ResultsSubject(s)
Magnesium/pharmacokinetics , Tablets , Administration, Oral , Adult , Area Under Curve , Biological Availability , Feces/chemistry , Humans , Injections, Intravenous , Isotopes , Magnesium/blood , Magnesium/urine , Male , Reference ValuesABSTRACT
An anion exchange HPLC-ICP-MS procedure allowing the simultaneous multielemental speciation analysis of arsenic, selenium, antimony and tellurium has been developed. Four arsenic species (As(III), As(V), monomethylarsonic acid and dimethylarsinic acid), two selenium species (Se(IV) and Se(VI)) may be determined in a single run as well as one antimony (Sb(V)) and one tellurium species (Te(VI)). Alternatively Sb and/or Te may be used as internal standards for As and Se speciation studies. Optimisation of ICP-MS conditions led to satisfactory relative (0.01 (Sb(V)) to 1.8 (Se(VI)) ng ml(-1)) and absolute detection limits (1-180 pg). Reproducibility ranged from 3.1 to 5.6% and the linearity was verified in the 0-200 ng ml(-1) range.
