Substoichiometric isotope dilution analysis for the determination of iron in biological materials and comparison with substoichiometric isotope dilution mass spectrometry

Substoichiometric isotope dilution analysis for the determination of trace iron has been studied by using synergistic extraction of iron(iii) with a s ubstoichiometric amount of 4-isopropyltropolone (Hipt) in the presence of a n excess of 3,5-dichlorophenol (DCP) in heptane, Optimum conditions for the substoichiometric extraction of iron(III) in mu g to sub-mu g levels were examined and the high selectivity for iron(III) toward various metal ions e ncountered in the analysis of biological materials was confirmed. The prese nt method was applied to a biological reference material (NIES, CRM No.9, s argasso) without any pre-separation and was successfully evaluated. Further more, substoichiometric stable isotope dilution mass spectrometry using the present extraction method was also used with the above sample. Applicabili ty and practicability was compared for both substoichiometric methods.