title: Development of a stable isotope approach for the inductively coupled plasma-mass spectrometry determination of oxidized metallothionein in biological materials.
abstract: The use of isotope dilution analysis (IDA) with inductively coupled plasma-mass spectrometry (ICP-MS) for the determination of oxidized metallothionein (MT) by a Cd-saturation method is investigated. The method developed here is a modification of an earlier methodology which used a radioactive Cd isotope ((109)Cd). While retaining the many advantages of this previous approach, the procedure presented here uses stable isotope ratio measurements ((114)Cd/(111)Cd) for the determination of MT. Experimental parameters governing the instrumental precision and accuracy for isotope ratio measurements of Cd by ICP-MS were characterized. Systematic errors, including mass bias, detector dead time, and spectroscopic interferences, could be easily corrected. The isotope dilution ICP-MS method was validated by the determination of very low levels of cadmium in biological certified reference materials (NIST SRM 2670 freeze-dried urine, IAEA H-8 horse kidney, and BCR TP-25 lichens). Finally, the IDA procedure was evaluated for the determination of oxidized MT by a Cd-saturation method previously developed using radioactive (109)Cd. The final procedure was applied to the quantification of MT in Long-Evans Cinnamon rat liver cytosol samples and the results were compared with data obtained for the same samples using the reference (109)Cd methodology. A good agreement between the analytical values obtained by both methods was observed.
authors.affiliation: Department of Physical and Analytical Chemistry, University of Oviedo, Oviedo, 33006, Spain.
authors.forename: J P
authors.initials: JP
authors.lastname: Valles Mota
authors.forename: A R
authors.initials: AR
authors.lastname: Linde Arias
authors.forename: M R
authors.initials: MR
authors.lastname: Fernández de la Campa
authors.forename: J I
authors.initials: JI
authors.lastname: García Alonso
authors.forename: A
authors.initials: A
authors.lastname: Sanz-Medel
mesh_terms: D000097:Acetonitriles; D000818:Animals; D002104:Cadmium; D006736:Horses; D007201:Indicator Dilution Techniques; D007554:Isotopes; D007668:Kidney; D008099:Liver; D013058:Mass Spectrometry / Q000379:methods*; D008668:Metallothionein / Q000032:analysis*; D010084:Oxidation-Reduction; D051381:Rats; D020332:Rats, Inbred LEC
chemical_list: D000097:Acetonitriles; D007554:Isotopes; D002104:Cadmium; D008668:Metallothionein; C032159:acetonitrile