Development of a stable isotope approach for the inductively coupled plasma-mass spectrometry determination of oxidized metallothionein in biological materials.
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.
Valles Mota
J P
JP
Department of Physical and Analytical Chemistry, University of Oviedo, Oviedo, 33006, Spain.
Linde Arias
A R
AR
Fernández de la Campa
M R
MR
García Alonso
J I
JI
Sanz-Medel
A
A
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
D000097:Acetonitriles; D007554:Isotopes; D002104:Cadmium; D008668:Metallothionein; C032159:acetonitrile