[Analysis of trace elements in biological materials by microwave induced plasma-mass spectrometry]

Analytical conditions have been established for determination of trace elements in biological materials by microwave induced plasma-mass spectrometry (MIP-MS). Possible elemental contaminants were checked in the water and reagents used, and during the wet-ashing process. Among 72 elements tested, contamination by Na, Mg, K, Ca, Fe, Ba, and Pb were observed. This contamination was estimated to occur mainly during the process of preparing samples due to the water, reagents and surroundings. Contamination by Ca, Mg, Zn and Pb from tubes for storage was also observed. Adequate conditions for multielement analyses in plasma and bone samples were evaluated. Both plasma and bone samples were digested by the wet-ashing technique before applying MIP-MS. The recovery rates of elements added were decreased depending on the contents of plasma or bone samples in the measuring solutions. The interfering effects of matrix modification due to organs were improved by correction with an internal standard. Recovery rates of elements added, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn, Ba, Pb and fourteen lanthanide elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were within 100 +/- 5% in analytical samples containing 1% volume of human plasma when Ga or Tl was used as the internal standard. Recoveries of Sn and Zn in the bone samples containing 0.1% bone as the original bone material, however, were 100 +/- 10% even after correction by the internal standard, suggesting the necessity of combined use of standard addition methods. The concentrations of V, Cr, Mn, Fe, Cu, Zn, Rb, Sr, Mg, and Ca in plasma from two healthy women were determined by MIP-MS. The data were consistent with the values reported elsewhere, and agreed very closely with those obtained by atomic absorption spectrometry. The accuracy of the values obtained by this method was confirmed using standard reference materials. These results indicate that MIP-MS is a useful method for multielement determination of biological materials.