Determination of rare earth elements in human blood serum by inductively coupled plasma mass spectrometry after chelating resin preconcentration

The determination of all rare earth elements (REEs) in human blood serum by inductively coupled plasma mass spectrometry (ICP-MS) was performed with the aid of chelating resin (Chelex 100) preconcentration after acid digestion with HNO3 and HClO4. When chelating resin preconcentration was carried out at room temperature, the recoveries of heavy REEs were lower than those of light REEs because of their stable complex formation with residual organic compounds remaining in the digested serum solution. These problems were overcome by heating the solution at 80 degrees C during the chelating resin preconcentration process. As a result, the recoveries for all REEs were improved to 92-102% in the case of a concentration factor of 4, where the analytical detection limits for REEs were below 0.2 x 10(-12) g ml(-1). Consequently, all REEs in individual human blood sera collected from five healthy volunteers could be determined by ICP-MS with good precision. The concentrations of REEs in human blood serum were extremely low, in the range from ca. 1 x 10(-12) g ml(-1) of Eu to ca. 230 x 10(-12) g ml(-1) of Ce.