Methodologies for the Determination of Low Concentrations of Lathanides in Biological Samples by ICP-MS

This work deals with the development of analytical methods for lanthanide determination in biological samples. One method consists of using capillary electrophoresis (CE) for lanthanide separation prior to the detection by inductively coupled plasma mass spectrometry (ICP-MS). The lanthanides are extracted from the sample solution by liquid-liquid extraction with bis(2-ethylhexyl)orthophosphoric acid (HDEHP) in toluene at pH 2.0 and then backextracted into an aqueous phase using 6 mol L-1 HNO3. After solvent evaporation, the residue is dissolved with water, and 32 nL of this solution injected into the capillary. A mixture of 6 mmol L-1 8-hydroxyisobutyric acid (HIBA) with pH 4.2 is used as the electrolyte solution. It is demonstrated that the lanthanides are separated under this condition. The other method consists of using a micro nebulizer-desolvation system for introducing the sample into the plasma of an ICP-MS. The oxide formation rate is remarkably decreased by using this introduction system, allowing accurate lanthanide determination. The developed methods were applied to the determination of lanthanides at the ng g(-1) levels in mussel tissue. The concentrations of the elements were below the detection limits of the CE-ICP-MS method, but detected and quantified by using the micro nebulizer-desolvation system