Determination of Lanthanoids in Hard Tissues of Shellfish by ICP-MS with Solvent Extraction

Abstract

The lanthanoids in shell of shellfish were determined by ICP-MS. The intensities of lanthanoids were very highly suppressed by large amounts of calcium ions, which made their determination difficult. It was necessary to separate any lantanoids from calcium. We applied the solvent-extraction method to separate the lanthanoids from the interfering calcium. The chelating agent was easy to form the chelate for lanthanoids; then, a reagent that could extract the chelate from the acid solution was chosen. 1-phenyl-3-methyl-4-trifluoroacetyl-5-pyrazolone (HPMTFP), in which the pKa value was 2.56, was chosen as the extraction reagent. Hard tissues of shell used in the present work were treated with inorganic acids. Lanthanoids were extracted with 0.01 mol/l-HPMTFP in diisobutyl ketone at pH 2 in order to separate it from the interfering calcium. The organic solvent, including the chelate, was decomposed in inorganic acid, and was made to be an aqueous solution. Lanthanoids in the solution were determined by ICP-MS. The lanthanoids content in the shell was found to be 0.82∼124 ng/g.