Application of capillary electrophoresis interfaced to double focusing sector field ICP-MS for nuclide abundance determination of lanthanides produced via spallation reactions in an irradiated tantalum target

An analytical procedure was developed using capillary electrophoresis (CE) coupled on-line to a double-focusing sector field inductively coupled plasma mass spectrometer (DF-ICP-MS) for the analysis of mixtures of lanthanide elements in aqueous samples with natural isotope abundances and in a sample taken from an irradiated tantalum target containing artificial nuclide abundances. A MicroMist AR30-1-F02 nebulizer with a Cinnabar small volume cyclonic spray chamber was used for ICP-MS sample introduction. The CE-ICP-MS interface featured a self-aspirating electrolyte make-up solution for electrical ground connection and control of nebulizer suction. The CE-ICP-MS method features fast run times and small sample sizes (approximate to 35 nL injection volume). Detection limits for the most abundant lanthanide isotopes were 0.72 ppb to 3.9 ppb, an improvement of as much as one order of magnitude compared to a quadrupole ICP-MS system using a similar experimental arrangement. Abundances of the most abundant isotopes of lanthanides were found to be within 0.1-2% of table values for natural samples while isotopes present in smaller amounts were within 3-5% of table values. The method was applied to samples taken from a tantalum material which was exposed to a high energy proton beam for the production of neutrons via spallation reactions. A large fraction of the spallation products were lanthanides containing nuclide abundances unlike natural samples. Thus, a chemical separation step prior to ICP-MS detection was required to avoid isobaric interferences for the accurate determination of nuclide abundances in such samples. The results of the nuclide abundance determinations were compared to theoretical calculations.