On-line isotope dilution analysis with ICPMS using reverse flow injection

A simple flow injection manifold is described to perform the addition of isotopic spikes to aqueous samples on-line with ICPMS. The analysis involves one multielement spike injection in the sample carrier and another injection of the spike solution in a standard carrier. This standard must contain one element which is not present in the spike solution, to allow the determination of the dispersion coefficient. The same standard also allows a reverse isotope dilution (ID) analysis, in addition to corrections for mass discrimination and any spectroscopic interference on one of the two isotopes used for the ID analysis. This flow injection approach, therefore, requires only one isotope free of spectroscopic interference for elements whose isotopic distribution does not vary in nature (two isotopes are still needed for other elements since the “natural” ratio must then also be determined). No preliminary analysis of the sample is required prior to the actual ID analysis. Furthermore, the concentration profile ...