School of Engineering and Science - Jacobs University

sample preparation methods are employed which isolate and concentrate the elements
of interest from undesirable matrix elements.
Table 2 contains interferences commonly observed in ICPMS analyses
performed within the JUB Geochemistry Lab. The inability of the low-resolution
DRC-e ICPMS to resolve interferences from the isotopes of interest does not
significantly inhibit the accurate determination of the 32 elements routinely analyzed,
as correcting for these interferences is possible through careful characterization and
quantification of the interfering polyatomic species. The majority of these corrected
interferences are for the REE (Table 2), as the REE can form significant amounts of
oxide and hydroxide species during ionization. For example, at typical instrument
settings as much as 3% of the Ce present in the sample solution will be ionized to
140 Ce 16 O + , and the
140 Ce 16 O + ion will consequently contribute to any Gd
determinations that utilize the
156 Gd isotope. The isotopes monitored for
quantification of the REE are therefore carefully selected to minimize these effects
and maximize analytical accuracy, though as seen in Table 2 a significant number of
corrections are necessary. While implementing such corrections is not trivial,
uncorrected values may result in reported concentrations for REE elements that are
erroneously high by as much as several percent, as illustrated by the example with
CeO + .
Corrections for polyatomic interferences are performed mathematically,
typically offline using commercially available spreadsheet software such as Microsoft
Excel (the approach followed at JUB). Interferences are identified and quantified by
analyzing solutions that contain relatively high concentrations (50-1000 μg/kg) of a
single element, and surveying the range of masses that might be affected by
interferences produced by oxide, hydroxide, chloride, or nitrogen species of that
particular element. For the REE, the most significant interferences are generated by
REE-oxides or -hydroxides, and therefore are found at 16 and 17 amu above the
interfering element (i.e., REE 16 O + and REE 16 O 1 H + ). The measured intensities of the
interfering element, and the various interferences it produces, allow calculation of
ratios expressing the relative amount of interfering species generated as a function of
the concentration of the interfering element. For example, if as mentioned above, 3%
of 140 Ce in the sample is ionized to 140 Ce 16 O + (i.e., 140 Ce 16 O + / 140 Ce equals 0.03), and if
the Ce concentration in the sample corresponds to a measured intensity of 100,000
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