School of Engineering and Science - Jacobs University

The method precision for elements present at low concentrations, particularly
in FeR-2 and JDo-1, is typically poorer (e.g., Nb, Ta, W, as well as Co in JDo-1).
However, some elements that are abundantly present at concentrations ranging from
several mg/kg to several percent also display poor RSD values. The BHVO-2 basalt
contains >1.5% Ti, yet suffers from a method precision of >10%, whereas Ba in JDo-
1 is present at a concentration (6.14 mg/kg) well above the quantification limit and
has an RSD above 20%. In the case of Ti, it is suspected that the poor ionization
efficiency of this metal may mean that the 10 μg/kg calibration standard is not
appropriate for quantification, as it produces a signal intensity that is not sufficiently
greater than that observed for the background acid matrix, and this will be discussed
in greater detail in the section regarding analytical accuracy. The poor method
precision observed for Ba in the JDo-1 dolomite (22.7%) results from an ‘outlier’ for
one of the three decompositions used in the calculation of the RSD value, as
measured Ba in two decompositions is 5.32 and 5.63 mg/kg, while Ba measured in
the third decomposition is 8.61 mg/kg.
To this point the discussion of analytical precision has been limited to the HF-
HClO 4 decomposition method, as much of the research conducted within the JUB
Geochemistry Lab focuses on whole-rock trace metal analyses, which necessitate
complete dissolution of all mineral phases within the sample powder. However, with
regard to analytical precision it is necessary to discuss the HNO 3 carbonate
decomposition as well. As the carbonate decomposition is used for limestone and
dolomite samples, the JDo-1 dolomite is the typical CRM included in decompositions
and analyses of these rock types.
Sample and method precision for JDo-1 using the carbonate decomposition
method are presented in Figure 9, and these measures of precision are comparable for
most elements. This suggests that the carbonate decomposition method does not
significantly increase the error budget for these elements, similar to that observed for
the HF-HClO 4 decomposition. The method precision is better than 5% (RSD) for 25
of the 32 elements analyzed, and several elements displaying poor method precision
(e.g., Rb, Cs, and Hf) are expected to be hosted in refractory mineral phases that
would be resistant to dissolution by nitric acid. Elements at or near the IQLs and
unlikely to be quantifiable in carbonate rocks at concentrations observed in JDo-1
include Sc, Nb, and Ta (see Fig. 4). For many elements the method precision as
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