School of Engineering and Science - Jacobs University

1.50 FeR-4 (n=2)
1.25
JUB / reference average
1.00
0.75
0.50
0.25
0.00
Sc Ti Co Ni Rb Sr Y Zr Nb Mo Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Pb Th U
Figure 13. Accuracy estimation for ICPMS analysis of iron-formation FeR-4, where n equals the
number of separate HF-HClO 4 sample decompositions and ICPMS analyses in 0.5 M HCl. Grey bars
represent variability in the calculated ratio that is due solely to uncertainty in the reference average.
Vertical lines represent the variability in the calculated ratio due to the uncertainty of the JUB data, and
all data are presented in App. 1. Good agreement is observed for most elements, with exceptions being
Sc, Ti, Co, Ni and U. Reference data for Nb, Mo, and Ta are not shown, and are available only from a
single published study by Yu et al. (2001), who found highly variable results for these elements when
comparing two different sample decomposition methods (HF-HClO 4 versus HF-H 2 SO 4 ). See text for
details.
Consequently, many trace metals have significantly lower concentrations in FeR-4
(e.g., Sc, Zr, Nb, the REE, Hf, Th). The precision of the JUB data is poorly
constrained by the limited number of analyses, though it seems comparable to, if not
significantly better than, the variation observed in literature reference values. The
relative accuracy of the FeR-4 data is presented in Figure 13, and is somewhat better
than that observed for FeR-2, except for elements with the lowest and highest masses
(Sc, Ti, Co, Ni, and U). Poor results for Sc are not unexpected as Sc literature values
for FeR-4 range from 1.1-1.5 mg/kg, which is similar in magnitude to the IQL
observed for Sc (~0.8 mg/kg, Table 2).
However, Ti, Co, and Ni are all present in FeR-4 at concentrations well above
their respective IQLs using the ICPMS methods described here (Fig. 4), so low
signal-to-noise ratios are not expected to adversely affect determinations of these
elements. For Co and Ni, the literature data are reported to only one significant digit
and concentrations of these two elements are apparently low (2 and 8 mg/kg,
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