School of Engineering and Science - Jacobs University

Figure 5. Diagram depicting various types of precision that may be defined for sample decompositions
and ICPMS analyses. Note that sample precision reflects raw uncorrected intensities (cps), while run
and method precision are calculated from corrected concentration data.
that of the sample precision for many elements, and also varies as function of rock
type (Fig. 7). Shales display slightly poorer run precision (3-5%), though this might
reflect the limited number of analyses where these CRMs were measured repeatedly.
For purposes of long term reproducibility, the method precision is the most suitable
measure of the standard deviation expected for a complete sample decomposition and
ICPMS analyses, as it describes the variability expected in concentration data when a
sample powder is dissolved numerous times over a period of months or years.
Comparisons of the three types of precision discussed here (sample, run, and method)
are presented in Figure 8 for CRMs of four different rock types. Of the 32 elements
analyzed, the method precision RSD is better than 5% for 25 elements in BHVO-2
(basalt), 31 elements in SGR-1b, 26 elements in FeR-2 (iron-formation), and 22
elements in JDo-1 (dolomite). The method precision is also comparable to the sample
and run precision, suggesting that any error associated with the HF-HClO 4 sample
decomposition method (e.g., weighing and/or dilution errors) is small compared to the
error inherent in the ICPMS analysis.
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