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Goldschmidt2013 Florence 3

Homogeneity of PGE in OKUM and MUH-1

Thomas Meisel

on 5 November 2014

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Transcript of Goldschmidt2013 Florence 3

Melcher and Meisel 2004
For Re-Os studies not a (real) problem
Different matrix/mineralogy?
Incomplete digestion?

Why routine measurement worse?
Only matrix-matched RM can be used for method validation (streetlight effect!)
Minimum test portion size is function of petrography and element

Heterogeneity of RM is dominant
Need for digestion methods for > 10 g for small measurement uncertainties of certified values
OKUM and MUH-1 PGE interlaboratory comparison (ILC) is now open

PGE certification
ILC can help
Organise own interlaboratory comparison (ILC) with homogeneous matrix-matched material
Was the measurement procedure you apply validated with RM under the streetlight?

Uncertainties of reference material property values need to be much smaller than that of routine measurement results

nugget effect!
of Streetlight and Nugget effects
or the homogeneity of PGE reference materials
Thomas Meisel, O.Marcus Burnham, Conny Kriete, Syed N. H. Bokhari and Toni Schulz
streetlight effect!
1 g!
1 g!
data set for this work
HPA acid digestion (no HF): 0.5 – 1 – 2 g
NiS fire assay: 2.5 – 5 – 7.5 – 10 – 15 g
Minimum 3 digestion each test portion size
Literature data included

The streetlight effect is a type of observational bias where people/scientists only look for whatever they are searching by looking where it is easiest (Wikipedia)
Streetlight effect
No RM available?
Reseachers tend to look for answers where the looking is good, rather than where the answers are likely to be hiding.

(David H. Feedman)
Steetlight effect
Was the measurement procedure you apply validated with RM under the streetlight?

2 g test portion is not enough (streetlight effect!). ID-MS does not help!
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