Number: 2005-035-2-500
Title: Trace elements analysis: role of grain size distribution
in solid reference materials
Task Group
Chairman: Maria Belli
Members: Ales Fajgelj,
Zoltan Mester, Umberto
Sansone, and Gemma Rauret
Objective:
Generally, solid reference materials (RM) of the same matrix from
different producers can present different particles size distributions
and this could affect the homogeneity of the material and the minimum
representative sample required for trace elements analysis. The final
aim of the proposed project is to develop a guide to be used by reference
materials producers and by the analytical community to select the most
appropriate particle size distribution of a considered reference material
to fit the analytical needs.
Description:
The existing guidelines for Reference Material (RM) producers do not
report any indication for the selection of the most appropriate particle
size distribution during the production of these materials. In the case
of solid RM, particle size distribution plays a vital role on the homogeneity
of the material and on the minimum representative sample required for
trace element analysis. Generally, RMs of the same matrix but from different
producers show different particle size distributions.For soil and sediment
RMs, particle size distribution can vary from <120 µm to <20µm.
From one side, finer particles can increase the homogeneity of the material
(between and within bottle homogeneity) but from the other side, the
RM obtained can be different, in terms of grain size, by the real samples
routinely analyzed in the laboratories (e.g. contaminated soil analysis
commonly is carried out on samples particle size < 2 mm). In addition,
the effect of particle size on extractable trace metals in soil RM has
been already observed [A. Sahuquillo et al., Certified reference materials
for extractable trace metals in soils: effect of the particle size,
1998, Fresenius J. Anal. Chem. 304-307]. It is also relevant
to point out that the production of RMs with finer particles has a negative
effect on the cost of RMs production. The proposed project will focus
on soil/sediment candidate RMs with different trace element contents.
The project will bring together the results of experimental work that
is being funded by different participants. The main aim is to investigate:
- the influence of grain size distribution on the within and between
bottles homogeneity;
- the influence of grain size distribution on the minimum sample required
for trace elements analysis;
- the influence of grain size distribution on the stability of trace
elements;
- the cost associated with the production of RMs with different particles
size distribution.
The results of the proposed project will be made available in a guide
that can be useful for RM producers to select fit for purpose methods
for RMs preparation and for the analytical community to select fit for
purpose RMs.
Progress:
Last Update: 6 June 2006
<project announcement published in
Chem. Int Nov/Dec
2006>