Dear listmembers,

I would like some comment on the following:

During our 13C in soil analyses we have noticed that the standard deviations
of some samples were better than others. In the beginning I thought this was
probably caused by contamination during weighing, so we analysed them again.
And again the same samples had a better standard deviation than others. All
samples have +/- the same carbon-content and were measured in the same

Of course I know that there is such a thing as a matrix-effect, but can it
really influence the results that much, even if the weighed amount and the
'type' is the same (type = all soils, just different fractions and different
locations)? I am talking about variations in standard deviation (n=3) of
about 0.1 (sdevs around 0.15 permil for 'worst' samples and about 0.05
permil for 'best' samples).

Thank you very much!



Peter Vervloedt
Laboratory of Applied Physical Chemistry
Faculty of Agricultural and Applied Biological sciences
Ghent University
Coupure, 653
9000 Gent

tel.: +32 (0)9 264 6048
fax.: +32 (0)9 264 6230

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