Hi Li and others,
> 
> You are right that the system is probably too new to be operative in any lab
> yet ­ if any is already sold.... Setting up such a system certainly will take
> some time before producing Œroutine¹ data. Let us invite the first users to
> report their experiences to the list.
> 
> About your statement on the good precision I think this is highly disputable
> as it is presented many times nowadays (also true for GC-IRMS or for some
> other methods). The given Œprecision¹ is only part of the combined uncertainty
> as properly should be given. What is done is giving a final delta value,
> generally with proper corrections on the delta value, but only with the
> uncertainty of the last part of the analytical procedure. Uncertainties of,
> for instance, the standard (or working reference) and on the Œpreparation¹ of
> the sample are omitted (or simply forgotten), thus producing a too optimistic
> uncertainty (just the statistical SD of the IRMS measurement in most cases).
> This is even worse with hydrogen, where the (relatively huge) uncertainty on
> the H3+ correction is left out completely...
> Specially if the results are used for interpretations based on small isotopic
> variations this can give erroneous conclusions, such as for
> (paleo-)thermometry, to name one case.
> 
> There is a strange tendency where the analyst giving the smallest precisions
> is considered the best one... (I call it the ŒGuiness Book of Records¹
> tendency). It would be better to consider those analysts reporting Œrealistic¹
> combined uncertainties as more reliable! We have seen such strange tendencies
> also for radiometric age dating. Those measuring the oldest ages (oldest rock)
> received more Œappreciation¹ than those giving the proper age of a rock (a
> rock is as old as it is... and giving the correct age in the proper way is the
> only importance here! Nice to have the oldest rock, but it is not of
> importance for the measurement procedure or the quality of the analyst at
> all).
> 
> I discussed this topic also with Andreas Hilkert some time ago. I like to add
> that it is not my aim to point my finger towards any company or a particular
> person. This , to my opinion, erroneous (or incomplete..) reporting of
> uncertainties has become very common by now.
> Accuracy is another story...
> 
> Best wishes,
> Pier.

**********************************************************************
Dr. Pier A. de Groot
Pastoor Moorkensstraat 16
2400 Mol - Achterbos
Belgium
Tel. +32 (0)14 326 205
e-mail: [log in to unmask]

Visit my WEB-site about my ³Handbook of Stable Isotope Analytical
Techniques² at:
http://users.pandora.be/handbook/index.html
last update: 17 Maart, 2004.
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