Re: Critics Allege Infant Mortality Rate

[Franz Schoenhofer <schoenho@via.at>]

At 12:54 27.04.2000 -0500, you wrote:
>
>However, your use of the phrase "to the extent" leaves me with the same
>question. If potassium is present in baby teeth, then K-40 is also present,
>and that presents an opportunity for the analytical technique to misidentify
>it and call it Sr-90. I assume that the tooth material would be pulverized
>and then subject to some extraction process to obtain the strontium in a
>solution that would be subject to liquid scint counting. Would a commonly
>used strontium extraction technique also capture potassium? 

No, it will not. Sr-90 is not simply extracted. Most traditional methods
use several steps of purification, which involve precipitation of
carbonates, chromates and/or oxalates, in order to remove disturbing ions
and radionuclides like calcium, rare earths and radium. Potassium will not
precipitate, it will be removed by filtration. Some methods use a final
precipitation step of Y-90 after ingrowth - no K-40 will be precipitated,
some other ones use solvent-extraction of Y-90 and measurement by liquid
scintillation spectrometry or Cherenkov measurement. Again no chance for K-40.

If so, how would
>one account for K-40 in the analysis? Gamma spec analysis seems the logical
>approach to me

It is not necessary (see above), furthermore the in any case negligible
amount of K-40 and the extremely low efficiency for K-40 gammas will give
you a result "below LLD". In case you thought measuring Sr-90 by gamma
spectrometry: Sr-90 and Y-90 are representatives of the famous "single beta
emitters".

Regards,

Franz


Franz Schoenhofer
Habicherg. 31/7
A-1160 Vienna
Austria
Tel.: +43-1-495 53 08
Fax.: same number
mobile phone: +43-664-338 0 333
e-mail: schoenho@via.at


Office:
Hofrat Dr. Franz Schoenhofer
Federal Ministry of Agriculture, Forestry, Environment and Water Management
Radiation Protection Department (BMLFUW I/8 U)
Radetzkystr. 2
A-1031 Vienna
AUSTRIA

phone: -43-1-71172-4458
fax: -43-1-7122331

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html