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Date: | Wed, 23 May 2007 14:04:30 +0200 |
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Dear Robert,
In stable isotope labs I would like to discourage everybody from using
ethanol for cleaning. You probably have been very careful to dry the
borosilicate containers prior to usage. However, if traces of ethanol
are left in the sample, it can enter the gas phase and finally end up in
the mass spectrometer. Here, in the EI mass spectrum, the base peaks of
ethanol are masses 45 and 46 (!), i.e. exactly those very sensitive
masses from which the isotopic information is obtained. Any isobaric
interference therefore should be avoided. In our Lab we strictly avoid
using ethanol for cleaning or for any other purpose (except for dry-ice
traps). Instead we routinely use methanol.
Regards Willi
Geldern, Robert van wrote:
> Hi,
> We did a quick test last year. There was no difference (within anlytical
> limits) of:
> - farbic new round bottom vials (borosilicate)
> However: I would recommend to clean them before first use.
> - vials cleaned with diluted acid over night, washed with deionized
> water and ethanol (HPLC grade)
> - vials only cleaned in deionized water and put in the lab washer.
>
> So we put our round bottom exetainers in a small plastic bucket with
> deiozed water to dissolve the phosphocic acid and the remains of
> non-100% carbonate samples. Then the vials go into the lab washer
> (inside they are cleaned with diluted acid and deionized water). We do
> not clean them with ethanol again, but some colleagues do so. In case of
> pure carbonates you may skip the bucket step.
>
> At university we cleaned the vials with deionzed water and ethanol only
> (no acid bath). This worked fine, too.
>
> Regards,
> Robert
>
>
--
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Willi A. Brand, Stable Isotope Laboratory [log in to unmask]
Max-Planck-Institute for Biogeochemistry (Beutenberg Campus)
Hans-Knoell-Str. 10, 07745 Jena, Germany Tel: +49-3641-576400
P.O.Box 100164, 07701 Jena, Germany Fax: +49-3641-577400
http://www.bgc-jena.mpg.de/
http://www.bgc-jena.mpg.de/service/iso_gas_lab/
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