Hi Alice,

 we have got a special balance for weighing in enriched samples that is 
placed where we deal with non-enriched samples,- also a special pair of 
tweezers, weighing plate for the tin capsules, western blot plates for 
capsule storage. We have  a special mill for enriched samples, too.
I always warn people to be careful with enriched samples - better to 
avoid cross contamiantion from the beginning, than to wonder about odd 
values of natural samples afterwards.

I always use the same autosampler. But the sampler and the rotating 
plate should be cleaned carefully  and well  after enrichement-analysis 
(as usual, q-tips, ethanol, perhaps Ultrasonic cleaning for the plate), 
or You are buying a second plate ;-) .
After that and some natural dummies, the system is ready for  natural 

Before, there were two mass spec, one for enriched samples, one for 
natural abundance, but since the old one is not working well, all 
samples are running on one machine. I try to avoid to analyse samples 
with enichment higher than 5%. If  a sample batch (from same trial) 
contains low and higher enriched samples, I sort them from low to high  
enr. I also put some dummies between renriched samples and my lowerr 
enriched references  to avoid  carryover.
( I was talking about non radioactive enrichement!)

Hope this helps.

Alice Chang schrieb:
> Hello all,
> I will be receiving soil and plant material that will be artificially 
> enriched with 13C and 15N. The samples will be run on continuous flow 
> EA-IRMS. After consulting the Isogeochem archives and some colleagues, 
> I know that I will have to change the reactor column chemicals after 
> running enriched samples and before running samples with natural 
> isotopic abundances. My question is, however, how to clean the various 
> (non-consumable) work surfaces that might come into contact with the 
> tracer material, such as the autosampler carousel, work benches, lab 
> glassware and analytical balances. Short of coming up with a set of 
> equipment for tracer work and a set for natural samples, has someone 
> out there come up with some sort of "clean lab" protocol to prevent 
> cross-contamination and transfer (e.g., from a wet lab to the 
> analytical lab on someone's shoes)? Is there a "Tracer-Be-Gone" 
> cleanser out there, or are tracers very difficult to get rid of? 
> Apologies if this is a silly question.
> Thanks very much.
> Alice Chang
> Department of Forest Sciences
> University of British Columbia
> Vancouver, BC, Canada


Rhein. Friedrich-Wilhelms-Universität Bonn
Deborah Rupprecht
Karlrobert-Kreiten-Str. 13
53115 Bonn

Tel. (049)0228-73 -2155, -1631