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[Q] cold trap

Charles Reese reese at chem.duke.edu
Wed Sep 13 15:17:35 EST 1995




glhurst at onr.com (Gerald L. Hurst) wrote:
>In article <rose.486.3056EFC4 at alf1.ngate.uni-regensburg.de>, 
>rose at alf1.ngate.uni-regensburg.de (Andreas Rose        t3077) says:
>>
>>I study the host-finding of a blood-sucking bug (Reduviidae - 
>Triatominae). 
>>I want to collect odors from the headspace of a sleeping person and see 
>>whether these are attractive in a behavioral test. 
>>
>>For the collection of the odors, I want to construct a cold trap. 
>
>[Snip]
>
>A dry ice-acetone trap should do the job. I would not use liquid
>nitrogen because it is cold enough to condense a trap full of
>liquid oxygen and solid CO2.
>
>Jerry
>
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You might also consider traping your odors on a solid adsorbent.  Coconut 
charcoal and polymer beads are commonly used.  You will get all but the 
most volatile odors.  You can also precoat the polymer (or glass) beads 
with substances like PEG, PVA etc. to trap the really volatile compounds. 
 After traping you can wash the trapped materials off with a little 
solvent (eg Meoh/CHCl3) and inject the concentrate directly into a GC or 
LC for analysis.  I used to trap effluents from a prep. GC this way and 
it is very efficient.  Its hard to cold trap dilute molecules from a gas. 
 You get a lot of areosol formation which just blows right on through.

Cheers
Charlie Reese




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