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Dear Gerard,

Thanks for the tip; actually, my technician was 
suggesting to inject air this morning, and I 
stopped her because of fear of damaging the 
column. I did not think of cooling down the GC 
oven, but we may try in the morning.

The other thing to try is fitting a wider 
capillary in the LN2 trap, as suggested by Klaus.

Frustrating, but the suggestions that keep arriving are promising ...

Thanks,

Clemente



>HI Clemente,
>
>Have you resorted to just injecting CO2 or N2 
>gas (gas tight syringe,  Ar looking at mass 40 
>would work too) to chase down the problem yet? 
>If the GC is not heated up, you can probably get 
>away with injecting a little air--that is to 
>say, you don't have to be paranoid about keeping 
>air out when you do these type of test 
>injections as long as the GC column is kept 
>relatively cool... You'll probably get some N2 
>separation from CO2 too if you do mixtures.
>
>good luck,
>
>gerry
>
>On 3/2/2015 9:30 AM, Clemente Recio wrote:
>>Wolfram,
>>
>>Sorry I missed that; I took it for granted.
>>
>>Water is removed by a Nafion just after the 
>>interface (combustion) oven and before the 
>>reduction oven.
>>
>>Having said that, from your comment, it is true 
>>that an inefficient Nafion might be a problem. 
>>I'll fiddle around changing He flows and will 
>>see what happens; thanks!
>>
>>Cheers,
>>
>>Clemente
>>
>>
>>>Dear Clemente,
>>>
>>>
>>>Where is the water trap in your set-up? It 
>>>seems to be missing from your schematic.
>>>
>>>The LN2 trap should be situated between water 
>>>trap and IRMS.  If the LN2 trap in your 
>>>schematic doubles as water trap and CO2 trap, 
>>>the capillary will become clogged with 
>>>freezing water long before it would become 
>>>clogged with solid CO2.
>>>
>>>Best,
>>>
>>>Wolfram


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