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hi all,

We had some issues with one of our EA-IRMS systems over the past 2 weeks 
whereby the lower (i.e. downstream) PTFE/silicone rings on the water 
trap are getting brittle and flake until there's not much left besides 
the PTFE. The upper one remains intact. This pushes unwanted stuff down 
the line and shows itself in higher m29 relative to m28 and consenquetly 
awful d15N data; d13C is not really affected.

We have been running GFF filters (fumed in HCl but oven dried 
afterwards) and a mix of soil & coastal sediment samples - nothing 
really new there.
We then get into the frantic routine that will be familiar to many - 
alternatingly baking out GC columns, swapping the GC column, replacing 
the Cu column and/or combustion column, replace connection between 
combustion and reduction column, run some standards, feeling pleased 
with yourself that the problem seems fixed, then notice it just 
resurfaces after a few hours.

While we've had something similar before it has never lasted this long 
and I'm particularly keen to hear if anyone has a solid explanation (I'm 
ready to take alternative facts at this point) on what's eating the 
silicone and why only at the bottom of the H2O trap - and whether they 
have found a way to avoid this.

Thanks in advance for any hints
Cheers
/Steven



-- 
Signature *Department of Earth & Environmental Sciences* 
<http://ees.kuleuven.be>
*KU Leuven*
*GoogleScholar* 
<http://scholar.google.be/citations?hl=nl&user=nrZTAQ0AAAAJ&view_op=list_works&pagesize=100> 
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