We have interfaced an OI 1030W TOC/TIC analyzer to our IRMS for measuring d13C on dissolved organic carbon.  All is well for freshwater samples but we’re having issues with higher salinity samples.  The TOC analyzer uses persulfate to oxidize the organic carbon to CO2.  From the TOC analyzer the CO2/He gas stream is routed through a heated copper column (300C), water trap, and GC column to clean up the gas stream and separate the CO2 before heading to the IRMS source.  

The reduction column is the same as we use for the EA – several inches of copper in the hottest part of the furnace with quartz chips above and below.  The column was intended to remove any residual chloride from the gas stream.  After a few dozen samples, the copper column clogs and restricts gas flow.  The copper is not all spent but interface of quartz chip and copper is all gummed together.  So my first question is: what is being formed that’s clogging this column?

Bouillon et al 2006 (L&O Methods 4:216-226) document another TOC-IRMS interface using both a combustion and reduction zone in a scrubbing column.  They use silvered cobaltic oxide to remove halides.  Our current plan is to go to this set up – combustion column with cobaltic oxide then the reduction column.   So now a few questions:  is chloride really my problem?  If so, is silvered cobaltic oxide my best bet for removing it?  How much do I need in the combustion column?  How long should it last?

Again, this is for fully marine samples oxidized to CO2 by persulfate.

All comments are appreciated.
- joy

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Joy Davis
Ph.D. Candidate
Ocean, Earth & Atmospheric Sciences
Old Dominion University
Norfolk VA
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