Dachun,

Doping of the carrier gas with choloropentane (and I have heard that a
mixture of carbon tetrachloride and toluene will also work) substantially
reduces the memory effect on a low temperature 1130C pyrolysis tube using
nickel carbon catalyst.  I am not sure if anyone has tried this with glassy
carbon or not.  See the reference below for details.

Hope this helps.

Paul Brooks.

Kirsten, K. J.  1977.  Improvement of Oxygen Determination Method in
Organic Compounds through Addition of Chlorohydrocarbon Vapor to Carrier
Gas.  Michrochemical Journal.  22, 60-64.



At 09:22 AM 4/2/04 -0800, you wrote:
>Hi,
>
>My working standard of water for d18O has value of -11.6 calibrated against
>SMOW and SLAP using CO2 equilibration. I cannot get the same calibrated
>value when I use glassy-C method. The value is about 0.5 heavier. Can
>anybody help me understand this.
>
>The only thing I worried is the carry over effect. I found the memory can
>carry over up to next 6 analysis from SLAP to SMOW. Even I used the seperate
>syringes.
>
>
>Cheers.
>
>Dachun Zhang
>Isotope Lab
>Zymax



Paul D. Brooks,
Center for Stable Isotope Biogeochemistry,
Dept. Integrative Biology MC3140,
3060 Valley Life Sciences Building,
UC Berkeley, Ca. 94720-3140.

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phone (510)643-1748,
FAX (510)643-1749

http://ib.berkeley.edu/groups/biogeochemistry/