We have some problems with our Mat252 with a dual inlet and a
Kiel-Carbo-Device for determination of carbon and oxygen isotope ratios of
First of all we observed a pressure (sample side) dependent drift in our
isotope ratios. The more samplegas we had, the heavier our isotope ratios
in oxygen and in carbon were. ( for example 200 microbar difference lead to
a ratio offset of 0.2 per mill in carbon and 0.3 in oxygen ). If we had a
sample pressure higher than 800 microbar, no fractionation was observed.
Our answer to solve these problems was cleaning the source, controlling the
capillaries and heating the machine for waterevaporation.
Afterwards we observed a totally obvious problem.The more samplegas we had,
the lighter our isotope ratios in oxygen and carbon became.
Now we started checking our bellows. We found a behaviour we don`t understand.
During calibration the display changed from 100 percent to 0, the bellow
startet at 100 percent, went to 40 and changed direction and stopped at 50
percent. During this last step the display showed 0 percent and jumped to
100 percent in the moment the bellow stopped at 50 percent.
Another time the I tried to open the bellow manually under Inlet
Control,but the bellow stopped opening at 50 percent and gave me the error
message: RT Bounds exceeded.
So maybe the not exactly working bellow could be the reason for the
I changed the electronic board for motorcontrol and I checked the variable
resistors but I did not solve the problems.
Is there anybody who could tell me what is wrong with our baby?
Many thanks in advance, Dirk Reese.
GEOMAR Research Center for Marine Geosciences
Stable Isotope Laboratory
Wischhofstraße 1-3, D-24148 Kiel, Germany
email: [log in to unmask]