Dear Arnaud,
I suspect this reply will see me being struck off Finnigan's
Christmas card list, at least for this year.
> I am working with a GC-C-IRMS from Finnigan (model DeltaPlus XL), =
> focusing mainly on C isotopes.=20
> I realized that I had to change the oxydation reactor quite often, =
> either because it gets used or because I break it. And this part is =
> really expensive.
It sure is.
> So I am wondering if it is possible to get reactors at a cheaper price, =
> or to build such a reactor. And if yes, is it worth it? how do you do it =
> and where do you find the Al2O3 tube and the Cu, Ni and Pt wires ?
Building your own oxidation tube is a fairly simple process albeit
one that requires a good deal of patience. Here's the DIY-guide to
making oxidation tubes.
First, order ceramic tubes (1/16" OD, 0.7mm ID) from GSG
Analytical. I used to get my tubes from their UK distributor. Here's
the parent's company (in Germany) URL:
http://www.gsg-analytical.com
Secondly, order metal wires (all 0.1mm diameter) in Puratronic
quality from Johnson Matthey (Alfa-Aesar in Europe). Here's their
URL:
http://www.alfa-chemcat.com/onlinecatalogue/online-catalogue.asp
Select your country and click on the relevant catalogue. You can
then search e.g. by product. For example, type in <copper wire>
and you will get a list of hyperlinks giving your more details such
as order numbers.
You will need copper wire, nickel wire and platinum wire. One of
each per oxidation tube should be fine. However, I tend to use two
Copper, two Nickel and one Platinum since this seems to extend
the life span of the oxidation tube.
(3) Threading the wires into the ceramic tubes is the part where the
air turns blue with swear words including some you never knew to
have used before.
Once you've managed that, you're almost there. Install the tube
into your furnace.
(4) By the way, get a friendly metal worker (perhaps at your
university's work shop) to expand the hole in the bottom Valco
union so you can push an 0.45mm OD capillary trough (basically
have him drill into the existing hole with an 0.5mm OD metal drill).
This way, you can insert the connecting capillary into the oxidation
tube saving you a lot of trouble later on caused by deposits of
condensed and only partially converted sample material at the
bottom of the oxidation tube. (Failing the conversion of your Valco
union, use a SGE 1/16" union instead).
The part of the fused silica sitting inside the oxidation tube has to
be stripped of the polyimide coating (I use my wife's creme brulee
torch; brilliant piece of kit; i the meantime we've got two, one for the
kitchen and one for the lab) and wipe the ashes off with a piece of
kitchen towel soaked in methanol. Note, the part of the capillary
being held by the ferrule should still be FS (i.e. polyimide coated).
Push the capillary in (gently does it) until you can feel it touching
the wires and then pull it back a tiny fraction before you tighten the
screw and ferrule holding the capillary.
(5) Once all the connections are tightened, increase the
temperature of your oxidation furnace to 600 C (in steps of 200 C at
a time), make sure backflush is ON and open the Oxygen valve.
For a new tube, oxidise at 600 C for at least 12 hours, then
increase the temperature in two steps (at 170 C each) to 940 C.
Once the furnace has reached 940 C you can switch the Oxygen
off (while the backflush remains ON).
Leave the system to its own devices for another 6 hours before you
entertain running samples
By the way, to make your own reduction tube follow steps (1) to
(3). The only difference being that the reduction tube is filled with 3
to 5 Copper wires.
Have fun.
Regards,
Wolfram
***********************************
Dr. W. Meier-Augenstein, CChem, MRSC
Senior Research Fellow
University of Dundee
School of Life Sciences
Division of Molecular Physiology
Old Medical School, Small's Wynd
DUNDEE DD1 4HN
Tel.: +44-(0)1382-34/5124, /4574, /4968
Fax: +44-(0)1382-34/5514
e-mail: [log in to unmask]
URL1: http://www.dundee.ac.uk/biocentre/SLSBDIV6wma.htm
URL2: http://www.dundee.ac.uk/anatphys/wma/meieraug.htm
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