I would like to contest that the point at which the 'air turns blue' is
actually when you tighten the valco fittings on the reactor, it makes a
'tink' noise and promptly falls apart. This most often happens in the
final stages of leak testing!

Cheers

Ian

---------------------------------------
Dr Ian D Bull
NERC Organic Mass Spectrometry Facility
Organic Geochemistry Unit
Biogeochemistry Research Centre
School of Chemistry
University of Bristol
Cantock's Close
Bristol  BS8 1TS
UK

Tel. +44-(0)117-9546967
Fax. +44-(0)117-9251295
Email: [log in to unmask]

"I do not feel obliged to believe that
the same God who has endowed us with
sense, reason, and intellect has
intended us to forgo their use."

                     - Galileo Galilei

---------------------------------------

On Thu, 30 Aug 2001, Wolfram Meier-Augenstein wrote:

> 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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