At 05:09 PM 5/1/2003 -0400, you wrote:
> Thank you for your quick reply. I'm thinking to use a continuous oxygen
>bleed as you suggested. My concern is if you set the oxygen level to 0.2 v
>at cup 44 (oxygen levels will be out of scale at cup 45 and cup 46), does
>that high level of O2 will shorten the lifetime of filament in the MS?
In short, no. We've only had one blown filament on our 252 in the 5 years
that we've been running an oxygen bleed.
>Air Quality Research Branch
>4905 Dufferin Street
>Toronto, ON M3H 5T4
>Emai: [log in to unmask]
>From: Paul Eby [mailto:[log in to unmask]]
>Sent: Thursday, May 01, 2003 2:40 PM
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] Combustion Furnace
>We have found better performance when a continuous oxygen bleed is used. As
>you have found, the oxygen in an oven can be consumed over a day and affect
>This can be accomplished using a tank of 1% O2 in UHP He, connected via a
>double ferrule between the column and the oven. The required flow is very
>low and difficult to set (something like 0.01mL/min), so you need a large
>pressure drop between the tank and the oven. A long piece of thin capillary
>(0.05mmID for instance) works fine.
>You can then set the amount of O2 reaching the oven by adjusting the
>pressure at the tank regulator and monitoring mass 32. On the mass 44 cup
>(measuring mass 32), we set the oxygen level to about 200mV (of course, you
>couldn't do that with a reduction oven after the oxidation oven). With a
>constant oxygen flow in, you don't have to worry about reoxidizing ever.
>University of Victoria
>At 01:38 PM 5/1/2003 -0400, you wrote:
> >Hello everyone,
> > I have run the stable carbon isotope composition of n-alkanes
> >standards (20ng/ul;n-C17 to n-C30)in GC-C-IRMS. I am using a Finnigan MAT
> >combustion furnace containing Cu, Ni, and Pt wires and maintained at a
> >temperature of 940 degree. I have some trouble with this kind of combustion
> >reactor since the offset between on-line and off-line was ~-0.5 to -1
> >and the negative shift continued to increase gradually after 2 or 3 runs. I
> >was wondering if there is anyway to improve the furnace performace.(I
> >reoxidized the furnace @940 for ~20' everyday).
> >Any input would be greatly appreciated.
> >Thanks in advance,
> >Wendy Zhang
> >Air Quality Research Branch
> >Environment Canada
> >4905 Dufferin Street
> >Toronto, ON M3H 5T4
> >Tel: (416)-739-5972
> >Emai: [log in to unmask]
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