----- Original Message -----
From: "Georges L. Paradis" <[log in to unmask]>
To: "Bruce Vaughn" <[log in to unmask]>
Sent: Monday, June 13, 2005 10:23 AM
Subject: Re: Isoprime advice requested


> Hi Bruce,
>
> The GV Isoprime has a built in water trap baking system.  I bake the water
> trap after each run for four hours at 60degC while pumping.  These are the
> default water trap baking parameters.
>
> Your statement that d18O will be affected, but d13C may not is
> interesting. When I get poor precision, the d13C and d18O usually tack
> each other.  In other words, if d13C goes lighter, so does d18O for a
> standard.  The magnitude is always greater for d18O.  Here's some
> questions that will verify my inexperience: What would you expect from
> water contamination? Lighter? Heavier?  Both d13C and d18O?
>
> Much thanks,
> Georges
>
>
> ----- Original Message -----
> From: "Bruce Vaughn" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, June 13, 2005 8:02 AM
> Subject: Re: Isoprime advice requested
>
>
>> Georges,
>>
>> I am coming late to this discussion, and may have missed part of it- But
>> was wondering how you are trapping out your water vapor?
>>
>> For what its  worth, most of our issues with getting good O18 numbers on
>> co2 (regardless of the prep system, or method of extraction) seem to
>> revolve around effective removal of water vapor from the sample, and
>> thorough removal of that water from the system between runs (ie. a
>> removable trap that gets baked/dried off line, or some kind of in situ
>> drying of the lines. Contamination between samples and even between runs
>> can be a real killer for o18, and may or may not affect the c13.
>>
>> Hope this helps...
>>
>> Cheers,
>> Bruce
>> _________________________________________________________
>> Bruce H. Vaughn, Senior Scientist Shipping:
>> Institute of Arctic and Alpine Research Attn: B. H. Vaughn
>> UCB 450 INSTAAR- Stable Isotope Lab
>> University of Colorado 1560 30th Street
>> Boulder, CO  80309 Boulder, CO  80303
>> http://instaar.colorado.edu/
>> http://instaar.colorado.edu/sil/
>> 303-492-7985 voice   303-492-6388 fax
>> 303-492-5495 lab email: [log in to unmask]
>> _________________________________________________________
>> "If there is magic on this planet, it is contained in water"
>>
>> -Loren Eisley
>>
>>
>> At 12:47 PM 6/8/2005, you wrote:
>>>Good Morning Everybody,
>>>
>>>We're struggling to get good precision with our GV Isoprime/Dual=20
>>>Inlet.  We are running 100ug carbonate samples/standards.  We've
>>>achieved=
>> =20
>>>the specified +/-0.05 d18O (1 sd) on some runs, but it doesn't last.
>>>Our=
>> =20
>>>last 4 runs resulted in +/- 0.07, 0.12, 0.22, 0.09 d18O (1 sd).
>>>
>>>The mass spec seems to be working beautifully as indicated by the peak=20
>>>shape, all open analysis, and single cold finger volume anlaysis with
>>>ref=
>> =20
>>>gas on both sides of the dual inlet.
>>>
>>>We learned some techiques from our esteemed and helpful GV service=20
>>>engineers regarding the carbonate prep line. These include replacing
>>>the=20
>>>prep line and heating the prep line between runs.  We saw improvements
>>>in=
>> =20
>>>performance, especially after heating the line.  Unfortunately, the
>>>good=20
>>>data quality deteriorates quickly (several runs).  We've experimented
>>>with=
>> =20
>>>heating the prep line continuously, heating between samples, and not=20
>>>heating at all.  Our latest experiments involve replacing the 1/16" ss=20
>>>prep line with fat tubing (1/4" convoluted ss tubing).  The fat tubing=20
>>>showed promising results at first, but alas, has deteriorated again
>>>(above=
>> =20
>>>data collected with fat tubing).
>>>
>>>I like the rapid pumpdown and definitive leak checking that the fat
>>>tubing=
>> =20
>>>allows.  My thought was that the increased conductance and lower
>>>surface=20
>>>area to volume ratio of the fat tubing would be a great benefit.
>>>
>>>When using 1/16" tubing, it is standard 316 ss tubing that is cut with
>>>a=20
>>>dremel tool.
>>>
>>>Any ideas or suggestions for further testing would be greatly
>>>appreciated.
>>>
>>>Take care,
>>>Georges
>>>
>> --
>>
>>
>