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Hi Georges,
If so, it's most likely that your MultiPrep (and/or DI) system has a small
leak during the sample preparation.
Wenbo

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Georges L. Paradis
Sent: Wednesday, June 08, 2005 1:29 PM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Isoprime advice requested


Hi Wenbo,
 
The acid density was 1.92 before it was degassed for 2 hours at 90degC using
a rotary vane pump with two liquid nitrogen traps.  
 
Thanks,
Georges
 
 ----- Original Message ----- 

From: Wenbo Yang <mailto:[log in to unmask]>  
To: [log in to unmask] 
Sent: Wednesday, June 08, 2005 12:22 PM
Subject: Re: [ISOGEOCHEM] Isoprime advice requested


Georges ,
Check the density of your acid and be sure to degas the acid before use it.
Good luck.
Wenbo Yang
 
-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Georges L. Paradis
Sent: Wednesday, June 08, 2005 9:47 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] Isoprime advice requested



Good Morning Everybody,
 
We're struggling to get good precision with our GV Isoprime/Dual Inlet.  We
are running 100ug carbonate samples/standards.  We've achieved the specified
+/-0.05 d18O (1 sd) on some runs, but it doesn't last.  Our 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
shape, all open analysis, and single cold finger volume anlaysis with ref
gas on both sides of the dual inlet.   
 
We learned some techiques from our esteemed and helpful GV service engineers
regarding the carbonate prep line. These include replacing the prep line and
heating the prep line between runs.  We saw improvements in performance,
especially after heating the line.  Unfortunately, the good data quality
deteriorates quickly (several runs).  We've experimented with heating the
prep line continuously, heating between samples, and not heating at all.
Our latest experiments involve replacing the 1/16" ss prep line with fat
tubing (1/4" convoluted ss tubing).  The fat tubing showed promising results
at first, but alas, has deteriorated again (above data collected with fat
tubing).  
 
I like the rapid pumpdown and definitive leak checking that the fat tubing
allows.  My thought was that the increased conductance and lower surface
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
dremel tool. 
 
Any ideas or suggestions for further testing would be greatly appreciated.
 
Take care,
Georges
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Georges L. Paradis
ICPMS Lab Manager
Department of Geological Sciences, Marine Science Institute
Unviversity of California Santa Barbara
Santa Barbara, CA 93106
805-893-7182
[log in to unmask]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~