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MessageHi 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 
  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]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~