HI Paul and All--
I followed your advice from 12/8/03 (thanks), but have been using
acetone in wash2 instead of ethyl acetate. The vacuum source is an old
"vacuum forceps" pump, though a fish tank pump may work, connected via
tygon tubing to end of plastic 1 mL syringe. The syringe has an 18 gauge
needle on it that I bent and inserted into the waste2 vial--on one side
to keep it out of the way of the PAL. You just have to make sure the
septa on the waste vial is sealing when you start up. First wash is with
distilled water (something like 8x).
take care
gerry
p.s. less than 1%memory correction, inj 0.5 uL per sample (~1.4 V
signal), auto adj all to 3V for runs, do 8 readings per run- with the
first one (or two) usually being discarded, slight standard drift until
bellows compression gets to 30%.
Paul Brooks wrote:
> Bill,
>
> I am not sure what version of the H/Device spreadsheet you have, my most
> recent one corrects for different drift rates in two different standards.
>
> As to the minimization of carryover in the syringe, we use a ethyl ether
> rinse and then to a vacuum waste, others may want to contact this list
> with
> their wash solutions.
>
> The theory is to use a dry organic solvent that forms an Aezotrope with
> water and then rapidly evaporates taking the water with it. Leaving a
> clean dry syringe.
>
> Paul Brooks.
>
>
> At 09:39 AM 4/6/05 -0500, you wrote:
>
>> Dear Bob and others,
>>
>> I am interested in the post-run correction discussion. We added an
>> HDevice in August of last year and I am gradually becoming more
>> experienced with the instrument. Our first order correction accounts
>> for drift caused by the gradual fractionation of the reference gas
>> during the run but I am noticing that there are other effects that
>> shift the values of my house standards. What kinds of corrections do
>> you typically employ? Paul Brooks has shared a copy of his spreadsheet
>> with me that corrects for drift and also takes into account a carry
>> over effect from the previous sample. You also mentioned a modified
>> PAL method to reduce the carry over between samples, exactly what steps
>> are you taking to achieve this?
>>
>> Regards,
>>
>> Bill Winston
>> Washington University
>> Earth and Planetary Sciences Building Room 110
>> Hoyt Dr. at Throop Dr.
>> St. Louis, MO 63130
>> 314-935-7475
>> [log in to unmask]
>>
>>
>> Date: Tue, 5 Apr 2005 10:43:47 -0700
>> From: "Robert D. Stickrod II" <[log in to unmask]>
>> Subject: Re: H/Device septa
>>
>> H-devicers,
>>
>> I switch over to a new Alltech septum, #78015, that's rated to a max
>> temp.
>> of 400C in an effort to avoid scraping out the partially melted, soft,
>> SGE
>> #041872 (max 320C). The first one is on my "Nelson/Dettman" style
>> reactor
>> so I can't report on how well it will survived but I don't plan to
>> change it
>> until the reactor is spent. No problems so far with >700 injections.
>>
>> Anybody interested in discussing post-run corrections? What's everyone
>> using? Paul's got a great spreadsheet if your standards drift
>> consistantly
>> over the run. Werner & Brand used a multiple pass correction. With my
>> dual-inlet capillaries crimped 20% further, the reference bellows drift
>> is
>> insignificant when compared to the raw precision of 16 standards
>> dispursed
>> over a run of 98 vials, so I'm now trying a simple two-point correction
>> with
>> sub-1‰ precision. I need the best precision for ice cores so had to
>> abandon
>> D/H by headspace with Pt due to the huge normalization "stretch".
>>
>> I'm also using a simplified PAL protocol that combines some of the best
>> ideas that others have developed recently. I have no syringe memory
>> even
>> when jumping from SLAP to VSMOW in adjacent vials.
>>
>> Bob
>>
>> ------------------------------------------------
>> Robert Brander, Lab Manager
>> Idaho Stable Isotopes Laboratory
>> www.cnr.uidaho.edu/isil
>> Department of Forest Resources
>> College of Natural Resources, Room 214
>> P.O. Box 441133, University of Idaho
>> Moscow, ID 83844-1133, U.S.A.
>> [log in to unmask]
>> lab: (208) 885-6512
>> fax: (208) 885-6226
>> cell: (509) 338-2814
>> ------------------------------------------------
>
>
>
>
> Paul D. Brooks, http://ib.berkeley.edu/groups/biogeochemistry/paul.htm
> Center for Stable Isotope Biogeochemistry,
> Dept. Integrative Biology MC3140,
> 3060 Valley Life Sciences Building,
> UC Berkeley, Ca. 94720-3140.
>
> [log in to unmask]
>
> phone (510)643-1748,
> FAX (510)643-1749
>
> http://ib.berkeley.edu/groups/biogeochemistry/
>
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