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
------------------------------------------------
>From: Paul Brooks <[log in to unmask]>
>Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] H/Device septa
>Date: Mon, 4 Apr 2005 14:33:13 -0700
>
>Steve, Robert, I am not sure what the maximum is but I have only had septa
>leak when cooling them down, not apparently through use. I am not sure how
>many injection I have made in a row without replacing the septa but it is
>hundreds, and I would normally expect them to last 1000 injections, 1000 uL
>of water, except I have cooled the reactor down when running 18O in the
>water.
>
>The septa get quite hot and appear to re-form into a plug that fills the
>void between the end of the reactor and the top of the steel plate. I
>suspect that they are very pliable when hot and holes bored in them simply
>close up at that temperature.
>
>I should note that as the reactor heats up I tighten the septa holder
>several times to make sure it is tight, then push an old syringe through
>several times by hand to make sure it can go through easily. I have bent
>several new syringes by putting them in the autosampler and then having it
>drive the needle into the septa, and bend if one has not been driven in
>manually first.
>
>Paul Brooks.
>
>
>
>At 11:47 AM 4/4/05 -0600, you wrote:
>>Robert,
>>
>>I recall vaguely that the manufacturer recommended 150 injections. I
>>always change them after approximately that many. Maybe I am too
>>cautious?
>>
>>> > I always use two septa on our H/Device, SGE 3041872 www.sge.com.
>>>>
>>>> Even if the chromium reactor isn't quite high enough to be
>>>> flush with the
>>>> metal top of the H/Device furnace, it will still seal this way.
>>>
>>>The difference is that yours are not teflon coated while the ones used
>>>here are coated (like the 3 layer SGE TCS series). The coated ones are
>>>not so flexible and will therfore not seal a reactor which is too short.
>>>
>>>I just used the septa which where already in use here in the lab.
>>>For the next order I will check the price of the SGE.
>>>Any experience how many injections can be performed on them?
>>>
>>>regards,
>>>Robert
>>>
>>>--
>>>Robert van Geldern
>>>Leibniz Institute for Applied Geosciences (GGA)
>>>S3: Geochronology and Isotopehydrology
>>>Stilleweg 2, 30655 Hannover, Germany
>>>phone: +49-(0)511-643-2313 (office), -2539 (lab)
>>>fax: +49-(0)511-643-3665
>>>mailto:[log in to unmask]
>>
>>
>>--
>>
>>
>>********************************
>>Steve Nelson
>>Dept. of Geology
>>S389 ESC
>>Brigham Young University
>>Provo. Utah 84602
>>
>>voice: 1-801-422-8688
>>lab: 1-801-422-5124
>>FAX: 1-801-422-0267
>>
>>CARPE CARP: seize the fish
>>********************************
>
>
>
>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/
|
