Toti:
Both Georges and Li have replied to your message before I had a
chance to, but I concur with their comments. These are the needles
that we have been using with our prototype MultiPrep (one of the
first manufactured) for the past 9 years and we have had good success
with them. The length from the tip to the upper weld is indeed about
9.0 cm, and the needles come with an extra length of the inner,
smaller diameter tubing above the upper weld to a length of 14.5 cm.
For our setup, I cut the upper inner needle portion so that it
extends about 1.5 cm above the upper weld, for a total length from
tip to tip of 10.5 cm. It is important to cut the inner tubing
gently with a file. It is too easy to collapse the thin walls of the
inner needle by using wire cutters, and its diameter is too small for
most stainless steel tubing cutters. Otherwise, you will have
difficulty inserting the silica capillary used to transfer the acid
from reservoir to needle tip.
I prefer to check the welds in the fashion that Georges mentioned,
rather than submerging the tip of the needle in water like Li does.
I put a rubber septum over the side port closest to the tip of the
needle, evacuate the needle under high vacuum for a few minutes, then
close the vacuum valve and open the line connecting the needle to the
pressure transducer section of our dual inlet. If the weld is good,
there is no rise on the transducer. If the weld is starting to break
down, the transducer will slow increase over several minutes. If the
weld is really bad, you won't be able to evacuate the needle.
Hope this helps!
Steve
>Hi Toti,
>
>Our Multiprep uses different kind of double hole needle from that of
>gasbench. I got double hole needles (part # M69-4072CD1,
>tel 603-880-3233 ) for our multiprep from GV US for US$ 99.57. They
>are very good in quality as I had some bad ones before from else
>where. The length from the tip to the welding part at the top is
>about 9 cm.
>
>For any new double hole needles, do check to see if there is
>any hole at the tip with microscope as it will affect your 18O
>eventually. I also do a leak check by sealing the side hole with a
>tape, flush some He through the transfer line while the tip is in
>water (surface is lower than the side hole). If you see bubbles
>don't use it.
>
>Good luck,
>li
>
>
> ----- Original Message -----
>From: Toti Larson
>Date: Wednesday, February 8, 2006 1:18 pm
>Subject: [ISOGEOCHEM] two holed needles
>To: [log in to unmask]
>
>> Does anyone know a supplier for two-holed needles that are used
>> on the
>> Multiflow (and maybe also the Gasbench?). The one I have right
>> now (that is
>> beat-up) is stainless steel 1.45mm OD and 9.5cm length. The
>> inner tube is
>> 0.7mm OD and is welded at the top and bottom
>>
>> Thanks,
>> Toti.
>>
>>
>>
>>
>>
>>
>
>
>Li Huang
>
>Laboratory for Stable Isotope Science
>University of Western Ontario
>London, Ontario
>Canada
>Phone: 1-519-661-3881
--
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