We've been making our own for a while now.
A 19Ga needle, ~4" (10cm), with a hole in the side, ~ 1cm up from the
tip, does the trick. We epoxy it in place--but there was mention on
Isogeochem that if the hole is far enough away from the tip, you don't
need to do that.
To drill the hole in the side yourself, clamp the needle between two
boards, with a small groove in one to hold it in place and a guide hole
in the other for the (dental) drill. It may take a little practice.
You can buy a custom made needle--we got some from Popper and Sons in
the states--but that only make sense if you buy in bulk.
The needle attaches to a standard 1/16" swagelok 3-way connector (or
metric equivalent). The glass capillary feeds straight through the
connector and down the needle. We still epoxy it in place at the bottom
of the needle--push extra through then snap that off when the epoxy
dries. You'll want a tight fit on the needle. We like to use a
stainless steel connector since you have have to over tighten the
standard 1/16" ferrules to get them to grip the needle. We'll use the
Valco ferrules (longer) in the swagelok fitting, or sometimes use a
brass swagelok ferrule with an extra backing ferrule. The capillary
ferrules are the standard GC capillary ferrules.
For attaching to the PAL holder, we use a 1/16" to 1/8" swagelok
reducing union. The key connection is the attachment to the needle. We
use a metal ferrule to tightly hold the needle in place--usually by
pre-swaging a steel valco ferrule in a valco union then sliding onto the
needle, or even getting it swaged (is that a word?) onto the needle
before starting anything else. On the 1/8" side, we'll use an 1/8" to
1/16" reducing ferrule as a guide only. Please note, when attached the
needle tip should not be below the bottom of the PAL's bottom needle guide.
The side arm is for the He feed. We're still using the steel capillary
originally from Thermo--but some are available from McMaster-Carr
We make homemade acid needles by just sharpened the stainless steel
capillary (from McMaster-Carr in the US). In this case were using a
1/16" to 1/8" adaptor to fit into the 1/8" swagelok union--use the parts
p.s. no, I've not gotten this up on the wiki yet :(
Jonathan Wynn wrote:
> Hello all,
> Has anyone out there successfully replaced the fused silica capillary
> in double-holed needles used by the Thermo Finnigan Gasbench?
> Suggestions or tips would be very welcome on how to extract the fused
> silica capillary from the needle's interior (what sort of glue is
> used?), and rethreading a replacement piece.
> Rather than treat these as consumables at ~$400/ea., it would be great
> if there were a simple method of replacing the capillary, which is not
> only susceptible to clogging (relatively easily solved), but the
> occasional breakage.
> Jonathan Wynn
> Department of Geology
> University of South Florida
> 4202 E Fowler Ave, SCA 528
> Tampa, FL 33620
> Tel. +1 (813) 974-9369
> Lab. +1 (813) 974-5278
> Fax. +1 (813) 974-2654
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