Hi all,
I have successfully used differend methods to unclog the needle:

1) just disconnect the fused silica capillary from the gasbench - fill an exetainer with water (or 
solvent) and use the pressure of the  He-flow from the gasbench through the steel capillary to 
pressurize the extainer. If you have a setup of the gas-bench with a flush needle for flushing 
exetainers with gas (as used for water equilibration) you can connect the steel capillary even 
to this gas line and use a higher pressure. Be careful to put a beaker below the end of the 
fused silica capillary as water will run very fast as soon the line is unclogged. After using 
water I usually used in the same way some ethanol and even very shortly acetone to dry the 
capillary after flushing with water.

2) if this does not work - it is possible to move a smaller capillary through the one of the 
needle - this sounds odd but I have successfully done it (I used an "old" capillary with ID 0.1). 
You have to enter the smaller capillary carefully from either side of the capillary (at the needle 
or the other end). Move it very carefully and eventually try the flushing with ethanol as 
described above to "lubricate".  In this way I removed just recently some silicon grease in the 
capillary that was accidentally deposited at some exetainers at sampling and went  into the 
capillary at the measurement.

As we are discussing gasbench needles I just wonder if and how other users protect the part 
of the fused silica capillary above the needle from breaking during handling. This happened 
to me already 3 times, although I am very careful (at least since the first breaking). The steel 
capillary just above it's entering the needle is flattened and therefore very susceptible to 
bending - and as the fused silica cannot be bent as much it breaks - within the yellow tubing, 
which not really protects it but rather gives a false impression of safety. I now have put some 
stiff plastic tube over this place and hope this will protect it from breaking ever again.

Margarete






On 8 Jun 2009 at 16:00, Joe Lambert wrote:

> Hi all,
> 
>     I was hoping someone could offer tips/advice for unclogging
>     GasBench
> sample needles where acid has crystallized in the silica capillary.
> There was some discussion in the past which involved adapting a small
> syringe to flush water through the capillary.  Is there an easy way to
> connect a syringe to the small capillary?  Other ideas?
> 
> Thanks,
> 
> Joe
> 
> 
> W. Joe Lambert
> Research Scientist
> Alabama Stable Isotope Laboratory
> University of Alabama
> Geological Sciences
> 202 Bevill Building
> 7th Avenue
> P.O. Box 870338
> Tuscaloosa, AL 35487-0338
> Phone: (205) 348-4404
> Fax: (205) 348-0818
> email: [log in to unmask]
> Visit our web-site: http:www.geo.ua.edu/asil
> 

Department für Chemische Ökologie und Ökosystemforschung
Fakultätszentrum fuer Oekologie
Universität Wien
Althanstr. 14,1091 Wien
Tel: 4277-54258
Fax: 4277-9542
e-mail: [log in to unmask]