I second Jen's recommendations. I usually keep an old syringe that is plugged or perhaps that does not work so good any more, just for the purpose of doing the first core in a new septum. There is a small degree of float in the septum holder and septum support that I usually start with the assembly more on the loose end, and core it once to ensure things are lined up. Then I tighten it slightly and core it a few more times. It is always best to have the retaining cap only as tight as it needs to be.
If the injector is cold or the septum tightened a lot, it has the habit of acting like a brick.
Hope this helps.
Manager, Stable Isotope Core Laboratory
Washington State University
School of Biological Sciences
Pullman, WA 99164-4236
Laboratory for Biotechnology and Bioanalysis (LBB2) Stable Isotope Core
After changing the septa I would manually pierce it with the needle 3-5 times. I am not sure why but it greatly reduced the number of bent needles we saw.
W.M. Keck Carbon Cycle AMS Lab
On Oct 10, 2014, at 7:44 AM, Patrick Griffin wrote:
Are you making your final tightness adjustments when the port is at operating temperature or when the port is cool? I have had problems with bending and coring in the past but seem to have found a way to avoid them. After replacing the septum I wait until the injector port is back up to temperature, loosen the cap until the port is no longer gas tight, and then tighten it to a position just slightly more snug than is required to maintain pressure. This may not resolve your issue because I've never had a Goldilocks problem where there's too loose, too tight, and just right -- instead I have found that a cap tightened at a low temperature is almost always too tight for operation once the temperature returns to operating specs. Your mileage may vary, but I figure even one forty dollar syringe is worth my two cents. Hope it helps.
Department of Geological Sciences
On Fri, Oct 10, 2014 at 9:54 AM, Jeff Salacup <[log in to unmask]> wrote:
Hello ever-helpful collective brain,
We're having problems either bending or plugging our Thermo 10uL syringes (PN 36500525). It usually occurs after a septum change (septum PN Restek 27116). It seems that if I don't tighten the septum cap enough, the needle bends, if I tighten it too much the needles effectively cores the septum, plugging the syringe. We're running a Thermo Trace Ultra GC with a Thermo AS3000 autosampler. I've been thru 4 syringes in the past 2 days ($$) and am wondering if there is some trick I'm unaware of.
Any help would be huge.
Jeff Salacup, Ph.D
Lecturer | Stable Isotope & Biogeochemistry Lab Manager
“… it’s not your life. It's life. Life is bigger than you… Life isn't something that you possess; it's something that you take part in, and you witness." –Louis C.K.