I've found my shimadzu HPLC auto-sampler tubing and six-way valve have become plugged with septum cores chopped out by the injector needle.
I've been using the manufacturer's product.
Are there any types of septa that are not prone to this rather frustrating problem ?
By Anonymous on Saturday, June 12, 1999 - 03:52 am:
I suspect this is a fault of the needle rather than the septa material. I only have experience with HP/Waters autosamplers. If anything the HP needle is not sharp enough as it often pushes the whole septum into the vial upon injection.(this can be avoided to a certain extent by making sure that the screw cap is very tight). We were using HP septa with 2ml vials and we did not encounter any clogging caused by broken pieces of septa. You could try these.
Just out of interest, is the septum rubber completely inert if it is submersed in a 2.5pH acidic solution? Curious to know if this may lead to extra peaks in a chromatogram.
By Robert on Monday, June 14, 1999 - 04:42 am:
we made quite good experiences with silicone/rubber septa 8-ST101 and 12-ST101
from Chromacol .
To remove the septum pieces I recommend to
purge the flowpath in reversed direction.
By Andrew Lyon on Monday, June 14, 1999 - 10:03 am:
In Reply to "anonymous": We have not observed any extra peaks on washing the septa with ph 2.5 acid. We have been using a teflon layered - silicone rubber septum, and most of our plugging problem is with small pieces of teflon. I am considering a switch to a silicone rubber septum problem and I will then have to re-test for contaminating peaks.
In Reply to "Robert": Thanks for the suggestion on the silicone rubber septum product. I agreed with your other suggestion about reversing flow, but the autosampler was plugged with hundreds of teflon cores that seemed to travel through the 0.2 mm HPLC tubing into the injector valve, which required disassembly and cleaning. Thanks, Andrew
By Leif on Wednesday, June 16, 1999 - 01:07 am:
Try to look on the tip of your needle i 15-20 magnification in comparison vith a new needle. If your old needle are corroded replace it with a new one.
By JD on Thursday, June 17, 1999 - 08:11 am:
Contrary to popular belief, the square-tipped needle of LC autosamplers tears its way thru the septum, and is not supposed to cut thru like a pointed GC needle. If the needle is rough on the edges or too sharp, it can act like a cork borer and cut cores from the septa rather than tearing thru and leaving a flap or ragged hole. Sometimes you can feel roughness at the tip of the needle. However, the easiest way to check this is the old substitution tests -- stick a new needle in and see if it fixes the problem. Alternatively, try a different configuration of septum. We use the silicon/teflon combination (single sided) with Shimadzu and do not see this problem.
By Scot Reynolds on Wednesday, June 23, 1999 - 09:41 am:
What model Shimadzu autosampler are you using?(SIL-6A,6B,9A,10A,10Ai,10Axl,10ADvp)
The needle design are slightly different for the various models and this information will help me address your problem.
Have the other recommendations improved your situation?
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