Chromatography Forum

Good afternoon,

I am hoping that someone on the forum might be able to shed some light on our injector issue. We had a COC injector port installed on the back inlet of our 5970a GC - FID.

When the autosampler (G4513 plugged into back inlet port) lowers to inject the sample - the A/S stops with a shudder and goes into fault mode - the plunger remains depressed. I can manually inject the sample at this point and then raise the injector. Needle is not bent.

I have tried realigning the A/S using the automatic align on the turret - and all seems OK. I can manually inject a sample, so I am happy with the alignment of the 0.53um guard column and associated COC parts and we have the 0.53 on column nut with septa in place. I have also changed the needle guide to the on column needle guide that came with the kit.

The needle is an 5ul Agilent on column syringe (5182 0836) with 0.32 needle, inlet pressure is 10psi has a septum purge of 15ml/min. These pressure were set by the Agilent engineer so I am not sure whether these are what we should be using - but thought I would include them if it help narrow down the A/S issue.

Many thanks for any help on this issue,

Matt

Hello

If sampler can put needle through septa and can't go up after injection perhaps it is too tight. Just don't tighten inlet nut too much (it squeezes septa)

Regards

Tomasz Kubowicz

Hello

If sampler can put needle through septa and can't go up after injection perhaps it is too tight. Just don't tighten inlet nut too much (it squeezes septa)

Regards

Tomasz Kubowicz

This would be the first thing I would look at too. Install septa, then nut, and tighten the nut until you have about a finger nail thickness gap between the top of the nut and the retainer clip. This should give enough pressure to seal the septa but not compress it too much.

Many thanks to Tomasz and James for your replies. Unfortunately this did not solve the problem. Just to confirm that the needle was not the issue, I removed the needle from the syringe barrel and tried another injection, and the same thing happened - so I think it may be something to do with the syringe carriage.

I have checked the logs, and I am getting the following error:

'Sampler Error #90 Auto injector back tower syringe error'

The tower itself is flashing red two times - the manual for which indicates that it is a syringe error - reinstate or replace syringe. Have done both - to no improvement.

Any further insights would be greatly appreciated

Hello

I see 3 possible problems:

1.Needle guide - make sure it is correct one, try to clean hole that needle goes through

2.COC inserts - make sure you have correct one:
*19245-20515 COC insert, 250-μm column, 6 identification rings
*19245-20525 COC insert, 320-μm column, 5 identification rings

3.In the case above do not wor I'd reload injector firmware (or upgrade to newest version)

NOTE: very first thing to check is to create GC method from scratch (do not use existing method - load DEF_GC.M and create based on default) and try if it helps

Regards

Tomasz Kubowicz