Chromatography Forum

Hi all,

I'm using an old Varian 3800 GC with a Saturn 2000MS for pesticides analysis. We have quite a few of these within our laboratory but with I'm currently expericing a repeated issue with the CP-8400 autosampler (which isn't the best designed autosampler in the world!) on one of my instruments. This particular 8400 is repeatedly crunching the syringe needle several vials into the run and I'm at a loss as to what's causing it.

Some details of what I've tried so far:

• Each time I replace the syringe, I recalibrate the vial 0 and injector port positions. Alignment seems to be correct and it successfully injects several samples (between 8 and 10) before crunching.
• I replace the septum that sits within the injector port each run, so I doubt that it's the septum hardening with age!
• I've moved the samples onto another GC with an 8400 autosampler and that has injected without any problems so I don't think it's the vial cap septa.

If anyone has any ideas, please help!

All the best,

Aviator

the same problem is observed in our GCMS with same configuration.I dont know why it happens.It usual happens when we are injecting LVI using 100µl SGE syringe and we need to change the needle within one or two months because of this problem.If we are using 10µl hamilton syringe it is working nicely.

Hi David,

It definitely seems like a known problem with this type of autosampler. Unfortunately we're also using the 10µl hamilton syringe and it has bent one every day this week. We had an engineer replace a control board within the GC but that's had no effect.

I'm changing the syringe type from side hole to a conventional one and I've replaced the lid on the wash vials (whose septa have never given any trouble in the past) with foil. I've also slowed the injection speed from 30 cm/s to 10 cm/s as I'm fairly sure it's not an alignment issue. However without actually seeing the crunch happen, I can't say for sure.

Oh well, fingers crossed for the weekend run!

You really do need to see what is happening - on another make of autosampler I had a slight mismatch on the alignment with the inlet. This would put a slight bend in the needle, which mis-aligned the tip even more, until it caught on the rim of the septum support inside the inlet and bent just enough that on the next sample vial it would hit the edge of the cap and do the Z-fold yoga position. Although it was hitting the sample vials it was the inlet alignment that was at fault.

Also, there are some kinds of vial septa that are very grippy when the needle tries to penetrate, even though they are soft.

Peter

Hi all,

I'm using an old Varian 3800 GC with a Saturn 2000MS for pesticides analysis. We have quite a few of these within our laboratory but with I'm currently expericing a repeated issue with the CP-8400 autosampler (which isn't the best designed autosampler in the world!) on one of my instruments. This particular 8400 is repeatedly crunching the syringe needle several vials into the run and I'm at a loss as to what's causing it.

Some details of what I've tried so far:

• Each time I replace the syringe, I recalibrate the vial 0 and injector port positions. Alignment seems to be correct and it successfully injects several samples (between 8 and 10) before crunching.
• I replace the septum that sits within the injector port each run, so I doubt that it's the septum hardening with age!
• I've moved the samples onto another GC with an 8400 autosampler and that has injected without any problems so I don't think it's the vial cap septa.

If anyone has any ideas, please help!

All the best,

Aviator

I am in quite the same boat, but have had ZERO problems with carousel injector calibration & programming. The poltergeist that has irreversibly (programmed into itself is the injector position location). Used to be that I could use the 8400 to use either the front or middle
positions as long as I selected "Both" on the AS menu on the 3800. Nowadays, it only recognizes injector "1" front position as the correct position (#2) that I wish to use. This occurred after a simple column change. {the logic "magically reset itself last week after the 8400 was accidentally dropped on to my Dell CRT screen}..but only lasted for the remainder of that day,

No former Varian service tech. has been able to solve this weird problem, but being that I am only interested in the middle inj. pos., the calibration proceeds nicely, EXCEPT for the fact that I ruined ~10 syringes last week, even at 5 of a max 30cm/sec inj speeed at only 75% needle depth.

Give me a tech exorcist or the fat psychic from "Poltergeist"!

I am currently about to try pre-cored, softer septa from Restek & perhaps a slightly larger (& stronger 23 gauge needle, even if I have to re-machine the bottom brass/gold bottom alignment pin on the bottom of the sled. The Power of Christ compels me to scream at the engineers of this piss-poor machine.

Vern Y.
MMTLMMJ.com
720-560-7166

I had the same problem. Lots of syringes went to an early grave. Doing the alignment wasn't fixing it. The fix was to follow Peter's advice. Watch the syringe go into the inlet. On our 3800, I had to move the inlet a bit. Two screws, a slight adjustment and it was back to work.
Bruker seems to have completely divested themselves of Varian knowledge and Agilent may have some parts remaining, be we are now our own service engineers.