Chromatography Forum

Hello,

I was hoping someone may shed some light on a recent issue we are having with Agilent GC/MS with Gerstel MPS2.

Recently it has been bending needles on a weekly basis. Much more than is normal.

We went ahead and changed out the two tension cords in the injection head, this helped a bit, but it is still bending needles.

We have not changed out the vials or septas that we were using before, so we are at a bit of a loss as to the cause. Any suggestions or help would be appreciated.

Regards,
R

Do you know where the bending is occurring? Inlet or vial?

Confirm the needle alignment on the GC/MS. Is the needle guide on the inlet in place and centered? We've bent more than one needle due to an improperly aligned needle guide.

Confirm the needle alignment on the GC/MS...

I am in agreement with this. Try watching injections to see WHEN it is occurring (ie., Vial or Inlet). IF it's at the inlet then check the alignment to the Stored Inlet position in the autosampler's memory (use the MPS 2 controller).

Depending on the Brand/Type of inlet you have it may be relatively easy to "move" it out of position during a simple septum or liner swap. I have had this happen to me on my new TriPlus RSH (Similar as CTC for Gerstel). It wasn't the autosampler's fault, but my own as I had pushed the SSL inlet out of position by only about 1mm. That can be enough to inject well most of the time until one random injection is off by 0.1mm to miss the inlet guide bevel.

Best of Luck,
Ty

Make sure that you are not over tightening the septa nut. On Agilent GC's, all that's needed is to tighten it until the C-ring on top of the nut stops turning with the nut.