Chromatography Forum

Dear all,

We are using an older type CTC combipal to do 50µl liquid injections. From time to time the autosampler is making a strange cracking noise like a motor that keeps pushing when it is at its final position, causing a gear-wheal (hope this is the correct english term for it) to slip.
It occurs right a the beginning of an injection-cycle, when the autosampler checkes its position, and at the end of the cycle when it returns to its home-position.
First it slightly raises the plunjer, to push it down again. It is in this downward-motion that the motor keeps pushing even when the plunjer is at its bottom position. It does not make this error while injecting or washing.

does anyone now if there is a setting to adjust this 'plunjer-end' position ?

kind regards
BMU

Take the syringe out and play with the plunger, is it moving nice and easily?

sry for this rather late repley.
syringe is working perfectly. plunjer is moving smooth yet not to loose so it seems fine.

BMU

Strange. I'm assuming you've got the correct syringe volume size selected in the settings?

If so, I' afraid I'm out of ideas without seeing it in action.

there is a 'universal' syringe-holder placed. Auto-syringe detect is set off and syringe-volume 100µl is selected (= correct)

strange thing is that it doesn't occure every time although there is no difference in the methode.

thanks a lot for your time anyway. If I stumble upon a cause I'll let you know.

BMU

I have had this problem which ended up with me bending plungers (see this thread viewtopic.php?f=2&t=21722)

It started with me with a jammed syringe and then it randomly happened. I replace both the drive motors and seem to fix it for 6 months but the problem is back.

Not sure what the problem so I await a good answer to your question.

I had this issue when we had a newer bruker combipal installed with a new GC. In the syringe settings menu there is a setting for the stroke length of your syringe. This is set too long which is causing the motor to try and push in the plunger further than it can go when it is doing its XYZ calibration on first move.

When i bought a certain type of SGE syringe for ours we had to change this setting and it sorted the problem.

Our problem just solved itself. I still have no idea what caused it.

I did notice that the 'elastic' bands that are used in every CTC or MPS-autosampler cause a fine black dust because they rub against a metal part each time the head moves. this dust collects on top of the syringe and if not cleand regularly it will be taken into the barrel by the plunger. Causing contamination and possible blocking of the needle.

BMU