needle or syringe problem!

[hxt]

Folks,

I am trying to see if the problem with my injection is with the needle or the syringe. When I run a method- using 100 ul injection, I do not see any withdrawl of the sample. I have run the method 5 times and when I measure the amount left in the vial, the needle only draws about 10 ul instead of the 100 ul. I am wondering if the syringe is not airtight or the needle has a problem. Any suggestions please ?

thanks

[Don_Hilton]

Can you take the suringe out of the instrument and examine it?

[lmh]

what instrument, what vials? More information needed!

[Consumer Products Guy]

Can you take the syringe out of the instrument and examine it?

Yeah, do this !!! Try sucking up solvent from a beaker, manually, and expelling.

I assume you have a syringe with a replaceable needle, or it really doesn't matter exactly what's wrong, bad is bad.

[Caged Alpinist]

It could be a mechanical problem with the plunger operating mechanism. If it's belt-driven, the belt may need replacing or the gear teeth that drive it may be partially stripped. More info about the type of autosampler/injector tower would be helpful.

Cheers,

A.W.

[hxt]

It does not seem to be a syringe problem as I tested this by removing the line that goes out from the syringe to the column. The HPLC is an alliance 2690. It seems to be a needle problem as it does not draw any sample from the vial. Might be a seal issue ?

[sam.pedraglio]

It does not seem to be a syringe problem as I tested this by removing the line that goes out from the syringe to the column. The

You could try this:
pick out you syringe alone and try to draw some solvent from a becker. If it couldn't be done, fill the syringe with a micropipette and try to push the solvent if the needle is stucked you wan't be able to do this, if you have a seal problem the solvent will exit from the rear side of your syrenge.

[lmh]

Ah! Check the depth of sample you have in the vial before you inject.

In Alliance modules, I believe the needle draws the sample through a hole in the side about 6mm from the tip of the needle. Given that the needle often doesn't descend right to the bottom of the vial, it's easy to underestimate the height up the tube that the sample must come in order to be reliably drawn. If the hole is sitting just below the meniscus, you may get inaccurate volumes taken up.

[hxt]

Great suggestions. The syringe pushes the solvent very well and I can actually measure this in a vial by disconnection the outflow from the syringe to the column. The problem exists between the sample and the needle that draws the sample. So it might be the needle and the seal pack component.
I can actually see how deep the needle goes from a side panel of the alliance so I am certain that it goes well into the sample component, that would rule out the needle depth issue.