Syringe Problems

[AndyA]

Currently I seem to be having an issue whenever I running some pharmacopeia methods for semi viscous materials most recent example is glycerol. I'm finding the autosampler bends the syringes this seems to mostly happen only with 5uL syringes.

The syringe is rinsed before and after injection with the solvent.

I am currently using a 7693.

I am just wondering if there is any recommendations on how to reduce this as I'm having to replace the syringe quite regularly.

[Consumer Products Guy]

On some model GCs, the plunger rate can be adjusted.

Are you injecting straight glycerin, or diluting in some solvent (assuming neat).

[AndyA]

Our Autosampler has to rates fast and slow. Our default is the fast setting.

We dilute the glycerol in water and then dilute again with water.

[Consumer Products Guy]

When we did the USP tests for glycerin, we injected 0.5 microliters from a 5 microliter syringe, and we rinsed the syringe with water. 7673 Autosampler.

[James_Ball]

The 7693 seems to put more pressure on the plunger than the 7673 did. We had one that was bending plungers, but the syringes seemed to be defective, they would become very stiff after only a few days, a new box of syringes solved that problem.

How soon after installing a new syringe does it bend?

It might be a good idea to remove the syringe every day and wipe the plunger with a damp Kimwipe and even use another to inject some water into the top of the syringe then push it through with the plunger, as some sample can escape up the sides of the plunger and if the water evaporates can become sticky and make the plunger difficult to move.

[AndyA]

The syringes bend at anything from about 20 injections to the high double figures there is no consistency to it.

[James_Ball]

If it is the sample that is causing the plunger to have resistance because it leaks by the plunger a little over time, maybe you could try one of the teflon tipped plunger syringes and see if those will last longer.

I have a feeling that a little sample is passing by the plunger and over time the water evaporates and leaves the higher viscosity sample there to increase the friction between the plunger and barrel.

[Pimi]

Hi!

Sorry I don't understand why you can't reduce plunger speed?

In our practice for 5 microlitter syringe draw speed - 150 uL/min and push 500 uL/min at Agilent 7693 + 7890B set up.

In fact a few time ago I have exact problem with any syringes. Problem was simple - not enough washing, and not enough of speed, and dirty sensor of tower, and old version tower controller driver.

So now for each syringe live long about 3 - 4 month

[AndyA]

The CDS software we use to run the GCs allows us to select the number of rinses we perform (which we do a minimum of 5 as default) allows for only two options on draw speed slow or fast.

There is no option for push speed.

[Consumer Products Guy]

I'll assume that you've tried syringes from different suppliers, syringes with PTFE plungers, and/or smaller volume syringes which have a reinforced plunger