Air Bubbles in Dionex Injector

[max_planck]

Hi all,

I am just wondering if any of you have been working with the new Dionex UltiMate® 3000 Rapid Separation LC (RSLC) HPLC System? As we have a problem with air bubbles in our injector. The Dionex service engineer is of no help as all he does is removing the air bubbles but not removing the cause of the air in the injector. The air returns every day after removing the bubbles and I start to think that the Dionex system might have a fundamental design fault.

Any ideas or suggestions as to why this is happening?

Thanks in advance!

[Mattias]

We are seeing the same thing, especially if the system has not been in use for a couple of days. I have never seen that airbubbles emerge during a run. Prime the syringe before every run is my suggestion.

It is likely to be a design fault, since we never see this with Agilent or Waters systems.

[Hfranz]

With an UltiMate 3000 RSLC system, this can only happen if the system is not properly installed. I have been working quite a lot with the system and have not seen a single bubble showing up. Make sure the autosampler is connected to a degassing chamber of the solvent rack. This can be done by splitting the flow of one of the solvent lines. By doing so, you can make sure that the autosampler is always using freshly degassed liquid. In case you have buffer salts in both eluent lines I would suggest to connect the sampler to an extra degassing channel. You might be aware that the solvent rack is available with different numbers of degassing channels. I am sure your Dionex representative is happy to inform you about all options.
Mattias: You are talking about the Summit system which is quite different in design, arn't you? There we suggest the priming procedure you probably refer to. The good thing with that procedure is that you can even schedule the washing procedure to be done before you enter the lab... As you state, during permanent operation, bubbles do not show up.

[Mattias]

Hfranz> You are correct, we have the Summit system. I assumed that the design of the newer system were the same - which was wrong.

[max_planck]

Thanks for your advice!

We have got two new Dionex systems now and I have removed those pump + injector wash bottles by inserting a T-piece and are directly drawing my own degassed system wash from the solvent reservoir. So far I have not observed any air bubbles. If they show up I will look into the auto sampler + degassing chamber option. Someone else suggested to me that it might had to do with the drawing speed of the injector. So I tried a few experiments but could not confirm that this was the cause for our air bubbles.

[Hfranz]

The drawing speed is definitely something to consider. Particularly with very volatile liquids you can easily create mini-bubbles when applying too high speed. However, this does not generate permanent bubbles, instead, they appear only during the drawing process. Typically, their effect is only a higher peak area RSD.
In a nutshell, optimizing the draw speed may lead to a higher area precision of your method.