Continously Decreasing Retention Times from Run to Run

[Hampow]

Thanks everyone! I will next call in on the manufacturer to check into it. I will post back on what they say and find. At the least, it has been a nice learning experience doing this troubleshooting session. Also, everyone pointed me to some useful resources for future reading, etc.

Thanks!

[Hollow]

You're welcome. That's what this forum is about.
And please let us know what the issue was. So we also can learn and remember for the next questions like this.

[Hampow]

The manufacturer has come in a number of times. They have not been able to figure it out. they are trying changing out or PM'ing things to see if something resolves it.

[Peter Apps]

Can you exclude the possibility that something in the air (CO2 for example, but could be other things floating around in lab air) is dissolving in the mobile phases while they are in the reservoir bottles ?. That would explain why pumping fresh solvent resets the retentions.

What are your analytes ?

Peter

[Hampow]

Can you exclude the possibility that something in the air (CO2 for example, but could be other things floating around in lab air) is dissolving in the mobile phases while they are in the reservoir bottles ?. That would explain why pumping fresh solvent resets the retentions.

What are your analytes ?

Peter

We are looking at tocopherols and tocotrienols.

I believe that we can exclude something dissolving into the mobile phases while in the bottles. Though the solvents are prepared daily, the purging that I reference is from the same reservoir solvents at the end of that set of runs. If something were dissolving into the solvents in the reservoir, then I would be just purging with the same tainted solvents at that mid day point.

Also, the same method runs fine on the other system in the same lab, with the same column (physically the same, moved from one system to the other). Though the solvent are prepped separately for each system, it is from the same stocks.

Thanks,
Mike

[Hampow]

The manufacturer is still unable to determine what is going on. They have been here going on a dozen times; fortunately under warranty. The tech coming in has said that they have never seen anything like this, and they thought that they had seen it all.