Retention time drift

[jill]

I am currently working on a potency method transfer (reversed phase, isocratic system) and have been observing random retention time drifts of the peak of interest. This drift is not a gradual drift, but a sudden drift (most of the times exceeding 10%) in one random injection and then in the subsequent injection, the peak of interest would elute at the typical retention time.

Some important facts about this method: Use of a Zorbax column; 50% organic/50% buffer mobile phase; 80% organic/20% buffer sample and standard diluent; heated column temperature.

Has anyone observed this type of drift? This has been seen on multiple LCs, multiple columns, and different preparation schemes for both mobile phase and diluent.

I am highly interested in hearing feedback you may have to offer.

Thank you.

[tom jupille]

One possibility is occasionally sucking an air bubble in the pump. When the retention time of the peak of interest shifts, do other peaks shift as well?

[Bryan Evans]

Are you sure you are using the correct buffer for
the mobile phase/diluent ?

[skunked_once]

I notice that your mobile phase is 50% organic but your sample/standard dissolution solvent is 80% organic. If your injection volume is too large, this could result in a plug of 80% organic traveling through the column causing a shift in retention time. It is best to dissolve the sample and standards in a solution that does not exceed the organic concentration of the mobile phase.

[John]

Hello Jill,
Does your peak area vary with retention time?
J

[ntruong]

Hi Jill,
Is your mobile phase mixed together? It happened to me 9 out of 10 when I used the mobile phase system 72:23:5 MeOH:H2O:THF for my analyses. The problem fixed after I mixed all reagents into one reservoir.