Drifting RT when volume increased

[littleman]

Hi,

I have been performing PV on an agilent 1200 system. I have got perfect results for reproducibility with 6 x 20ul injections and also perfect injector acc with 6 x 20 and 6 x 500ul injections. When running injector linearity my peak areas are fine but as the volume increases the RT drifts out.

Does anyone have any ideas how i could resolve this? I have tried with 2 different columns and still have the issue.

Thanks
LM

[tom jupille]

What flow rate, and how much does your retention time shift?

[littleman]

Flow rate is 1ml/min and retention time shifts gradually through injections of 5ul, 10ul, 50ul and 100ul. RT is 1.91 mins at 5ul and then 2.02 at 100ul. Previous years PV's show no such drift on the same system. Flow rate is also coming out perfect in our tests at 0.5, 1 and 2ml/min.

[HPLCaddict]

Is this really a retention time drift or is the peak just wider with the higher volume and thus the peak maximum aka retention time shifted a bit? I myself wouldn't really worry if the peak maximum shifts by ~0.1 minutes when increasing the injection volume 20-fold.
BTW what's the capacity factor of that peak? Is it retained enough or is it sitting in the solvent front?

[Johnny Rod]

Is your sample made in the same solvent mixture as the mobile phase?

[littleman]

Yes it is definitely a drift, peak starts and ends later than initial 5ul injection, all peaks are retained enough. We are only seeing it as an issue as all of our other systems and previous tests on this system have shown no drift at all under the same conditions.

Yes the sample is made in the same solvent mixture as the mobile phase.

[Coffo]

Have you changed the delivery or eject speed of the sample injector at all ?

[Leni]

Hi,

I have been performing PV on an agilent 1200 system. I have got perfect results for reproducibility with 6 x 20ul injections and also perfect injector acc with 6 x 20 and 6 x 500ul injections. When running injector linearity my peak areas are fine but as the volume increases the RT drifts out.

Does anyone have any ideas how i could resolve this? I have tried with 2 different columns and still have the issue.

Thanks
LM

Are you using a column or restriction capillary(or deadvolume, tubing etc.).
If you are using a column it can happen that Tr shift. (Maybe column is exhauted?!). We do PV without column (restriction capillary)