Chromatography Forum

Hello,

I received a method from a client, and ran it for the first time last night. The retention time of the main peak bounces around in a 2-3 minute range, with no clear trend on which direction it is changing throughout the run. I used a brand new column. I first pumped with 100% organic for a couple hours, then at initial conditions for a few hours, before starting the run. It says the method is validated, so it doesn't seem like it would be an actual method issue. I don't see any problems with the pressure traces. Thoughts? Someone mentioned that they didn't think the "wash" time at the end of the run was long enough, but since the method is validated that seems likely not the case.

Hi,

We can't help unless you post the actual method...

randi912d wrote:
I don't see any problems with the pressure traces. Thoughts? Someone mentioned that they didn't think the "wash" time at the end of the run was long enough, but since the method is validated that seems likely not the case.

The time before the next injection is more commonly termed equilibration time than "wash" time. The column needs a certain volume (like 10 column volumes or more) of initial mobile phase composition to chemically re-equilibrate with gradient runs.

Lengthen the time/column volumes of equilibration and see if that helps.