Chromatography Forum

Hello everyone,
I’ve observed a significant shift in the retention time for ammonia, which has increased from a consistent 4 minutes to approximately 12 minutes. The method had been well established with a retention time around 4 minutes, and this change occurred unexpectedly over the weekend.

To troubleshoot, we have already taken the following steps:

Replaced the column

Flushed the suppressor

Flushed the system with deionized water

Cleaned the check valve

Inspected all connections

Primed the system to remove any air

Despite these efforts, the issue persists. Any insights or suggestions you can offer would be greatly appreciated.

What about the retention times of other cations?
What about the flow rate accuracy? Did you verify it by measuring with a volumetric flask and a stopwatch? What about the pressure ripple?
How do you prepare the eluent? Do you use electrogeneration?

Any clicking noise from the motor? That is a sign that it is failing and it can shifts RTs. What about the column temperature? If that changes the RT would shift.