Chromatography Forum

Greetings all! I have what I hope should amount to an easy topic. I am very familiar with the old chemstation software controlling the Agilent 1100 series LCs. However we recently upgraded to a 1260 with the new Agilent OpenLab CDS Chemstation Edition rev. C.01.02 [14]. I am having an issue writing a column equilibration method. The issue is I am trying to start the quat pump at 0.1 ml/min and slowly ramp up to 0.6ml/min. The problem I run into is there is always some extra time attached to the end of the timetable graph that reverts back to my original flowrate (0.1ml/min). This is not present in the timetable itself. The posttime is set to "Off".

Has anyone run into a similar situation with the new software and/or found a way around this issue?

is the method set only to ramp up?
have you tried to have 1-2 minutes more at 0.6 flow?
you can also do a "second run", with an isocratic method with flow at 0.6ml/min

Thank you for the reply,

Yes the method is a warm-up method to bring an Aminex HPX-87H sugar column up to operating conditions (both flow and temperature). Additional flow time at 0.6ml/min does not help as the timetable always automatically adds a few minutes as the original flow rate which results in an immediate drop in flow from 0.6 to 0.2 but then an immediate spike from 0.2 to 0.6 a few minutes later when the actual analytical method kicks in, and this spike in flow is obviously undesirable from a pressure and column life standpoint.

In the 1100 pump settings, you can set the flow ramp speed (I think what it's called - it's in the pump parameters section with the compressibility settings on the A.10 Chemstation) to (I think) 0.1mL/min/min. When you turn on the pump, it won't go immediately to 0.6mL/min - it will ramp at 0.1mL/min^2 to 0.6mL/min, then hold there. I know the B.04 Chemstation had the same feature available for the binary 1290 pump - it was in the Advanced Tab of the pump parameter settings and was called "Maximum flow gradient" and had a ramp up and ramp down setting that did the same thing. However, I've never seen the OpenLab CDS interface - is OpenLab so different from the B.04 Chemstation that this is no longer available, or is it just not available on the 1200-series quaternary pumps?

If it's still there, you can make a method called warm_up that you load without turning the pump on, that has the lowest ramp-up setting you can program. When you activate the method, the pump turns on and starts slowly making its way to 0.6mL/min. You can figure out how long you want that to go for, and the next line in the sequence (or the next method you activate) would be your normal method.