Chromatography Forum

What is the linear gradient and step gradient in HPLC?

Please share

linear gradients change gradually... step gradients change suddenly.

Linear gradient is like 50/50 for five minutes, then going to 90% at nine minutes.

Step gradient is like 50/50 for five minutes then immediately changing to 90% at five minutes. In the old days it was felt that columns couldn't handle dramatic changes in pressure well.

One can also do flow rate programming as well.

CPG, you mean linearly increasing to 90% during 4 min.?

CPG, you mean linearly increasing to 90% during 4 min.?

Yes, that's what I meant, like on Agilent ChemStation. With ChemStation you set the composition at the times (e.g. 50% at 5 minutes and 90% at 9 minutes) and ChemStation changes it linearly over those 4 minutes. So 60% at 6 minutes, 70% at 7 minutes, etc.

http://bp1.blogger.com/_p1FRxLAXQkw/SH1 ... 00-h/a.JPG

shapes of the gradients