linear gradient and step gradient in HPLC

[sanS]

What is the linear gradient and step gradient in HPLC?

Please share

[lmh]

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

[Consumer Products Guy]

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.

[HW Mueller]

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

[Consumer Products Guy]

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.

[Jiri Urban]

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

shapes of the gradients