Retention time calculations for a different column.

[mbreslav]

I am trying to validate use of 150-x4.6 mm RPHPLC column instead of 125x4 mm column (same stationary phase), with gradient elution. If this was an isocratic separation, the correlation coefficient would be [(150/125)X(4.6/4)^2 = 1.587 calculated based on linear velocity. But I have a gradient.... and it seams to me that the dwell time should be involved as well. Are there calculators available on a web? Is there a way to use a DryLab for that? Thanks...

[Uwe Neue]

Neglecting the delay volume, just scale the flow rate with the square of the i.d.. Then scale the gradient volume, including the subsections of the gradient, with the ratio of the column volumes.