Chromatography Forum

Does anyone know of anywebsite that has a van Deemter calculator. Where you could input the molecular weight, temperature, particle diameter, column diameter etc, and it would calculate the optimal flow rate.

I have recently done some van Deemter calculations (the hard way) and the results seem a bit low. For example, for a 3 um particle, and a 4.6 mm column, and an analyte with a molecular weight of 150, I get an optimal flow rate of ~0.35 mL/min.

I don't know - it seems low to me.

Thanks in advance.
Adam

Assuming you calculated it for water, it is about right.

Lately I did quite a few experimental Van Deemter determinations (100% aqueous mobile phase) and they came out at about the same flow rate (optimum between 0.2 and 0.4mL/min, 4.1mm ID columns).

You can download a demo version of the DryLab software from Rheodyne (the link is in the "sponsored by" box at the top of the screen. Just use the default example. You can play games with the water/ACN ratio, analyte molecular weight, column dimensions, particle size, flow rate, and even get into playing with stationary phase pore diameter and packing quality. Strictly speaking, it uses the "Knox equation" (the version where the A-term has a weak dependence on linear velocity).

Granted that much of that is well hidden, but it's all documented in the on-line help.

Thanks guys. That helps quite a bit.

Adam