Chromatography Forum

For years now, I have run column heaters in the direction of the column. If the setup is vertical than I don't change it and vice versa. Recently, I was told that they should be horizolntal at all times.

What is the concensus opinion on this? Please provide examples why or at least include a link to the information.

Other wise I'm going to keep on diong what I do.

Thanks

Chuck

Charles,
I would think that there may be a problem with vertical alignment temperature gradient if it is an air heated column oven. If it is a contact heater, then I don't see a problem.

Vertical orientation may set up a convection current flowing inside the insulation of the contact heater. Confirm the temperature is correct at either end.
J

Charles,

what is the RSD of your RT?
do you find it to be bad?

how is your column heated up? via contact or air circulation?

remember that heating is done in a closed compartment. with air circulation it is also forced to move, so you cannot talk about upward diffusion of the heat and of temp. differences between top and bottom, unless your fan is too slow or broken or the sealing might be damaged somewhere, or your door does not close tightelly.
but check your RT RSD.
were you told that by a sales rep?

If there's a fan (forced air heater), orientation doesn't much matter. If it's a conduction type thing (like Agilent), it probably matters some (worth mapping w/ a thermocouple).

If your column heater works by lighting a campfire under the column, then you get better results with a horizontal arrangement...

If your column heater works by lighting a campfire under the column, then you get better results with a horizontal arrangement...

I disagree, particularly if the column is mounted in a chimney above the campfire. You will get a much better draft (and much less smoke) with a vertical orientation.

Sorry, I couldn't resist

Seriously, as Uwe implied, it shouldn't make much difference; the important thing is to get good heat transfer into the column.

For one thing, the engineers who spent all that time tweaking the design for uniform temperature did it in only one orientation. If you were to ask them to double their testing by changing the orientation, they would rebel.

I have a tube filled with metal segments. Each contacts the heating element of the heater which then transfers it to the column. I assume its by contact but sometimes I wonder if its functioning properly.

On occasion I'll remove a column and notice a difference between the lower half of the column and upper half. That is if its vertical.

What would be the main problems faced in that event of uneven heating?

Chuck

First, retention times may not be as reproducible as they could be. If the temperature is nonuniform across the width of the column, it will lower efficiency and symmetry.

Of course, I was joking above with the camp-fire column heater...

To be serious, however: I do not see a reason that a column orientation should play a role. The heat transfer in the metal wall of the column is much, much higher than for example in the surrounding air. One would need to blow some cold air at a very high speed across the column, before one gets a radial temperature difference. Of course, you can do this experiment with a vertically oriented column as well as with a horizontally oriented column. So orientation is not the issue...

It is possible to observe temperature differences between the column inlet and the column outlet. To me this means that there was a weakness in the preheating of the incoming solvent before it reached the column. It is difficult (= requires special techniques) to get the solvent temperature at the column inlet to exactly the same temperature as the column outlet, and in some circumstances, this may even be impossible, and not only difficult. Thus the observation of a temperature difference between the column inlet and the column outlet is not impossible, but this has nothing to do with the vertical or horizontal orientation of the column.

To Charles: if you are observing a difference in column temperature from column inlet to outlet by touching the column, I suggest to check, how efficient your preheating of the incoming solvent is.

Now, I have to admit that I can not resist the fun of the picture of columns heated in a flame. I am considering putting some columns on the barbecue next summer...