I'm fairly new to prep chrom and have a quick question (I hope). Does the column temperature have any effect on the loading on a column (we're talking reverse phase if that makes a difference) and before anyone asks, I cannot tell what I am separating.

Regards,
Mark

Temperature has only a minute effect on most things in chromatography. I would not use temperature as a tool in prep.

-Temperature has certainly an effect on the viscosity of the solvent: increased temp will lead to lower back pressure and/or allows higher flow rates. This can be important with some pumps.
At higher temps peaks tend to be sharper and show somewhat less retention.
-Sometimes increased temp also results in increased solubility of your compounds....
-Heating up your injection solution might increase analyte solubility and allow smaller injection volumes (because of higher concentrations).
There are a number of effects one could imagine, some of them could be relevant for your problem, others not.

At higher temperature, you also need a weaker solvent. With respect to sample solubility, this may end up as a wash. The real problem is to get the large solvent volumes used in prep to the desired temperature.
The reduction in backpressure is a real effect, no doubt. But now you need to add some tubing to bring the solvent up to temperature, which also increases backpressure. I have not done any calcualtions on how much one needs, but this may end up as a wash as well.

Just a few thoughts on Uwe s answer:
weaker solvent: I' have mentioned shorter retention times. As resolution is usually not effected that seems to be be an advantage. I wouldn't go for weaker solvents.
thermal equilibration: Main goal in prep. LC is throughput; reproducibility is secondary. In prep LC I would accept non-equilibrated conditions. I have heard reports that feeding heated columns with cooler solvent will increase separation. (imagine the viscosity effect of having warmer solvent at column wall than in the middle)
However, all depends on the intended purpopse.

Alex,
All the papers I have seen about adding an unheated solvent stream to a heated column have shown a decrease in efficiency (witness all the papers at the last PittCon meeting). I would be interested to see how this would INCREASE efficiency. (Not looking to argue, just trying to understand and see if there is something I may have overlooked.)

Regards,
Mark

Mark,

If you look in the recent literature, there are a number of examples shown where a modest temperature difference between the incoming fluid temperature and the column temperature is actually beneficial. I speculate this may be due to the fact that there is a modest focusing effect when sample in cooler eluent hits the top of the column which overshadows the other possibly deleterious effects as long as the temperature delta between the incoming fluid and the column temperature is less than 10 degrees Celsius. The effect seems to be somewhat column dependent and the benefit is only seen one incoming fluid is cooler than the column temperature.