Buying a new column

[Dori]

Hi! I need to buy a new column. So far now, I've been using a Styragel HR1 Column, 5 µm, 7.8 x 300 mm (THF). I've seen there is a Styragel HR1 Column, 5 µm, 4.6 x 300 mm (THF) which can cut the solvent consumption.

Will I obtain the same results? Will I be able to compare old results with new results? Will I have to modify the flow rate (currently I use 1 ml/min)?

So, should I change column or buy the same one I have?

Thanks.

[shaun78]

It depends what you are after. If the solvent savings is important to you, then scale it down. If you really do not care, then leave it the same.

If you do scale down the column, you should maintain similar chromatograpy as long as you closely follow the method transfer calculations. If you are unfamiliar with those, see the following article: http://www.restek.com/restek/images/ext ... AN1033.pdf

You are going to have to change the flow rate and the injection volume.

Back when the acetonitrile scare was in high gear I scaled down a good number of our analytical methods from a 4.6 mm column to a 3.0 mm column to cut solvent consumption. I rarely had troubles when I did so as long as I adjusted column flow to maintain linear velocity and injection volume to maintain column load.

[Ken Tseng]

If you need to compare old data with the new ones frequently, I would suggest keep using the same column. It will make your life easier.

Using a more narrow id will save solvent usage, but the performance will be different...you will need to spend some time intially to optimize the separation condition. Although, in this case, the change is not too drastic, it should be fairly quick.

If you are starting a new project, why not look into other newer columns from Jordi Labs, Tosoh, or other manufacturers. You may be surprised to find one that works better.

[unmgvar]

if it is the same chemistry
as a rule of thumb all you need to do is divide the squares of the cross sections of your column
in your case
adjust flow rate to about 0.35 of the original one and set injection volume as well in the same degree
so for example of you worked at 1.0 ml per min you know can go for 0.35
if the injection volume was 10ul know you need 3.5ul

pretty easy at a start, now pay attention that these settings for a standard analytical low pressure system can be problematic, and might require optimization