Dear forum friends,

I would like to start a conversation regarding the use of 3 micron columns.
Now, I am ready to improve a method currently working on 5 micron columns. Could I get the same relative retention times between peaks?

Thank you and regards

Yes. Relative retention should not be altered. By adjusting your flow you can get chromatography identical to that from larger-particle columns. However then the only advantage is lower solvent consumption.

Watch out for dwell volume effects from your chromatograph (not a problem in isocratic separations).

You can use a shorter column for the same separation power. Then your analysis time becomes shorter. This is the true power of 3 micron relative to 5 micron.

so, when you adjust the flow, the separtion with 3 micron-columns is the same as with 5 micron-columns, but the analysis0times are shorter am i right?

if you are using a 5 microns column in this moment is better because in my experience the 3 micron has a shorter life

As a rule, 5 um columns have 2 um frits; 3 um columns have 0.5 um frits. The columns do not have shorter lives. They just get plugged more easily. If your samples and mobile phases are particle free, they will last just as long as 5 um columns.

Hi jclark,

Not all manufacturers use 0.5 micron frits at the inlet of 3 micron columns. Some have discovered that this creates rapid clogging of columns and are using a 2 micron frit at the column inlet. With this trick the lifetime of 5 micron columns and 3 micron columns is the same, and most importantly, not a problem.

Best regards
Uwe Neue

To someone who already improves a 3 micron chromatography from 5 micron.

If I have a retention time for a main peak on 5 micron column, to reproduce the chromatography on 3 micron, should I change the flow to get the same retention time?

In that conditions, relative retention times for other peaks will be different or not?

Best regards,
Manuel Gomez

Part of the question should be the length of the column. If you are using a 3 micron and a 5 micron column of the same length, you should get the same chromatography at the same flow rate, but with slighly narrower peaks on the 3 micron column and higher pressure on the 3 micron column. There is no primary reason why the relative retention times should be different.
Most people are interested in shorter run times. Under these circumstances, it makes no sense to use a 3 micron column and a 5 micron column of the same length. To get the true advantage of three micron columns, you should reduce the column length in proportion to the change in particle size. Is this what you are doing?

Hi Uwe and other forum members,

thanks for your answer. I am trying to improve resolution and not to get shorter run times. 3 micron column will be shorter than 5 micron (supplier availability and pressure reasons), so to get the same retention time a relatives retention time (selectivity), Do I need to decrease flow, do not I? But, Do you know any relationship between flows? (I mean, I can extrapolate flow when differents diameters are used, or I can calculated sample loading or volume, but I do not know (other than experimental)any way to calculated equivalent flow from 5 to 3 micron at diferent lenghts.
Please, any suggestion could be very useful for me. Thank you and best regards.