How Does Column Diameter Affect Column Chromatography?

Preparation is key for column chromatography – every element of your setup will have its own impact on the analysis and results. Column diameter is no exception, of course. In this post, we explain the effect it has on column chromatography, and how it impacts other factors.

What does diameter do to column chromatography?

In column chromatography, a sample substance moves through the column with the help of a mobile phase. They're separated based on their interaction with the stationary phase, resulting in different retention times. In other words, molecules can be separated and detected based on the type of interaction between the mobile and stationary phase, and how long it takes them to pass through the column.

So, how does column diameter fit into this equation? As you can imagine, a wider diameter makes it easier for the mobile phase to pass through. Conversely, a narrower column means it takes longer for it to do so.

Understandably, this has a knock-on effect for sensitivity. Less time spent in the column means lower sensitivity, while more time allows for higher sensitivity. As such, wider diameter typically leads to lower sensitivity, while narrow diameters correlate to higher sensitivity.

There is also an impact on the sample size too. Wider columns require a larger sample with more solvent for analysis to work, while narrow columns can work with a smaller sample and less solvent as a mobile phase.

Diameter vs other factors

Of course, diameter isn't the only factor involved with column choice. Columns can also vary in their length and the amount of pressure they're capable of.

Starting with length, this can have a similar effect as diameter. Shorter columns cut the analysis time, which can reduce sensitivity. On the flipside, longer columns increase analysis time and can improve results.

Based on the above, it stands to reason that a long, narrow column would provide the best results because it increases analysis time, heightens sensitivity and doesn't require a larger sample.

However, it would require much more pressure to push the mobile phase through the column. Columns can only withstand a certain degree of pressure, while pumps need to be able to provide the sufficient pressure, so this needs to be factored into the selection too.

Learn more about columns

If you'd like to read more about columns and how they can improve separations, take a look at the article, ‘µ-Pillar Array Column – an Innovative Approach for the Separation and Characterisation of Complex Biological Samples’. It highlights how µ-pillar array columns can overcome many of the problems with standard packed-bed columns.