Dry packing of a chromatography column in three steps

If your chromatography application allows for reusable glass columns, then you need to be confident you are filling them and re-filling them correctly. Here I explain the dry packing process and give you details on how to equilibrate a dry-packed column. I’ve even included a picture to help you visualize the process, so you don’t dry out in the midst of reading.

My wife and I have this habit of trying to save and re-use plastic items that come into our possession. We try to re-use plastic bags as garbage bags or grocery bags. We try to save old yogurt containers and ice cream tubs and use them for storage, etc. We try to re-purpose plastic bottles and caps for gardening, artwork. You get the point. It’s good for the wallet and it’s good for the environment.

The amount of plastic we use in the laboratory and for chromatography is also staggering. Disposable, one-time-use items are often necessary to ensure results remain flaw-free and contamination-free. But in some cases, it is possible to make purchasing decisions that can save some money and protect the environment.

For example, self-packing of chromatography glass columns is a suitable and economical solution for some cruder purifications. You need to consider how much time you invest in re-filling. You should also be aware of the risk that the column won’t be professionally packed, so separation efficiency and reproducibility may suffer. But if you make the decision to self-pack, I am here to help you along the way.

There are two ways to fill a glass column, dry or slurry packing. In this blog post, I would like to explain to you how dry packing works, so you can get the best possible results from your chromatography system.

Dry packing using a compressed gas is a fast, easy process, but the packing density is not as dense. This approach is therefore more suitable for medium to big sized silica particles (25-200 μm). If you have smaller particles, you should instead use a slurry of silica and solvent to fill the glass column via a pump. I will explain the process of liquid loading to you in a future blog post.

Regardless of whether you choose dry packing or slurry packing, the packing process can be divided into three phases:

  1. Preparation
  2. Filling
  3. Compacting

To dry pack materials into a separation column, you need the following equipment:

  • Separation column
  • Filling vessel
  • Silica
  • Nitrogen cylinder
  • Funnel

During the preparation step, you need to wash the column until clean and to leave it to dry completely. For the filling step, you need to clamp the column vertically and the screw on the filling vessel. Then you should loosely introduce the silica with the help of a funnel. The filling vessel should be packed with the silica to such an extent that at least 10% of the column volume is in excess.

Importantly, you should never tap the column or cause any vibrations, as this would lead to inevitable separation of the particles and render the column useless.

During the compacting step, nitrogen is blown from the nitrogen cylinder through the column until a hissing is no longer audible. You should then close the main valve of the nitrogen cylinder and release the pressure completely. This procedure is very important to prevent the column bed from coming apart when the nitrogen hose is detached.

The column is now ready for equilibration.

chromatography, glass column, dry packing

How do you equilibrate a dry-filled column?

Well, you need to carry out the equilibration directly with the solvent required for the separation. I would recommend to discard the first 100 to 200 ml of liquid from a freshly filled column and only then to circulate the solvent. This precautionary step prevents any fine silica gel particles that have been washed out from entering the pump. Once air stops emerging from the column and the base line of the detector is stable, you can proceed with the separation.

For more information on column maintenance, filling, loading and storage, check out our free webinar on chromatography consumables and sample loading or free chomatography guide.

I think you should be all set with this. In case you are looking for further reading while waiting for the next post, check out what other choices besides silica you have for the stationary phase in previous blog material . Hope this post was not too dry for you, if it was, stick around, the next chromatography one will certainly be wetter.

Till next time,

The Signature of Bart Denoulet at Bart's Blog