Slurry packing of chromatography columns can be just as fun as it sounds

Who does not love a good mud slurry! You know, the feeling of sinking down to your knees on the sea floor at tide out or watching kids jump in puddles and re-emerge covered in mud! I do love mud slurries, but I love slurries when it comes to chromatography as well. Here, I describe the slurry packing process of glass columns and compare this approach to the dry packing process.

It’s nice to have a choice in life and sometimes one choice fits, sometimes the other is the way to go. As I wrote before, I don’t necessarily want to carry 10 kg of fruits and vegetables in a paper bag (but cloth would do). Ice cream can be easier and cleaner to eat from a cup with a spoon, but those ice cream cones sure taste delicious and sometimes you just have one hand free. And I might want to take the scenic route to enjoy a drive somewhere. Other times, I really want to get somewhere fast, so I hop on the highway.

I think you get my point. Choice is always a good thing to have! And in the lab it is the same. For some applications, different methods can lead to the same desired results. And even better, usually methods can be adapted to give you choice that better suits your needs.

In the last chromatography post, we discussed how to dry pack a column. Now I’d like to give you a choice. You can also slurry fill a column! Just to reiterate, self-packed columns offer lower separation efficiency and reproducibility levels than professionally packed columns. But self-filling chromatography columns enables the purification of simple mixtures in a more economical way.

As a side note, flash cartridges are typically available in a large variety and they are rarely used for self-packing. Reuse of the polypropylene hardware is limited and not very robust when it comes to re-assembly.

Typically, glass columns are the first choice for self- and re-packing.

There are two ways to re-fill a glass column, dry and slurry packing. Dry packing is fast and easy. The approach relies on compressed gas. With dry filling, the packing density is not as dense, so this method is better suited to medium to big sized silica particles (25-200µm).

For smaller particles, I’d recommend using a slurry of silica and solvent, filled via a pump into the glass column.

How does slurry packing of glass columns work?

Well, you need to gather some equipment:

  • Separation column
  • Slurry filling vessel
  • Slurry solvent
  • Funnel
  • Beaker

First, you need to wash, clean and dry the column. Then you need to suspend the silica gel in the solvent. A typical ratio is 1 g of silica to 2-3 ml of solvent. Here are a few more examples:

Column
ID x L (mm)
Silica gel
(g)
Slurrying process
(ml of solvent)
26 x 460150300 - 600
36 x 460270500 - 900
49 x 460470800 - 1200
70 x 46010002000 - 2500

Then you clamp the column vertically and screw on the slurry filling vessel. You are now ready to introduce the slurry into the column from the filling vessel. Completely fill the filling vessel up with solvent, then connect the column inlet to the pump. Using the pump, pump 1-2 column volumes of solvent till the silica is nicely compacted.

Take a look at the image below for a visual representation of the process:

slurry packing, slurry packing process, wet packing, chromatography, chromatography columns

Columns that prepared with the slurry packing approach do not require an additional equilibration step. You are free to use the columns with your chromatography system immediately after the flow of 1-2 column volumes through the adsorbing material.

So there you have it. Depending on your application, your silica size and your budget, you can buy a pre-packed cartridge or fill a glass column with the dry packing or slurry packing method. I got a lot more column-related information packed in our free Chromapedia Volume 2: Consumables and Sample Loading. It should fill your head with enough knowledge and keep you busy at least until the next blog post. But of course, it’s your choice to make!

Till next time,

The Signature of Bart Denoulet at Bart's Blog