Shutting down your LC during a quarantine period?

It certainly does not only pertain to a quarantine period, but certainly more likely during the current Covid-19 crisis. Some of you might be needing to shut down your projects for a while. If you will not be using your LC column for more than 3 days, here are some recommendations and tips that might help.

  1. If you have any buffer salts in either of your mobile phases, your column must be flushed to remove these salts before storage. To do this, pump a solvent mixture that is between 50-90% water for several column volumes to remove the salts. (Be careful not to use more than 90% water if your column is not fully/100% aqueous compatible.) If you have acids or bases present, they should be removed also in the same way. Removal of acids or bases is even more critical for stronger acids such as TFA, phosphoric, nitric, and hydrochloric acids.
  2. After flushing to remove the salts and other modifiers, flush the column with a solvent mixture that is at least 50% organic to prevent microbial growth. For example, if you normally use 70% water 30% methanol on a reversed phase column for your application, you would need to flush it with 50% water 50% methanol. You can actually go up to as much organic as you like, but try not to introduce any solvents that you wouldn’t normally use for your application For instance, if your application uses methanol and water with buffer, don’t introduce acetonitrile or IPA- that will just make it harder to equilibrate when you start up again. I like to keep a little bit of water in the system, just to make sure there are not any surprises in pump performance that might be triggered by drastic changes from organic to aqueous.
  3. Remove the column from the instrument and plug the ends with proper threaded plug nuts, such as our catalog #25016. Some users like to keep instruments attached and keep the pump operating at a low flow rate. This is really not necessary and is more risky when the instruments are going to be unattended. It is best to just remove the column and plug the ends.
  4. Something not frequently mentioned is recordkeeping. Make sure to write down what solvents are in the column, so that when the column needs to be used again you will know what solvents are miscible with the storage solvents. It is also useful to make note of what solvents were last used in the instrument. This can help to avoid precipitation of solid buffers in the lines or miscibility issues, which can both contribute to pressure issues and column damage.
  5. When you are ready to use the column again, check your records to make sure the solvent lines in the instrument are compatible and miscible with what you need to use. If the instrument was used for something different or solvents not used in your application were introduced, make sure to give the instrument adequate time to purge the solvent lines and get everything switched over to your mobile phases. Sometimes IPA is used as a bridging solvent in switching between two immiscible solvents, however, this may not always be necessary. As I mentioned earlier with regard to column flushing, it is best not to introduce something different if you do not need to, as it can make equilibration more difficult and takes longer to get going again.

 

I purposely did not discuss shutdown of the instruments, as that is a topic best handled by your instrument manufacturer. Also, our customers use a variety of instrument brands and the recommendations by the manufacturer may vary.

 

Here are links to some other blog posts that could be helpful and relevant:

LC Columns Usage and Care instructions https://www.restek.com/pdfs/700-02-002.pdf

https://blog.restek.com/can-i-use-a-100-aqueous-mobile-phase-with-my-lc-column/

https://blog.restek.com/resurrecting-an-old-reverse-phase-lc-column-should-i-could-i-how-would-i/

https://blog.restek.com/do-reverse-phase-hplc-columns-really-need-conditioning/

https://blog.restek.com/live-long-and-prosper-how-to-make-your-hplc-columns-last-longer/

 

Here’s hoping you found this information helpful and wishing you the best.

 

 

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