LC During Long Vacation

[syx]

I’ve found recommended storage for degasser from its instruction manual. When leaving the degasser unused for a long time, the flow path should be cleaned with distiller water adequately, fed with methanol, and replace with the clean air for drying.
There is indicator light in our degasser. When we returned to work after a week Christmas-new year vacation, we found that abnormal vacuum system led was turn on . It turned to normal indication after 1-2 days of usage. I did not find any explanation about what kind of abnormality will be appeared when there was solvent in the flow path during storage. Why should it be kept dry?

[Rafael Chust]

Basically, it has the same logic as the system storage.

The idea to store with organic solvent + water is to avoid microorganisms contamination (possible with 100% water) and salt formation (100% organic).

Since manufacturers hate people calling for service, the wisest idea is to recommend to keep it dry... eventually your HPLC manual states the same!

Coming back to the beginning question, I was teached over 20 years ago to store my HPLC in the same typical solvent I used for analysis - but without the buffer. No problems found ever since...

[amaryl]

Basically, it has the same logic as the system storage.

The idea to store with organic solvent + water is to avoid microorganisms contamination (possible with 100% water) and salt formation (100% organic).
Since manufacturers hate people calling for service, the wisest idea is to recommend to keep it dry... eventually your HPLC manual states the same!

Coming back to the beginning question, I was teached over 20 years ago to store my HPLC in the same typical solvent I used for analysis - but without the buffer. No problems found ever since...

Why there will be salt precipitation in case of 100% organic solvent unless you don't let leave LC system in last run mobile phase containing buffer. 100% Organic solvent can not cause microbial growth.

Regards,

Amaryl.

[Rafael Chust]

Exactly, Amaryl, thanks for the input!

Anyway, I believe it is implicit that precipitation of salts are caused by changing to 100% organic without taking care of washing the system with "plain" (read, "without buffer") water previously.

I personally don't like leave the system still in 100% organic because it might "dries" the polymers used for sealing the pistons. I see this problem with Waters and Gynkotek pumps from colleagues in the past.

[amaryl]

Yes, you need to remove the buffer with HPLC grade water before running organic solvent.

Siswanto, suggested me to use some % age of organic solvent say 5% since using 100 % water may collapse the ODS packing.

Some people prefer 100 % water to remove buffer for 20-30 mins at 1.0 ml/min and later run 50:50 MeOH :water (usually preferred for washing).


Regards,

Amaryl.

[syx]

Amaryl, I am not talking about column storage or flushing in this post, but the system when we would not to use it for a long time. About collapsed column, you have read it how and why. You could decide which ODS column cleaning method is the best.

I personally don't like leave the system still in 100% organic because it might "dries" the polymers used for sealing the pistons. I see this problem with Waters and Gynkotek pumps from colleagues in the past.

What type of organic solvent that made the seal “dried”? Please give me further enlightenment about this phenomenon.
I need the explanation about the effect of organic solvent that be kept in the system for a long time to the degasser (maybe to its membrane?). Could it be due to that “drying effect” too?

[amaryl]

[quote="syx"]Amaryl, I am not talking about column storage or flushing in this post, but the system when we would not to use it for a long time. About collapsed column, you have read it how and why. You could decide which ODS column cleaning method is the best.[quote]

I know the answer moved out of track of question. But I didn't do this

Amaryl.

[Rafael Chust]

Dear Syx:

I think the discussion went towards the column when I tried to present a "complete" HPLC storage procedure - including the treatment you might do with your column too, to have it ready for analysis when you come back.

Concerning polymer "dryness", it is a known phenomena (just check membrane filters compatibility charts) that if you leave some polymers in 100% organic solvents they become "dry" and breakable, loosing their elasticity.

I have experienced that while servicing HPLC pumps from colleagues and customers in the past, as the seals were completely "baked", dark, hard and sometimes it even comes into dust if you move it around your fingers.

That is one of the main reasons manufacturers ask to keep the systems dry - they never know how far creativity of chemists might go when comes to maintain and store the systems...

Therefore, since degasser membranes and flowpaths are polymers, same logics applies...

I hope this clarifies some of your questions...

[syx]

Rafa, Thank you for the enlightenment.
I am not storing column in the HPLC if I have clean it and would not to use it more than a night.