Working in column limits

[rick1112]

(sorry if the topic sounds abstract… )

Hi

All the columns come with its own pre-described limits on pH, temperature and back pressure (mechanical stability). So is it advisable to work on the end points on these limits, let say for eg. A column says its stable for a pH range on 2-8, so can safely work at pH 2 or 8..and in case of back pressure if the limit is 275 bar can I have work on 250 0r 240 bar?

if so any precautions and how long can i work in such conditions

Thank you

[JGK]

I would say, that at the extreme limits of use you should expect a shorter column life and be vigilant regarding changes observed.

Formula one cars can drive a over 200mph but have a very short maintenance cycle, as with most systems working on the edge

[Uwe Neue]

Such statements about pH limits are usually corroborated by tests. However, you must also understand that a column with a pH limit of 2 is not infinitely stable at pH 2.1, nor does it fall apart immediately at pH 1.9.

The pH stability and the temperature limit interact. Something that is very stable at pH 7 at room tmeprature may not be stable at the same pH at 70 degrees. I used to explain these limits in the form of circles or ovals. Something that has a good stability at room temperature at pH 2 to 8 has its best stability at elevated temperature at pH 5 or thereabouts. In reality, the failure mechanisms are more complex and varied, but you can use this as a rule of thumb.

The pressure limit is a clearer limit, since it probably depends on the packing pressure and the mechanical stability of the packing.