mobile phase switch from reverse phase to normal phase

[jiangds06]

If mobile phase does not switch well, will it cause clogging?
for example from water/ACN to iPrOH/Hexane. If it does not switch well, then four solvent will present in the column simultaneously. But still, I do not think it will clog the column.

[prepcolumn]

yes it does not clog because you don't have any buffer to cause clogging in your example . But if you have buffers in your RP mobile phase then it clogs.

But the problem switching from NP to RP or vice versa is the miscibility of the solvents you are using.

[jiangds06]

So it only cause UV detection and pressure fluctuation problem, right?

yes it does not clog because you don't have any buffer to cause clogging in your example . But if you have buffers in your RP mobile phase then it clogs.

But the problem switching from NP to RP or vice versa is the miscibility of the solvents you are using.

[Consumer Products Guy]

yes it does not clog because you don't have any buffer to cause clogging in your example . But if you have buffers in your RP mobile phase then it clogs.

But the problem switching from NP to RP or vice versa is the miscibility of the solvents you are using.

Correct. Typically one would flush everything with IPA (isopropyl alcohol) as the interim step between RP and NP, and between NP and RP.

[jiangds06]

If it is not properly switched, what will happen?

yes it does not clog because you don't have any buffer to cause clogging in your example . But if you have buffers in your RP mobile phase then it clogs.

But the problem switching from NP to RP or vice versa is the miscibility of the solvents you are using.

Correct. Typically one would flush everything with IPA (isopropyl alcohol) as the interim step between RP and NP, and between NP and RP.

[prepcolumn]

Simply; you cannot control any of your chromatographic and instrument parameters because of immiscible phase formation..

[jiangds06]

will a overnight IPA flushing restore the column performance.
Or column can be permanently damaged by emulsion formation in the column?

Simply; you cannot control any of your chromatographic and instrument parameters because of immiscible phase formation..

[prepcolumn]

just try and wish to be lucky..

[uzman]

For reverse phase columns , even pure hexan causes no significant problem , simply you may wash the column with Tetrahydrofuran , then water and return back to your mobile phase.
( Long term use of Tetrahydrofuran may cause hardening of PEEK materials and may burst them )

For normal phase columns , mostly for silica , water and alcohols cause deactivation of column , so you can not get separation.
According to my experience , the most effective way to recover a silica column is washing with pure ethyl acetate for half an hour at 1ml/min flow rate.
Then wash it with hexane for another half an hour and return back to your NP mobile phase.

Good luck.

[jiangds06]

Thanks a lot.
How about Polysaccharide Chiral HPLC Columns? Does emulsion formation damage this phase?

For reverse phase columns , even pure hexan causes no significant problem , simply you may wash the column with Tetrahydrofuran , then water and return back to your mobile phase.
( Long term use of Tetrahydrofuran may cause hardening of PEEK materials and may burst them )

For normal phase columns , mostly for silica , water and alcohols cause deactivation of column , so you can not get separation.
According to my experience , the most effective way to recover a silica column is washing with pure ethyl acetate for half an hour at 1ml/min flow rate.
Then wash it with hexane for another half an hour and return back to your NP mobile phase.

Good luck.

[tom jupille]

Those are a different animal because the stationary phase is not (usually) bonded to the substrate. That means that residual water can actually damage the packing material.

[jiangds06]

this column is also can be used in Reverse phase, so probably this is a different animal you mentioned.
Will switching from NP to RP damage the column?

Those are a different animal because the stationary phase is not (usually) bonded to the substrate. That means that residual water can actually damage the packing material.

[tom jupille]

Will switching from NP to RP damage the column?

The best answer to that would come from the column manufacturer.