Hello,

I have tested the separation of two rotamers on an RP 18 Zobrax 75 mm/3,5 um narrow bore column, lovering the temperature of the column down to 6 deg C. The separation of the compound was not toal but satisfying.
Before, at 35 deg C no separation was observed.
Next day independently from the temperature the column has a strange behaviour as it were at 6 deg C the day before, even if the temp. is raised up to 60 deg C. Also partial separation of chiral compounds is observed.
The mobile phase used is 65 MeOH 35 Water with 5 mM ammonium formate buffer (for MS).
On a 50 mm RP-18 RR Zorbax no such phenomenon is observed, the temperature effect is absolutely reversible (from +5 to 60 deg C).
It is possible to get the column back to its original state 'behaiour' or is definitely damaged?
Please help,

Best Regards,

TotosR