Chromatography Forum

Dear member,
do you have any experience using ion pair chromatograpy that have long period for coloum equilibration?
I have method using sodium hexan-sulfonate 2g in 1L and buffered at pH 3. At first, I suspect it have a drifting forward retention time. But after i run the method for 2 days, the retention time begin constant.
But, running the LC for 2 days for equilibration seems like wasting cost and time.

Thank U

Ion pair methods are notorious for long equilibration times. Two days, while not usual, is not unheard of.

Check the quality of the hexane sulfonate you are using. If it has a significant amount of longer-chain material, what may be happening is that the column is initially equilibrating quickly with the C6, but the longer chain stuff accumulates slowly.

Another thought is that you might want to store the column in the mobile phase. That will shorten the column lifetime, but may be worth it in terms of shortening the time required to get up and running.

Many ion-pairing applications can be run using HILIC mode, and allthough the equilibration time is longer in HILIC than RP it is still much faster than ion-pairing.