Coupled Columns

[Hassel Hoff]

I have had success retaining glycolic acid on a polar endcapped C18 column. It sounds like you get decent retention of the hydroquinone with or with out ion pair reagents. I used the Phenomenex Synergi Hydro RP. Should work for both compounds with a pretty simple MS compatable mobile phase.

[syx]

HILIC does not work, both peak could not be separated though we used 95% acetonitrile or methanol in mobile phase.
I will back to RP-LC, using gradient run from 100% aqueous mobile phase.

[HW Mueller]

Could it be that now you gave up too early on HILIC regarding variation of pH? Doesn´t make sense that your compounds should not separate.

[Einar Ponten]

In what solvent are your samples?

Try to dissolve in as much acetonitrile as possible or reduce injection volume for water samples.

In HILIC a large volume injection of sample in water is just as bad as a large volume injection of sample in acetonitrile on a RP column.

[Uwe Neue]

syx,

I would use a quick gradient from 90% acetonitrile to 50% acetonitrile on your silica column. Once you know where your compounds elute, you can use an isocratic run to optimize everything. I do not recommend to use any acid in your first runs, since the acid in the mobile phase will pull the analytes into the mobile phase and reduce retention. If there is need to do so, you can always add some acid later during finetuning.

[syx]

Wow, thanks for the responds.
We have used mobile phase as the solvent. In last experiment we did not use acid in the mobile phase, just a mixture of water and organic solvent. Both analytes were eluted too early, about 3.7 minutes.