Chromatography Forum

I'm running a silica column with pure hexane and not getting any retention for dimethylfuran
or my xylene mixture. Everything comes unretained. I'm using UV detection. I can inject them
separately and see an unretained peak. My mobile phase is 100% hexane but I ramp up to
50% EtOH over 8 minutes. I can inject a blank hexane and see nothing.

Should I expect retention for these components? I can not run reversed phase or GC.

I would expect retention, but how much would depend on the specific surface area of the silica. Another factor is the fact that silica is very touchy about the trace water content of the mobile phase (water adsorbs to and deactivates the silica). The same is true about alcohols, so one possibility is that you are not allowing sufficient re-equilibration time after running the gradient to EtOH (it can take a looooong time).