Loooong retention time again----please help

[excalibur30]

Hello every one,

I have a problem with the long retention time. I try to make analysis of resveratrol. The chromatographic conditions as below:

Column: ODS c18 (250x4.6mm id, 5 um)
Detector: UV (306 nm)
Loop vol: 20 mL
Temp: 25 degree centrigrad
Mobile phase: ACN/Water/Acetic Acid (24.9/75/0.1)
Flow rate: 1 mL/min.

I found the retention time as 14.3 min.

When I changed the mobile phase as (19.9/80/0.1), and increased the flow rate as 1.3 mL/min. I got the retention time as 9.3. But the peak isnt still sharp enough I need to decrease the retention time more but I couldnt. Please help.

Note: When I tried to decrease the ratio of the ACN to %15 I couldnt find any peak. I think the ratio of 20% is suitable for ACN for this analysis.

[DR]

Increase %ACN and/or use a shorter version of the column (I'm assuming that there is just 1 peak of interest here...)

[sfe-co2]

Yay...increasing ACN proportion, not decrease it.

[sfe-co2]

oh yeah...make sure the strength of the solvent that is used to dissolve your sample is less than that of the mobile phase.

[excalibur30]

thank you for your suggestions