Dear Sasha,

In Reverse Phase Chromatography solubility is always limited as solvophobic interactions play a key role in the separation process. A sample solubility of 0.1%-0.2% is good enough for LC-MS analysis. Note that for most people, a sample that dissolves only 0.1% it is said "insoluble". So, I suggest trying to dissolve some 1.5 mg of your active fraction in 1.0 mL of absolute methanol (stir for at least half an hour; sonication could help a lot)), filter and inject in the chromatograph. Run using absolute methanol as eluent for at least 50 min. Good luck.

Use the extract at very low concentration in ACN or MeOH/water.

Hi Andrei! yes I will try this but also I am considering GC/MS instead then I do not have this worry of switching to RP solvents.

Interested

Dear Sasha,

In Reverse Phase Chromatography solubility is always limited as solvophobic interactions play a key role in the separation process. A sample solubility of 0.1%-0.2% is good enough for LC-MS analysis. Note that for most people, a sample that dissolves only 0.1% it is said "insoluble". So, I suggest trying to dissolve some 1.5 mg of your active fraction in 1.0 mL of absolute methanol (stir for at least half an hour; sonication could help a lot)), filter and inject in the chromatograph. Run using absolute methanol as eluent for at least 50 min. Good luck.

You may heat your extract in a water bath up to a safe temperature and while in the water bath slowly add your solvent and try to dissolve it. As already mentioned above, sonication in addition to the heat. Then proceed fast with filtering and injection.