Complicated Mixture

[Uwe Neue]

I agree with Promochrom. You may have better luck with a high organic concentration in your sample solution, i.e. use HILIC...

[Patrik Appelblad]

I agree with the last two posts. HILIC would be the next logical step.
Pyridoxal, an analogue to compound A, is eluting at 6 minutes on a 15 cm ZIC-HILIC column, using ACN/NH4-formiate 10mM; 90:10 V/V as mobile phase. I would expect B and C to be more retained.

[anupama]

You can find pka value for compound and according to that you can adjust pH or you can use ion pairing reagent.May be it can help.

[syx]

I still try this and that... please be patient to wait the result...

[syx]

We found no problem when inject methanolic solution of dipyrone. The stability is ok. But when we mixed with thiamine and pyridoxine, dipyrone was degraded! I think there is reaction between them...