analysis of N-(4,4'-Difluorobenzhydryl)piperazine by HPLC

[zhengmin]

Hello everyone:
Now I ask for help again, I analysis N-(4,4'-Difluorobenzhydryl)piperazine with C18、C8，CN column, the mobile phase system is water-ACN, the main peak has serious tailing, I use 0.1% TEA, the peak are all tailing no mater the MP pH is 3.8, 5.5 or 7.0. how can i do? can you give me some suggestion for about it.
thanks of all
zhengmin

[MG]

TFA (instead of TEA) on the C18 or C8 might sharpen up the peak, if you are not averse to using TFA. If you are using an older generation of stationary phase, switching to a modern "encapped" or "base deactivated" phase will help, too, but chances are that you are already using one of these.

[maris]

pKa of piperazine -NH group is ~ 9.7, so, if you deceided to work at low pH ~ 3 it seems resonable, but I don't understand how you have rich the desired pH with TEA only. I agree with MG's recommendation.

[zhengmin]

The peak is also tailing when the pH of mobile phase is 3.5. I adjust the pH by H3PO4.

[maris]

Use column with base deactivaed silica-gel support