By Anonymous on Tuesday, February 25, 2003 - 08:33 am:
I would like to know how you determine the conc. or % ion pair reagent to use in the mobile phase for related substances separation. For example, should I use 0.07% TFA, 0.1% TFA or 0.2%TFA? Is there a stoicheometric calc of TFA to drug conc ratio or do you try different % and check chromatography? I notice a related substances co-elute with 0.1%TFA but not with 0.07%TFA. Why? I would appreciate if you could point me to a source literature.
By A.Nonymous on Tuesday, February 25, 2003 - 09:04 am:
It's not a point of calculation, it's just a fact wether it works or not without getting too concentrated. You will see some differences in retention when you change your ion-pair concentration. Drylab has a feature for it to determinate the optimum concentration of you ionpair reagent.
I hope this helps, but I have no literature references, I'm sorry.
Good luck
By Anonymous on Wednesday, February 26, 2003 - 06:52 am:
You must otimize the concentration of ion pair reagent (IPR). Generally by increasing the amount of IPR, your capicity factors reaches a plateau and then starts a decrease.
Good luck
By GREG KOVAC on Wednesday, February 26, 2003 - 11:57 am:
it,s usual work with concentrations of IPR about 5*10exp-3 M.