rosiglitazone

[zompa]

Hi everybody,

Can anyone give any suggestion about the hplc method for Rosiglitazone?
I'm just starting...
NH4CH3COO 0.01M pH=7 60% CH3CN 40%.
Column Phenomenex Hexyl-Phenyl
Detector UV 254 nm
Good resolution... Anyway I'd like to know if anyone has developed anything to compare and make it better.
Thanks.

[Uwe Neue]

Don't start with ammonium acetate at pH 7, start with a buffer, i.e. ammonium acetate at pH 4.75.

[zompa]

thanks, Hue.

I'll try soon.

[zompa]

sorry.. I meant Uwe.

[Rafael Chust]

First of all, Uwe's suggestion is a very important rule of thumb. Always use a "controlled" buffer system and avoid a solution with stuff you might not control.

Second, like in football, if you have a good team, don't change it! And if you have a team good enough to win the championship, do not expend a fortune with a galactic player... chromatography translation: if you have a good separation with the right eluent system - preferably isocratic - STUCK TO IT!

[zompa]

Hi Rafael,

Good to hear from you..
I thought that NH4AcO buffer strength is max at around 7 because of the Ammonium, while if I had used Na+ it would have been 4.8.
Anyway, I found that the separation has to be improved.
I'm going to try 4.8 soon... I thought I'd sorted it out too soon.
If you have any suggestion please let me know.
Thanks.

[zompa]

Rafael,

Do you mind if I e-mail you?
Thank you.

[syx]

I thought that NH4AcO buffer strength is max at around 7 because of the Ammonium, while if I had used Na+ it would have been 4.8.

The pKa of ammonium (ammonia) is 9.2 and acetate is 4.8... Buffer is only effective within ±1 pH unit from its pKa. How could Zompa said that NH4OAc buffer strength is max at around 7?

[Rafael Chust]

Rafael,

Do you mind if I e-mail you?
Thank you.

No problem... since I made my e-mail "public", I do not mind any contact either by e-mail or MSM

[zompa]

Sorry everybody,

I was talking nonsense about the buffer power..

Zompa.