Benzodiazepines HPLC conditions

[Zydrunas Stanius]

Hello,


I am trying to develope hplc method for benzodiazepines. Used phosphate buffer pH 3,7 and acetonitrile or methanol. Used isocratic and gradient conditions. 250 mm and 150 mm C18 column, with 5 micron particles. still can't reach full seperation for few of those diazepines. As i have DAD, not MS, need to resolve them anyway . So maybe someone of you knows hplc conditions for seperation of as many benzodiazepines as it could be . maybe it would fit for my mixture of diazepines. Almost all articles are dealing only with 3 or 4 ones in one run. So not good for me.

thank you in advance

[rhaefe]

Well, Google found this article:
http://igitur-archive.library.uu.nl/pha ... Benzos.pdf

I know it is MS-MS but it gives you the retention data of 33 benzodiazepines. You can easily find out which can be separated just by HPLC-DAD.

cheers,

Robert

[Uwe Neue]

It is not clear how many peaks you want to resolve.

Also, did you use mixtures of acetonitrile and methanol, or just the two solvents.

For some compounds in your class, a change of the pH is useful. Did you explore this, for example by going to a pH 7 phosphate buffer?

Did you ever play with temperature to finetune a separation?