Antibiotics in culture - any difference in salt form vs pure? - (May/17/2012 )

Hi all,

I'm doing some susceptibility testing and am purchasing antibiotics. I had a question about whether to use the salt form or the pure form, for example for piperacillin:

http://www.scbt.com/datasheet-205808-piperacillin-sodium.html
http://www.scbt.com/datasheet-205807-piperacillin.html

I would think the pure form hydrolyzes in solution anyway. But in what situations would one be better than the other?

Thanks!

Solubility in water is usually the reason for making the salt form.