ampcillin sodium - (Aug/13/2007 )

Dear everyone, when I prepare ampcillin stock solution, I feel confuse about ampcillin sodium powder. If I use ampcillin soduim as atibiotic for E.coli, is there a big problem?

Hi Lucy,

There is no problem with using the ampicillin sodium salt. The sodium is just there to balance out the acid group on the ampicillin and will dissociate when you make up the solution.

When you are making up the solution, remember that the ampicillin sodium salt weighs 23g/mole more than the free acid, so you have to take that into account for your calculation of how much solid to add to your solution.

e.g. for 1 litre of 1M ampicillin, you need to add 349g/L
but for 1 litre of 1M ampicillin-sodium, you need to add 372g/L


Nick

we always use ampicillin-sodium to make ampicillin antibiotic

As others have written, You are fine with using ampicillin sodium salt.