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Making ampicillin solution - Ampicillin trihydrate not dissolving (Jul/23/2009 )

Hi all,

I am trying to dissolve ampicillin trihydrate in distilled water at a concentration of 50mg/ml.

I wanted to prepare 50ml of ampicillin solution. So I used 2.5gm of ampicillin to dissolve in distilled water.I made it upto 50 ml.

But I have difficulty dissolving it. It remains as a ilky white solution and after few mins I can see the precipitation (remains insoluble).

Is there a solution for this?

Regards
MS

-miraclestrain-

I the ampicillin stock too old?

miraclestrain on Jul 24 2009, 01:00 PM said:

Hi all,

I am trying to dissolve ampicillin trihydrate in distilled water at a concentration of 50mg/ml.

I wanted to prepare 50ml of ampicillin solution. So I used 2.5gm of ampicillin to dissolve in distilled water.I made it upto 50 ml.

But I have difficulty dissolving it. It remains as a ilky white solution and after few mins I can see the precipitation (remains insoluble).

Is there a solution for this?

Regards
MS

-T C-

Have you adjusted the pH see if that helps?

-genehunter-

Normally the sodium salt is used in making stock solutions. The trihydrate is soluble only at 10 mg/ml, while the sodium salt is soluble at more than 50 mg/ml. Add NaOH to form the sodium salt and it should go into solution. Next time order the sodium salt.

-phage434-

Hi there,

Thanks, it did work as you told, can you be bit more specific about the sodium salt? Say if you were given ampicillin trihydrate what will add to make a concentration of 50mg/ml?

thanks

-miraclestrain-

1 mole of ampicillin trihydrate needs 1 mole of NaOH to form the sodium salt. Determine the molarity of the 50 mg/ml solution (I don't off hand know the MW of ampicillin trihydrate), and add sufficient 1 M NaOH solution to form the sodium salt. Do this at below final volume, and top up the volume to its final value.

-phage434-