[sid94]

I am struggling with the a concept wondering if anyone can help?
having tested the solubility of ibuprofen in various buffer solutions, I have found that the pH of the solutions  has decreases by at least 3 pH units, eg 9 to 6. I think this is something to do with the buffer capacity I cant seem to understand it fully?
also can ibuprofen form salts with the buffer solutions? thus increasing solubility further? eg one buffer used was lysine buffer

[Borek]

If the pH changes while you dissolve ibuprofen, buffer doesn't work, period.

Yes, that's equivalent of stating the buffer capacity was too low.

[sid94]

If the pH changes while you dissolve ibuprofen, buffer doesn't work, period.

Yes, that's equivalent of stating the buffer capacity was too low.

thanks for your reply.
okay, so it can be said that the buffer capacity was so low that it allowed ibuprofen to form salts and still solubilise? also, the buffer doesn't work, but on a molecular level, I don't understand why hasn't it worked?
thank you

[Borek]

it can be said that the buffer capacity was so low that it allowed ibuprofen to form salts and still solubilise?

Ionization is the simplest way o solubilizing large organic molecules.

the buffer doesn't work, but on a molecular level, I don't understand why hasn't it worked?

I have a general feeling you don't know how the buffer works and how the concentrations of acid and conjugate base depend on the solution pH. These are crucial things for understanding what is happening in your solution. I suggest you start with any general chemistry text where these things are explained.

[Babcock_Hall]

You might want to start off with a slightly simpler issue, such as how the solubility of ibuprofen changes with pH.  Then see if you can explain why in terms of intermolecular forces.