Pepsin interference

[rc_12321]

We have been asked to develop a method for dissolution which uses 1% pepsin in 0.1 M HCl as medium.Initially we have had a method where evry thing is fine in 0.1 M HCl.But when medium is changed from 0.1 M HCl to 1% Pepsin in 0.1M HCl WE HAVE FOUND a lot of unwanted junk which makes my peak of interest gets almost suppressed.We are unable to get good peak shapes in this medium.Our compound is a HCl salt and pKa is 9.95 (as base).Could any body please help us .

[Kostas Petritis]

I really do not see why you will use pepsin as it will just digest every protein into peptides (at one point it will start digesting itself) and will create these interferences... What was the reasoning on using pepsin anyways?

[rc_12321]

Kostas, we are working for a dissolution method development .The medium is 1% pepsin in 0.1N HCl .We should not change it.More over we are working at 205 nm.Any help is highly appreciated.

[Kostas Petritis]

I am not very familiar with dissolution methods; all I am saying is that if you put pepsin in an acidic pH is going to be active and stat digesting any proteins that may be in the medium (including maybe pesin itself) to peptides . Any contaminants like keratins etc will also be digested and produce peaks at 205 nm...

Is it a common practice to use this medium for dissolution method development?

[zokitano]

It is not a common practice to use this kind of medium for dissolution testing (as far as I know). The main reason for using it, is because by this way, the medium mimics the original composition of the gastric juice.
But it definetely is more complex matrix than the regular 0,1M HCl commonly used as a simulation of a human gastric juice.

Regards