PMSF stability in RIPA buffer - (Apr/07/2014 )

I have used RIPA buffer with PMSF for cell lysis of some salivary cells (cheek cells). But I have some extra RIPA buffer left over with PMSF in it. I have stored it in the deep freezer compartment. Will the PMSF get degraded, since PMSF is unstable in water (aqueous medium)? Also for how long can I store?

Looking forward to a quick reply.

Thank you in advance. 

pmsf is very short lived in water (on the order of 30 minutes). if you want to use your stored ripa then you'll have to replenish the pmsf.

If there is any residual PMSF won't the concentration change? 

there will probably not be any residual pmsf but, even if there is, it shouldn't make a significant difference.

oh alright.