Expired chemicals - (Oct/10/2008 )

Mostly the lyophilized chemicals are supplied in larger packings and are used for several years without any change in the results. Some do have a specific expiration date of 1-2 years. Is it ok to use them after the expiration date ?

Well, the expiry date is probably a conservative estimate of when the product is too old. If it has been stored well it should be ok. But ultimately it is your risk and up to you whether you want to use it or not.

run a small test. And see if the lyophilized enzyme/chemical is still working. As killerkoz17 has mentioned if stored well it should still be okay.