linearity problem

[subathrai]

am trying to develop a uv and rp lc method in glimepride (2 mg)+rosiglitazone (2 mg)+metformin (500mg)bilayer tablet
my doubts -
1. suggest me a linearity range
2. in this metformin is sustained release and the rest is immediate release; this may produce any problem in the method?
3. what are the possible methods to develop methods in uv and rp lc : any suggestions?

[grzesiek]

1. ICH Q2(R1) should have this kind of info
2. should have not for HPLC
3. ? literature search, trial and error, scouting gradients, DOE ...