[rekhasharma]

Why if compound is not soluble in methanol then absorbtion can not be measured but fluroscence can be measured? in both cases electron first excites. so what is the problem in absorbtion.

[nj_bartel]

Solubility isn't an all or nothing thing.  I'm pretty sure fluoresence analysis is significantly more sensitive than absorbtion analysis, so a lower concentration will permit fluoresence than absorbtion analyses.