What is difference among as is basis ,as such basis and solvent free basis assay?
Assay on as is basis and as such basis are same when you calculate the assay of substance in the condition in which you got that for analysis (no drying) or not calculated using LOD or water content.
I never hear about solvent free basis.
Formula
Assay on as is basis and as such basis, both are same and solvent free basis assay only you need to calculate the percent quantity of Residual solvent present in API on that basis calculate the assay on solvent free basis.