Polyamic acid was analyzed using organic solvent SEC (GPC) column, GPC LF-804. Polyamic acid is a precursor of polyimide. It is a multi-ionic polymer which contains positive and negative electric charges. Here, analysis under two different mobile phases were compared: (1) NMP alone and (2) with LiBr and phosphoric acid added to NMP. By adding LiBr and phosphoric acid, ionic interactions was suppressed and this resulted in producing better (sharper) peak shape.