Abstract: Nitrosylruthenium nitrato complexes can be isolated by TBP extraction chromatogra-phy and cation exchange. The complexes consist of five species: Tetranitrato (D4), Trinitrato (D3),Dinitrato (C, B) and mononitrato (A1) and non-nitrato (A(?)). The highly extractable species are D3 and D4. The percentage of anionic and neutral species determined by isolation with trialkyl-methyl ammonium nitrate Levextrel is equal to that of D3 and D4. Therefore, the highly extractable species D3 and D4 must be anionic or neutral species.