The reversed-phase thin-layer chromatography of metal ions with tributyl phosphate

Abstract

About sixty-five metal-containing ionic species have been chromatographed on thin layers of cellulose impregnated with tributyl phosphate (TBP) at various concentrations of aqueous hydrochloric acid. A mechanism for the chromatography may be explained in terms of the ability of the metal ions to form chloro complexes, viz., that those metal ions which readily complex with chloride ion are readily extracted by the TBP and consequently have low R_F values. Conversely, those metals which do not form chloro complexes are not retained by the TBP and hence have high R_F values.

Attention is drawn to the similarities between the known liquid-liquid extraction behaviour of the metal ions in the TBP-hydrochloric acid systems and the behaviour of these ions in the TBP-hydrochloric acid chromatographic systems. A strong resemblance has also been found between the R_F spectra (R_Fversus hydrochloric acid) of the metal ions and the behaviour of these ions in resinous anion-exchange-hydrochloric acid systems. The latter similarity has been used as evidence for the suggestion that the TBP on the layers functions as a liquid anion exchanger, i.e., that TBP-solvated protons, ion-associated with chloride ions, can undergo ion exchange with the metal chloro complex—(TBP)_o+(HCl)_aq⇌(TBPH + Cl^–)_o(nTBPH + Cl^–)_o+(MCl_x^–n)⇌ MCl_x^–n(TBPH⁺)_no+(nCl^–)_aq.

The suffix “o” refers to the organic phase and the suffix “aq” refers to the aqueous phase.