Multi-spot paper chromatograms of sodium orthophosphate.
The formation of two zones on paper chromatograms was investigated by chromatographing orthophosphoric acid and the primary, secondary and tertiary sodium salts, using pyridine-ethyl acetate/water as mobile phase. Movement of the species from the origin depends on washing the paper with acid and suggests an exchange of protons for sodium as a prerequisite condition. Washing with EDTA does not alter this requirement. Zone movement and multi-spot formation require that the forming solvent contain at least 5% of water (v/v). Between this value and saturation, increasing water content enhances zone disengagement. A solute spot of a sodium salt exchanges with the protons to produce a fast-migrating protonated phosphate species. If the solute sample has a sodium content less than the amount of exchangeable protons, a single fast spot is produced ; if the concentration exceeds this capacity, a second slower spot results.
Rommel
M A
MA
Department of Chemistry, University of Arizona, Tucson, Arizona, U.S.A.
Keller
R A
RA