Gel chromatographic behavior of the oxo acids of phosphorus

Abstract

A number of oxo anions of phosphorus which contain one to four phosphorus atoms in the molecule were eluted with potassium chloride solutions on Sephadex columns. The K d values of the oxo anions of phosphorus were measured as functions of the concentration and pH of the eluents, sample concentration and gel prosoity. K d values obtained by both the column and batch method were compared to each other. The main conclusions are as follows. (1) When pure water was used as an eluent, extremely low K d values were observed because of the electrostatic repulsion between the sample anions and the negatively charged gel matrix. (2) The K d values increased with increasing concentration of potassium chloride. This may be due to the variation in the degree of hydration of sample anions. (3) At sample concentrations lower than 10 −2 gram atom P per 1 the elution curves were symmetrical, while unsymmetrical elution curves were obtained at the higher sample concentrations. (4) The K d values did not depend on the pH values of the eluent. (5) The most satisfactory separation of ortho-, di- and triphosphate anions was carried out on a Sephadex G-25 column. (6) The effective sizes of the oxo anions of phosphorus in aqueous solution were stimated from the gel chromatographic data.