COLUMN EFFICIENCY AND ELECTROLYTE EFFECTS OF INORGANIC SALTS IN AQUEOUS GEL CHROMATOGRAPHY

A number of polyphosphate and metaphosphate salts of sodium were eluted from columns containing Bio-Gel P-2, Sephadex G-10, G-25, and G-50 with electrolyte solutions. Elution orders for the linear polyphosphate, Na5P3O10, and the cyclic metaphosphates, Na4P4O12, and Na3P3O9, were in the order Na4P4O12 < Na5P3O10 < Na3P3O9, as expected from a steric exclusion mechanism. The peaks for Na16P14O43 and Na9P7O22 were broad, confirming the reported heterogeneity of these preparations. Elution of a sample salt different from the eluent salt often resulted in two positive peaks, one caused by the sample salt and the other by eluent salt. The peak for the eluent salt was attributed to a Donnan “diffusion effect” and its size depended directly upon the sample concentration and the composition of both the sample and eluent. Zone broadening was investigated and compared to theory where possible. Although peak width increased only with the square root of column length, the separation of Na5P3O10, Na4P207, and Na2HPO4 did not appear to improve on going from a 63-cm to a 500-cm column. Decreasing the flow rate decreased the plate height to values equal to the particle diameter of the swollen gel, and increased peak skewing for salts eluted with water from Sephadex gels. Plate heights also decreased by as much as 50% upon increasing the temperature from 22.0 °C to 50.0 °C. © 1969, American Chemical Society. All rights reserved.