SEPARATION OF SOME CHLOROPHENOXYACETIC ACID CONGENERS ON A POROUS GRAPHITIZED CARBON COLUMN

The retentions of twelve phenoxyacetic acid derivatives were measured on a porous graphitized carbon (PGC) column using dioxane-water mobile phases without additives and with added sodium acetate, acetic acid a nd lithium chloride. Good linear correlations were found between the c apacity factors and the dioxane concentration in the mobile phase. The number of substituents on the benzene ring and their hydrophilicity m ost strongly affected the retention behaviour of phenoxyacetic acid de rivatives with dioxane-water eluents. Sodium acetate had the greatest effect on both retention and selectivity, emphasizing the considerable role of the degree of dissociation of solutes on their retention on a PGC column.