SIZE-EXCLUSION CHROMATOGRAPHY OF ORGANIC ACID-MASKED ALUMINUM COMPLEXES AND THE DETERMINATION OF COMBINED ACID ALUMINUM RATIO OF THE FRACTIONS/

Four kinds of preparations of masked aluminum complexes were prepared by adding sodium citrate at 1:2, sodium tartrate at 1:2, sodium acetat e at 1:4 and 3:1 equivalents to aluminum equivalent. The masked prepar ations were separated by size-exclusion chromatography and the fractio ns were analyzed for aluminum content by atomic absorption spectroscop y and for combined organic acid by ion chromatography. More than 50% o f the added citrate or tartrate was taken up as an aluminum complexed component. A major proportion of polynuclear complex species combined the described acid at 0.2-0.6 equivalent ratio in the preparation. The effect of tartrate was so remarkable that it produced a considerable amount of enlarged molecular-sized complexes with tartrate content 0.6 -0.8 in equivalent ratio on one hand and also produced a certain amoun t of small molecular-sized complexes with high tartrate contents incre asing toward 1.0 in equivalent ratio on the other hand. Uptake of acet ate by aluminum complex molecules was only 2.5% of the added acetate e ven at the addition at 3:1 equivalent ratio. However, such a high conc entration of acetate broke down the size of aluminum complexes in the solution.