Effect of nonionic surfactant as a dispersant on aluminum-aluminon lake

Abstract

The color of aluminum-aluminon lake in the solution was altered by kinds of added dispersants and their concentrations. The dispersibilities of gum arabic, starch and several surfactants for the lake were examined and it was concluded that nonionic surfactant such as Triton X-100(TX-100) was most useful dispersant. From the absorption maximum of the lake (λmax)-ET value relationship in the various solvents and the increase in stability of the lake by the addition of TX-100 in water, it may be assumed that the phenyl or carboxyl groups in aluminon is linked by a hydrogen bond to the polyoxyethylene chains in the micelle surface or in the micelle mantle. The recommended procedure for the determination of aluminum is as follows: Take an aliquot of sample solution (under 40 µg of Al). Add 3 cm3 of 1% aluminon, 1.5 cm3 of 1 mol dm-3 acetate buffer (pH=4.8) and boil the solution. Then add 1.5 cm3 of 20% TX-100 and make the solution to 30 cm3 with water. Measure the absorbance at 537 nm against the reagent blank. The color of the solution was stable within 1 d after coloration. The molar absorptivity of complex was 2.2×104 and obeyed Beer's law between 6.5×10-7 mol dm-3 and 5.0×10-5 mol dm-3 of aluminum. The proposed method was applied to the determination of aluminum in a seaweed and the result was in good agreement with that obtained by the Pyrocatechol Violet method. © 1981, The Japan Society for Analytical Chemistry. All rights reserved.