Spectrophotometric determination of aluminum(III) using the color reaction between o-hydroxyhydroquinonephthalein and aluminum(III) in the presence of a combination of surfactants, and its application.

The color reaction between o-hydroxyhydroquinonephthalein (Qnph) and aluminum (III) was examined in the presence of various surfactants alone or in combination (cationic, anionic, nonionic and amphoteric surfactants) in weakly acidic media. A simple, rapid and sensitive spectrophotometric determination of aluminum (III) (0-2.0 μg of aluminum (III) in a final volume of 10 ml, at 555 nm) was developed by using the Qnph-aluminum (III) complex in a mixed micelle system of zephiramine (tetradecyldimethylbenzylammonium chloride) as a cationic surfactant and Brij 35 (poly (oxyethylene) dodecylether) as a nonionic surfactant. This proposed method (apparent molar absorptivity of 2.1×105 l·mol-1·cm-1) showed good reproducibility, and the influence of foreign ions was reduced to 1/4-1/10 of that in the previous method with Qnph alone in weakly basic media. The method was used for the determination of aluminum (III) in pharmaceutical preparations (aspirin aluminum). Further, since aluminum may leach out of aluminum packaging of the kind widely used for instant foods, this proposed method was applied to the assay of aluminum (III) in biological specimens (calf serum and human urine), and in leaching solution used on aluminum foil. The recovery was good, and it was found that the leaching solution contained significant amounts of aluminum (III).