Analytical Sciences

Collection of Trace Heavy Metals on Dithizone-ImpregnatedAdmicelles for Water Analysis

Masataka HIRAIDE andWataru SHIBATA

Department of Molecular Design andEngineering, Graduate School of Engineering, Nagoya University, Chikusa,Nagoya 464-8603, Japan

Admicelles formed on alumina were studied from theviewpoint of separation vehicles in trace analysis. Gamma-alumina (1.5 g)was suspended in 40 cm³ of water and mixed with 10cm³ of ammoniacal solution containing 1.5 mg of dithizone and100 mg of sodium dodecyl sulfate. The mixture was acidified to pH 2, wherethe anionic surfactant was strongly adsorbed on the positively chargedalumina surface to form dithizone-impregnated admicelles. Metalcontaminants in the admicelles were thoroughly removed by washing with 4mol dm^-3 nitric acid. The quantitative adsorption from water wasperformed at pH 2 - 9 for Cu, pH 3 - 9 for Pb and pH 4 - 9 for Co, Ni andCd. For seawater, simultaneous collection required adjusting the pH toca. 8. Humic and fulvic acids did not interfere with the separation.The admicelle column was substantially stable during adsorption anddesorption, which allowed the same column to be used at least three times.The proposed method was combined with inductively coupled plasma-massspectrometry for the analysis of seawater. (Keywords: Adsorption, admicelle, dithizone, water analysis, ICP-MS)

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