DETERMINATION OF LEAD IN ZINC AND ZINC-ALUMINUM ALLOYS BY ICP-AES AFTER COPRECIPITATION WITH MANGANESE-DIOXIDE

Trace amounts of lead in zinc and zinc-aluminium alloys were determined by ICP-AES after coprecipitation with manganese dioxide. After the sample (1.000 g) was dissolved in 7 M nitric acid, the sample solution was adjusted to pH 2.0 approximately 2.5 with ammonium hydroxide solution. For manganese dioxide precipitation, manganese nitrate solution and permanganate solution were added to the test solution. After filtration, the precipitate was dissolved in 2 M nitric acid and a small amount of hydrogen peroxide. Quantitative recovery of lead required at least 30 mg of the resulting manganese dioxide precipitate. The recovery of lead was dependent on the pH value of the sample solution and quantitative above pH 2. On the other hand, although 99.7% of the zinc content could be recovered from the resulting precipitate in the tested pH range of 0.2 approximately 3.8, that of aluminium decreased with increasing pH value due to increased formation of aluminium hydroxide. Lead analyses obtained by the present method showed good agreement with the certified values.