COPRECIPITATION OF TRACES OF HEAVY-METALS WITH INDIUM HYDROXIDE FOR GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

Nanogram quantities of copper(II), chromium(III) and manganese(II) in a 100-ml water sample were quantitatively coprecipitated with indium hydroxide at pH 9.5. The precipitate was centrifuged and dissolved in 0.5 M hydrobromic acid. The desired heavy metals in the solution (5 ml) were directly determined by graphite-furnace atomic absorption spectrometry, where the indium was nearly completely removed by volatilization as bromide at the ashing step. Though no loss of the analytes mentioned above was observed, cadmium and lead were significantly lost during the ashing stage. The time required for the coprecipitation and determination was about 30 min.