Multielement preconcentration of trace heavy metals in water by coprecipitation and flotation with indium hydroxide for inductively coupled plasma-atomic emission spectrometry

Microgram quantities of Cr(III), Mn(II), Co, Ni, Cu (II), Cd and Pb in 1200-mL samples are quantitatively coprecipitated with indium hydroxide at pH 9.5. After adding ethanolic solutions of sodium oleate and dodecyl sulfate, the precipitates are floated with numerous tiny nitrogen bubbles to the solution surface, and then collected in a small sampling tube. The procedure is simple and rapid, and suitable for operation at sampling spots. The heavy metals in the dissolved precipitates are determined by inductively coupled plasma-atomic emission spectrometry. The concentrations of the heavy metals are increased 240-fold, and those of alkali and alkaline earth metals in artifical seawater are reduced to 1/50 to 1/20 for Na and K, and ca. 1/2 for Mg, Ca, and Sr. 2 figures, 4 tables.