Admicelle-mediated collection followed by flotation for the preconcentration of trace metals in fresh waters

Dithizone-impregnated admicelles were prepared by mixing silica particles with dithizone and cetyltrimethylammonium chloride in 0.1 mol L⁻¹ aqueous ammonia. The resulting admicelles were added to 1000 mL of sample solution and dispersed by stirring for 15 min. Traces of Ni(II), Cu(II), Ga(III), Cd(II), Pb(II) and Bi(III) in the solution were simultaneously incorporated into the admicelles at pH 7.5-9. With the aid of a rising stream of numerous tiny bubbles, the admicelles were floated on the solution surface and collected in a small sampling vessel by suction. The metals were desorbed from the admicelles with dilute nitric acid and determined by inductively coupled plasma-mass spectrometry. The proposed method offered a 100-fold multielement preconcentration and it was applicable to the analysis of river and pond waters.