Collection of trace metals with cationic surfactant-silica particles followed by flotation with an anionic surfactant for seawater analysis.

The analysis of seawater for trace metals is important for pollution monitoring and better understanding of marine systems. The present paper describes an efficient preconcentration method for the determination of trace metals in seawater. Trace metals [Ni(II), Cu(II), Ga(III), Cd(II), Pb(II), and Bi(III)] in 1,000 mL of seawater sample were complexed with ammonium pyrrolidinedithiocarbamate and sorbed onto silica particles covered with cetyltrimethylammonium chloride. After the addition of sodium dodecyl sulfate, the particles were floated to the solution surface by bubbling and then collected by suction. The trace metals were desorbed with dilute nitric acid and determined by inductively coupled plasma-mass spectrometry. The rapid 200-fold preconcentration was demonstrated with certified seawater samples.