AUTOMATED-DETERMINATION OF MERCURY AT ULTRA-TRACE LEVEL IN WATERS BY GOLD AMALGAM PRECONCENTRATION AND COLD VAPOR ATOMIC FLUORESCENCE SPECTROMETRY

Mercury in water samples is oxidized to its divalent ion form by an acid digestion procedure. The mercury is then reduced to its elemental form by a stannous chloride solution in a continuous flow system. The mercury vapour is separated and an aliquot is diverted into a gold wire absorber via a flow injection valve to form an amalgam. The mercury is then thermally desorbed and is swept with a stream of argon into a flow cell of an atomic fluorescence spectrometer where the fluorescence is measured at 253.7 nm. The operation of the analytical system is fully automated. The detection limit of the method is 2 ng l-1, and the precision is 3% R.S.D. The results for standard reference materials agree closely with the certified values.