DETERMINATION OF COPPER(II) AND NICKEL(II ) WITH DIRECT ATOMIZATION GRAPHITE-FURNACE AAS FOLLOWING COLLECTION OF PYRROLIDINEDITHIOCARBAMATECOMPLEX ON MICRO-MEMBRANE FILTER

A new highly effective preconcentration method of Cu(II) and Ni(II) in water samples which involved the filtration of pyrrolidinedithiocarba mate (APDC) complexes of these metal ions on a micro-membrane filter ( MMF, cellulose nitrate, diameter: 4 mm, pore size: 0.45 mu m) was deve loped. It was possible to determine metal ions concentrated on the MMF surface by GFAAS in which the MMF was introduced directly into a cup- type graphite cuvette. Over 95% of Cu(II) and Ni(II) were recovered as APDC complexes by the MMF at pH values from 4 to 9. DDTC was also eff ective for the recovery of Cu(II) and Ni(II); however, some additions such as Zephiramine and/or coprecipitants (excess Cu(II) for NI(II)) w ere required for quantitative recovery. The recoveries of other metal ions, Co(II), Pb(II), Mn(II) and Cd(II) were less than 90%. For the MM F direct ashing technique on GFAAS, addition of 20 mu l of 5% H2SO4/DM F was effective to minimize variation. A 5 ml aliquot of Cu(II) or Ni( II) sample containing less than ppb-level was enough for one analysis. The sensitivities (3X sigma of blank solution) was 40 ppt for Cu(II) and 100 ppt for NI(II). Relative standard deviation (n=6) was 4.7% for Cu(II) and 2.2% for Ni(II). An application of the method for Cu(II) a nd Ni(II) in river water was also described.