Determination of Trace Amounts of Cu(II), Ni (II), Co(II) and Cd(II) in River Water by Preconcentration of Their Rubeanates on a Micro-membrane Filter and Atomic Absorption Detection Using Direct Ashing Method

Abstract

A new highly effective preconcentration method for Cu (II), Ni(II), Co (II) and Cd ( ) in water samples which involved the collection of rubeanic acid complexes of these metal ions on a micro-membrane filter (MMF, cellulose nitrate, diameter: 4 mm, pore size: 0.20 μm) was developed. It was possibleto determine metal ions concentrated on a surface of the MMF by GFAAS in which the MMF was introduced directly into a cup-type graphite cuvette. More than 95% of Cu (II), Co (II), and Cd (II) were recovered by adding a salting out reagent (NaCl) and/or a coprecipitant (excess Cu (II)). For the MMF direct ashing technique on the GFAAS, an addition of 20 Ml of 5 vol% H2SO4/DMF was effective to reduce the variation of results. Only 5 ml of each samples of sub-ppb level of Cu (II), Ni (II), Co (II) and Cd (II) was enough for one analysis. The detection limits (3 × σ of blank solution) for Cu(II), Ni(II), Co (II) and Cd(II) are 80, 95, 50 and 1.6 ppt, respectively. An application of the method for the determ ination of Cu (II), Ni(II) and Cd (II) in river water was also described.