Solvent extraction of Pb(II) from acid medium with zinc hexamamethylenedithiocarbamate followed by back-extraction and subsequent determination by FAAS

Zinc hexamethylenedithiocarbamate, Zn(HMDC)(2), was used for the extraction of Pb(II) from HCl and HNO3 media into 2,6-dimethyl-4-heptanone (DIBK). Th e kinetic stability of Pb(HMDC)(2)/DIBK after extraction was found to decre ase with increase in acid concentration and time, however, its stability is better in comparison with that of ammonium pyrrolidine dithiocarbamate (AP DC). The half lives of Pb(HMDC)(2)/DIBK extracted from 10(-4), 10(-2), 0.1, and 1.0 mol l(-1) HCl were 600, 360, 300 and 240 min, respectively. The lo garithmic conditional extraction constant, logK(ex)' of Pb(HMDC)(2), was 5. 6 +/- 0.3. Lead(II) was quantitatively extracted with 2.41 x 10(-3) mol l-L Zn(HMDC)(2) in DIBK from 10-4 to 1 mol l(-1) HCl and from 10(-4) to 2 mol l(-1) HNO3 solutions. The applicability of the chelating agent for the extr action of lead in real samples was confirmed by analysis of standard refere nce materials, the results of which were in good agreement with the recomme nded values. The detection limit based on three times the standard deviatio n of eight replicate procedural blanks was 0.07 mu g l(-1). (C) 1999 Elsevi er Science B.V. All rights reserved.