Solvent effect on the self-adduct extraction of zinc(II) with 5-(4-nitrophenylazo)-7-(4--ethyl-1-methyloctyl)-8-quinolinol

The extraction of zinc(II) with 5-(4-nitrophenylazo)-7-(4-ethyl-1-methyloctyl)-8-quinolinol(HNEQ) was investigated using chloroform, 1,2-dichloroethane, isobutylmethyl ketone (MIBK), and l-octanol as diluents. HNEQ exhibited a higher extractability toward zinc(II) than did 8-quinolinol and Kelex 100. The extractability of zinc(II) with HNEQ increased in the following order of chloroform < 1,2-dichloroethane < MIBK < l-octanol. The extraction constants (K(ex,n) = [Zn(NEQ)(2)(HNEQ)(n)](org)[H(+)](2)/[Zn(2+)][HNEQ]((2+n))(org) and the formation constants (beta(s,n)=[Zn(NEQ)(2)(HNEQ)(n)](org)/[Zn(NEQ)(2)](org) [HNEQ](n)(org)) of the self-adduct complexes [Zn(NEQ)(2)(HNEQ)(n)] in the organic solvents were dependent on the characteristics of the organic solvents. MIBK and l-octanol provided larger formation constant of the self-adduct complex than did chloroform and 1,2-dichloroethane. This may be ascribed to the coordination of MIBK or l-octanol to the Zn(II) HNEQ complex and/or to the hydration of Zn(II)-HNEQ complex with MIBK or 1-octanol. It was also found that Zn(II)-HNEQ strongly absorbs at 522 nm (lambda(max)=8.40 x 10(4) cm(-1) mol(-1) 1, chloroform) and 543 nm (lambda(max)=8.40 x 10(4) cm(-1) mol(-1) 1, 1-octanol).