COPRECIPITATION BEHAVIOR OF 5,8-POLYQUINOLYL POLYDISULPHIDE FOR TRACE-ELEMENT PRECONCENTRATION FROM AQUEOUS-SOLUTION

The oxidation product of SH-containing reagent such as 5,8-dimercaptoquinoline was used for the coprecipitation of traces of non-transition and transition d-element from aqueous solution. The coprecipitation behaviour of 5,8-polyquinolyl polydisulphide (PQPD) for the preconcentration of V(IV), Cr(III), Mn(II), Fe(III), Co(III), Ni(II), Cu(II), Zn(II), Ga(III), As(III), Se(IV), Mo(VI), Ru(III), Pd(II), Cd(II), In(III), Au(III), Hg(II), Ir(III), Os(III) and Pt(II) is discussed. In special cases the coprecipitation of the inner complex of 5,8-dimercaptoquinoline is compared with that using quinoline-8-thiol. The formation of the PQPD solid phase and the coprecipitation of inner complex compounds of 5,8-dimercaptoquinoline occur over a wide range of acidity from 1.5 mol l-(1) HCl to pH 12. For all the above elements the recovery is more than 95%, with the exception of Ir(III), for which it is 85%. For the coprecipitation it is sufficient to use 60 mg of 5,8-dimercaptoquinoline for 1 l of aqueous solution, in contrast to quinoline-8-thiol, where 100 mg are needed.