This work was optimized by a selection of optimum conditions including the selection of the supporting electrolyte, its pH, concentration of the cupferron, and accumulation potential and time.
Standard solutions of 1 g [L.sup.-1] of Bi(III) and cupferron (N- nitrosophenylhydroxylamine ammonium salt) were obtained from Merck (Darmstadt, Germany).
Next the acetate buffer, cupferron, and triply distilled water were introduced in order to obtain 10 mL of the solution containing 0.1 mol [L.sup.-1] acetate buffer (pH = 4.6), 1 x [10.sup.-4] mol [L.sup.-1] cupferron.
Preliminary works showed that cupferron was a suitable complexing agent for the determination of Bi(III) and Pb(II) when an acetate buffer was used as a supporting electrolyte [37, 38].
The concentration of cupferron ranged from 1 x [10.sup.-6] mol [L.sup.-1] to 5 x [10.sup.-4] mol [L.sup.-1] in the presence of 2 x [10.sup.-8] mol [L.sup.-1] of each of metal ions and 0.1 mol [L.sup.-1] acetate buffer (pH = 4.6).