Sequential Spectrophotometric Determination of Copper (II) and Zinc (II) Ions in Alkaline Aqueous Solution

Zincon is widely used as a colorimetric reagent for determining the concentrations of heavy metals in aqueous solutions. Copper and zinc are often found in the same aqueous sample and zincon can be used to determine the concentration of both ions at different reaction pH conditions (e.g., pH 5 and 9). Reportedly, zincon forms a precipitate under acidic conditions, which may decrease the precision and accuracy of metal ion determination. In this communication, a novel sequential analysis technique for the determination of copper and zinc is reported. The precipitation problem was eliminated at a pH of 9, and the concentration of zinc ions was successfully determined by treating a copper-zinc binary mixture with zincon, and masking and demasking reagents. The concentration of copper ions was determined by treating the same copper–zinc solution with only zincon. The accuracy of the concentrations of copper and zinc ions determined using the proposed sequential analysis technique was ± 13%.