Simultaneous Determination of Nickel and Cobalt by Extraction-Voltammetry in Soil and Leafy Samples

Abstract

A simple, sensitive and reliable analytical method with simultaneous voltammetric determination of nickel and cobalt is described. Simultaneous voltammetric determination of Ni and Co, based on adsorptive accumulation of Ni (II) and Co (Il)-xanthate (potassium propyl xanthate, PPX) after extraction into methyl isobutyl ketone on hanging mercury drop electrode (HMDE) in a single solution at a potential of −0.75 V in the 0.2 M HCl-CH3COONa solution of pH 3.0 is reported. The reduction peaks of Ni (II)-PPX and Co (II)-PPX complexes were observed at a potential of −0.99 V and −1.125 V, respectively, by scanning the potential in the negative direction in the differential pulse mode. Extraction parameters such as pH, PPX concentration and instrumental parameters such as adsorption time, adsorption potential, scan rate etc. are optimized, and the optimized conditions are used for the determination of Ni and Co in soils and leafy vegetables. Interferences of other metal ions are studied. The lower detection limits are found to 0.35 μg/1 and 0.30 μg/1 for nickel and cobalt, respectively. The precision and accuracy is demonstrated by the analysis of certified reference materials (CRM's).