Direct and simultaneous spectrophotometric determination of Ni (II) and Co (II) using diethanoldithiocarbamate as complexing agent

P A Antunes,G Bannach,E T G Cavalheiro,G O Chierice

doi:10.1590/s0100-46702009000200001

Abstract

A direct spectrophotometric method for simultaneous determination of Co(II) and Ni(II), with diethanoldithiocarbamate (DEDC) as complexing agent, is proposed using the maximum absorption at 360 and 638 nm (Co(II)/DEDC) and 390 nm (Ni/DEDC). Adjusting the best metal/ligand ratio, supporting eletrolite, pH, and time of analysis, linear analytical curves from 1.0 10-6-4.0 10-4 for Co(II) in the presence of Ni 1.0 10-6-1.0 10-4 mol L-1 were observed. No further treatment or calculation processes have been necessary. Recoveries in different mixing ratios were of 99%. Interference of Fe(III), Cu(II), Zn(II) and Cd(II), and anions as NO3-, Cl-, ClO4-, citrate and phosphate has been evaluated. The method was applied to natural waters spiked with the cations.

Highlights

Several methods have been proposed for the simultaneous determination of Co(II) and Ni(II)
The present work is based on the differences in the color of solutions containing Co(II) or Ni(II) and dithiocarbamates (DTC)
In these experiments the concentration of the metal was fixed in 1.0.10-4 mol L-1, and the ligand was varied in the range 1.0 10-5-8.0 10-3 mol L-1, with each cation separately in phosphate buffer

Summary

Introduction

Several methods have been proposed for the simultaneous determination of Co(II) and Ni(II). DEDC was synthesized by the reaction of ethanolamine and carbon dissulphide in presence of ammonium hydroxide into an ice bath, and recrystallized from ethanol/water mixtures, as described elsewhere [20]. In these experiments the concentration of the metal was fixed in 1.0.10-4 mol L-1, and the ligand was varied in the range 1.0 10-5-8.0 10-3 mol L-1, with each cation separately in phosphate buffer (pH=7). The controller salt influence was investigated using Kcl, NaCl, KNO3, NaNO3, NaClO4, and McIlvaine buffer system at fixed ionic strength of 0.50 mol L-1. The influence of the temperature on the absorbance was investigated from 15-41°C, using a thermostatic bath (± 1oC)

Evaluation of the effect of interferents

Results and Discussion

Conclusions