Investigation of the effect of water structure modifiers in aqueous solution for the electroanalysis of metal ions

Abstract

Supportingelectrolytes are used in excess amount for making the electrochemical process purely diffusional for the electroanalysis.The addition of supporting electrolytes is essential for the successful performance of electrochemical experiments. It decreases the solution resistance and suppresses the electrostatic migration of ionic species towards the electrodes to achieve a diffusion-controlled process. Although supporting electrolytes have advantages, but still, it has some problems. The problems are; it mostly increases the ionic strength of the solution and greatly affects the activities of ions present in the solution. Water structure modifiercan be an alternativeoption to replace supporting electrolytes for electroanalysis.In this work, we addeda water structure breaker, urea, non-electrolyte in aqueous solution to achieve the diffusion-controlled process. It has been observed that urea can increase the conductivity of the solution by the alteration of the water-structure.Different concentrations of urea have been added to the solution of various salts, such as iron, lead, cadmium in absence and presence of an insufficient amount of supporting electrolyte and their electrochemical behavior has been observed by cyclic voltammetry (CV). Shift in electrochemical peak potential and peak current support the influence of urea on electroanalysis. It has been also observed that a diffusion-controlled calibration is possible in the presence of urea. On the other hand, the addition of fructose,water-structure maker increases aqueous solution resistance and resulted in difficulties in achieving the diffusion-controlled process without supporting electrolytes.Therefore, we think and hope that this process will be very helpful for establishing a conceptual basis for proposingan alternate procedure in developing a low-cost electrochemical protocol for the electroanalysis of metal ions.

Keywords: supporting electrolyte (KCl); urea; fructose; cyclic voltammetry (CV); metal ions (Fe3+, Pb2+ and Cd2+)