Electrochemical studies of zinc in zinc–insulin solution

Abstract

The electrochemical determination of zinc arising from zinc–insulin complexes was investigated and it was demonstrated that zinc in zinc–insulin solution can be measured in the presence of dissolved oxygen by square-wave anodic stripping voltammetry (SWASV) at mercury thin-film electrodes on glassy carbon disc minielectrode and cylindrical carbon fibre microelectrode substrates. Reoxidation signals arise from complexed zinc at low insulin concentrations (< 100 nmol l^–1) and from labile zinc at higher concentrations; the latter can be quantified through linear calibration curves. Batch injection analysis with SWASV was successfully tested for the determination of zinc in zinc–insulin solutions in small sample volumes. Since intracellularly stored insulin exists in the form of a zinc–insulin complex, these techniques are very promising for the indirect study of insulin release from pancreatic β-cells.