Voltammetric determination of lithium ions in pharmaceutical formulation using a lambda-MnO2-modified carbon-paste electrode

A screen-printed disposable sensor for the anodic stripping voltammetric (ASV) analysis of heavy metals was prepared by integrating a HgO-modified working electrode, Ag/AgCl reference electrode, and carbon counter electrode on a polycarbonate strip. The working electrode was screen-printed with phenol resin-based carbon ink containing fine particles of mercuric oxide as a built-in mercury precursor. The mercuric oxide particles exposed on the surface were reduced to fine mercury droplets by in situ or pre-cathodic conditioning in order to allow them to behave as heavy metal collectors in the anodic stripping analysis. The reference and counter electrodes were also screen-printed using commercial silver paste ink modified with finely ground AgCl powder and commercial carbon ink, respectively. The analytical characteristics of the sensor were evaluated using Pb and Cd as probe metals. Detailed preparation procedures and analytical characteristics of the sensor are described.