Voltammetric determination of lithium ions in pharmaceutical formulation using a λ-MnO2-modified carbon-paste electrode Original Research Article

A sensitive and selective λ-MnO2-modified carbon-paste electrode is proposed for voltammetric determination of lithium ions in pharmaceutical formulation. The various parameters that can influence the voltammetric response of the proposed electrode (carbon-paste composition, pH electrolyte, potential scan rate and interference of several ions) were investigated. The best voltammetric response was reached for an electrode composition of 25% (m/m) λ-MnO2 in the paste, borate buffer solution of pH 9.0 and scan rate of 5 mV s−1 in the voltammetric measurements. The proposed electrode responds to lithium ions in the concentration range from 8.0×10−5 to 2.2×10−2 mol l−1 with a detection limit of 3.6×10−5 mol l−1. The concentrations of lithium ions in a pharmaceutical formulation (tablet) using the proposed electrode and atomic absorption spectrophotometry are in agreement at the 95% confidence level and within an acceptable range of error.