A Closed 50-μ L Three-Electrode Minicell for Green Voltammetry Without O2 Interference

Abstract

We report the construction and testing of a three-electrode electrochemical minicell for waste-minimizing and chemical resource-sparing green voltammetry. The minicell has a lid with boreholes for the working and reference electrodes and a stand with integrated 50- $\mu \text{L}$ Pt electrolyte container that also serves as the counter-electrode. In initial functionality tests the cell performed accurate voltammetric quantification of Pb2+, a pollutant in water and whisky, the drug paracetamol in a solution of a commercial tablet and, with a biosensor as working electrode, glucose in blood serum. The minicell was designed to be gas-tight, which allowed its use without electrolyte loss through evaporation, permitting uninterrupted, stable voltammetry scans for at least 11 hours. The gas-tightness of the minicell also enabled cathodic redox voltammetry to be performed free of interference by the electroreduction of dissolved oxygen, after electrolyte supplementation with glucose oxidase, catalase and glucose to perform enzymatic O2 scavenging. The new minicell design is a practical, economical and environmentally-aware option for electroanalysis of pollutants, drugs, biomarkers and physiological or pathological constituents of body fluids. Moreover, it is a green tool for the electrochemical characterization and stability testing of organic and inorganic redox compounds and redox enzymes, especially when the absence of O2 is necessary, for work under conditions in which oxygen reduction would interfere with the signal from the target. Since the minicell is compact and portable it can, in combination with a laptop-operated portable minipotentiostat, easily be used outside the laboratory and should therefore be applicable in on-site green environmental and clinical sample testing.