Spatially Averaging Electrodes

Abstract

In contrast to many optical techniques, both the potentiometric and voltammetric measurement approach are only capable of reporting the concentration of the analyte of the sample solution that exists adjacent to the diffusion layer. Therefore, electrochemical measurement techniques in general cannot be used to assess 3D averaged bulk concentrations of inhomogeneous samples. This may pose a problem in very small samples which cannot be optically analyzed and where homogenization by stirring is difficult. We discuss the concept of spatially averaging electrodes that can, due to their designed geometry, report 3D spatially averaged bulk concentration of inhomogeneous samples that have some type of symmetry. Within a given type of symmetry an infinite variation of concentration distributions may exist. Electrode geometries for samples with two different types of symmetries, hemispherical and cylindrical, are discussed. Alternate designs with intrinsic redundancies to correct for any systematic errors in the measurement are also shown.