Computer-Assisted Processing of Current Step Signals in Single Blocking Impact Electrochemistry

International audience ; Current step signals related to single entity collisions in blocking impact electrochemistry were analyzed by computer-assisted processing for estimating the size distribution of various particles. In this work, three different types of entities were studied by single blocking impact electrochemistry: polystyrene nanospheres (350 nm-diameter) and microspheres (1 µm-diameter), phospholipid liposomes (300 nm-diameter) and two different strains of Gram-negative bacillus bacteria (Escherichia coli and Shewanella oneidensis). The size estimations of these different entities from the current step signals analysis were compared and discussed according to the shape and size of each entity. From the magnitude of the current step transient, the size distribution of each entity was calculated thanks to a new computer program assisting in the detection and analysis of single impact events in chronoamperometry measurements. The data processing showed that the size distribution obtained from electrochemical data agreed with the dynamic light scattering and atomic force microscopy data for nanospheres and liposomes. In contrast, the size estimation calculated from electrochemical data was underestimated for microspheres and bacteria. We demonstrated that our computer program was efficient for detecting and analyzing the collision events in single blocking impact electrochemistry for various entities from spherical hard nanoparticles to micron-sized rod-shaped living bacteria.