In Situ Mapping of H₂, O₂, and H₂O₂ in Microreactors: A Parallel, Selective Multianalyte Detection Method

Abstract

Determining local concentrations of the analytes in state of the art microreactors is essential for the development of optimized and safe processes. However, the selective, parallel monitoring of all relevant reactants and products in a multianalyte environment is challenging. Electrochemical microsensors can provide unique information on the reaction kinetics and overall performance of the hydrogen peroxide synthesis process in microreactors, thanks to their high spatial and temporal resolution and their ability to measure in situ, in contrast to other techniques. We present a chronoamperometric approach which allows the selective detection of the dissolved gases hydrogen and oxygen and their reaction product hydrogen peroxide on the same platinum microelectrode in an aqueous electrolyte. The method enables us to obtain the concentration of each analyte using three specific potentials and to subtract interfering currents from the mixed signal. While hydrogen can be detected independently, no potentials can be found for a direct, selective measurement of oxygen and hydrogen peroxide. Instead, it was found that for combined signals, the individual contribution of all analytes superimposes linearly additive. We showed that the concentrations determined from the subtracted signals correlate very well with results obtained without interfering analytes present. For the first time, this approach allowed the mapping of the distribution of the analytes hydrogen, oxygen, and hydrogen peroxide inside a multiphase membrane microreactor, paving the way for online process control.

Electrochemical Microsensor for Microfluidic Glyphosate Monitoring in Water Using MIP-Based Concentrators

“…This data shows excellent performance of the sensor for GLY measurements and the appropriate method application leading to reproducible and stable electrochemical properties of the electrode. Hereby, we achieved sensitivities for GLY comparable to highly electroactive substances such as hydrogen peroxide . A lower concentration of H 2 SO 4 led to higher sensitivity but increasingly non-linear behavior.…”

Automated 3D Microphysiometry Facilitates High-Content and Highly Reproducible Oxygen Measurements within 3D Cell Culture Models

“…Next to optical fiber sensors, also electrochemical microsensors can be used with the system. For example, label-free electrochemical immunobiosensors could be employed for continual in situ monitoring of soluble biomarkers secreted by the cells. ,, The minimally invasive and label-free microphysiometry approach enables the repeated screening of multiple time points using a single sample facilitating the study of kinetics and recovery effects of metabolic parameters after drug exposure and, thereby, overcomes the limitations of end-point assays. This approach does not only reduce the overall sample number required for long-term studies with multiple time points but is also advantageous for studies with expensive biomaterials and drugs or where low cell numbers are limiting the number of technical replicates.…”

Electrochemical methods for neural interface electrodes

“…The H 2 O 2 oxidation current is seen at 800 mV, and is not dependent on oxygen (figure 5(B) blue vs green curve). In the cathodic part, if both O 2 and H 2 O 2 , their reduction currents superimpose linearly [26], and the highest reduction current can be observed (figure 5(B) green curve).…”