26, 31, 32 Compared to other hydrodynamic electrodes such as the RDE, the channel electrode is more amenable to miniaturization and adaptation to on-line analysis, i.e. An advantage of these hydrodynamically swept electrodes is that the system quickly reaches steady state at a fixed flow rate, which simplifies the instrumentation and permits accurate and precise measurements at very low sample concentrations. Hydrodynamic electrodes 29, 30 are those where convection is the main form of mass transfer and it includes electrodes that move through an otherwise still solution, such as the rotating disc electrode (RDE), and stationary electrodes over which a solution flows, such as the channel electrode. 28 performed in-channel amperometric detection of cathecol and dopamine in a capillary electrophoresis microchip, with an polyelectrolytic gel salt bridge (PGSB) to reduce the influence of the high voltage electrophoresis on the amperometric detector.Д®lectrochemical detection is often performed in the presence of a hydrodynamic flow. 27 used a three-electrode amperometric detector integrated into a capillary electrophoresis poly(dimethylsiloxane) (PDMS) chip to measure dopamine, with an integrated platinized decoupler to isolate the interference of the separation electric field. 24, 25 Amperometric detection is widely used because of its sensitivity, reliability and selectivity. The most common applications of electrochemical detection include amperometric and potentiometric detection, 23 as well as electrochemical impedance spectroscopy (EIS).

Compared to other microfluidic detection methods such as fluorescence, 16 non-fluorescent optical measurements, 17, 18 mass spectrometry, 19, 20 chemiluminescence and electrochemiluminescence, 21, 22 electrochemical detection methods offer a balance between sensitivity and selectivity and has the advantage of simple instrumentation and low electrical power consumption.

3, 15Д®lectrochemical detection of an analyte is based on a measurable electrical signal generated during redox reactions of electroactive species. 14 Microfluidic analysis has been widely studied due to its inherent advantages of high sensitivity, high speed, portability, automation, and low-cost. 3 Microfluidic devices have been used in various analytical operations, such as sample preparation, 4, 5 injection, 6, 7 sample handling, 8, 9 reaction, 10 separations, 11- 13 and detection. Microfluidics include systems where tiny amounts of fluids (10 в€’9 to 10 в€’18 L), are processed or manipulated using channels with dimensions of tens to hundreds of micrometers. 2 demonstrated the Ој-TAS concept with a microchip that was capable of quantitative analysis in microchannels with a few nanoliters of volume. 1 first proposed the concept of a вЂњminiaturized total chemical analysis systemвЂќ (Ој-TAS), which utilized a silicon-based chip for sample separation and detection. Miniaturized electrochemical analytical tools have been largely improved since Manz et al. Experimental and simulated currents showed the same trend but differed by 41% in simulations of the ideal geometry, which improved when channel and electrode imperfections were included. While microdisk channel electrodes have been simulated before using a finite difference method in an ideal 3D geometry, here we predict the limiting current using finite elements in COMSOL Multiphysics 5.3a, which allowed us to easily explore variations in the microchannel geometry that have not previously been considered in the literature. The platform was evaluated electrochemically by oxidizing a potassium ferrocyanide solution at the working electrode, and a typical limiting current behavior was observed after running linear sweep voltammetry and chronoamperometry, with flow rates 1вЂ“6 ОјL/min. A commercial leak-less reference electrode was utilized, and a coiled platinum wire was the counter electrode. The working electrode was a 100-Ојm diameter Pt microdisk, located flush with the upper face of a 150 Ојm Г— 20 Ојm Г— 3 cm microchannel, smaller than previously reported for these types of removable electrodes. A microfluidic platform for hydrodynamic electrochemical analysis was developed, consisting of a poly(methyl methacrylate) chip and three removable electrodes, each housed in 1/16вЂќ OD polyether ether ketone tube which can be removed independently for polishing or replacement.

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