The hydrodynamics of the amperometric detector flow cell with a rotating disk electrode

Abstract

Series of photographs of the sample flow pattern in the flow cell with a stationary as well as a rotating disk electrode (RDE) were taken with a motor-driven camera. With the stationary electrode, the flow pattern in the cell was mushroom-like. Rotating the electrode generated a secondary fluid motion in the flow cell which manifested itself as vertical circulation of the solution present in the flow cell. A qualitative hydrodynamic explanation of the observed flow patterns is given. Peak broadening effects induced by the RDE in the flow cell were observed only at very fast rotation speeds and high nozzle heights. The response surface of the amperometric detector flow cell with the RDE as a function of the rotation speed and the nozzle height was measured by applying the detector in combination with high-performance liquid chromatography, flow injection analysis and continuous flow analysis. Model curve-fitting calculations indicate that the flow pattern in the flow cell can be laminar or turbulent, depending on the exact cell geometry, rotation speed and nozzle height.