Effect of change in angle between microelectrode surface and jet direction in flow system on current response in solutions of different ionic strength.

The influence of stream orientation versus surface of microelectrode detector was examined in the range between vertical and parallel flow for various jet velocities and various levels of supporting electrolyte. The flow cell was equipped with a conical body Pt microdisk electrode, and the measurements involved voltammetry and chronoamperometry. Ferrocene, two its charged derivatives (sodium ferrocenylo sulfate and ferrocenylomethyltrimethylamino hexafluorophosphate) and sodium iodide were employed as the substrates in the experiments. The strongest convectional transport and the highest signal of the analytes was obtained for alpha = 60 degrees (alpha is the angle between the electrode surface and the stream direction). The measured current increased by up to 1.85 times versus the traditional setup, and therefore, this new geometry of the detector is analytically advantageous. The value of alpha corresponding to the highest signal tended to decrease to approximately 45 degrees in the absence of supporting electrolyte provided that either flow rate or analyte concentration was above a certain threshold value. The experiments indicated that the interplay of the convectional and migrational components in the analyte transport is different for the charge increase and the charge cancellation processes. These experimental facts were confirmed by digital simulation results.