HYDRODYNAMICALLY GENERATED AMPEROMETRIC DIFFERENCE CURRENTS USING PARALLEL-FLOW STREAMS

An alternative approach to hydrodynamic modulation in flow streams has been designed which is not influenced by the rate of relaxation of th e diffusion layer. Reticulated vitreous carbon flow through working el ectrodes was used in gravity-driven dual-flow lines. Two working elect rodes were used, one in each of two independent flow lines. Each flow line contained a complete electrochemical cell, and the working electr ode of each cell was maintained at the same potential. The flow rates were different in each flow line, but the solution of analyte was the same. The difference current between the two working electrodes was me asured using operational amplifier circuitry. Criteria for the selecti on of flow rates are presented. The dual-flow stream has the advantage s of real-time background correction and automatic offset of solid ele ctrode surface or history effects. Hydroquinone was used as a test sys tem, and detection limits were in the subnanomolar region.