The developments in modern electrochemical instrumentation and their impact on electrochemical techniques are reviewed in Chapter 1. New potentiostat designs are discussed, particularly multichannel potentiostats for use with arrays of working electrodes. The fundamentals of flow cell design for electrochemical detection systems are also examined. Finally the recent applications of electrochemical detection with LC, FI A and CE are reviewed. Chapter 2 describes the design and development of a 4-channel computer-controlled potentiostat (expandable to 16 channels) for use with an amperometric array in flowing injection analysis. Control of the purpose instrumentation was effected with a 486-33 MHz personal computer and Analog Devices RTI-815 and RTI-817 data acquisition\control cards which were responsible for hardware control functions and data acquisition via digital and analog control lines. The control software was developed using Microsoft QuickBASIC. The instrumentation developed was used with both linear and radial flow cell configurations which were constructed "inhouse". The design was based on the utilisation of common reference and counter electrodes to reduce the complexity of the electrode arrangement. A variety of applications were demonstrated for the system, these included the determination of metal ions in solution and the use of dual sensors for the measurement of glucose in the presence of common clinical interferences. The design and application of a fountain type flow cell for use with sequential injection analysis (SIA) is discussed in Chapter 3. The unique flow characteristics of the fountain cell make it suitable for use with planar detectors such as glassy carbon electrodes, particularly arrays of these electrodes spaced at equi-distances from the inlet. The flow characteristics of the fountain cell were analysed with two different electrode array configurations. The development of an on-line polymerisation procedure for pyrrole using the fountain cell is also discussed. The development an electrochemical detection system for use with capillary electrophoresis (CE) is described in Chapter 4. The system was based on the use of an end column decoupler to separate the working electrode from the high voltages required for separations. Both amperometric and voltammetric detection was implemented with the system using carbon fiber microelectrodes. Dynamic background subtraction was utilised to improve the signal to noise ratio. A number of the parameters affecting voltammetric detection were investigated. The system was applied to the determination of phenolic acid mixtures following separation by CE.