Microdialysis (MD) is a sampling technique that can be employed to monitor biological events continuously. When it is coupled to an sensitive and selective analytical system online

microdialysis can provide near realtime information on the time-dependent concentration changes of analytes in the extracellular space.Online systems for the analysis of microdialysis samples enable fast

selective and sensitive analysis while preserving the temporal information. It can improve the stability of the samples and save the time and cost. When developing an online assay based on microdialysis sampling

several parameters must be taken into consideration. These parameters include: the recovery of the probe

volume of sample available for analysis

concentration range of analyte in the sample

sensitivity and limit of detection of the analytical method scheme and the speed of analytical method. Analytical methods employed for online analysis include liquid chromatography (LC)

capillary (CE) and microchip electrophoresis and flow-through biosensor devices. Factors that affect the online systems include the interfaces

the column and the detectors was discussed.