If two homogeneous bulk phases meet there is a region of finite thickness where the properties changed that region is called interface. At a molecular level the thickness of the interfacial region is not zero, and it is significant. The properties of interfacial region can be important for colloid systems, especially for dispersions, where the surface to volume ratio is not negligible. Electrochemistry at liquid –liquid interface is concerned with three main types of charge-transfer reactions, namely- (a) ion-transfer (IT) reactions from one phase to another; (b) IT reactions assisted by the presence of a completing agent; and (c) Electron transfer(ET) reaction between hydrophilic and hydrophobic redox couple. Analytical chemistry from its very beginning took advantage of the unique properties of paper as a sensor substrate. For a long time, paper served mainly as a mechanical support for pH indicators and lateral flow assays, but more recently it is enjoying an unprecedented boost in interest due to its introduction to microfluidic and microelectro mechanical systems (MEMS). Absorbency and the ability to transport fluids solely by means of capillary action are often cited as its main advantages but also of considerable importance is its abundance and low price.