Chromatography
                                          Chromatography is a separation technique based on a very simple concept of chemistry. Concept of interactions is very important subject of chemistry, the sample to be analyzed is allowed to interact with two physically different phases. Mobile phase and Stationary phase

The sample to be analyzed most often holds a mixture of numerous components to be separated. The targeted molecules to be analyzed are called analytes.
The mobile phase, either a liquid or a gas, facilitate mobility of the sample components through a region containing the stationary phase which is either a solid or a liquid, which is called the sorbent. stationary phase which is either a solid or a liquid, which is called the sorbent. Stationary phase have ability to “bind” some types of analytes. The molecular components in the sample distribute themselves between the mobile phase and stationary phase and thus have the opportunity to interact with the stationary phase. Separation efficiency depends on mode and extend of interaction. Some of the sample molecules are favorably bound by the sorbent and spend more time in the sorbent and their movement retarded
through the chromatographic system. On the other hand molecules with weak affinity with the sorbent spend more time with the mobile phase and are more easily eluted from the chromatographic system. The many interactions that exist between analytes and the stationary phase sorbent facilitate separation of mixture containing molecules.
X, Y, Z= Analyte molecules, Stationary phase (sorbent),
Mobile phase
The general procedure of moving a mixture containing analytes through a chromatographic system is called development. The mobile phase can be collected as a function of time at the end of the chromatographic system. The mobile phase, now called the effluent, contains the purified analytes. Fractions that are collected at different times will contain the different components of the original sample.  After completion of chromatographic process separated samples are detection with the help of appropriate detection technique. In summary, molecules are separated because they differ in the extent to which they are distributed between the mobile phase and the stationary phase. Chromatographic separations may be designed to accomplish two types of objectives either preparative or analytical, or both. A preparative technique is one that can be utilized for the purification of a relatively large amount of a biological material (mg or g). The purpose of such an experiment would be to obtain purified material for further consumption, characterization or study. Analytical procedures on the other are used most often to determine the purity of a sample; however, they may be used to evaluate any physical, chemical, or biological characteristic of sample.