 This method of separation is called gel, molecular sieve or size-exclusion mechanism of separation.  Size exclusion

 Vertical ascending

 Vertical descending

 Horizontal

 The polar drugs are adsorbed temporarily on the polar stationary phase surface. The most common stationary phase used for this purpose is silica. Silica has a chemical composition similar to glass SiO2. xH2O Silicic acid Silica

 Adsorption  Partioning

The carrier is a gas such as nitrogen or helium. The column is long to retain the analyte longer and it is filled with polydimethylsiloxane particles or relevant derivatives.

 FID (flame ionisation detector)

 ECD (electron capture detector)  This detector has a radioactive element. The radioactive element can produce a rich field of electrons. Once the compounds contain electronegative elements such as halogens reach the electron field they will capture some of the electrons and this change in the electrical field will give a response proportion with the concentration of the halogenated analytes. This detector is widely used in the analysis of halocompounds such as pesticides and herbicides