Chromatography

Chromatography

1. Chromatography uses two phases

   • MOBILE PHASE: Where the molecules can move this is always a liquid or gas
   • STATIONARY PHASE: Where the molecules cant move. This can be a solid or a really thick liquid
   • The components in the mixture seperate out ass the mobile phase moves across the stationary phase
   • How quickly a chemical moves depends on how it distributes itself between the two phases. The mlecules of each chemical constantly move between the mobile and stationary phases. They are said to reacha dynamic equilibrium - at equilibrium the amount leaving the stationary phase is balanced as the amount leaving the mobile phase

2. In Paper Chromatography the stationary phase is the paper

   • In paper chromatography , a spot of the substance being tested is put onto a bassline on the paper. The bottom of the paper is placed in a beaker containing a solvent (mobile phase). The solvent moves up the paper. The chemicals in the sample dissolve in the solvent and move between it and the aper setting up an equilibrium between the solvent and the paper. When they are in the mobile phase they move up the paper. Before the solvent reaches the top of the paper the paper is removed from the beaker. The diffrent chemicals in the sample form seperate spots on the pape. The chemicals that spend more time in the mobile phase form spots further up
   • How much time is spend on each phase depends on how soluble the chemicals are in the solvent and how attracted they are to the paper

3. TLC: Thin layer chromatogrpahy is similar to paper chromatography but the stationary phase is a thin layer of solid