CHROMATOGRAPHY

CHROMATOGRAPHY

1. CHROMATOGRAPHY USES TWO PHASES

   • CHROMATOGRAPHY IS A METHOD USED TO SEPARATE AND IDENTIFY THE SUBSTANCES IN A MIXTURE. THERE ARE LOTS OF DIFFERENT TYPES OF CHROMATOGRAPHY -- BUT THEY BOTH HAVE 2 PHASES
     • A MOBILE STAGE
       • WHERE THE MOLECULES CAN MOVE. THIS IS ALWAYS A LIQUID OR A GAS
     • A STATIONARY PHASE
       • WHERE THE MOLECULES CAN NOT MOVE. THIS CAN BE A SOLID OR A REALLY THICK LIQUID
   • THE AMOUNT OF TIME THE MOLECULES SPEND IN EACH PHASE DEPENDS ON TWO THINGS:
     • . HOW SOLUBLE THEY ARE IN THE SOLVENT
       • HOW ATTRACTED THEY ARE TO THE STATIONARY PHASE
       • MOLECULES WITH HIGHER SOLUBILITY IN THE SOLVENT ARE LESS ATTRACTED TO THE STATIONARY PHASE
         • THEY WILL SPEND MORE TIME IN THE MOBILE PHASE THAN THE STATIONARY PHASE -- SO THEY WILL BE CARRIED FURTHER UP THE PLATE

2. 1. THE COMPONENTS IN THE MIXTURES SEPARATE OUT AS THE MOBILE STAGE PHASE MOVES OVER TO THE STATIONARY PHASE - THEY ALL END UP IN DIFFERENT PLACES IN THE STATIONARY PHASE

   • 2. THIS HAPPENS BECAUSE EACH OF THE CHEMICALS IN A MIXTURE WILL SPEND DIFFERENT AMOUNTS OF TIME DISSOLVED IN THE MOBILE PHASE AND STUCK TO THE STATIONARY PHASE
     • 3. HOW FAST A CHEMICAL MOVES THROUGH THE STATIONARY PHASE DEPENDS ON HOW IT DISTRIBUTES ITSELF DURING THE TWO PHASES

3. IN THIN-LAYER CHROMATOGRAPHY THE MOBILE PHASE IS A SOLVENT

   • IN THIN LAYER CHROMATOGRAPHY TLC THE STATIONARY PHASE IS A THIN LAYER OF A SOLID (E.G SILICA GEL OR ALUMINUM OXIDE POWDER ) ON A GLASS OR PLASTIC PLATE. THE MOBILE PHASE IS A SOLVENT (E.G ETHANOL)
     • METHOD
       • 1. DRAW A LINE NEAR THE BOTTOM OF THE PLATE ( USE THE PENCIL TO DO THIS -THE PENCIL MARKS ARE INSOLUBLE AND WON'T MOVE WITH THE SOLVENT WHEREAS INK MIGHT) PUT A SPOT OF THE MIXTURE TO BE SEPARATED ON THE LINE
         • 2. PUT SOME OF THE SOLVENT INTO A BEAKER. DIP THE BOTTOM OF THE PLATE (NOT THE SPOT) INTO THE SOLVENT
           • 3. PUT A WATCH GLASS OVER THE BEAKER TO STOP ANY SOLVENT FROM EVAPORATING AWAY
             • 4.THE SOLVENT WILL START TO MOVE UP THE PLATE WHEN THE CHEMICALS IN THE MIXTURE DISSOLVE IN THE SOLVENT, THEY WILL MOVE UP THE PLATE TOO
               • 5. YOU WILL SEE THE DIFFERENT CHEMICALS IN THE SAMPLE SEPARATE OUT FORMING SPOTS AT DIFFERENT PLACES ON THE PLATE
                 • 6. REMOVE THE PLATE FROM THE BEAKER BEFORE THE SOLVENT REACHES THE TOP MARK THE DISTANCE THE SOLVENT HAS MOVED IN PENCIL

4. PAPER CHROMATOGRAPHY IS SIMILAR TO TLC

   • PAPER CHROMATOGRAPHY IS VERY SIMILAR TO TLC, BUT THE STATIONARY PHASE IS A SHEET OF CHROMATOGRAPHY PAPER -- OFTEN FILTER PAPER
     • THE MOBILE PHASE IS A SOLVENT SUCH AS ETHANOL IN TLC

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