Paper Chromatography

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Paper Chromatography

• Identifying the components of a mixture

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Chromatography
Chromatography is a method for separating
mixtures into their components based on physical
and/or chemical properties of the components.
Developed around 1903 by Russian Mikhail
Semenovich Tswett in which he separated plant
pigments on diatomaceous earth with alcohol
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Uses for Chromatography

• Chromatography can be used to
• Qualitatively analyze the components of a mixture
• Qualitatively identify the components of a
  mixture using known compounds
• Quantitatively determine the amount of a
  component in a mixture using standard samples
• Purify individual components by separating them
  from the other compounds in a mixture

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The Basics

• Mixture is placed on stationary phase
• Mobile phase passes over the stationary phase
• Mobile phase dissolves the components
• Mobile phase carries the individual components a
  certain distance through the stationary phase,
  depending on their attraction to both of the
  phases

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Solvent Front
Chromatographed Spot
Rf ratio of spot distance to solvent front
distance
Put the spotted paper in a developing tank
Origin line
Solvent
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Principles of Paper Chromatography

• Capillary Action the movement of liquid within
  the spaces of a porous material due to the forces
  of adhesion, cohesion, and surface tension. The
  liquid is able to move up the filter paper
  because its attraction to itself is stronger than
  the force of gravity.
• Solubility the degree to which a material
  (solute) dissolves into a solvent. Solutes
  dissolve into solvents that have similar
  properties. This allows different solutes to be
  separated by different combinations of solvents.
  
• Separation of components depends on both their
  solubility in the mobile phase and their
  differential affinity to the mobile phase and the
  stationary phase.

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Investigation What Dyes are in the MMs and Food
Colors?

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Preparing the Chromatography Paper

• Obtain an 7 x 8 cm of chromatography paper
• With a pencil (why?), draw an origin line 1 cm
  above the bottom edge of the strip. Near the top,
  ID the chromatogram
• Mark the origin line with a lane mark each cm. No
  lane can be closer than about 1 cm from the edge

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Preparing the Chromatography Paper

• ID each lane and record what each lane is spotted
  with
• Place a spot from each solution on the origin
• More than one strip may be required to analyze
  all of the solutions

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Developing the Chromatograms

• Add chromatographic solvent to a sufficiently
  large beaker to a depth of less than 1 cm
• Place the spotted paper in the beaker carefully
• Ensure the solution does not go above the origin
  line
• Develop the chromatogram until the solvent front
  is about 2 cm from the top of the paper

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Developing the Chromatograms

• Remove the chromatogram and place on a paper
  towel, trace the solvent front with pencil, and
  let the chromatogram dry in the oven for a few
  minutes.
• After the chromatogram is dry, calculate the
  retention factors, Rf, and tabulate the values
• Determine the dye content of each of the
  unknowns

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Considerations

• Small spots are generally better but harder to
  see after developing
• UV lamps, if available can (sun)burn your eyes
  but UV is stopped by the plastic of your goggles
• UV lamps are low power but extended exposure can
  cause a mild (sun)burn
• Dont eat the MMs theyve been in the lab
  awhile

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Writing Procedure Proposals

• Clearly state your experimental methods and how
  those procedures will yield solutions to the
  problems addressed in the investigation.
• State what data you plan to collect and how you
  will analyze the data.
• Include proposed data tables.
• State all the materials you plan to use
  including, if possible, concentrations and
  quantities.
• Describe the safety hazards associated with your
  analysis and appropriate precautions you will
  take to avoid personal injury.
• Each team member must sign and date the procedure
  proposal before turning it in.

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Author List

• This investigation, Author
• 3 Introduction and Conclusion
• 1 Discussion
• 2 Data/Results and Experimental
• This investigation, Author
• B Introduction, Conclusion, Data/Results
• A Discussion and Experimental

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