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Chemistry LibreTexts

In-class Problem Set #4 – Ion-Exchange Chromatography

Problem #1

After completing this problem, the student will be able to:

  1. Describe a scheme using ion exchange chromatography that would enable you to deionize water.
  2. Explain why high capacity ion exchange resins are desirable for deionizing water.

Problem #2

After completing this problem, the student will be able to:

  1. Explain why high capacity ion exchange resins are not desirable for analytical (trace analysis) separations.

Problem #3

After completing this problem, the student will be able to:

  1. Justify the order of retention for Li(I), Na(I), and K(I) on a cation exchange column based on their attractiveness toward the resin.
  2. Justify the order of retention for Li(I), Na(I), and K(I) on a cation exchange column based on their attractiveness toward the mobile phase.
  3. Relate which of the two situations (attractiveness toward the resin or mobile phase) is more significant in affecting retention order for ions of the same charge but different size.
  4. Justify the order of retention on a cation exchange column for two ions that have the same size but a charge of +1 or +2 based on their attractiveness toward the resin.
  5. Justify the order of retention on a cation exchange column for two ions that have the same size but a charge of +1 or +2 based on their attractiveness toward the mobile phase.
  6. Relate which of the two situations (attractiveness toward the resin or mobile phase) is more significant in affecting retention order for two ions of the same size but different charge.

Problem #4

After completing this problem, the student will be able to:

  1. Describe and rationalize a detection scheme for ion chromatography that would allow for the measurement of the conductivity of the analyte ions while selectively removing the conductivity of the eluent ions.
  2. Describe and rationalize a detection scheme that would allow you to detect ions separated in ion chromatography using indirect spectrophotometric methods.

After lecture material on bonded phase liquid chromatography, the student will be able to:

  1. Explain the difference between a normal and reversed-phase separation
  2. Predict the retention order for compounds separated on a normal or reversed phase liquid chromatographic column.
  3. Determine the effect of pH on the elution time and retention order of compounds separated by reversed-phase liquid chromatography.
  4. Describe how liquid chromatography can generally be used to separate pairs of enantiomers.
  5. Describe the technique of ion-pairing chromatography.

After lecture material on gas chromatography, the student will be able to:

  1. Draw and describe the basic setup of a gas chromatograph
  2. Describe the difference between a split and splitless injection and justify when and why you would want to use each
  3. Describe the different injection technique for gas chromatography.This includes the use of liquid injection and adsorbent traps.
  4. Describe the purge and trap method
  5. Predict the retention order for a series of compounds separated by gas chromatography.
  6. Describe the following detection devices for a gas chromatograph, including their advantages
    1. Flame ionization
    2. Thermal conductivity
    3. Electron capture
    4. Mass spectrometry