Chemical and Physical Foundations of Biological Systems Section: Content Category 5C

Separation and purification methods
Analysis of complex mixtures of substances ― especially biologically relevant materials ― typically requires separation of the components. Many methods have been developed to accomplish this task, and the method used is dependent on the types of substances which comprise the mixture. All of these methods rely on the magnification of potential differences in the strength of intermolecular interactions.

The content in this category covers separation and purification methods including: extraction, liquid and gas chromatography, and electrophoresis. The topics and subtopics are below:

Topic Level Key:

The abbreviations found in parentheses indicate the course(s) in which undergraduate students at many colleges and universities learn about the topics and associated subtopics. The course abbreviations are:

BC = first-semester biochemistry
OC = two-semester sequence of organic chemistry

Please note topics that appear on multiple content lists will be treated differently. Questions will focus on the topics as they are described in the narrative for the content category.

Separations and Purifications (OC, BC)

  • Extraction: distribution of solute between two immiscible solvents
  • Distillation
  • Chromatography: Basic principles involved in separation process
    • Column chromatography
      • Gas-liquid chromatography
      • High pressure liquid chromatography
    • Paper chromatography
    • Thin-layer chromatography
  • Separation and purification of peptides and proteins (BC)
    • Electrophoresis
    • Quantitative analysis
    • Chromatography
      • Size-exclusion
      • Ion-exchange
      • Affinity
  • Racemic mixtures, separation of enantiomers (OC)

To support your studies, see the following video tutorials below from the Khan Academy MCAT Collection. The videos and associated questions were created by the Khan Academy in collaboration with the AAMC and the Robert Wood Johnson Foundation.