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Intensive General Chemistry

Learn about the principles and techniques of gas and liquid chromatography for chemical separations. Understand the concepts of retention time and volume, qualitative and quantitative analysis, as well as different types of detectors and HPLC equipment.

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Intensive General Chemistry

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  1. Intensive General Chemistry Chemical separations II Isabelle Vu Trieu ilv2@columbia.edu http://ull.chemistry.uakron.edu

  2. Phase 1 A A A A A A A Phase 2 A A A A Gas versus Liquid chromatography Mobile phase Gas or Liquid Stationary phase Partition constant: K = aA(stationary)/ aA(mobile)

  3. Chromatography - Principles • Retention time (tr) : time required for a given component to emerge from the column • Retention volume (Vr) : volume of mobile phase required for a given component to emerge from the column Vr = tr x F Flow rate

  4. A typical chromatogram Retention time Adjusted retention time Hold-up time

  5. Qualitative “Blind” method Indicate the presence /absence of a substance (not what it is) Only one piece of information (Tr) Quantitative Analysis based on: Peak height Peak area Calibration & standards External standard Internal standard Qualitative / quantitative analysis

  6. GC instrumentation

  7. Carrier gas

  8. Injection port

  9. Columns wide bore capillary Open (coated) Higher capacity Better resolution

  10. Thermal conductivity General purpose Non destructive Detect the change in resistance of a wire based on variations of the thermoconductivity of the gas evolving from the column Flame ionization Specific (combustible sample only) Destructive Measure the current due to the production of ions when burning the sample in a flame Detectors

  11. HPLC equipment

  12. Sample injector Sampling Loop system:

  13. Normal phase Stationary phase is polar Ex: silica, alumina Mobile phase is non-polar Ex: hexane Reverse-phase Stationary phase is non-polar Ex: carbon chain bonded to silica Mobile phase is polar Ex: water, methanol Columns: Columns are packed, typically 10-20 cm long, 5mm id

  14. Detector:

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