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Foundation GPC Training Course Theory

This course provides an in-depth look into Gel Permeation Chromatography (GPC), detailing its principles, mechanisms, and column technology. Learn how GPC separates polymer molecules based on size, and how to interpret retention times, peak widths, scaling, and resolution for efficient polymer analysis. Discover key aspects like molecular weight distribution (Mw/Mn), resin synthesis, and column calibration, enhancing your understanding of polymer characterization. Suitable for beginners and advanced users alike.

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Foundation GPC Training Course Theory

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  1. Foundation GPC Training Course Theory

  2. Nomenclature Gel Permeation Chromatography GPC Size Exclusion Chromatography SEC Gel Filtration Chromatography GFC

  3. Types of Liquid Chromatography Interactive adsorption, partition, ion exchange, etc Non-interactive GPC, SEC, GFC

  4. Why do GPC ? MWD determined by GPC • GPC is the only technique for characterising polymer molecular weight distribution • As Mw/Mn decreases the strength and toughness of the polymer increases • However as Mw/Mn decreases the polymer becomes more difficult to process • GPC provides key information to predict the processability and material properties of a polymer

  5. Size Exclusion Mechanism

  6. GPC Separation Mechanism • Polymer is prepared as a dilute solution in the eluent and injected into the system • The GPC column is packed with porous beads of controlled porosity and particle size • Large molecules are not able to permeate all of the pores and have a shorter residence time in the column • Small molecules permeate deep into the porous matrix and have a long residence time in the column • Polymer molecules are separated according to molecular size, eluting largest first, smallest last

  7. GPC Column Technology • Columns are packed with porous particles, controlled pore size and particle size • Columns are produced by slurry packing technique, packed at pressures in excess of 2000psi • Column dimensions typically 7-8mm i.d., 250-600mm in length

  8. Synthesis of Porous Particles • High cross-link content gives a rigid, low swelling product with a well-defined pore structure

  9. SEM Images of Porous Particle of PLgel 10µm Media

  10. Elution Profile of Different Molecular Sizes

  11. Elution Profile – Nomenclature Exclusion volume (Vo) - Upper MW limit (also known as void volume) Total permeation volume (Vt) – Lower MW limit Pore volume (Vp) – Working resolving range of MW Vp = Vt - Vo

  12. PLgel Individual Pore Size Column Calibration Curves

  13. PLgel MIXED Column Calibration Curves

  14. Plate Counts • A measure of the efficiency of a chromatographic system is the plate count • Column is divided into a number of theoretical plates • Plates are defined as the smallest cross-sectional slice in which the mobile and stationary phases are in equilibrium • The smaller the width (known as height) of the plate, the quicker the system comes to equilibrium and the greater the efficiency • Plate counts controlled by the Van Deemter relationship

  15. Determination of Column Performance tR = retention time W½ = peak width at 50% peak height W5s =peak width at 4.4% peak height L = column length in meters Efficiency (½ height) N=5.54(tR/W)2 L Plate count efficiency (5s) N=25(tR/W5s)2 L Symmetry =W1/W2

  16. Resolution in GPC • Resolution Rs = 2(V1-V2) (W1+W2) • Specific Resolution per Molecular Weight Decade Rsp = 0.25s D • Elution Volumes of peaks 1 and 2 are V1 and V2 • Peak Widths of peaks 1 and 2 are W1 and W2

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