Foundation GPC Training Course

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) N5.54(tR/W)2 L Plate count efficiency
(5s) N25(tR/W5s)2 L Symmetry W1/W2
16
Resolution in GPC

• Resolution Rs 2(V1-V2) (W1W2)
• Specific Resolution per Molecular Weight Decade
  
• Rsp 0.25 s D
• Elution Volumes of peaks 1 and 2 are V1 and V2
• Peak Widths of peaks 1 and 2 are W1 and W2