2. liquid chromatography
DESCRIPTION
TRANSCRIPT
CHROMATOGRAPHY
Chromatography
Chromatography basically involves the separation of mixtures due to differences in the distribution coefficient of sample components between 2 different phases.
One of these phases is a mobile phase and the other is a stationary phase.
Definition:
Different affinity of these 2 components to stationary phase causes the separation.
Concentration of component A in stationary phase
Concentration of component A in mobile phase
Distribution Coefficient
Kinds of Chromatography
1. Liquid Column Chromatography
2. Gas Liquid Chromatography
Liquid Column Chromatography
A sample mixture is passed through a column packed with solid particles which may or may not be coated with another liquid.
With the proper solvents, packing conditions, some components in the sample will travel the column more slowly than others resulting in the desired separation.
A + B + C OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO
OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOO OOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOO OOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOO OOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO OOOOOOOOOO OOOOOOOOOOO OOOOOOOOOOO
Sample (A+B+C)
Column
Solid Particles(packing material- stationary phase)
Eluant (eluate)
DIAGRAM OF SIMPLE LIQUID COLUMN CHROMATOGRAPHY
A
B
C
Solvent(mobile or moving phase)
Diagram of Simple Liquid Column Chromatography
Basic liquid chromatography modes are named according to the mechanism involved:
1. Liquid/Solid Chromatography (adsorption chromatography)
A. Normal Phase LSC
B. Reverse Phase LSC
2. Liquid/Liquid Chromatography (partition chromatography)
A. Normal Phase LLC
B. Reverse Phase LLC
3. Ion Exchange Chromatography
4. Gel Permeation Chromatography (exclusion chromatography)
Four Basic Liquid Chromatography
Liquid Solid Chromatography
Si - O - H
Normal phase LS Reverse phase LS
Silica Gel
The separation mechanism in LSC is based on the competition of the components of the mixture sample for the active sites on an absorbent such as Silica Gel.
Liquid Solid Chromatography
Si - OH
HEXANE
OH
C-CH3
CH3
CH3 - CCH3
CH3
OH
OH
CH3
CH3
Water-Soluble Vitamins
1. Niacinamide 2. Pyridoxine
N
CONH2
N
CH2OHCH2OH
HO
H3C
3. Riboflavin
N
NNH
NCH2
HOCHHOCHHOCHCH2OH
O
OH3C
H3C
ClN
S
N
NH3C
CH2
NH2
CH3
CH2CH2OH
4. Thiamin
Water-Soluble Vitamins
0 5 10 15 20
Column: u Bondapak C18 Solvent: MeOH Sample: Water-Soluble Vitamins
Inject1
2
3
4
Liquid-Liquid Chromatography
ODPN (oxydipropionylnitrile)
Normal Phase LLC Reverse Phase LLC
NCCH 3CH2OCH2CH2CN(Normal)
CH3(CH 2)16CH3 (Reverse)
The stationary solid surface is coated with a 2nd liquid (the Stationary Phase) which is immiscible in the solvent (Mobile) phase. Partitioning of the sample between 2 phases delays or retains some components more than others to effect separation.
MOBILE PHASELIQUID
Liquid-LiquidChromatography (Partition)
Liquid-SolidChromatography (Adsorption)
Liquid Solid
Normal Phase Reverse Phase Normal Phase Reverse Phase
Mobile Phase -
Nonpolar
Stationary phase - Polar
Mobile Phase - Polar
Stationary phase -
Nonpolar
FORMAT
STATIONARY PHASE
Types of Chromatography
Ion-Exchange Chromatography
SO3- Na+
Separation in Ion-exchange Chromatography is based on the competition of different ionic compounds of the sample for the active sites on the ion-exchange resin (column-packing).
Mechanism of Ion-Exchange Chromatography of Amino Acids
SO3-
SO3-
Na+
COO-
H3N+
Na+
COOHH3N
+
pH2
pH4.5
Ion-exchange Resin
H3N+
SO3-
SO3-
SO3-
SO3-
SO3-
SO3-
H3N+
COOH
OH
COOH
COOHH3N
+
H3N+OH
COO-Na+
H3N+
COO-
Na+
Na+
H+ OH- = H2O
H+ OH- = H2O
Na+
Na+
pH3.5
Mobile PhaseStationary Phase
Exchange Resin
pH4.5
Chromatography of Amino Acids
Gel-Permeation Chromatography is a mechanical sorting of molecules based on the size of the molecules in solution. Small molecules are able to permeate more pores and are, therefore, retained longer than large molecules.
Gel-Permeation Chromatography
• Polar Solvents
Water > Methanol > Acetonitrile > Ethanol > Oxydipropionitrile
• Non-polar Solvents
N-Decane > N-Hexane > N-Pentane > Cyclohexane
Solvents
Sample Type LC Mode Positional isomers LSC or LLC
Moderate Polarity Molecules LSC or LLC
Compounds with Similar Functionality LSC or LLC
Ionizable Species IEC
Compounds with Differing Solubility LLC
Mixture of Varying Sized Molecules GCC
Selecting an Operation Mode
Schematic Diagram of Liquid Chromatography
Detector
1. Ultraviolet Detector
200-400nm 254 nm
2. Reflective Index Detector
Universal Detector
High Performance Liquid Chromatography
High Performance Liquid Chromatography
Retention Time
Time required for the sample to travel from the injection port through the column to the detector.
Response
Retention Time5 10 15 20 25
A
B
C
D
Selectivity
Ratio of Net Retention Time of 2 components.
(Distribution Coefficient) X2 - X0X1 X0-
Response
Retention Time
X
X
X
1 3 6
2
1
0
– Selectivity
SelectivitySelectivity
Resolution Equation
V - V
1/2(W + W )2
2
1
1R =
Response
Volumes
W WW W
V
V1
1 2
2
21
Resolution
Height Equivalent to a Theoretical Plate
Length of a column necessary for the attainment of compound distribution equilibrium measure the efficiency of the column.
Theoretical plates (N) = 16 ( )XY
2
X
Y
Importance of Theoretical Plates (N)
Theoretical Plate, Selectivity and Height Equivalent to a Theoretical Plate
1
2
3
4V
VV
V
W W W W
2
1
0
1
2
4
3 4
3
V
V0 = 1.0 (Minutes) V1 = 5.0, V2 = 7.0, V3 = 11.0, V4 = 13.0
W1 = 1.0, W2 =1.0, W3 = 1.0, W4 =1.0
Chromatogram of Orange Juice Compounds
General Factors Increasing Resolution
• Increase column length• Decrease column diameter• Decrease flow-rate• Pack column uniformly• Use uniform stationary phase (packing material)• Decrease sample size• Select proper stationary phase• Select proper mobile phase• Use proper pressure• Use gradient elution
LC Application in Food System
CarbohydratesAmino acids, proteinsVitamins, A, D, E, KNucleosides (purines and pyrimidines)Fatty acids, fatsAflatoxinsAntioxidantsContaminants of packaging materialsCarotenoids, chlorophyllsSaccharines