An Introduction to Chromatography What is chromatography? The separation of a mixture by distribution of its components between a mobile and stationary.

An Introduction to Chromatography

• What is chromatography?

• The separation of a mixture by distribution of its components between a mobile and stationary phase over time– mobile phase = solvent or gas– stationary phase = column packing material

Purpose of Chromatography

• AnalyticalAnalytical - determine chemical composition of a sample

• PreparativePreparative - purify and collect one or more components of a sample

Classification of Column Chromatographic MethodsGeneral Classification Specific Method Stationary Phase Type of Equilibrium

Liquid-liquid orpartition

Liquid adsorbed on solid Partition betweenimmiscible liquids

Liquid bondedphase

Organic liquids bonded on asolid surface

Partition between liquidand bonded phase

Liquid- solid oradsorption

Solid Adsorption

Ion exchange Ion exchange resin Ion exchange

Liquid chromatography(LC)(Mobile phase: liquid)

Size exclusion Liquid in interstices of apolymeric solid

Partition/sieving

Gas-liquid Liquid adsorbed on solid Partition between gas andsolid

Gas-bonded phase Organic species bonded to asolid surface

Partition between gas andbonded phase

Gas Chromatography(GC)Mobile phase: gas

Gas-solid Solid Adsorption

Two-stagepressure regulator

Carrier gas supply

Flow controller

Rotameter

Flow splitter Syringe

Injector

Detector

Temperature controlled

zonesColumn

Schematic of a Gas Chromatograph

Carrier Gas Supply

300Vdc

Injector and Detector

300Vdc

Injection types

A Capillary Column for GLC

Fused silica tubingdc 0.3 mm

df 1 mL = 15 - 60 m

Polydimethylsiloxane (silicone)• Good for retaining and separating

nonpolar solutes by boiling point

A thin layer of nonvolatile stationary phase is coating on the inner wall of the

tubing (WCOT)

Some Common Stationary Phases for Gas-Liquid Chromatography Stationary phase Common trade

name Maximum temperature

Common Applications

Polydimethyl siloxane OV-1,SE-30 350 General purpose nonpolar phase; hydrocarbons; polynuclear aromatics; drugs; PCB”s

Poly(phenylmethyl dimethyl) siloxane (10% phenyl)

OV-3, SE-32 350 Fatty acid methyl esters; alkloids; drugs; halogenated compounds

Poly(phenylmethyl) siloxane (50% phenyl)

OV-17 250 Drugs; steroids; pesticides; glycols

Poly(trifluoropropyldimethyl) siloxane

OV-210 200 Chlorinated aromatics; nitroaromatids; alkyl substituted benzenes

Polyethylene glycol Carbowax 20M 250 Fatty acids; alcohols; ethers; essential oils; glycols

Poly( dicyanoallyldimethyl) siloxane

OV-275 240 Poly unsaturated fayyt acids; rosin acids; free acids; alcohols

SiO

OH

SiO

OH

SiO

OH

SiO

OH

Si OH + Si ClCl

CH3

CH3

Si O Si Cl

CH3

CH3

Si O Si Cl +

CH3

CH3

CH3OH Si O Si OCH3

CH3

CH3

12

3

4

5 6 78

9

87

65

5

43

21

0 10 20 30

Isothermal at 45oC

0 10 20 30

Isothermal at 145oC

0 10 20 3030 60 90 120 150 180

TimeTemperature(oC)

Programmed from 30o to

180oC

Effect of temperature on gas chromatograms

Capillary GC-MS

Fused silica Column

Transfer Line

Quadruple MSGC Data system

Sample

Carrier

Packed column GC-MS Interface

To MS

Skimmer

To vacuum pump

Nozzel

From GC

Jet separator

Gaseousion sources

Mass analyzer

Ion transducer

Signalprocessor

Ion inlet

Vacuum pump

10-5 to 10-8 torr

Components of a Mass Spectrometer

Sample inlet

• batch inlet

• direct probe inlet

• chromatographic inlet

Vacuum pump

Heating coil

Ionization chamber

Direct insertion probe

A sample probe for inserting a sample directly into an ion source

Direct probe

Molecular leak

Repeller

Electron beam

HeaterShield

Filament

1st accelerating slit

Focusing slit

2nd accelerating slit

Anode

To mass analyzer

Ions with unstabletrajectories

Ions with stabletrajectories

Ion source

Dc and ac oltages

Quadruple Mass Spectrometer

Continuous Dynode Electron Multiplier

Resistive conductivesurface

GND

2kV