Transcript The world of Separation Science

Department of Chemistry, Faculty of Science
Universiti Teknologi Malaysia
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Analytical Chemistry Course
Gas Chromatography (GC)
Hashim and Mohd Daniel
Department of Chemistry, Faculty of Science
Universiti Teknologi Malaysia
81310 Skudai, Johor, Malaysia
[email protected]
Outline
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Introduction to GC
Instrumentation
Injector
Oven
Columns
Applications
Gas Chromatographic equipment
GC
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Gas chromatography is a chromatographic technique that
uses a gas as the mobile phase and either a liquid or solid
as the stationary phase.
The analytes are adsorbed or dissolved in the stationary
phase due to an equilibrium based on the vapor pressure
and other additional interactive forces.
The mobile phase in GC is referred to as the carrier gas
because ther is little interaction between the analyte and the
gas phase.
Gas-solid chromatography (GSC) uses a solid stationary
phase while gas-liquid chromatography (GLC) uses a liquid
stationary phase that is bonded or coated onto a solid
support.
GC Instrument
Pressure
regulator
Valve
Injector
Detector
Work Station
Column
Oven
Carrier gas
Integrator/Plotter
A schematic diagram of a capillary gas chromatograph.
GC Instrument
Two-stage regulator
Carrier
gas
Injector
Detector
Integrator/Plotter
or Work Station
Column
Oven
A schematic diagram of a gas chromatograph.
GC Instrument
Gases for GC
Split/splitless injector for GC
Penutup septum
Septum
Laluan
pembersih
septum
Laluan
keluar
Injap
Gas pembawa
Pemanas
Liner
Ferul grafit
Turus rerambut
Rajah 6.2 Gambarajah skema sejenis peranti untuk penyuntikan
berpecah. Peranti ini juga boleh digunakan untuk penyuntikan tidak
berpecah dengan pengawalan injap-injap berkenaan.
Oven temperature
Akhir
Akhir
Cerun II
Suhu
Cerun II
Penyejukan
Suhu
Menanti
Suntik
Suntik
Cerun I
Bersedia
Permulaan
Masa
Suhu isoterma
Penyejukan
Menanti
Suntik
Suntik
Cerun I
Bersedia
Permulaan
Masa
Rajah 6.3 Contoh kitar suhu
teraturcara bagi ketuhar
kromatografi gas.
Isothermal vs temperature-programmed GC
C8
C10
C12
C14
C16
0
20
C8
C10
C12
C14
40 min
C16
C18
C20
0
20 min
Rajah 6.4 Pemisahan GC sebatian-sebatian n-alkana menggunakan turus HP-101
(metilpolisiloksana), 50 m x 0.32 mm I.D., ketebalan 0.3 m. (a) GC isoterma pada
140 oC. (b) GC suhu teraturcara 50 - 230 oC dengan kadar 4 oC minit1.
GC Columns and stationary phases
 Heart of the chromatographic system
 Determine efficiency and selectivity
GC columns: packed vs open tubular
Turus silika
4 mm I.D.
Turus terpadat
Lapisan poliimida
Lapisan fasa cecair
0.2 mm I.D.
Turus tiub terbuka
(jenis WCOT)
Rajah 6.5 Gambarajah skema turus terpadat dan turus tiub terbuka
rerambut tipikal.
Packed columns
Three components
 Column tubing
 Support material
 Liquid stationary phase
Column tubing
 Criteria
Inert, thermally stable, coil up
 Types
Copper, stainless steel, glass
 Typical sizes
1-3 m long, 1/16, 1/8,1/4 inch OD, 2-3 mm ID
 Inner surface silylated
To reduce interaction with polar analytes
Packing materials
Fasa cecair
Penyokong
pepejal
Tapak aktif
100  m
Si
OH
O
Si
OH
O
Si
Diatomite support
surface
OH
Rajah 6.7 Gambarajah skema menggambarkan keratan rentas contoh padatan
yang terdiri daripada bahan penyokong yang tersalut dengan fasa cecair.
Support materials
Criteria
Unreactive towards analyte and liquid phase,
uniform particles and pore size
Diatomaceous earths – Chromosorb
Particle sizes
Analytical column: 80-100, 100-120 mesh
Preparatory column: 40-60, 60-80 mesh
Chemical treatment
AW – removes metallic impurities
AW-DMCS – remove silanol groups
Examples of GC support materials
E.g.GC packing materials
Non-diatomite support materials
Porous Polymers
- Porapak Polymers
Chromosorb 101 (PSDVB), 103 (PS)
Tenax Polymers
- 2,6-diphenyl-p-phenylene oxide
Carbopacks support - Inertness can be manipulated
Adsorbents
- Molecular sieve
Silica gel
- inertness can be manipulated
Carbon molecular
sieves
Open tubular columns
 No support material
 Liquid phase coated on wall of column (WCOT)
 Flexible fused silica
Coated with polyimide layer
Temp. < 350oC or else coating pyrolysed
 ID: 0.1 – 0.75 mm
 Film thickness: 0.1 – 5 m
 Column length: 5-50 m
 As ID and film thickness , sample capacity ,
but efficiency 
 Typical analytical column: 25 m x 0.22 mm x 0.25 m
Liquid phase requirements
 High solubility
 Differential solubility (high )
 Low vapour pressure (maximum
 temperature)
 Low viscosity (minimum temperature)
 10% vs. 5% : more plates, but 2 x tR
 Use light loading (3%) for high boilers
 Use heavy loadings (20%) for gases
Non-polar liquid phases in GLC
 Hydrocarbon phases: Squalane (C30H62),
Apolene (C87 hydrocarbon), Apiezon L(-(CH2)n-)
- Separation of non-polar molecules:
n-alkanes
 Alkylsilicone liquid phases: SE-30,
OV-1,
OV-101
 Dimethylsilicone (-(-Si(Me)2-O-)- polymer):
BP-1, Ultra-1, DB-1
GC on non-polar liquid phases
230 °C
50 °C
2 °C/min
Hydrocarbons
Essential oil
(Cymbopogon
nardus)
Column: Ultra 1, 30 m x 0.25 mm x 0.25 mm
Polar liquid phases in GLC
 Substituted silicone liquid phases:
methylphenyl silicone
- OV-105, CP-Sil 58
 Ester liquid phases:
- Poly(diethylene glycol adipate) DEGA
- Poly(diethylene glycol succinate) DEGS
 Polyether liquid phases:
Carbowax 200 to Carbowax 20M
(Polyethylene glycol, PEG)
- HP20-M, BP-Wax, BP20
GC on polar liquid phase
230 °C
50 °C
4 °C/min
Hydrocarbons
Essential oil
(Cymbopogon
nardus)
Column: HP-20M (Carbowax 20M)
Other phases
 Free fatty acid phase (FFAP) or
 Carbowax 20M impregnated with
terephthalic acid (Carbowax 20M-TPA):
- Separation of free carboxylic acids
C1 to C7
 Chiral liquid phases with amino acid
derived centers
 Separation of enantiomers
- Chirasil-L-Val, Chirasil-D-Val
- -Dex, -Dex, -Dex
Liquid stationary phases
Liquid stationary phases and applications
Gas-solid chromatography
Porous polymer phases
Porous polymer phases
Factors in selecting stationary phase
 Nature of analyte
 Stationary phase type
 Column internal diameter
 Film thickness
 Column length
Packed vs Open tubular columns
Factor
Packed Column
Open Tubular
Efficiency
low to moderate
high
Sensitivity
low
high
Operation
easy
less easy
Sample
amount
Price
large
small
low
high
Effect of column internal diameter (ID)
Characteristics
Open Tubular
Packed Column
2 mm
0.20 mm
0.32 mm
0.75 mm
Column ID
5.30 ng
400 –
500 ng
10,000 –
15,000 ng
Efficiency
2000
Theoretical plates, n
5000
3000
1170
Optimum flow rate
(mL/min)
0.4
1.4
5.0
Sample capacity
(each component)
20,000 ng
20
Column conditioning
 Condition at
A. 20 oC higher than analysis temp
B. at least 10-20 oC less than stated max. operational temp of phase
 Never condition at column’s max temp
 Program temp slowly to conditioning temp (2-4 oC/min)
 Cool down slowly (nonbonded phase)
 Purge column with carrier gas for 1/2 hr before heating over
 Very high carrier gas flows can be used for conditioning
 Conditioning time varies with your need
GC Applications
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Petrochemical
Environmental
Pharmaceutical
Oleochemical
Others
Thank you