Title: Gas Chromatography (GC)
1Gas Chromatography (GC)
Department of Chemistry, Faculty of Science
Universiti Teknologi Malaysia ____________________
__________ Analytical Chemistry Course
- Hashim and Mohd Daniel
- Department of Chemistry, Faculty of Science
Universiti Teknologi Malaysia - 81310 Skudai, Johor, Malaysia
marsin_at_kimia.fs.utm.my
2Outline
- Introduction to GC
- Instrumentation
- Injector
- Oven
- Columns
- Applications
-
3Gas Chromatographic equipment
4GC
- 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.
5GC Instrument
 A schematic diagram of a capillary gas
chromatograph.
6GC Instrument
 A schematic diagram of a gas chromatograph.
7GC Instrument
8Gases for GC
9Split/splitless injector for GC
Rajah 6.2 Gambarajah skema sejenis peranti untuk
penyuntikan berpecah. Peranti ini juga boleh
digunakan untuk penyuntikan tidak berpecah dengan
pengawalan injap-injap berkenaan.
10Oven temperature
Rajah 6.3 Contoh kitar suhu teraturcara bagi
ketuhar kromatografi gas.
Suhu isoterma
11Isothermal vs temperature-programmed GC
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.
12GC Columns and stationary phases
- Heart of the chromatographic system
- Determine efficiency and selectivity
13GC columns packed vs open tubular
 Rajah 6.5 Gambarajah skema turus terpadat dan
turus tiub terbuka rerambut tipikal.
14Packed columns
- Three components
- Column tubing
- Support material
- Liquid stationary phase
15Column 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
16Packing materials
Rajah 6.7 Gambarajah skema menggambarkan
keratan rentas contoh padatan yang terdiri
daripada bahan penyokong yang tersalut dengan
fasa cecair.
17Support 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
18Examples of GC support materials
19E.g.GC packing materials
20Non-diatomite support materials
Porous Polymers - Porapak Polymers
Chromosorb 101 (PSDVB), 103
(PS) Tenax Polymers - 2,6-diphenyl-p-pheny
lene oxide Carbopacks support - Inertness can be
manipulated Adsorbents - Molecular
sieve Silica gel - inertness can be
manipulated Carbon molecular sieves
21Open tubular columns
- No support material
- Liquid phase coated on wall of column (WCOT)
- Flexible fused silica
- Coated with polyimide layer
- Temp. lt 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
22Liquid 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
23Non-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
24GC on non-polar liquid phases
230 C
2 C/min
50 C
Hydrocarbons
Essential oil (Cymbopogon nardus)
Column Ultra 1, 30 m x 0.25 mm x 0.25 mm
25Polar 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
26GC on polar liquid phase
230 C
Hydrocarbons
4 C/min
50 C
Essential oil (Cymbopogon nardus)
Column HP-20M (Carbowax 20M)
27Other 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
28Liquid stationary phases
29Liquid stationary phases and applications
30Gas-solid chromatography
31Porous polymer phases
32Porous polymer phases
33Factors in selecting stationary phase
- Nature of analyte
- Stationary phase type
- Column internal diameter
- Film thickness
- Column length
34Packed vs Open tubular columns
Factor Packed Column Open Tubular
Efficiency low to moderate high
Sensitivity low high
Operation easy less easy
Sample amount large small
Price low high
35Effect of column internal diameter (ID)
Open Tubular
Packed Column
Characteristics Column ID 2 mm 0.20 mm 0.32 mm 0.75 mm
Sample capacity(each component) 20,000 ng 5.30 ng 400 500 ng 10,000 15,000 ng
EfficiencyTheoretical plates, n 2000 5000 3000 1170
Optimum flow rate(mL/min) 20 0.4 1.4 5.0
36Column 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 columns 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
37GC Applications
- Petrochemical
- Environmental
- Pharmaceutical
- Oleochemical
- Others
38Thank you