Gas Chromatography (GC) - PowerPoint PPT Presentation

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Gas Chromatography (GC)

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Title: Gas Chromatography (GC)


1
Gas 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
2
Outline
  • Introduction to GC
  • Instrumentation
  • Injector
  • Oven
  • Columns
  • Applications

3
Gas Chromatographic equipment
4
GC
  • 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.

5
GC Instrument
  A schematic diagram of a capillary gas
chromatograph.

6
GC Instrument
  A schematic diagram of a gas chromatograph.

7
GC Instrument

8
Gases for GC
9
Split/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.
10
Oven temperature
Rajah 6.3 Contoh kitar suhu teraturcara bagi
ketuhar kromatografi gas.
Suhu isoterma
11
Isothermal 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.
12
GC Columns and stationary phases
  • Heart of the chromatographic system
  • Determine efficiency and selectivity

13
GC columns packed vs open tubular
 Rajah 6.5 Gambarajah skema turus terpadat dan
turus tiub terbuka rerambut tipikal.
14
Packed columns
  • Three components
  • Column tubing
  • Support material
  • Liquid stationary phase

15
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

16
Packing materials
Rajah 6.7 Gambarajah skema menggambarkan
keratan rentas contoh padatan yang terdiri
daripada bahan penyokong yang tersalut dengan
fasa cecair.
17
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

18
Examples of GC support materials
19
E.g.GC packing materials
20
Non-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
21
Open 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

22
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

23
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

24
GC 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
25
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

26
GC on polar liquid phase
230 C
Hydrocarbons
4 C/min
50 C
Essential oil (Cymbopogon nardus)
Column HP-20M (Carbowax 20M)
27
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

28
Liquid stationary phases
29
Liquid stationary phases and applications
30
Gas-solid chromatography
31
Porous polymer phases
32
Porous polymer phases
33
Factors in selecting stationary phase
  • Nature of analyte
  • Stationary phase type
  • Column internal diameter
  • Film thickness
  • Column length

34
Packed 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
35
Effect 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
36
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 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

37
GC Applications
  • Petrochemical
  • Environmental
  • Pharmaceutical
  • Oleochemical
  • Others

38
Thank you
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