gas chromatography

Gas ChromatographyCompiled by : Imanuelle Orchidea

3325102413

Definition • A chromatographic technique in which the

mobile phase is a gas

Gas

Liquid

Solid

Gas –Liqui

d/ Gas-Solid Chromatograph

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perekam

Tabu

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Rangkaian penghubung &

penguat

Mobile phase

• Inert gas ( He, Ar, N2)• Carry the sample• Flow rates determined with a flow meter

placed at a column outlet

Column type Flow rate

Packed column 25-150 mL/min

Capillary column 1-25 mL/min

Chromatographic Columns

Packed columns

Capillary columns

Packed Columns

– Glass/stainless steel/copper/aluminum– 2-6 m in length, internal Ø 2-4mm– Particle Ø ranging from 37-44 µm to 250-354 µm– diatomaceous earth, glass beads, fluorocarbons

polymers– Handle larger samples– Pressure needed to move mobile phase limits it’s

length

Capillary Columns

• Open tubular column– Wall-coated– Support-coated

• Fused silica coated with protective polymer• Up to 100 m in length• Internal Ø 150-300 µm, megabore up to 530

µm• Handle smaller samples ( < 10-2 µL)

• Photo of capillary column, taken from Harvey, David .T. Modern Analytical Chemistry

Stationary phase• Choice of stat. phase selectivity• Criteria :

– CHEMICALLY INERT– THERMALLY STABLE– LOW VOLATILITY– APPROPRIATE POLARITY

• R – SiR2 – O - (SiR2 – O)n – SiR3

• HO – CH2 – CH2 – (O – CH2 – CH2)n – OH

STAT.PHASE POLARITY TRADE NAME (T)LIMIT APPLICATIONS

Squalane Non-polar Squalane 150 Low boiling aliphatic hydrocarbons

Apezion L Non-polar Apezion L 300 AmidesFatty acid methyl estersHigh boiling aliphatic HC

TerpenoidsPolydimethyl

siloxaneSlightly SE-30 300-350 Alkaloids*

Amino acid derivatives ** Drugs# pesticides##

Phenols & steroids50% methyl-50%phenyl

polysiloxane

Moderate OV-17 375 *, #, ##, Polyaromatic hydrocarbons

Polychlorinated biphenyls50%TFP-

50%MPSOModerate OV-210 275 *,**, #, halogenated compounds,

ketones, phenols50% CYP-50% phe-me-PSO

Polar OV-225 275 Nitriles, pesticides, steroids

PEG Polar Carbowax 20M

225 Aldehydes, esters, ethers, phenols

Introduction of samples

1. All constituents must be volatile2. Appropriate concentration3. Must not degrade the separation

Volatile analyte from Non volatile matrix:1. Liquid-liquid extraction2. Solid phase extraction SPME3. Headspace sampling4. Cryogenic focusing

Injecting the sample

• Split injection• Splitless injection• On-column injection

Schematic diagram of an injector for packed column GC

Detectors in GC

Thermal Conductivity

Flame ionization

Electron captured

Another detectors

• Flame photometric detector• Thermionic detector• FT-IR (GC-FT-IR)• MS (GC-MS)

Quantitative applications

• Environmental analysis• Clinical analysis/forensic may include• Consumer goods• Petroleum industry

Analysis of Chlorinated Pesticides in Water