gas chromatography

31
GAS LIQUID CHROMATOGRAPHY

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A complete presentation on gas chromatography, illustrating the basics, operation and different instrumentation components of the whole system. Kindly comment if this presentation helps you or if you like this.

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Page 1: Gas Chromatography

GAS LIQUID CHROMATOGRAPHY

Page 2: Gas Chromatography

• Principles

Partition of molecules between gas (mobile phase) and liquid (stationary phase).

Gas Liquid Chromatography

Page 3: Gas Chromatography

Most Common Stationary Phases

1. Separation of mixture of polar compoundsCarbowax 20M (polyethylene glycol)

2. Separation of mixtures of non-polar compoundsOV101 or SE-30 (polymer of methylsilicone)

3. Methylester of fatty acidsDEGS (diethylene glycol succinate)

Page 4: Gas Chromatography

Filters/Traps

Air

Hyd

rog

en

Gas C

arrier

Column

Gas Chromatography

• gas system• inlet• column• detector• data system

Data system

Syringe/Sampler

Inlets

Detectors

Regulators

H

RESET

Page 5: Gas Chromatography

Schematic Diagram of Gas Chromatography

Page 6: Gas Chromatography

Detector

• Flame Ionization Detector (Nanogram - ng)

High temperature of hydrogen flame (H2 +O2 + N2)

ionizes compounds eluted from column into flame. The ions collected on collector or electrode and were recorded on recorder due to electric current.

Page 7: Gas Chromatography

Exhaust

Chimney

Igniter

Hydrogen Inlet

Column Effluent

Collector Electrode

Schematic Diagram of Flame Ionization Detector

Page 8: Gas Chromatography

Measures the changes of thermal conductivity due to the sample (g). Sample can be recovered.

 

Thermal Conductivity Detector

Page 9: Gas Chromatography

Thermal Conductivity Detector

Principal: The thermal balance of a heated filament

Electrical power is converted to heat in a filament and the temperature will climb until heat power loss form the filament equals the electrical power input.

The filament may loose heat by radiation to a cooler surface by conduction to the molecules which contact with the filament.

Page 10: Gas Chromatography

Thermal Conductivity Basics

When the carrier gas is contaminated by sample , the cooling effect of the gas changes. The difference in cooling is used to generate the detector signal.

The TCD is a nondestructive, concentration sensing detector. A heated filament is cooled by the flow of carrier gas.

Flo

w

Flo

w

Page 11: Gas Chromatography

When a separated compound elutes from the column , the thermal conductivity of the mixture of carrier gas and compound gas is lowered. The filament in the sample column becomes hotter than the control column.

The imbalance between control and sample filament temeprature is measured by a simple gadget and a signal is recorded

Thermal Conductivity Detector

Page 12: Gas Chromatography

Relative Thermal Conductivity

Compound Relative Thermal Conductivity

Carbon Tetrachloride 0.05

Benzene 0.11

Hexane 0.12

Argon 0.12

Methanol 0.13

Nitrogen 0.17

Helium 1.00

Hydrogen 1.28

Page 13: Gas Chromatography

Thermal Conductivity Detector

Page 14: Gas Chromatography

• Responds to all compounds

• Adequate sensitivity for many compounds

• Good linear range of signal

• Simple construction

• Signal quite stable if carrier gas glow rate, block temperature, and filament power are effectively controlled

• Nondestructive detection

Thermal Conductivity Detector

Page 15: Gas Chromatography

Electron Capture Detector

Analyses for pesticide, Insecticides, vinyl chloride, and fluorocarbons in foods.

Most sensitive detector (10-12 gram)

Page 16: Gas Chromatography

Electron Capture Detector

ECD detects positive ions of carrier gas by the anode electrode.

63Ni emits particles.

Ionization : N2 (Carrier gas) + (e) = N2+ + 2e. The N2

+ establish a “base line”

X (F, Cl and Br) containing sample + (e) X-

Ion recombination: X- + N2+ = X + N2, The “base line” due to the

N2+ will decrease and this decrease constitutes the signal.

The more the halogen containing X compounds in the sample, the less the N2

+ in the detector

Page 17: Gas Chromatography

Electron Capture Detector

Page 18: Gas Chromatography

Electron Capture Detector

Page 19: Gas Chromatography

Chromatogram of Compounds from Fermented Cabbage

Page 20: Gas Chromatography

Chromatogram of Orange Juice Compounds

Page 21: Gas Chromatography

Gas Chromatography Application

Page 22: Gas Chromatography

Semi-Quantitative Analysis of Fatty Acids

C

C

C

Dete

ctor

Resp

onse

Retention Time

14

16

18

Pea

k A

rea

Sample Concentration (mg/ml)

2

4

6

8

10

0.5 1.0 1.5 2.0 2.5 3.0

The content % of C fatty acids =C

C + C + C

= the content % of C fatty acids14

14

Page 23: Gas Chromatography

Tentative Identification of Unknown Compounds

Res

pons

e

GC Retention Time on Carbowax-20 (min)

Mixture of known compounds

Hexane

Octane Decane1.6 min = RT

Res

pons

e

Unknown compound may be Hexane

1.6 min = RT

Retention Time on Carbowax-20 (min)

Page 24: Gas Chromatography

Res

p on s

e

GC Retention Time on SE-30

Unknown compound

RT= 4 min on SE-30

Res

pons

e

GC Retention Time on SE-30

HexaneRT= 4.0 min on SE-30

Retention Times

Page 25: Gas Chromatography

Advantages of Gas Chromatography

• Very good separation

• Time (analysis is short)

• Small sample is needed - l

• Good detection system

• Quantitatively analyzed

Page 26: Gas Chromatography

Disadvantages of Gas Chromatography

Material has to be volatilized at 250C without decomposition.

R C OH CH3OH H2SO4

O

R C O CH3

O

CH2 O C R

CH O C R

CH2 O C R

O

O

O

CH3OH

O

R C O CH3

CH3ONa

Fatty Acids Methylester

Reflux

+ 3

Volatile in Gas Chromatography

Volatile in Gas Chromatography

+ +

Page 27: Gas Chromatography

Gas Chromatogram of Methyl Esters of Fatty Acids

Page 28: Gas Chromatography

Effects of OH groups of Carbohydrates

OH

O

OH

OHHO

CH2

OH

1

23

4

5

6

Page 29: Gas Chromatography

OH

O

OH

OHHO

CH2OH

1

23

45

6

+ Si

CH3

CH3

CH35Cl

O-Si(CH3)3

O

O-Si(CH3)3

O-Si(CH3)3(CH3)3-Si-O

CH2O-Si(CH3)3

1

23

45

6

5HCl+

Derivation of Glucose with Trimethylchlorosilane

Glucose Trimethylchlorosilane

Page 30: Gas Chromatography

Effects of Derivation

• Time consumption

• Side reaction

• Loss of sample

Page 31: Gas Chromatography

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