slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
GAS LIQUID CHROMATOGRAPHY PowerPoint Presentation
Download Presentation
GAS LIQUID CHROMATOGRAPHY

Loading in 2 Seconds...

play fullscreen
1 / 39

GAS LIQUID CHROMATOGRAPHY - PowerPoint PPT Presentation


  • 244 Views
  • Uploaded on

GAS LIQUID CHROMATOGRAPHY. Principles Partition of molecules between gas (mobile phase) and liquid (stationary phase). Most Common Stationary Phases. 1. Separation of mixture of polar compounds Carbowax 20M (polyethylene glycol) 2. Separation of mixtures of non-polar compounds

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'GAS LIQUID CHROMATOGRAPHY' - Jimmy


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

GAS LIQUID CHROMATOGRAPHY

Principles

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

most common stationary phases
Most Common Stationary Phases
  • 1. Separation of mixture of polar compounds
  • Carbowax 20M (polyethylene glycol)
  • 2. Separation of mixtures of non-polar compounds
  • OV101 or SE-30 (polymer of methylsilicone)
  • Methylester of fatty acids
  • DEGS (diethylene glycol succinate)
gas chromatography

H

RESET

Air

Hydrogen

Gas Carrier

Gas Chromatography

Filters/Traps

Data system

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

Regulators

Syringe/Sampler

Inlets

Detectors

Column

slide6

DETECTORS

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.

slide7

Exhaust

Chimney

Collector Electrode

Igniter

Polarizing Electrode

Column

Hydrogen

Effluent

Inlet

Schematic Diagram of Flame Ionization Detector

schematic diagram of flame ionization detector
Schematic Diagram of Flame Ionization Detector

Collector

Detector electronics

 - 220 volts

Flame

Chassis ground

Jet

Signal output

Column

slide9

Thermal Conductivity Detector

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

thermal conductivity detector
Thermal Conductivity Detector

Principal: The thermal balance of a heated filament

Electrical power is converted to heat in a resistant 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 and by conduction to the molecules coming into contact with it.

thermal conductivity basics

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

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.

Flow

Flow

slide12

Thermal Conductivity Detector

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

Its resistance increased, and this imbalance between control and sample filament resistances is measured by a simple gadget and a signal is recorded

slide15

Thermal Conductivity Detector

  • Responds to all compounds
  • Adequate sensitivity for many compounds
  • Good linear range of signal
  • Simple construction
  • Signal quite stable provided carrier gas glow rate, block temperature, and filament power are controlled
  • Nondestructive detection
electron capture detector
Electron Capture Detector

For pesticide analysis (picogram).

Accept electrons of carrier gas.

electron capture detector17
Electron Capture Detector

ECD detects ions in the exiting from the gas chromatographic

column by the anode electrode.

3H or 63Ni which emits  particles.

Ionization : N2 (Nitrogen carrier gas) +  (e) = N2+ + 2e

These N2+ establish a “base line”

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

Ion recombination : X- + N2+ = X + N2

The “base line” will decrease and this decrease constitutes the signal.

Insecticides, pesticides, vinyl chloride, and fluorocarbons

slide24

GLC ADVANTAGES

1. Very good separation

2. Time (analysis is short)

3. Small sample is needed - ml

4. Good detection system

5. Quantitatively analyzed

slide25

DISADVANTAGES OF GAS CHROMATOGRAPHY

Material has to be volatilized at 250C without decomposition.

slide27

6

6

CH

CH

OH

OH

2

2

O

O

5

5

4

4

1

1

OH

OH

HO

HO

OH

OH

2

2

3

3

OH

OH

The Effects of OH groups of Carbohydrates

slide28

CH

3

Si

5Cl

CH

3

CH

3

6

CH

OH

2

O

5

4

1

OH

HO

OH

2

3

OH

Derivation of Glucose with Trimethylchlorosilane

+

Glucose

Trimethylchlorosilane

6

CH

O-Si(CH3)3

2

O

5

+

5HCl

4

1

O-Si(CH3)3

(CH3)3-Si-O

O-Si(CH3)3

2

3

O-Si(CH3)3

effects of derivation
Effects of Derivation

1. Time consumption

2. Side reaction

3. Loss of sample

slide30

THIN LAYER CHROMATOGRAPHY

Stationary Phase ---------> Silica Gel

Mobile Phase -------------> Solvent (developing)

slide33

Thermal Conductivity Detector

The detector contains two filaments: one exposed only to carrier gas, while the other is exposed to the carrier gas for sample analysis.

When the gas for the sample analysis is only carrier gas , the two filaments can be balanced.

Instead of a direct measurement of filament temperature, the filament resistant, which is a function of temperature, is measured.

slide34

Thermal Conductivity Detector

The ability of a colliding molecule to carry off heat depending on its thermal conductivity. Hydrogen and helium have high thermal conductivity and therefore will be more efficient at “cooling” a heated filament than other gases will

thermal conductivity detector35
Thermal Conductivity Detector

The TCD will respond to any substance

different from the carrier gas as long as its

concentration is sufficiently high enough.

slide38

Electron Capture Detector

Electron capture compound, X (highly electonegative element), tends to capture free electrons and increase the amount to ion recombination

X (F, Cl and Br) + e  X-

Ion recombination : X- + N2+ = X + N2

The current will decrease and this decrease constitutes the signal.

Halogens, lead, phosphorous, nitro groups, silicone and polynuclear aromatics.

Insecticides, pesticides, vinyl chloride, and fluorocarbons