Gas chromatography is a technique used to separate components in a crude drug sample using an inert gaseous mobile phase. The sample is vaporized and injected into a column containing a stationary liquid phase. Components are transported through the column at different rates depending on their interaction with the stationary phase, allowing separation. Common carrier gases include hydrogen, helium, and nitrogen. Detectors like the flame ionization detector and thermal conductivity detector measure separated components to identify them. Gas chromatography is used for qualitative and quantitative analysis in applications like food analysis, pollutant detection, and separation of materials.

1. GAS CHROMATOGRAPHY
ABDULLAH KHALIL
2014-1545
MA’AM AYESHAASHRAF

2. Introduction
Gas chromatography – It is a process of separating component(s) from
the given crude drug by using a gaseous mobile phase.
It involves a sample being vaporized and injected onto the head of the
chromatographic column.
The sample is transported through the column by the flow of inert,
gaseous mobile phase.
The column itself contains a liquid stationary phase which is adsorbed
onto the surface of an inert solid.
Two major types
• Gas-solid chromatography (stationary phase: solid)
• Gas-liquid chromatography (stationary phase: immobilized liquid)

4. Components of Gas
chromatography
Carrier gas - He (common), N2, H2, Argon
Sample injection port - micro syringe
Columns -2-50 m coiled stainless steel/glass/Teflon
Detectors
-Flame ionization (FID)
-Thermal conductivity (TCD)
-Electron capture (ECD)
-Nitrogen-phosphorus
-Flame photometric (FPD)
-Photo-ionization (PID)

5. Gas Chromatography - Columns
Packed columns;
Packed columns contain a finely divided, inert, solid support material
coated with liquid stationary phase.
1.5 - 10m in length and internal diameter of 2 - 4mm.
Capillary columns;
WALL COATED OPEN TUBULAR (WCOT);
capillary tube whose walls are coated with liquid stationary phase.
SUPPORT COATED OPEN TUBULAR (SCOT).

8. Detectors
Electron capture detector(ECD)
Electrons are supplied from a 63-Ni foil
lining the detector cell. A current is
generated in the cell.
Electronegative compounds capture
electrons resulting in a reduction in the
current. The amount of current loss is
indirectly measured and a signal is
generated.

9. 3. Nitrogen Phosphors Detector
(NPD)
Compounds are burned in a
plasma surrounding a rubidium
bead supplied with hydrogen and
air.
Nitrogen and phosphorous
containing compounds produce
ions that are attracted to the
collector.
• The number of ions hitting the
collector is measured and a signal
is generated.

10. 2. Flame ionization Detector (FID)
Compounds are burned in a hydrogen-air flame.
• Carbon containing compounds produce ions that are attracted to the
collector.
• The No. of ions hitting the collector is measured and a signal is
generated

11. Continue…
3. Nitrogen Phosphors Detector (NPD)
Compounds are burned in a plasma surrounding a rubidium bead supplied with
hydrogen and air.
Nitrogen and phosphorous containing compounds produce ions that are
attracted to the collector.
• The number of ions hitting the collector is measured and a signal is
generated.
4. Thermal Conductivity Detector (TCD)
A detector cell contains a heated filament with an applied current.
As carrier gas containing solutes passes through the cell, a change in the
filament current occurs.
• The current change is compared against the current in a reference cell.
• The difference is measured and a signal is generated.

12. 5. Flame Photometric Detector (FPD)
Compounds are burned in a hydrogen-air flame. Sulfur and phosphorous
containing compounds produce light emitting species (sulfur at 394 nm and
phosphorous at 526 nm).
A monochromatic filter allows only one of the wavelengths to pass. A
photomultiplier tube is used to measure the amount of light and a signal is
generated.
A different filter is required for each detection mode.
6. Photo ionization Detector (PID)
Compounds eluting into a cell are bombarded with high energy photons
emitted from a lamp.
Compounds with ionization potentials below the photon energy are ionized.
The resulting ions are attracted to an electrode, measured, and a signal is
generated.

13. Applications of Gas
Chromatography
Qualitative Analysis – by comparing the retention time or volume of the
sample to the standard
Quantitative Analysis- area under a single component elution peak is
proportional to the quantity of the detected component/response factor of the
detectors.
Miscellaneous-analysis of foods like carbohydrates, proteins, lipids, vitamins,
steroids, drug and pesticides residues, trace elements
Pollutants like formaldehyde, carbon monoxide, benzen, DDT etc
Dairy product analysis- rancidity
Separation and identification of volatile materials, plastics, natural and
synthetic polymers, paints, and microbiological samples
Inorganic compound analysis