GAS CHROMATOGRAPHY

1. GAS CHROMATPGRAPHY

2. TOPICS
Introduction to Gas Chromatography
Principle
Instrumentation
Injector
Column oven
Types of column
Types of Detectors
GC-MS
Applications

3. Introduction
Mobile Phase : Gas , Helium , Hydrogen , Nitrogen and Air
Stationary Phase : liquid , Solid
Principle :
 The sample solution injected and vaporized into the instrument,
where enters a gas stream which transports the sample into a
separation tube known as the "column”.
 The various components are separated inside the column on the basis
of their boiling points and affinity with stationary phase

4. Procedure:

7. Instrumentation

8. Injector
Technique : Manual / automatic with injector / syringe
Injection System
1. Packed Column Injections : Whole sample is introduced at once,
0.1 -10µL, 150°C-250°C
2. Split/ split-less injection : Sample is injected into the headspace
• Split mode : ratio of 1:10 to 1:100
• Split less mode : whole content is injected directly into the sample
septum
3. Cool on Column Injection :
Sample is injected on the head of column , no discrimination or
degradation , no back flash

9. Column Oven
Fan for uniform distribution of air
Isothermal
Temperature ramping at a constant rate
Programming rates
Temperature ramping , temperature is increased gradually to elute all the
components of the mixture with respect to their volatility in reasonable
time

10. Column
Packed columns
Diatomaceous earth : calcium silicate
Silanized to remove the polar silanol group (Si-OH)
Further mechanically coated with variety of liquid stationary phases
Nitrogen used as carrier gas
Low resolution as compared to capillary column
Adequate for routine quality control testing
 2-5mm in diameter , 1.5-10 m in length

11. Column
Capillary Column
Made up of fused silica
Coated with polyamide film or aluminum
Internal diameter 0.15-0.5mm
Liquid Stationary phase thickness :0.1-0.5µm
Most common coating –organosilicon polymers
SCOT : temperature resistant -375°C
WCOT : mostly carbomer -240°C
High resolution
Widely applicable

12. Detector
Flame ionization Detector
Principle : compounds are burnt and ionized .
That increase in the flow of current between jet and collector
Detect Hydrocarbons
Insensitive to compounds containing Carbon- oxygen, nitrogen or
chlorine bond
Sensitivity : 100pg-10µg

13. Detector
Electron Capture Detector :
Principle : Compounds having high affinity for electrons enter the
detector
Capture the electrons produced by radioactive source and reduce the
overall current
Highly sensitive for halogen containing compounds
 Sensitivity : 50fg-1pg
Environmental monitoring of chloroflorocarbons

14. Detector
Nitrogen Phosphorous Detector
Nitrogen – Phosphorous containing compounds react with heated bead
of alkali metal
And produce Cyano compounds and various phosphorous cation
That increase the flow of current
Sensitivity : pg-ng
Used for the detection of drugs in bodily fluids

15. Detector
Thermal Conductivity Detector
 Universal Detector
 Non destructive
 Used to measure water in
peptides like gonadotrophin,
menotropin
Radiochemical Detector
 Used to detect
radioactive isotopes
 Widely used in
labelling studies
FT-IR Detector
Used in structure elucidation
Qualitative detector
sensitivity : 10ng

17. Parameters Governing Capillary GC performance
Carrier Gas type & Flow
• Hydrogen/ Helium : 30-50cm/s- high efficiency
• Nitrogen 10-20cm/s- low efficiency
Column Temperature
• As temperature increases – resolution decreases- less interaction with
stationary phase
Column length : directly related to resolution
Film thickness : related to enhanced column efficiency
Internal Diameter : inversely proportional to column efficiency

18. GC-MS
Hyphenated technique
GC coupled with MS as Detector

19. Ionization
1. Electron Impact Ionization
This is original type of ionization employed in the Mass Spectroscopy. In this
type of ionization high energy electron strike with analyte molecules and
cause extensive fragmentation and ionization of analyte.

20. Chemical Ionization:
Positive Ion Chemical ionization (PICI)
A reagent gas is introduced into the ion source, gas lose electrons to form positive
adduct ions. These positive ions react with the hydrogen of analyte and convert
the analyte into positive ion.

21. Chemical Ionization:
Negative Ion Chemical Ionization (NICI)
• In this type of ionization low energy electrons are introduced in ionization
chamber these electrons are captured by analyte molecules to produce negative ions.

22. Comparison of EI MS Vs CI MS

24. Quadrupole Mass analyzer
 Four parallel conducting rods of hyperbolic cross section
Rods are connected to radio frequency and DC
Potential of both is set to get the desirable ion (stable trajectory )
New innovation is triple Quard instruments
High sensitivity and selectivity
Reduce background noise

25. Time of Flight Mass Analyzer
Principle : the velocities of two ions are created by uniform electric
field applied to all the ions at same time, causing them to accelerate
down a flight tube.
Lighter ions travel faster and strike the detector first so that the m/z
ratio of ions is detected.

26. Application
Pharmaceutical Analysis :
• Quantitative analysis of different drugs like inhalation anesthetics ,
valproic acid.
• Quantification of Volatile Solvents like methanol, ethanol
• Determination of Residual Solvents
• Determination of Degradation Residues (glutaraldehyde in polymeric
films)
Bioanalysis :
• Determination of drugs and their metabolites in blood

27. Application
Forensic Science :
• Used to identify the cause of death by analyzing Biological samples
Environmental Science :
• Pollutants in air
Food Sciences:
• Pesticides , contaminations , insecticides
Research & Development :
• Qualitative analysis of herbal extracts
• Qualitative analysis of secondary metabolites
In space Sciences :
• To analyze the composition of planets and meteoroids and their
atmosphere,