Introduction to gas Chromatography ,Principle of gas chromatography Instrumentation of gas Chromatography Type of detectors of gas chromatography Advantages of gas chromatography Disadvantages of gas chromatography Applications of gas chromatography

1. GAS CHROMATOGRAPHY
By
R.PRIYANKA
(Regd.No:616233704010)
M. Pharmacy 2nd year
Pharmaceutical analysis and quality assurance
SrinivasaRao college of pharmacy, P.M.palem, Visakhapatnam

2. Contents
 Introduction
 Principle
 Instrumentation
 Advantages
 Disadvantages
 Applications

3. INTRODUCTION
 The chromatographic technique requires that a solute undergoes distribution
between two phases one of them is fixed (stationary phase) and other one is
moving (mobile phase).
 Gas chromatography is a analytical technique that helps to
separate and analyze a mixture of organic vaporizable or
volatile compounds without their decomposition.

4. PRINCIPLE
 The organic compounds are separated due to difference in their partitioning
behavior between the mobile gas phase and the stationary phase in the
column.
 In this the mobile phase is a gas and liquid which is coated on the solid
support is used as stationary phase.
 The mixture of components to be separated is converted into vapour and
mixed with gaseous mobile phase. the component which is more soluble in
the stationary phase travels slower and elute later , which is less soluble in
the sp travels faster &elute out first.

5. INSTRUMENTATION
 The gas chromatography consists of following components.
 1.Gas supplying units –carrier gas ,flow regulators & flow meters ,pressure
regulators.
 2.Sampling units
 3.Column
 4.Temperature programmer
 5.Detectors
 6.Recorders

6. Instrumentation
 Carrier gas (mobile phase) supply:
N2, He, H2
 Flow control
 Injector
 Column
 Detectors
 Computer/recorder

7. Carrier gas supply
 Function: to provide carrier gas to chromatographic column
 Carrier gas carries sample to column.
 Tank, needle valve, flow meter, pressure gauge
 Type of carrier gases → depends on column & detector
 Capillary columns: H2, He.
 Packed columns: N2
 TCD, ECD: N2
 FID: He

8. Carrier gas supply
 Ideal carrier gases: pure & dry
 Impure & moisture: harm the column, ↓performance of
 detectors, adversely affect quantification of trace analysis.
 Measures:
 Tubing (gas source → GC)→uncontaminated.
 Molecular sieve beds → ↓moisture, hydrocarbon, oxygen content.

9. Requirements of a carrier gas
 Inertness
 Suitable for the detector
 High purity
 Easily available
 Cheap
 Should not cause the risk of fire
 Should give best column performance

10. Flow control
 Regulates the carrier gas flow in GC
 Constant flow of carrier gas → column efficiency
 & reproducible elution time.
 Magnitude of carrier gas flow rate depends →
 type of column
 Packed column – 10-60ml/min
 Capillary column – 1-2ml/min

11. Injection port
 The injection port consists of a septum through
which a syringe needle is inserted to inject the
sample.
 The sample is injected into a stream of inert gas
usually at an elevated temperature by a micro syringe.
 The vaporized sample is carried into acolumn packed with the stationary
phase.
 To ensure rapid & complete solute volatilization temp of injector → 30-50
degree
celsius>column temp

12. Injection techniques
Split
Splitless

13. Columns & its types
Packed column Capillary( open tubular column)
 1 - 4mm ID; 1 - 5 m length
 Glass/stainless steel coil
 Packed solid particles either
porous/non-porous coated
with thin (1 μm) film of
liquid
 0.1 - 0.5 mm I.D. (ID); 10 -
150 m length
 Thin fused-silica.
 Inner wall coated with thin (0.1-
5 μm) film of liquid (stationary
phase)

14. Capillary(open tubular) column
3 layers
 1. Polyamide coating – strong water proof barrier
 2. Thin fused-silica- minimize chemical reactivity, uniform surface for
stationary phase
 Stationary phase

15. Stationary phase
 Polymer – inner surface of fused silica layer
 Thickness, uniformity, chemical nature → influences the
 separation of components in sample.
 Mc stationary phase silicon polymer used → poly siloxane

16. Detection Systems
 The detector is the device located at the end of the
column which provides a quantitative measurement of
the components of the mixture as they elute in
combination with the carrier gas.

17. Types of Detectors in GC
To measure the separated analytes as they elute from the
column.
 Universal unit → detect most analytes
 Thermal conductance detector (TCD)
 Mass spectrometer (MS)Selective detectors → detect
specific substances
 Flame Ionization Detector (FID) → hydrocarbon
 Electron capture detector (ECD) → electronegative groups

18. Flame Ionization Detector (FID)
 Compounds that produce ions when burned in an H2-air
flame → organic cation → releases electron → detected by collector electrode
→ generation of current.
 Mc detector used for clinical analysis
 Magnitude of current α mass of carbon material delivered to detector →
used for detection &
quantification of eluting solutes.
 Advantages → simple, reliable, sensitive, linearity.
 Disadvantage – destroy all the sample.
 Uses → detects hydrocarbon including fatty acids.

19. Types of Gas Chromatography
Detectors
Non-selective
• Responds to all compounds present in carrier
gas stream except the carrier gas itself
Selective
 Responds to range of compounds with a
common physical or chemical characteristic
Specific
• Responds to a single specific compound only
 Detectors can also be grouped into concentration or
mass flow detectors

20. Thermal conductance detector(tcd)
 Universal detector → most of the analytes
 Difference in thermal conductivity between the carrier gas and sample gas
causes a voltage output

21. Electron capture detector (ECD)
 Selective type of detector – electronegative groups- halogens (F, Cl , Br,
I), peroxides , quinones, & nitro groups
 Principle – reaction b/n electronegative groups & thermal
electrons(radioactive source) →Thermal electrons captured on the electrode
→
If electron capturing compound is present the number of thermal electrons on
the electrode (standing current) is decreased.
ECD Advantages
 Highly sensitive
 Easy to use
 reliable
 Selective

22. computer
 Regulates mobile phase composition, flow rate, column detector temp
 Electronic signals generated by detectors are recorded
in the
form of chromato graghic peak at varied function of time
 Area, height, retention time ,base width of chromato
graghic
peak is measured to compute analyte concentration of
each peak.

23. ADVANTAGES OF G.C
 Very high resolution power, complex mixtures
can be resolved into its components by this
method.
 Very high sensitivity with TCD, detect down to
100 ppm
 It is a micro method, small sample size is
required
 Fast analysis is possible, gas as moving phaserapid
equilibrium

24. •Limited to volatile sample.
•Not suitable for thermally labile samples.
•Samples be soluble and don’t react with the column.
• During injection of the gaseous sample proper
attention is required.

25. Applications of GC
 Separation & identification of lipids, carbohydrates & proteins.
• Separation & identification of amino acids in urine by GC-MS for
 diagnostic purpose.
 Measurement of drugs & other metabolites in biological fluids.
 Used for toxicological analysis of biological fluid by using ECD.
 Analysis of pesticides in soil, water, food.
 Forensic analysis of blood and urine alcohol levels by using PEG-SP IN GC.