Gas Chromatography or Gas Liquid Chromatography is a technique applied for separation, identification and quantification of components of a mixture of organic compounds by selective partitioning between the stationary phase and mobile phase inside a column followed by sequential elution of separated components. The technique is suitable for separation of compounds having following characteristics :
- High volatility
- Thermal stability
- Low molecular weights
Why not start with a short video?
In case you are new to Gas Chromatography simply spend about 2 to 3 min on the introductory video on what constitutes a GC system.
Glossary of GC terms
The glossary will help you familiarize with the terminology in case you are not already familiar with the technique
|Stationary Phase||A solid phase which absorbs the sample components and later releases them in a sequential manner|
|Mobile Phase||A stream of carrier gas used for transporting sample from injection port to the column to the detector|
|Column Oven||A compartment inside which the column is mounted. It maintains a constant temperature or a varying temperature in response to a set temperature programme.|
|Detector||A device which gives the signal response in terms of area counts under a peak|
|Column Efficiency||Expressed in terms of HETP expresses the resolving power of the GC column|
|Packed Column||A steel or glass tube wound as a coil which holds the stationary phase|
|Capillary Column||A fused silica capillary column that holds the liquid absorbent on the tube on its walls|
|Autosampler||A device capable of holding several samples, standard vials and automatically injects a predetermined sample volume into the gas chromatograph|
|Injector||Manual or automated device for precise sample volume introduction|
|FID||Flame Ionisation detector which responds to most organic compounds|
|TCD||Thermal Conductivity detector. Universal and nondestructive detector|
|ECD||Electron Capture detector. For compounds containing electronegative elements such as halogens|
|NPD||Nitrogen Phosphorus detector. Specific for compounds containing nitrogen or phosphorus|
|FPD||Flame photometric detector.Specific for sulphur and phosphorus containing compounds|
|MSD||Mass Selective detector|
|GC – MS||Hyphenated technique using a combination of GC and Maas spectrometer|
|Fronting||Distortion of peak where the peak front appears distorted|
|Peak Tailing||Distortion of peak where the tailing end of the peak appears distorted|
|Heart Cutting||A method which employs two columns of different selectivity. A selected portion of effluent from first column is passed to the second column|
|Temperature Programming||Changing temperature of column oven in a predetermined manner using a program|
|Retention Time||Time between injection and the maximum of the peak response|
|Syringe||Hand held device capable of injecting selected volume into the chromatograph|
|HETP||Height Equivalent to a theoretical plate. It is a measure of column efficiency and is expressed as an numerical value without units
H = L/N
The larger the number of theoretical plates the lower is HETP and better is the column efficiency
|Septa||Rubber or silicone discs which are used inside the injector for introduction of sample into the chromatographic system. The syringe needle penetrates this disc at the time of sample injection|
|Ferrule||A plug made from graphite or grass for holding the column gas tight into the oven|
|Gas Regulator||Device comprising of a controller to record and control pressure in the gas line and also monitor the pressure inside the cylinder|
|Gas Filter||A wall mounted assembly comprising of packed cartridges capable of removing moisture, hydrocarbons, oxygen and other impurities from the inlet gases|
|PLOT||Porous Layer Open Tubular column where an absorbent is bonded to the inner surface of the column. Useful for analysis of permanent gases or high volatility liquids.|
|SCOT||Support Coated Open Tubular column. A liquid stationary phase is supported on a solid support which is coated to the inner surface of the capillary common.|
|Split Injection||Injection mode where a portion of the vaporized sample is vented out and only a small portion enters the column head. This is used for highly concentrated samples|
|Splitless Injection||Sample injection where purge valve is closed and the entire sample enters the column. The purge valve is then opened to flush the injector|
|WCOT||Wall Coated Open Tubular column. The stationary phase is bonded to the inside wall of the capillary column|
|On-Column Injection||The syringe needle enters and delivers the sample onto the top of the column head|
|Leak test||A process to establish that all connections are leak free|
|Pre-vent||A design of sample inlet that splits the injected sample and vents out a portion. The residual portion is only directed to the column. This is suitable when samples are highly concentrated|
Refresh your basic skills by registering for the free e-course on GC which will provide you an introduction to the technique and even prepare you for an interview if you are applying for a job in a laboratory equipped with a GC system.
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Want to read all the AAS free course modules right now? Here are all links to all the modules for you!
- Module 1 : Introduction to Gas Chromatography Course and its Objectives
- Module 2 : Evolution of Gas Chromatography
- Module 3 : Introduction to Gas Chromatography and Its Parts
- Module 4 : Role of Gases in Gas Chromatography
- Module 5 : Types of Gas Chromatography Injectors
- Module 6 : Types of Gas Chromatography Columns
- Module 7 : Types of Stationary Phases
- Module 8 : Types of Gas Chromatography Detectors
- Module 9 : Gas Chromatography Applications
- Module 10 : Top 10 Interview Questions on Gas Chromatography
Library of Published Articles
See the list of published articles related to GC specially prepared for upgradation of your laboratory skills and bring about exposure to new concepts and developments. You willl find that the list is ever growing with inclusion of new published articles as and when they are published.
- Recommendations for switching from Gas cylinders to Laboratory gas generators
- What is Multi- dimensional GC?
- How to prevent damage to Capillary GC columns
- Benefits of Automated replacement of GC liners
- Types of Liners and their Selection
- Sample Injection Techniques for Capillary Column Gas Chromatography
- Minimization of influence of random fluctuations in operating conditions in GC analysis
- Why very long capillary GC columns are not preferred?
- Sample Injection Practices in Gas Chromatography
- How Gas Chromatography can contribute to your career prospects?
- How detector characteristics influence Gas Chromatographic response?
- Peak Height or Peak Area? – Which is the right choice for quantitative chromatographic calculations
- Importance of Colour Coding for Gas Cylinders and Lines in Laboratories
- 10 Similarities between High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC)
- How are Gas Chromatography (GC) and High Performance Liquid Chromatography(HPLC) different?
- Advantages of Gas Chromatography (GC) over Thin Layer Chromatography (TLC)
- How is Gas Solid Chromatography different from Gas Liquid Chromatography?
- Useful Tips for Extending the useful life of a GC Capillary Column
- Now GC Method Optimization and Development on your fingertips!
- Temperature Control of the Gas Chromatographic Column
- Factors Governing the Resolution of peaks in the Gas Chromatogram
- How to save your time by preventing Gas leaks before running the Gas Chromatograph?
- Importance of Gas leak detection before starting Gas Chromatographic Analysis
- Gas Chromatography in Petroleum Refining Industry
- Chromatographic Techniques for Analysis of Flavours in Foods
- Useful tips on Handling and Care of GC Capillary Columns
- Which type of gas regulator is suitable for Gas Chromatography?
- Why Capillary Columns are preferred over Packed Columns in Gas Chromatography
- Hydrogen, Helium or Nitrogen – Which is most suitable as a Carrier Gas?
- How to handle Gas Chromatographic Gases Safely?
- How Derivatisation is useful in GC analysis?
- How to Choose a Gas Chromatographic Detector for my Analysis?
- Why is Leak checking necessary before starting Gas Chromatography analysis?
- GC Free E-Course : Introduction to Gas Chromatography
- Benefits of Split /Splitless Injection in Capillary Gas Chromatography
- Why is Conditioning necessary for GC Columns?
- Four Key Considerations for choice of Capillary Gas Chromatographic Columns
- Gas Purification Requirements in Gas Chromatography
- Factors Governing Choice of Sample Injection Syringe in Gas Chromatography
- Why are HPLC columns shorter than GC columns?
- Know your GC Chromatogram
- The results are in – Gas Chromatography is the next free e-course!
- Gas Chromatography