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Gas Chromatography

Gas Chromatography (GC) - 


The chromatographic technique where the mobile phase is a gas.
GC is currently one of the most popular methods for separating and analyzing compounds.  This is due to its high resolution, low limits of detection, speed, accuracy and reproducibility.
GC can be applied to the separation of any compound that is either naturally volatile (i.e., readily goes into the gas phase) or can be converted to a volatile derivative.  This makes GC useful in the separation of a number of small organic and inorganic compounds.
Equipment:
A simple GC system consists of:
1. Gas source (with pressure and flow regulators)
2. Injector or sample application system
3. Chromatographic column (with oven for temperature control)
4. Detector & computer or recorder



Carrier gas: He (common), N2, H2
Pinlet 10-50 psig
Flow = 25-150 mL/min packed column
Flow = 1-25 mL/min open tubular column
Column: 2-50 m coiled stainless steel/glass/Teflon
Oven: 0-400 °C ~ average boiling point of sample
Accurate to <1 °C
Detectors: FID, TCD, ECD, (MS)
Mobile Phase: GC separates solutes based on their different interactions with the mobile and stationary phases. 
Carrier gas – Main purpose of the gas in GC is to move the solutes along the column, mobile phase is often referred to as carrier gas.
Common carrier gas: include He, Ar, H2, N2. 

CLICK HERE👉GC Practical Experiment

Advantages Gas-solid chromatography (GSC):
- long column lifetimes
- ability to retain and separate some compounds not easily resolved by other GC methods, viz. 
geometrical isomers, permanent gases etc.

Disadvantage: 
- very strong retention of low volatility or polar solutes
- catalytic changes that can occur on GSC supports
- GSC supports have a range of chemical and physical environments, viz. different strength retention sites ‚ non-symmetrical peaks‚ variable retention times

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