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Gas chromatography - Coggle Diagram
Gas chromatography
Application
Quantification of drug lacks chromophores
Characterization of raw material used in synthesis of drug molecules
Limit test for solvent residues
Characterization of volatile oil ,fatty acid , proprietary cough mix
Characterization of non formulated drugs
Quantitative analysis
Limitations
Small quantity of sample can be injected
During injection of sample proper attention is required
Sample requires derivatization
Aqueous solution and salts cannot be injected
Only thermally stable and volatile compounds can be analysed
Detectors
Flame ionisation detector
Detects carbon and hydrogen containing compound
Advantages
In combination with capillary GC it can detect as low as 100pg-10 ng
High sensitivity
Disadvantages
Destruction of sample
Insensitive to carbon atom attached to oxygen ,nitrogen or chloride
Thermal conductivity detector
Based on two concepts
Hotwire
Thermistor
Advantages
Simplicity
Larger linear dynamic range
Response to organic and inorganic species
Non destructive
Electron capture detectors
Selectively detects halogens
Application
Determination of chlorinated insecticide ,and analysis of drugs in body fluid
Carrier gas( mobile phase )
Chemically inert ,purified , compatible with detectors
Nitrogen ,helium, argon ,carbon dioxide
Column
Packed column
Diatomaceous earth coated with liquid Stationary phase
Capillary column (open tubular column)
Support coated open tubular column
The inner wall of capillary is lined with thin layer of support materials such as diatomaceous earth ,onto which the stationary phase has been adsorbed
Porus layer open tu ular column
The inner surface of column Has an embedded layer that contains stationary phase
Wall coated open tubular column
Consist of capillary tube whose walls are coated with liquid stationary phase
Sample injector
Micro syringe
Two mode of injection
Split
Split less
Introduction
Seperation based on partition coefficient
Mobile phase :Gas
Inert gas is used
Stationary phase : liquid ,solid
Circular to control the pressure of gas
Sample injection
Sample is vapourised and injected onto the chromatographic column via heated injection port
Instrumentation