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GAS CHROMATOGRAPHY Partition of molecules between gas (mobile phase ) and liquid which is quoted on to a solid support is used as stationary phase The mixture of components to be separated is converted to vapour and mixed with gaseous mobile phase

Instrumentation of Gas Chromatography:

Instrumentation of Gas Chromatography

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Detectors: Flame ionization detectors Thermal conductivity detectors Electron capture detectors Nitrogen phosphorus detectors

Flame Ionization Detector:

Flame Ionization Detector These ionization detectors are based on the electrical conductivity of the carrier gas The carrier gas like nitrogen if in pure state does not induce current since there is no ionization, when hydrogen is mixed with nitrogen or organ and passed in between platinum cathode and silver guage anode will produce a current that can be amplified and recorded

Flame Ionization Detector:

Flame Ionization Detector Advantages

Flame ionization detector:

Flame ionization detector

Thermal Conductivity Detector:

Thermal Conductivity Detector

Thermal Conductivity Detector:

Thermal Conductivity Detector Measures the changes of the thermal conductivity due to sample ( u g). Sample can be recorded. Operates on the principal of the Thermal balance of the heated filament. Electrical power is converted to heat in a filament and the temperature will be increased until heat power loss form the filament equals the electrical power input. The filament may loose the heat by radiation to cooler surface by conduction to the molecules which contact with the filament

Electronic Capture Detector:

Electronic Capture Detector

Electronic Capture Detector:

Electronic Capture Detector

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It contains two electrodes with column effluent passing between them. One of the electrode is treated with radio active isotope which emit electrons. These electrons are collected by the anode when a potential of 20 Volts is applied. The difference of current is amplified and recorded as output. The carrier can be Hydrogen, Organ, Nitrogen etc

Electron Capture Detector:

Electron Capture Detector Advantages It is highly sensitive even nano gram quantities can be detected Halogenated components, several pesticides etc can be detected using this type of connector Disadvantages It can be used only for compounds with electron affinity

Nitrogen Phosphorus Detector:

Nitrogen Phosphorus Detector It is also called as thermionic detector. It is very sensitive and specific detector with design based on the FID. Physically the sensor appears to be very similar to the FID but infact operates on an entirely different

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It differs from that the of the FID by a rubidium or ceisum chloride bead contained inside a heater coil situated close to the hydrogen jet. The bead is situated above the jet and heated by the coil, over which nitrogen carrier gas mixed with Hydrogen passes When a solute that contains nitrogen or phosphorus is eluted, the partially combusted nitrogen and Phosphorous materials are absorbed on the surface of the bead . The absorbed material reduces the work function the surface and thus electron emission is increased and the current collected at the anode rises

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Adavntages It is highly sensitive than the Electron Capture Detector Disadvantages Its Performance deteriorates with the time

Applications of Gas Chromatography:

Applications of Gas Chromatography Qualitative Analysis Checking the purity of the Compound Presence of Impurities Quantitative Analysis Multicomponent Analysis and determination of mixture of drugs

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