Gas Chromatography Oleh : Rohayati, S.Pd SMK Negeri 13 Bandung

Separation procedure of dissolved substance by a dynamic differential migration process in chromatographic system Chromatographic system consists mobile phase and stationary phase‏ Usage -Purification of chemical substance -Qualitative and quantitative analysis of component in mixture According to the mobile phasei: -Liquid chromatography (mobile phase is liquid) - Gas chromatography (mobile phase is gas)‏ CHROMATOGRAPHY

Gas Chromatography

 Gas chromatography is used to analyse a mixture consisting many components. One or more of the components should have vapour pressure.  The vapour pressure or volatile property causes the component vaporized /separated at high temperature and move with de gas mobile phase (carrier gas) in the column.

GC basic principle Separation of a chemical substance from the mixture based on the boiling point difference

GC DIAGRAM

Factors influence the GC analysis 1. Carrier Gas Common carrier gas are N 2, He, Ar, H 2 and CO 2. They should be inert, high volume and pressure. Used in pure and dry condition 2. Detector Common detector are FID (Flame Ionization Detector) and TCD (Thermal Conductivity Detector) ‏. FID has a high sensitivity on many substance.

Factors influence the GC analysis 3. Column There are 2 types of column : a)Crated column 2 m length and 1-3 mm diameter, made of diatomae soil b)Capillary column m length and 0,02-0,2 mm diameter, made of refractory glass.  Filling material of column consist of phenyl dimethylpolysyloxane, polyethylene glycol or polymer like DB-Wax  Column consist of liquid mobile phase adsorbed in to inert solid layer.

Factors influence the GC analysis 4. Stationary phase Commonly the stationary phase in GC is a liquid coats buffer material. This buffer material is stable and isn’t vaporized at the separation condition. Example: phenyl silicon, poly ethylene glycol, alkyl- phtalate 5. Temperature Temperature for GC analysis is about – C

Factors influence the GC analysis 6. Retention Time Retention time : time needed by the substance to stuck in the column. Retention time measured start from the time sample injected until the maximum peak reached by the substance. Component of mixture sample identified based on the retention time.  Retention time influenced by:  (a) the substance’s boiling point  (b) solubility in liquid phase  (c) column temperature  Separation times are various, start from a few seconds to several hours for a mixture with component

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