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GLC: Gas-Liquid Chromatography . Renee Y. Becker CHM 2210-2211 Valencia Community College. GLC. Used to separate and analyze compounds Sample has to be able to be vaporized without decomposition Based on boiling point/vapor pressure Typical uses Testing purity
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GLC: Gas-Liquid Chromatography Renee Y. Becker CHM 2210-2211 Valencia Community College
GLC • Used to separate and analyze compounds • Sample has to be able to be vaporized without decomposition • Based on boiling point/vapor pressure • Typical uses • Testing purity • Separation of components of mixture • Relative amounts can be determined • Prepare pure compounds from a mixture
Similar to fractional distillation • Both separate the components of a mixture primarily based on BP and VP • Fractional distillation used for large scale • GC used on a microscale
Phases • Mobile phase • Inert carrier gas (usually He or N) • Stationary phase • Layer of liquid or polymer on inert solid support • Inside a glass or metal tubing (COLUMN)
Compound is injected with syringe into sample injector • Compound is carried by carrier gas and vaporized • Vaporized sample interacts with walls of column • Some samples interact more some less • Due to interaction samples elute at different times • Retention times • Comparison of retentions times is what is useful • A detector monitors the outlet stream from the column
Retention time can be used to identify if method conditions are constant • The area under the curve is directly proportional to the amount of compound
Temp is controlled at injection port, column and detector Column can be made specific for your needs Longer the column the better the separation
Variables We Can Change • Inlet Temp • Detector Temp • Column Temp • Type carrier gas • Carrier gas flow rate • Stationary phase • Diameter and length of column • Sample size
Detector Response Retention Time (sec) Mixture of 1-butanol, butanal, and 2-butanone