Gas Chromatography Operation

Chromatography

• Chromatography is a laboratory method used to separate components in a mixture according to their interactions with a stationary phase and a mobile phase.
• The mixture's constituent parts separate from one another to form unique bands or spots as they move through the stationary phase at varying rates.

Components of Chromatography

• Stationary Phase: a liquid layer adsorbed on a solid substrate or a solid phase, where molecules interact differently according to their properties.
• Mobile Phase: a gaseous or liquid component that propels the mixture through the stationary phase.
• Separated Molecules: the mixture's components interact with the phases, causing them to separate according to their affinities.

Types of Chromatography

• Paper Chromatography: uses a liquid solvent as the mobile phase and a piece of paper as the stationary phase.
• Thin-Layer Chromatography (TLC): uses a thin layer of an adsorbent substance, such as alumina or silica gel, as the stationary phase, and a solvent as the mobile phase.
• Column Chromatography: uses a stationary phase packed in a column, and a mobile phase that carries the sample mixture through the column.
• Gas Chromatography (GC): uses a mobile gas phase and a stationary phase inside a column to separate, identify, and quantify components of a mixture of organic compounds.

Paper Chromatography

• Spots the sample onto the paper using a capillary tube.
• Develops the chromatogram by submerging the paper in the mobile phase, which moves up the paper by capillary action.
• Dries and detects the separated components by spraying with a detecting solution.

Types of Paper Chromatography

• Ascending Chromatography: the mobile phase travels up the paper.
• Descending Chromatography: the mobile phase travels down the paper.
• Ascending-Descending Chromatography: the mobile phase first travels up and then down the paper.
• Two-Dimensional Chromatography: the paper is developed in two perpendicular directions using different solvents.
• Radial or Circular Chromatography: the paper is circular, and the components separate into concentric circular zones.

Applications of Paper Chromatography

• Separation and identification of amino acids, organic acids, alkaloids, polysaccharides, proteins, and pigments.
• Assessment of pollutants, drugs, and food colors.
• Monitoring chemical processes and compound purification.
• Forensic analysis of drugs and their metabolites.
• Investigating ripening and fermentation processes.

Thin-Layer Chromatography (TLC)

• Uses a thin layer of an adsorbent substance, such as alumina or silica gel, as the stationary phase.
• Separation results from the varied affinities of the analytes for the stationary phase as they ascend the TLC plate at different speeds.
• Applications include pharmaceutical preparations, clinical analysis, forensic studies, industrial chemistry, food chemistry, environmental toxicity, water analysis, pesticide analysis, cosmetics, plant materials, and herbal analysis.

Column Chromatography

• Basic principle: differential adsorption of compounds in a mixture onto a stationary phase as they move through a column at different rates due to differences in their affinity for the stationary phase.
• Retardation factor (Rf): the ratio of the distance traveled by the solute to the distance traveled by the solvent.
• Components of Column Chromatography: stationary phase, mobile phase, column, and sample mixture.

Applications of Column Chromatography

• Isolation of active constituents.
• Separation of compound mixtures.
• Removal of impurities or purification of compounds.
• Isolation of metabolites from biological fluids.
• Estimation of drugs in formulations or crude extracts.

Gas Chromatography (GC)

• Analytical technique used for separating, identifying, and quantifying components of a mixture of organic compounds.
• Key components: mobile phase (carrier gas), sample injector, column, detector, and data system.
• Operation: injecting the sample into the heated injector, where it vaporizes and enters the carrier gas stream, separating inside the column based on interactions with the stationary phase, and measuring the quantity of each component as it exits the column.

Applications of Gas Chromatography (GC)

• Environmental monitoring for volatile organic compounds, pesticides, and industrial chemicals.
• Pharmaceutical research and manufacturing.
• Food and flavor analysis.
• Petrochemical and fuel analysis.
• Forensic toxicology.
• Metabolomics and lipidomics research.