Graduate
  1. Physical Chemistry  1.1. Thermodynamics  1.1.1. Laws of Thermodynamics  1.1.2. Enthalpy and heat capacity  1.1.3. Entropy and free energy  1.1.4. Phase Equilibrium  1.1.5. Statistical thermodynamics  1.1.6. Thermodynamic cycle  1.1.7. Fugacity and activity  1.2. Quantum Chemistry  1.2.1. Principles of quantum mechanics  1.2.2. Schrödinger Equation  1.2.3. Particle in a box  1.2.4. Operators and eigenvalues  1.2.5. Atomic orbitals  1.2.6. Molecular orbital theory  1.2.7. Perturbation theory  1.2.8. Valence bond theory  1.2.9. Hybridization and chemical bonding  1.3. Chemical kinetics  1.3.1. Rate laws and reaction mechanisms  1.3.2. Collision theory  1.3.3. Transition state theory  1.3.4. Enzyme Kinetics  1.3.5. Chain Reactions and Polymerization  1.3.6. Photochemical reactions  1.4. Statistical mechanics  1.4.1. Partitioning functions  1.4.2. Molecular distribution functions  1.4.3. Boltzmann Distribution  1.4.4. Bose–Einstein and Fermi–Dirac statistics  1.5. Spectroscopy  1.5.1. Rotational Spectroscopy  1.5.2. Vibrational Spectroscopy  1.5.3. Electronic Spectroscopy  1.5.4. Nuclear magnetic resonance spectroscopy  1.5.5. Mass Spectrometry  1.5.6. Raman Spectroscopy  1.5.7. Electron paramagnetic resonance spectroscopy  1.6. Surface and colloidal chemistry  1.6.1. Absorption isotherm  1.6.2. Surface tension and wetting  1.6.3. Colloidal Stability  1.6.4. Catalysis  1.6.5. Emulsions and micelles  1.7. Electrochemistry  1.7.1. Nernst equation  1.7.2. Electrochemical cells  1.7.3. Conductivity and mobility  1.7.4. War  1.7.5. Fuel cells  1.7.6. Electrolysis
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic reactions  2.2. Spectroscopy and structural determination  2.2.1. UV-Vis Spectroscopy  2.2.2. IR Spectroscopy  2.2.3. NMR Spectroscopy  2.2.4. Mass Spectrometry  2.2.5. X-ray crystallography  2.3. Stereoscopic  2.3.1. Chirality and optical activity  2.3.2. Structural analysis  2.3.3. Geometrical isomerism  2.3.4. Dynamic Stereochemistry  2.4. Organometallic Chemistry  2.4.1. Organolithium and organomagnesium reagents  2.4.2. Palladium-catalyzed cross-coupling reactions  2.4.3. Transition Metal Complexes  2.4.4. Metal–carbon bond  2.5. Polymer chemistry  2.5.1. Polymerization mechanism  2.5.2. Polymer Characteristics  2.5.3. Biodegradable Polymer  2.5.4. Conducting polymer  2.5.5. Supramolecular polymers  2.6. Medicinal chemistry  2.6.1. Drug design and development  2.6.2. Pharmacokinetics and pharmacodynamics  2.6.3. Structure-activity relationships  2.6.4. Molecular docking and drug screening
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Crystal field theory  3.1.2. Ligand field theory  3.1.3. Spectrochemical Series  3.1.4. Chelation and stability  3.2. Organometallic Chemistry  3.2.1. Metal Carbonyls  3.2.2. Catalysis by organometallic complexes  3.2.3. Metallocenes  3.3. Bio-inorganic chemistry  3.3.1. Metalloproteins and enzymes  3.3.2. The role of metals in biological systems  3.3.3. Metal ion transport and storage  3.4. Solid state chemistry  3.4.1. Crystal Structures  3.4.2. Band theory of solids  3.4.3. Superconductors  3.4.4. Defects in the crystal  3.5. Lanthanides and Actinides  3.5.1. Electronic configuration in lanthanides and actinides  3.5.2. Coordination chemistry of the lanthanides  3.5.3. Magnetic Properties of Lanthanides
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.2. Spectroscopic Techniques  4.2.1. Atomic absorption spectroscopy  4.2.2. X-ray diffraction  4.2.3. Inductively coupled plasma spectroscopy  4.3. Electroanalytical methods  4.3.1. Potentiometry  4.3.2. Voltammetry  4.3.3. Colometry  4.4. Mass Spectrometry  4.4.1. Ionization Technique  4.4.2. Fragmentation Pattern  4.5. Chemometrics  4.5.1. Multidisciplinary analysis  4.5.2. Machine Learning in Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.1.1. Force fields and energy minimization  5.1.2. Monte Carlo simulation in molecular dynamics simulations  5.2. Quantum chemical methods  5.2.1. Hartree–Fock theory  5.2.2. Density functional theory  5.2.3. Semi-empirical methods  5.3. Computational drug design  5.3.1. Molecular Docking  5.3.2. QSAR Modeling  5.3.3. Virtual Screening
  6. Biochemistry  6.1. Enzyme Kinetics  6.1.1. Michaelis-Menten kinetics  6.1.2. Inhibition mechanism  6.2. Metabolism and Bioenergetics  6.2.1. Glycolysis  6.2.2. Citric acid cycle  6.2.3. Electron transport chain  6.3. molecular Biology  6.3.1. DNA replication and repair  6.3.2. Protein synthesis  6.3.3. Gene Regulation  6.4. Structural Biochemistry  6.4.1. Protein Folding  6.4.2. Membrane Biophysics
  7. Environmental Chemistry  7.1. Atmospheric Chemistry  7.1.1. Greenhouse gases  7.1.2. Ozone depletion  7.1.3. Air pollutants and smoke  7.2. Water Chemistry  7.2.1. pH and water hardness  7.2.2. Wastewater treatment  7.2.3. Aquatic Chemistry  7.3. Soil Chemistry  7.3.1. Heavy metal contamination  7.3.2. Soil pH and Buffering  7.3.3. Nutrient cycling  7.4. Toxicology and Chemical Safety  7.4.1. Toxicokinetics  7.4.2. Risk Assessment in Toxicology and Chemical Safety in Environmental Chemistry  7.4.3. Effects of pollutants on the environment

Graduate → Analytical chemistry → Chromatography ↓


Gas Chromatography


Gas chromatography (GC) is a valuable analytical tool widely used in chemistry to separate and analyze compounds that can be vaporized without decomposition. This technique allows scientists to identify and quantify various substances within a test sample. GC is particularly important in analytical chemistry for its accuracy and adaptability, which makes it applicable in a variety of fields such as forensic science, environmental analysis, medical research, and quality control in the food and beverage industry.

Principle of gas chromatography

Gas chromatography works on the principle of partition between two phases: a mobile phase and a stationary phase. The mobile phase is an inert gas known as the carrier gas that carries the vaporized sample through a column containing the stationary phase. The stationary phase is usually a liquid or polymer on an inert solid support inside the column. As the sample components travel along the column, they interact with the stationary phase to varying degrees, leading to different retention times and separations of these components.

Mobile phase

The mobile phase in gas chromatography is typically a carrier gas. Common carrier gases include helium, nitrogen, and hydrogen. The choice of carrier gas affects the resolution, speed, and sensitivity of the chromatography process. Helium is often preferred because of its inertness, although nitrogen and hydrogen are also commonly used because of their low cost.

Stationary phase

The stationary phase in a GC column is usually a liquid coated on a solid support material, or sometimes a solid itself. The composition of the stationary phase is important because it affects the solubility and interaction of various analytes with the stationary phase. The interaction between the analytes and the stationary phase determines the separation of the components.

Example of interaction: Analyte + Stationary Phase <-> Analyte-St. Phase Complex

Instrumentation of gas chromatography

A typical gas chromatography system consists of several major components: the injector, column, oven, detector, and recorder or data system.

  • Injector: The sample is introduced into the gas chromatograph through an injector. It is often vaporized here (if it is not already in gas form) and mixed with a carrier gas.
  • Column: The column, which contains the stationary phase, is where the separation of the components takes place.
  • Oven: The column is placed in an oven, which maintains the temperature needed for optimal separation. The temperature can be programmed to change during the run, called temperature programming, which enhances separation.
  • Detector: The detector identifies and quantifies the components separated from the column. Common detectors include flame ionization detectors (FID), thermal conductivity detectors (TCD), and mass spectrometers.
  • Data system: The output from the detector is recorded, usually producing a chromatogram, which shows the peaks corresponding to the different components of the mixture.

Operational procedure

The process of gas chromatography analysis typically involves several steps, ranging from sample preparation to interpretation of the results.

  1. Sample preparation: The sample must be in a form that can be injected into the gas chromatograph, usually a liquid or gas.
  2. Injection: The sample is injected into the injector port, where it is vaporized if necessary. The carrier gas then carries the vaporized sample into the column.
  3. Separation: As the sample passes through the column, it is separated into its component parts based on their interaction with the stationary phase.
  4. Detection: The separated components go to the detector, which provides a signal corresponding to the quantity of the component.
  5. Data analysis: A chromatogram is produced by analyzing the detector signal. The peaks in the chromatogram correspond to individual components, which can be identified and measured.

Applications of gas chromatography

Gas chromatography is essential in many applications due to its ability to separate and analyze complex mixtures. Some important areas include:

Forensic science

In forensic science, GC is used to analyze substances found at crime scenes, such as drugs, explosives, and other volatile compounds. For example, GC can help determine the level of alcohol in blood or urine samples, which is important in investigating drunk driving accidents.

Environmental analysis

GC is important for monitoring pollutants such as pesticides, herbicides, and heavy metals in the environment. It is also used to analyze air and water quality, providing valuable information for environmental protection and research.

Example of pollutant analysis: Air Sample -> GC Analysis -> Identification of VOCs (Volatile Organic Compounds)

Medical research

In the medical field, gas chromatography aids in drug discovery and development by analyzing biochemical compounds. Researchers use GC to investigate metabolic pathways and identify biomarkers for diseases.

Benefits and limitations

Benefit

  • High resolution: GC provides high-resolution separation of complex mixtures.
  • Quantitative analysis: This allows accurate quantitative analysis of compounds.
  • Sensitivity: Gas chromatography is sensitive and can detect trace amounts of analytes.
  • Versatility: GC is adaptable to a wide range of analyses in different fields.

Boundaries

  • Sample type: Only volatile and thermally stable compounds can be analyzed.
  • Complexity: Interpreting the results can be complex and may require additional software or expertise.
  • Equipment cost: Setting up a gas chromatography system can be expensive.

Conclusion

Gas chromatography is an integral technique in analytical chemistry, with its ability to efficiently separate and analyze volatile and semi-volatile compounds. Although it has its limitations, its advantages of high resolution, sensitivity, and versatility make it indispensable in various scientific and industrial fields. With ongoing advances in technology and methodology, gas chromatography is constantly evolving, offering improved capabilities and applications.

carrier gas inlet Sample Injection Column Detectors

Graduate → 4.1.1


U
username
0%
completed in Graduate

← Prev (4.1)
Chromatography
Next (4.1.2) →
High Performance Liquid Chromatography

Comments 



Gas Chromatography

https://www.chemistryelite.com/g/4.1.1?ceal=en