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 ↓


Thin Layer Chromatography


Thin layer chromatography (TLC) is a chromatographic technique used to separate non-volatile mixtures. It is a powerful tool in the field of analytical chemistry, providing a simple, rapid, and cost-effective means to identify, analyze, and separate components within a mixture. This method can be used for both qualitative and quantitative purposes.

Principle of thin layer chromatography

TLC is based on the principle of adsorption chromatography. It consists of a stationary phase, which is usually a plate coated with a thin layer of an adsorbent material such as silica gel, and a mobile phase, which is a solvent or combination of solvents that travels to the stationary phase by capillary action. As the solvent travels, it carries with it various components of the mixture. These components move at different rates depending on their adsorption in the stationary phase and their solubility in the mobile phase.

Components of thin layer chromatography

1. Stationary phase

The stationary phase in TLC is usually a plate coated with a thin layer of an adsorbent material such as silica gel, alumina or cellulose. Silica gel is the most commonly used adsorbent due to its high polarity, good performance and availability. The plate may be glass, aluminium or plastic, and the choice of plate depends on the specific requirements of the experiment.

2. Mobile phase

The mobile phase in TLC is the solvent or solvent mixture that passes through the stationary phase, carrying with it the various components of the sample. The selection of the mobile phase is important as it determines the separation efficiency. It is chosen based on the polarity of the compounds being separated.

3. Sample

The sample is the mixture that contains the various components to be separated. It is spotted or applied near the base of the stationary phase plate. If the substances are colorless, visualization techniques may be needed to check the results.

Process of thin layer chromatography

  1. Preparation of the TLC plate: The TLC plate is selected and prepared by drawing a base line about 1 cm from the bottom. This line is where the sample will be applied.
  2. Application of the sample: Using a capillary tube or a microliter syringe, a small drop of the sample is applied to the baseline of the TLC plate.
  3. Developing the plate: The plate is then carefully placed in a developing chamber containing the mobile phase. Make sure the solvent level is below the baseline where the sample is applied.
  4. Visualization: Once the solvent front has traveled a sufficient distance, the plate is removed and allowed to dry. In the case of colorless compounds, visualization agents such as iodine vapor or UV light may be necessary.
  5. Analysis: Measure the distance traveled by each component from the baseline and the distance traveled by the solvent front. The Rf value for each component is calculated using the formula: 
    Rf = (distance travelled by the substance) / (distance travelled by the solvent front)

Applications of thin layer chromatography

TLC is widely used in various fields due to its versatility and ease of use:

  • Identification of compounds: TLC can quickly identify compounds by comparison with known substances or by using specific Rf values.
  • Purity testing: By looking at the spots on the TLC plate, the purity of the sample can be determined; extra spots may indicate impurities.
  • Monitoring reactions: TLC is an excellent tool for monitoring the progress of chemical reactions, since it can show both reactants and products.
  • Separation of plant extracts: In pharmacognosy and botanical studies, TLC is used extensively to separate plant extracts and identify components.

Advantages and limitations of thin layer chromatography

Benefit

  • TLC is simple and inexpensive compared to more advanced chromatographic techniques such as HPLC or GC.
  • Multiple samples can be processed at once, saving time.
  • TLC plates are disposable, reducing the risk of cross-contamination between samples.

Boundaries

  • TLC does not provide highly accurate quantitative data.
  • The resolution of TLC may not be sufficient for components with similar characteristics.
  • It requires manual measurements, which can lead to human error.

Example calculation

Suppose that during the experiment a compound moves 3 cm on the TLC plate while the solvent front moves 6 cm. The Rf value is calculated as follows:

Rf = (distance travelled by substance) / (distance travelled by solvent front) = 3 cm / 6 cm = 0.5

An Rf value of 0.5 indicates that the compound migrated to half of the TLC plate relative to the solvent front.

Visual representation

Consider a TLC setup in which the stationary phase is represented by a rectangle and the mobile phase is traveling upward, carrying the components:

    
    
        
        
        
        Baseline
        Solvent Front
        
        Sample space

In this visual representation, the blue dot symbolizes the sampling site, while the thick lines indicate the baseline and solvent front.

Conclusion

Because of its simplicity and effectiveness in separating mixtures, thin-layer chromatography remains a valuable technique in analytical chemistry. Despite its limitations, it provides a quick and efficient way to analyze, identify, and observe the behavior of chemical substances in both academic and professional settings.


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Thin Layer Chromatography

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