Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → Matter and its nature → Separation Techniques ↓


Chromatography


Chromatography is an important technique in chemistry that is used to separate the various components of a mixture. It is important for students learning the basic concepts of chemistry to understand this technique. This article explains the various aspects of chromatography, including its principles, methods, and applications, with an aim to provide a deeper understanding.

What is chromatography?

Chromatography is a technique for separating mixtures into their components, based on the different ways each component interacts with two phases: a stationary phase and a mobile phase. It is widely used in analytical chemistry to identify and quantify each part of a mixture.

Fundamentals of chromatography

The basic principle of chromatography is based on the difference in the partition behaviour of the components of a mixture. When a mixture is moved by a mobile phase over a stationary phase, different components travel at different rates. This results in the separation of the components.

Stationary phase

The stationary phase is the phase that does not move. It may be a solid or a viscous liquid adsorbed on a solid surface. The choice of the stationary phase depends on the nature of the mixture being separated.

Mobile phase

The mobile phase is the phase that moves and transports the mixture through the stationary phase. It can be liquid or gas. The interaction between the mobile phase and the stationary phase affects the separation of the mixture.

Types of chromatography

There are several types of chromatography, each with a specific application depending on the physical state of the mobile and stationary phases. We will explore the most commonly used types:

1. Paper chromatography

        Paper chromatography uses a strip of paper as the stationary phase. A sample is applied to the paper, and the paper is immersed in a solvent (the mobile phase). As the solvent moves up the paper, it carries with it components of the mixture, which are separated based on their affinity for the paper and the solvent.

For example, when water-soluble inks are analyzed using paper chromatography, the pigments in the ink move at different speeds on the paper, resulting in a colored pattern.

2. Thin layer chromatography (TLC)

        In thin layer chromatography a thin layer of adsorbent material such as silica gel is spread on a glass or metal plate as the stationary phase. The sample is applied to this layer, and the plate is placed in a chamber with a suitable solvent. The components move on the plate and are identified by comparing their speeds in front of the solvent.

TLC is often used to monitor the progress of a reaction or to analyze the purity of a substance.

3. Column chromatography

        Column chromatography uses a column filled with a solid adsorbent as the stationary phase. The sample mixed with the solvent is poured into the column, and the different components are separated as they move down the column at different rates.

It is often used in the purification of chemical compounds. Components are separated due to their different interactions with the stationary phase surface and their solubility in the mobile solvent.

4. Gas chromatography

        Gas chromatography is used for volatile substances. It involves a gas as the mobile phase and, often, a liquid stationary phase glued to a solid support inside the column. As the sample vaporizes and travels through the column, its components are separated based on their volatility and interactions with the column surface.

This method is particularly useful in drug testing and the analysis of complex mixtures of volatile compounds.

5. High performance liquid chromatography (HPLC)

        High-performance liquid chromatography involves a high-pressure pump to push the solvent through a densely packed column, improving separation efficiency. The stationary phase is usually small particles inside the column, providing a large surface area for separation.

HPLC is widely used for qualitative and quantitative analysis in the pharmaceutical and food industries.

Process of chromatography

The chromatography process generally consists of the following steps:

  1. Preparation: The sample is prepared, often by dissolving it in a solvent to form an analyte solution.
  2. Introduction: The sample is applied to the stationary stage.
  3. Separation: The mobile phase flows over the stationary phase, and the components of the sample distribute themselves between these two phases.
  4. Detection: The separated components are detected and analyzed, often using ultraviolet light, fluorescence, or other detection methods.

Factors affecting chromatography

Several factors affect the chromatography process:

  • Adsorbent materials: The selection of materials for the stationary and mobile phases can greatly affect the separation process. Different materials have different selectivity and adsorption properties.
  • Polarity: The polarity of the elements in a mixture affects how they separate. Polar compounds have different affinities for a polar solute or solvent.
  • Solubility: Components having higher solubility in the mobile phase will move faster into the stationary phase.
  • Temperature: In gas chromatography, temperature can greatly affect the separation by affecting both volatility and flow rate.

Applications of chromatography

Chromatography is an essential tool in many fields. Its applications are as follows:

  • Forensic science: It is used to identify substances such as drugs or toxins by analyzing blood samples, tissues, and other biological evidence.
  • Pharmaceutical industry: Helps analyze the purity of drugs, identify compounds, and even study the interactions between different chemicals.
  • Environmental science: Used to analyze pollutants in water and air samples.
  • Food industry: Used to analyze food components, ensure food safety by detecting contaminants and preservatives.

Visualizing chromatography

Here's a simple example showing chromatography in action:

        
        
          
          
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In this example, a strip of paper represents the stationary phase. The different coloured spots represent the separation of the components of the mixture, which move along the mobile phase.

Conclusion

Chromatography is an essential technique in chemistry and many related fields. By understanding and applying its principles and various types, we can effectively analyze complex mixtures, aiding innovations in science and industry. The ability of this technique to uncover detailed information about the components of a mixture proves invaluable in both research and practical applications.


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Chromatography

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