Difference Between Partition and Adsorption Chromatography
Partition Chromatography is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. It is especially important in learning about separation techniques, mixture analysis, and how chemical substances interact with different phases. Students preparing for chemistry exams or real-life lab work frequently encounter this topic.
What is Partition Chromatography in Chemistry?
A partition chromatography refers to an analytical separation technique where the components of a mixture are distributed between two immiscible liquid phases. This concept appears in chapters related to chromatography, separation methods, and chemical analysis, making it a foundational part of your chemistry syllabus.
Principle of Partition Chromatography
The principle of partition chromatography is based on the difference in solubility (or partition coefficient, K) of the components of a mixture between the stationary phase (a liquid held on a solid support) and the mobile phase (another liquid that moves). Each compound distributes itself between these two phases according to its affinity, leading to separation.
The partition coefficient (K) is expressed as:
K = (Concentration of solute in stationary phase) / (Concentration of solute in mobile phase)
Compounds with a higher affinity for the stationary phase move slower, while those with a greater affinity for the mobile phase move faster.
Stationary and Mobile Phases in Partition Chromatography
| Phase | Description | Examples |
|---|---|---|
| Stationary Phase | A thin liquid layer supported on a solid substrate (e.g., water trapped in cellulose fibers of paper in paper chromatography). | Water on paper, liquid on silica gel |
| Mobile Phase | An immiscible liquid that moves through or over the stationary phase and carries the compounds with it. | Methanol, acetone, or other organic solvents |
Types of Partition Chromatography
- Paper Chromatography – Uses cellulose paper as the stationary phase with water as the immobile liquid. Very popular in schools and labs.
- Column Chromatography (liquid-liquid) – Stationary phase is a liquid coated on solid support inside a column; the mobile phase flows through by gravity.
- Thin Layer Chromatography (TLC), Liquid-Liquid Type – In some cases, stationary phase is a uniform thin liquid layer.
- High-Performance Liquid Chromatography (HPLC) – Advanced, uses high pressure and fine liquid stationary phase on a column.
Diagram and Stepwise Procedure of Partition Chromatography
Below is a typical setup and the procedure for paper chromatography,
- Place small drops of the sample mixture on the line using a capillary tube.
- Hang the paper so that its lower edge just touches the mobile phase (solvent) in a chamber, but not the samples.
- Cover the chamber and let the solvent rise by capillary action. Components partition between water (in cellulose) and the rising solvent.
- Remove the paper when the solvent front nears the top, and mark the front immediately.
- Visualize the separated spots (use UV light if colorless), calculate Rf values if needed.
Examples and Applications of Partition Chromatography
The most well-known example of partition chromatography is paper chromatography, often used for:
- Identifying components of inks, dyes, or plant pigments.
- Analyzing amino acids or nucleic acids in a mixture.
- Testing drug purity and detecting adulterants.
- Forensic examination of crime samples.
- Qualitative and quantitative separation in biochemical labs.
Modern techniques like HPLC and paper chromatography use the partition principle for accurate analysis of pharmaceuticals, food, beverages, and biological samples.
Difference Between Partition and Adsorption Chromatography
| Feature | Partition Chromatography | Adsorption Chromatography |
|---|---|---|
| Basis of Separation | Liquid-liquid partitioning | Liquid-solid adsorption |
| Stationary Phase | Liquid (held on a solid) | Solid |
| Examples | Paper chromatography, some HPLC types | Column chromatography, TLC (silica gel) |
| Mechanism | Solubility differences | Surface adhesion differences |
Relation with Other Chemistry Concepts
Partition chromatography is closely related to topics such as chromatography, adsorption chromatography, and types of chromatography, helping students build a clear understanding of separation techniques used in analytical and practical chemistry.
Try This Yourself
- Explain why water is considered the stationary phase in paper chromatography.
- Name two real-life uses of partition chromatography in the medical field.
- Draw and label the setup for a simple paper chromatography experiment.
Lab or Experimental Tips
Remember: When performing paper chromatography, always use a pencil (not ink) to draw the baseline. Mobile phase selection is crucial—choose a solvent in which the substances of interest are soluble but the stationary phase is not washed away. Vedantu educators use easy analogies in their live classes to help memorize the flow of phases: "stationary stays, mobile moves!"
Final Wrap-Up
We explored partition chromatography—its definition, principle, diagram, uses, and comparisons with other techniques. This knowledge helps in a variety of scientific, industrial, and everyday applications. For further study, live classes and easy-to-read notes on Vedantu provide more tips for mastering chromatography topics.
Related Vedantu Resources
FAQs on Partition Chromatography Explained: Principle, Types & Applications
1. What is partition chromatography?
Partition chromatography is a method used to separate components of a mixture. The separation is based on the differences in how each component distributes, or partitions, itself between two immiscible liquid phases: a stationary liquid phase and a mobile liquid phase.
2. What is the fundamental principle of partition chromatography?
The principle is based on the differential solubility of compounds in two immiscible liquids. A substance with higher solubility in the stationary phase will move slower, while a substance more soluble in the mobile phase will move faster, leading to their separation. This distribution is governed by the partition coefficient of each component.
3. What are the roles of the stationary and mobile phases in this technique?
In partition chromatography, the phases have distinct roles:
- Stationary Phase: This is a liquid film that is immobilised on an inert solid support. For example, in paper chromatography, water trapped in the cellulose fibres acts as the stationary phase.
- Mobile Phase: This is a liquid that is immiscible with the stationary phase. It flows over the stationary phase, carrying the components of the mixture at different rates.
4. What are some common examples of partition chromatography?
Common examples that illustrate the principle of partition chromatography include:
- Paper Chromatography: Used to separate coloured pigments like ink or plant extracts.
- Liquid-Liquid Column Chromatography: Where a liquid stationary phase is coated onto solid packing material in a column.
- Gas-Liquid Chromatography (GLC): A variation where the mobile phase is a gas and the stationary phase is a non-volatile liquid coated on a solid support.
5. How does partition chromatography differ from adsorption chromatography?
The key difference lies in the separation mechanism and the nature of the stationary phase:
- Mechanism: Partition chromatography relies on the solubility of components between two liquid phases. Adsorption chromatography relies on the differential adhesion (adsorption) of components to the surface of a solid stationary phase.
- Stationary Phase: In partition, it is a liquid coated on a solid support. In adsorption, it is a solid adsorbent like silica gel or alumina.
6. Why is it essential for the stationary and mobile phases to be immiscible?
The immiscibility of the two phases is crucial because it creates a distinct interface where the partitioning can occur. If the phases were miscible, they would mix to form a single solution. This would eliminate the two-phase system required for components to distribute themselves based on their relative solubilities, and no separation would be possible.
7. How does the partition coefficient (K) influence separation efficiency?
The partition coefficient (K) is the ratio of the concentration of a solute in the stationary phase to its concentration in the mobile phase. A low K value means the component is more soluble in the mobile phase and travels quickly. A high K value means it is more soluble in the stationary phase and travels slowly. The difference in K values between components directly determines the effectiveness of the separation—the larger the difference, the better the separation.
8. In paper chromatography, what is the Rf value and what is its importance?
The Rf value (Retardation factor) is the ratio of the distance travelled by the solute to the distance travelled by the solvent front on the chromatogram. As per the CBSE/NCERT curriculum for 2025-26, it is a characteristic constant for a given compound under specific conditions (same stationary and mobile phases, temperature). Its importance lies in identification; by comparing the Rf value of an unknown spot with that of a known substance, one can identify the component.
9. What are some real-world applications of partition chromatography?
Partition chromatography is widely used for analysis and separation in various fields:
- Pharmaceuticals: To separate and purify antibiotics or analyse drug formulations.
- Biochemistry: For the separation of amino acids, carbohydrates, and peptides.
- Forensics: In the analysis of drugs, poisons, or ink samples from evidence.
- Food Industry: To detect adulterants, preservatives, or artificial colours in food products.
10. Can techniques like TLC and HPLC be considered forms of partition chromatography?
Yes, under certain conditions. While Thin Layer Chromatography (TLC) is primarily an adsorption technique, it can have a partition mechanism if the stationary phase (like silica gel) absorbs moisture from the air, creating a thin liquid layer. Similarly, High-Performance Liquid Chromatography (HPLC) can operate on the partition principle in its 'reversed-phase' or 'normal-phase liquid-liquid' modes, where the stationary phase is a liquid chemically bonded to a solid support.
