The main difference between the mobile phase and stationary phase is that the mobile phase is the solvent moving through the column, whereas the stationary phase is the substance, which stays fixed inside the column. Furthermore, the mobile phase can be either liquid or gas while the stationary phase is a solid or liquid supported on a solid. Moreover, components of the mixture with similar properties to the mobile phase elute earlier while the components of the mixture with similar properties to the stationary phase elute later.
Mobile phase and stationary phase are the two types of separating media used in chromatography. Generally, chromatography is the technique used to separate components of a mixture.
Key Areas Covered
1. What is Mobile Phase
– Definition, Types, Function
2. What is Stationary Phase
– Definition, Types, Function
3. What are the Similarities Between Mobile Phase and Stationary Phase
– Outline of Common Features
4. What is the Difference Between Mobile Phase and Stationary Phase
– Comparison of Key Differences
Key Terms
Column Chromatography, Liquid and Gas Chromatography, Mobile Phase, Planer Chromatography, Stationary Phase
What is Mobile Phase
The mobile phase is the phase, which flows through the chromatographic medium. Generally, the mixture to be separated is dissolved in the mobile phase. Also, it passes through the structure of the chromatography, holding the material called the stationary phase. Significantly, differential migration is the principle of chromatography. Therefore, different components of the mixture travel at different speeds based on the differential interactions of these components towards the mobile phase and stationary phase.
Figure 1: Basic Principle of Chromatography
Furthermore, the mobile phase in chromatography can be either a liquid or a gas. For instance, liquid chromatography (LC) is the type of chromatography, which uses a liquid mobile phase. On the other hand, gas chromatography (GC) is the type of chromatography, which uses a gas mobile phase. However, in HPLC, a non-polar solvent such as hexane is used in the normal phase while a polar solvent such as methanol is used in the reverse phase.
What is Stationary Phase
The stationary phase is the phase, which is fixed into the column. Here, a polar stationary phase is used in the forward phase chromatography while a non-polar stationary phase is used in the reverse phase. For instance, based on the bed shape of the stationary phase, there are two types of chromatography. They are column chromatography in which the stationary phase bed occurs within a tube and planar chromatography in which the stationary phase occurs as a plane. Significantly, paper chromatography and thin-layer chromatography are the two types of planar chromatography.
Figure 2: Reverse Phase Gradient Elution
Moreover, the stationary phase always has opposing properties to the corresponding mobile phase of the chromatography. On the other hand, each phase makes interactions with the components of the mixture with similar properties. Thereby, when the stationary phase is non-polar, non-polar components of the mixture tend to stay with the stationary phase while polar components tend to move along with the mobile phase, which is polar as well. At the end of the chromatography, by sending a solvent gradient with decreasing polarity, the non-polar components staying in the stationary phase can be eluted out.
Similarities Between Mobile Phase and Stationary Phase
- Mobile phase and stationary phase are the two separating media used in chromatography.
- Always they have opposing properties.
- Significantly, components of the mixture with similar properties to each phase tend to stay in that particular phase during chromatographic separation.
Difference Between Mobile Phase and Stationary Phase
Definition
The mobile phase refers to the liquid or gas, which flows through a chromatography system, moving the materials to be separated at different rates over the stationary phase while stationary phase refers to the solid or liquid phase of a chromatography system on which the materials are to be separated or selectively adsorbed.
Significance
The mobile phase is the solvent moving through the column while the stationary phase is the substance, which stays fixed inside the column.
Types
The mobile phase can be either liquid or gas while the stationary phase is a solid or liquid supported on a solid.
Separation of Components
Components of the mixture with similar properties to the mobile phase elute earlier while the components of the mixture with similar properties to the stationary phase elute later.
Types of Phase
A non-polar solvent such as hexane is used in the normal phase while a polar solvent such as methanol is used in the reverse phase in HPLC while a polar stationary phase is used in the forward phase chromatography while a non-polar stationary phase is used in the reverse phase.
Types of Chromatography
Based on the type of mobile phase, there are two types of chromatography; liquid chromatography and gas chromatography, while based on the type of stationary phase, there are two types of chromatography; column chromatography and planer chromatography.
Conclusion
The mobile phase is the type of medium, which passes through the column, eluting components of the mixture with similar properties to that of the mobile phase. Generally, it can be either a liquid or a gas. On the other hand, the stationary phase is the type f medium of chromatography, stay fixed to the column. In contrast, components of the mixture with similar properties to the stationary phase tend to stay in the column, eluting later. However, the stationary phase can be either solid or liquid. Therefore, the main difference between mobile phase and stationary phase is their function in chromatography.
References:
1. “Principles of Chromatography.” Khan Academy, Khan Academy, Available Here.
Image Courtesy:
1. “Kromatografia” By EjupPod – Own work (CC BY-SA 3.0) via Commons Wikipedia
2. “Reverse Phase Gradient Elution Schematic” By Nategm – Own work (CC BY-SA 4.0) via Commons Wikimedia
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