Key Difference – Stationary vs Mobile Phase
The key difference between stationary and mobile phase is that stationary phase does not move with the sample whereas mobile phase moves with the sample.
Stationary phase and mobile phase are two important terms in chromatography, which is a technique of separation and identification of the components in a mixture.
CONTENTS
1. Overview and Key Difference
2. What is Stationary Phase
3. What is Mobile Phase
4. Side by Side Comparison – Stationary vs Mobile Phase in Tabular Form
6. Summary
What is Stationary Phase?
Stationary phase of a chromatographic technique is the compound used to separate components in a mixture. However, this phase does not move with the components. It can be either a solid compound or a liquid supported on a solid.
There are two major types of chromatographic techniques as column chromatography and planar chromatography. In column chromatography, the stationary phase is filled into a tube known as the column. Here, the column can be filled in two ways: sometimes the whole column is filled with the stationary phase (known as packed column). Other times the column is filled with the stationary phase, leaving a path in the middle of the column for the movement of the mobile phase (open tubular column).
Figure 1: Planar chromatography: (1-chromatographic chamber, 2-stationary phase, 3-solvent front, 4-mobile phase)
In planar chromatography, on the other hand, the separation is done on a planar structure such as a paper or a plate. The stationary phase can be either a paper or a liquid allied on a plate. Furthermore, thin layer chromatography uses papers made of cellulose or plates applied with silica gel. Here, the stationary phases are cellulose and silica, respectively.
What is Mobile Phase?
Mobile phase in chromatography is a compound used to separate components in a mixture. Most importantly, this phase can move along with the components. Consequently, the mobile phase runs through the stationary phase along with the sample. The sample dissolves in the mobile phase and migrates through the stationary phase. The mobile phase is either a liquid or a gas.
Figure 2: Gas Chromatography
For example, in gas chromatography, the mobile phase is a gas. In liquid chromatography and paper chromatography, the mobile phase is a liquid. The mobile phase should be a good solvent for the sample. In paper chromatography, the mobile phase should have opposite polarity to that of the stationary phase. This is because this difference in polarities of stationary phase and mobile phase helps to separate the polar, moderately polar and nonpolar components in the mixture.
What is the Difference Between Stationary and Mobile Phase?
Stationary vs Mobile Phase |
|
| Stationary phase of a chromatographic technique is the compound used to separate components in a mixture, but it does not move with the components. | Mobile phase in chromatography is a compound used to separate components in a mixture, and it can move along with the components. |
| Movement | |
| The stationary phase does not move. | The mobile phase migrates through the stationary phase. |
| Phase of Matter | |
| The stationary phase is either a solid compound or a liquid, supported on a solid. | The mobile phase is either a gas or a liquid. |
| Sample Dissolution | |
| The stationary phase may or may not have interactions with the components in the sample. | The mobile phase completely dissolves the sample. |
Summary – Stationary vs Mobile Phase
Chromatography is a biochemical technique that separates, identifies and sometimes quantifies the components in a sample. The technique has three major requirements, which are sample, stationary phase and mobile phase. The key difference between stationary and mobile phase is that stationary phase does not move with the sample whereas mobile phase moves with the sample.
Reference:
1. Jabir, Jabir. “Mobile Phase in Chromatography.” LinkedIn SlideShare, 5 Jan. 2015, Available here.
2. “Chromatography.” Wikipedia, Wikimedia Foundation, 10 Apr. 2018, Available here.
Image Courtesy:
1. “Chromatography tank” By Theresa Knott (CC BY-SA 3.0) via Commons Wikimedia
2. “Inverse and analytical gas chromatography B” By Dvstechnique – Own work (Public Domain) via Commons Wikimedia