A Guide to Basic Chromatographic Terminology

Chromatography is a difficult enough technology to fathom at the best of times and the number of technical terms used can be daunting. This handy guide clarifies some of the more frequently used terms to aid understanding.

Absorption

In chromatography, absorption signifies the process by which a solute partitions into a liquid-like stationary phase.

Adsorption

The process by which a chemical entity is accumulated on a surface.

Mobile Phase

The eluate moving through the column. In gas chromatography (GC) this will be a gas, and in liquid chromatography (LC) a liquid.

Stationary Phase

The substance that remains in one place in the column. In GC this will be a liquid of high-viscosity, which clings to the inner walls of the column; in LC it will be some sort of packing, either solid or gel-based.

For more information on both the mobile and stationary phase, please see the article Reviewing the Importance of the Stationary and Mobile Phases in Chromatography.

Capillary Column

A column whose inner diameter is under 0.5 mm.

Eluate

The mobile phase exiting a column.

Eluent

The mobile phase entering a column.

Elution

The passage of the mobile phase through the column to transport solutes.

High Performance Liquid Chromatography (HPLC)

The name given to the one of the most modern forms of column liquid chromatography. It is characterized by high flow rates and high back column pressure.

Heart-Cutting

The term used in preparative chromatography and column switching for the collection of the centre of the peak of a solute.

Robustness

The extent to which a method of chromatography and its results will remain unaffected by minor changes in the parameters of the method (equipment, environment, etc.). To learn more about which factors influence the robustness of a technique, read the article: What is a Robust Method?

Partition Chromatography

A type of chromatography based on a thin film formed on the surface of a solid support by a liquid stationary phase. Solute equilibrates between the mobile phase and the stationary liquid.

Flow Rate

The amount of mobile phase that has passed through the column per unit time. The units are millilitres per second (mL/sec) or, more commonly, millilitres per minute (mL/min).

Linear Velocity

The time it takes for the mobile phase to pass through the column. Generally expressed as either centimetres per minute (cm/min) or metres per second (m/s). It is estimated as the column length divided by the time it takes for a non-retained compound to pass through the column.

Interstitial Volume

The volume between the particles in a packed column.

Solute

The term for the sample components being analysed.

Validation

A programme which guarantees the accuracy, specificity, precision and robustness of a method or process. To learn more about the benefits of validation, read the article: Why are Methods Validated?

Void Volume

The volume of the empty column before the mobile phase is passed through it. Ideally this volume should be exactly the same as that of the mobile phase itself.