In chromatography, the stationary phase is always a solid matrix. True or False?

• A. True
• B. False
• C. Sometimes
• D. Not applicable

Answer: (B)

In chromatography, how compounds interact with the stationary phase depends on the mechanism, not on the stationary phase being a solid. The stationary phase can be a solid surface that adsorbs analytes (adsorption chromatography) or a liquid layer that analytes dissolve into and partition from the mobile phase (partition chromatography). For example, in gas chromatography, a thin liquid film is often coated on the inner walls of the capillary columns, and compounds separate based on their distribution between the moving gas and that liquid film. In other formats like TLC or many solid‑phase HPLC columns, the stationary phase is a solid material, sometimes with covalently attached groups. Therefore, the stationary phase is not always a solid matrix.