Reversed-phase liquid chromatography (RPLC) In reversed-phase chromatography, how is the stationary phase typically characterized?

Introduction / Context:
Reversed-phase liquid chromatography (RPLC) is the most widely used HPLC mode. Knowing that the stationary phase is hydrophobic clarifies why more hydrophobic analytes are retained longer and why mobile phases are water–organic mixtures.

Given Data / Assumptions:

• Stationary phase is typically alkyl-bonded silica (C18, C8, C4).
• Mobile phase is relatively polar (water with methanol or acetonitrile).
• Elution strength increases with higher organic content.

Concept / Approach:
In RPLC, “reversed” refers to the polarity reversal relative to normal-phase chromatography: the stationary phase is non-polar and the mobile phase is polar. Hydrophobic interactions dominate retention.

Step-by-Step Solution:
Identify hydrophobic bonded phases (e.g., C18).Relate increased organic solvent to decreased retention of hydrophobic solutes.Select the option that explicitly states a non-polar stationary phase.

Verification / Alternative check:
Gradient runs from high water to high organic shorten retention of hydrophobes, consistent with a hydrophobic stationary phase.

Why Other Options Are Wrong:
Polar stationary phase (option b) describes normal-phase/HILIC, not reversed phase.Option c is imprecise; the stationary phase chemistry does not change between runs.Option d contradicts established RPLC principles.

Common Pitfalls:
Confusing RPLC with HILIC; assuming polarity depends only on solvent, not bonded phase.

Final Answer:
Non-polar (hydrophobic) surface such as C18-bonded silica.