Chromatography (A-level only) common mistakes

Common mistakes

• Confusing stationary and mobile phases

  Students often mix up the roles of stationary and mobile phases.

  Fix itRemember that the stationary phase does not move and is responsible for the interaction with the analytes, while the mobile phase is what carries the analytes through the system.

• Incorrect Rf value calculation

  Students often confuse the distances when calculating Rf values, leading to incorrect results.

  Fix itAlways ensure to use the distance traveled by the compound in the numerator and the distance traveled by the solvent front in the denominator.

• Misinterpreting Rf Values

  Students often confuse higher Rf values with higher polarity.

  Fix itRemember that higher Rf values indicate a greater distance traveled by the compound, which typically means lower affinity for the stationary phase, not higher polarity.

• Misunderstanding Rf values

  Students often confuse Rf values, thinking they can be greater than 1.

  Fix itRemember that Rf values are always between 0 and 1, as they represent a ratio of distances.