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Difficulty: MediumPaper and Column Chromatography

Arrange the following sequential steps of a paper chromatography experiment in the correct procedural order from start to finish.

  1. 1Draw a light baseline using a lead pencil about 2 cm2\text{ cm} from the bottom edge of the filter paper strip.
  2. 2Apply a small, concentrated spot of the sample mixture onto the baseline and allow it to dry.
  3. 3Suspend the paper strip in a sealed chamber, ensuring the solvent level remains strictly below the baseline.
  4. 4Remove the strip when the mobile phase nears the top and immediately pencil-mark the solvent front.

Answer

The correct procedural order is: (1) Draw a light baseline using a lead pencil about 2 cm2\text{ cm} from the bottom edge of the filter paper strip, (2) Apply a small, concentrated spot of the sample mixture onto the baseline and allow it to dry, (3) Suspend the paper strip in a sealed chamber, ensuring the solvent level remains strictly below the baseline, and (4) Remove the strip when the mobile phase nears the top and immediately pencil-mark the solvent front.
The correct sequence follows standard analytical chromatography protocol: first, a graphite pencil baseline is drawn at the base of the paper strip. Next, the mixture is spotted onto this origin baseline. The paper is then placed into the developing tank with the mobile phase level kept below the baseline to allow upward capillary migration. Finally, the paper is removed before the solvent reaches the top edge, and the solvent front is marked immediately for accurate distance measurements.

Step-by-Step Solution

1
Determine paper preparation step
Draw a pencil baseline near the bottom edge of the paper.
Graphite from a lead pencil is insoluble in the mobile phase and will not contaminate the chromatogram.
2
Determine sample application step
Spot the sample mixture onto the pencil baseline and dry it.
Deposition onto the origin line must occur before the paper contacts the developing solvent.
3
Determine development step
Place the paper into the chamber with the solvent line positioned below the baseline.
Maintaining the solvent level below the baseline allows the solvent to ascend by capillary action, carrying solute components upward rather than dissolving them into the bulk solvent.
4
Determine experiment termination step
Remove the paper strip and mark the solvent front.
Immediate marking of the solvent front ensures accurate measurement of mobile phase migration distance for RfR_f calculations.

Key Concept

Laboratory procedural steps and operational principles of paper chromatography
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Topics

Paper and Column Chromatography

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