Understanding the Concept:
Paper chromatography is a traditional planar separation technique where cellulose filter paper serves as the stationary support phase, holding a bound layer of water, while a liquid mobile phase ascends or descends the sheet via capillary action.
Step 1: Review the true advantages of Paper Chromatography
• Separation of ionic and polar compounds (Option A): The cellulose framework contains abundant hydroxyl (\(\text{-OH}\)) groups that tightly bind water molecules, creating a highly polar environment ideal for partitioning water-soluble polar species, amino acids, and ionic salts.
• Low cost and simplicity (Option C): The method requires only standard filter paper sheets and minimal development glassware, making it very economical.
• Small sample volumes (Option D): Samples are applied as micro-dots using simple capillary tubes, requiring only a few microliters of material.
Step 2: Identify the limitation (Option B)
Paper chromatography suffers from significant structural limitations, notably poor separation efficiency for large, complex macromolecules (such as high-molecular-weight polymers or complex proteins). The cellulose fibers in paper are relatively large and irregular, leading to significant Eddy diffusion and slow mass transfer rates, which cause broad, smeared bands. For large biomolecules, modern high-efficiency techniques like HPLC, Gel Electrophoresis, or Size Exclusion Chromatography are required.
Therefore, high separation efficiency for large molecules is not an advantage of this method.