Centrifugation, dialysis, solvent extraction, and ultrafiltration rely on distinct physical properties for separating mixtures in biochemistry and biotechnology. The correct matching is option (D): P-1, Q-2, R-4, S-3.​

Correct Answer

Option (D) P-1, Q-2, R-4, S-3 pairs each method accurately with its primary property. Centrifugation separates based on density (1), as denser particles sediment faster under centrifugal force. Dialysis exploits diffusivity (2), allowing small solutes to pass through a semi-permeable membrane while retaining larger molecules. Solvent extraction depends on solubility (4), partitioning compounds between immiscible solvents based on relative affinities. Ultrafiltration uses size (3), filtering particles via membrane pore size.​

Option Analysis

• (A) P-4, Q-2, R-1, S-3: Incorrect; centrifugation links to density, not solubility, and solvent extraction mismatches density.​

• (B) P-3, Q-1, R-2, S-4: Wrong; centrifugation does not primarily use size (though size affects rate), dialysis ignores density.​

• (C) P-1, Q-3, R-2, S-4: Flawed; dialysis relies on diffusivity, not size, and solvent extraction on solubility over diffusivity.​

• (D) P-1, Q-2, R-4, S-3: Correct, as explained above with property-method alignment standard in bioprocess engineering.​

Key Concepts

These methods are essential in molecular biology labs for isolating proteins, cells, or metabolites:

• Centrifugation: Density-driven pelleting in gradients like sucrose.​

• Dialysis: Diffusion-based purification, e.g., buffer exchange.​

• Solvent extraction: Solubility partitioning, common in natural product isolation.​

• Ultrafiltration: Size-exclusion for concentration, retaining >10 kDa species.​