Ultra-centrifugation is primarily employed to separate which class of suspended particles from a liquid?

Introduction / Context:
Centrifuges exploit centrifugal acceleration to enhance settling. Ultra-centrifuges achieve extremely high rotational speeds and fields (>10^5 g), enabling separation of particles that would be essentially non-settling under gravity, such as macromolecules and colloids.

Given Data / Assumptions:

• Device: ultra-centrifuge (very high g).
• Objective: separate extremely small particles.
• Fluid properties are typical for aqueous/organic media.

Concept / Approach:
Stokes-law settling velocity scales with particle size squared. For colloidal particles in the 1 nm to <1 microm range, gravitational settling is negligible; Brownian motion dominates. Ultra-centrifugation amplifies the effective body force, producing measurable sedimentation even for macromolecules and viruses.

Step-by-Step Solution:
Identify particle size regimes: coarse, fine, colloidal.Match capability: only ultra-centrifuges generate sufficient g to sediment colloids in practical time.Exclude dissolved species; they require separation by diffusion/membranes, not centrifugation.

Verification / Alternative check:
Analytical ultracentrifugation is standard in biochemistry for proteins, nucleic acids, and viruses.

Why Other Options Are Wrong:
Coarse/fine particles: lower-speed centrifuges or thickeners suffice.Dissolved species: no particulate phase to sediment.

Common Pitfalls:
Assuming any centrifuge can separate colloids; only very high g and carefully chosen run times make this feasible.

Final Answer:
Colloidal particles (nanometre to sub-micrometre)