Zoncentrifugering

Zoncentrifugering is a process in centrifugation aimed at separating or analyzing mixtures by establishing and preserving distinct zones of composition within a centrifugal field. In this approach, a gradient or zoned medium is used to guide different components into spatially separated regions, producing bands or layers rather than a uniform sediment.

Principle: Under rotation, particles experience an outward centrifugal force that increases with speed and radial position. When the medium contains density or viscosity variations arranged to form zones, components migrate until each occupies a region that matches its physical properties. Diffusion and convection can blur zone boundaries, so conditions are chosen to favor stable zoning.

Methods and equipment: Zoncentrifugering typically uses standard centrifugation hardware—tubes in fixed-angle or swinging-bucket rotors—but with media designed to produce zones, such as density gradients or layered phase systems. Samples are loaded, the rotor is accelerated to a set speed, held for a defined duration, and zones are recovered by fractionation or direct analysis of interfaces.

Applications: The technique is employed where high-resolution separation is required between constituents of similar density or size. It has applications in biochemistry for separating proteins, nucleic acids, or organelles; in polymer science for resolving phase-separated blends; and in environmental or materials analysis for characterizing particulate distributions in complex suspensions.

Terminology and context: The Dutch term zoncentrifugering emphasizes the zonal outcome of the process. It is related to, but distinct from, other gradient-based centrifugation methods such as density-gradient centrifugation and isopycnic centrifugation, which rely on continuous changes in density to position samples at specific interfaces.