A **core shell particle** consists of a non-porous core in the center and a porous layer outside of the core.

A core-shell structure makes theoretical plate increase 50%, so that a 2.6 μm core shell particle column shows the same theoretical plate as a 1.8 μm totally porous particle column.

**Schematic view of a core-shell silica**

- A term
- Eddy diffusion (d
_{p}is particle diameter) - B term
- Longitudinal diffusion (D
_{m}is diffusion coefficient) - C term
- Mass transfer

**H**(height equivalent of one theoretical plate) represents the column length per one theoretical plate. The lower the H, the higher the performance.

Van Deemter plot is a curve using the value derived from the above equation as a function of the theoretical plate height and **u** (mobile phase linear velocity). Van Deemter Equation contributs A, B and C term individually.

A core-shell particles can be reduced all the values of these three terms.

The size distribution of a core shell (SunShell) particle is much narrower than that of a conventional totally porous particle, so that the space among particles in the column reduces and efficiency increases by reducing Eddy Diffusion (multi-path diffusion) as the A term in Van Deemter Equation.

Diffusion of a solute is blocked by the existence of a core, so that a solute diffuses less in a core shell silica column than in a totally porous silica column. Consequently B term in Van Deemter Equation reduces in the core shell silica column.

As shown in the below figure, a core shell particle has a core so that the diffusion path of samples shortens and mass transfer becomes fast.

This means that the C term in Van Deemter Equation reduces. In other words, HETP (theoretical plate) is kept even if flow rate increases.

A 2.6 μm core shell particle shows as same column efficiency as a totally porous sub-2 μm particle.

**SunShell series is here using the core-shell particles!**