# 2019/10/10

## The exclusion limit of the gel filteration

The exclusion limit of the gel is the size above which materials (e.g., proteins) will elute in the void volume of the column. It is impossible to separate particles whose size are alrger than the exclusion limit. Therefore, the limit must be taken into consideration when we try to separate particles being large in size.

## Importance of RCF (rather than RPM)

The RCF is important for centrifugation rather than the RPM, because separation can be improved by not angular velocity but centrifugal force. The centrifugal force, RCF, is a function of both the rotation speed, RPM, and the radius of the centrifuge. This means that consideration of only RPM does not make sense but of RCF does.

The number of theoretical plates, $N_t$, can be calculated by following equation:$$N_t=\frac{H}{\mathrm{HETP}}$$where $H$ is the total height of the column and HETP is the height equivalent to a theoretical plate, which can be calculated with the van Deemter equation.