Line-start, incremental centrifugal technique

In the line-start technique the centrifuge disc is filled with clear liquid and allowed to attain its running speed. A small volume of buffer liquid is then introduced. The suspension is then introduced at time t = 0. The start radius is assumed to be at the mid-point of the suspension radius. 

Since all the particles emanate from the same starting point, the Stokes diameter is determined using equation (8.4) with r as the measurement radius and 8 as the midpoint of the suspension layer 

There is some disagreement as to whether the optical attenuation using the line-start technique is proportional to surface or volume distribution or whether it varies in a complex manner with d, . The consensus is that a volume relationship applies. 

A w edge shaped detector window (with radial sides, circular inner and outer sides), centered on r and spanning r, to rj where h I 

The suspension in the window will contain particles with diameters in the size range d =d,, ( -p) to dj d, (] +6) where c/ is the diameter of the particle just entering the window and d2 the diameter of the particle just leaving it  

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In homogeneous, incremental, centrifugal techniques matters are more complex since the particles move in radial paths hence the measured concentration is less than the original concentration (Figure 7). This problem does not occur with centrifugal line-start method at a fixed measurement radius. 

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