Bio-Rad Rotofor® and Mini Rotofor Cells - Manual (Page 16)

4.2 Power Supply
1. Never operate the Rotofor cell with the cover removed. When focusing power
is applied to the jacks without the cover in place, several high voltage elements
become exposed. To avoid personal injury due to accidental contact with these
elements, always operate the cell with the cover in place.
2. Attach the high voltage leads to the power supply, and the Rotofor cell is ready
for use. To begin rotation, flip the toggle switches to ON and RUN.
3. Power supply:
Standard Rotofor chamber - Set the supply to 15 W constant power and begin
the run.
Mini Rotofor chamber- Set the supply to 12 W constant power and begin the run.
The starting voltage and current will vary depending on the salt concentration of the
sample. For example, if the salt concentration of the sample is 10 mM, the starting
voltage will be 300–500 V, and the current will be 24–40 mA. The maximum power
that can be dissipated is about 15 W for an initial fractionation when the Rotofor cell
is operated at 4°C. If more than 15 W is applied to the cell, overheating can damage
the cell. The applied power is too high if the current increases or remains constant,
rather than decreases, during a run. If a constant power supply is not available,
check the graph in Figure 4.1 to determine the optimum starting voltage and
increase the voltage manually in increments over time. The voltage should be
increased as the run progresses to keep the power at a constant 12 W.
4. A typical run is completed in 3–5 hours. To monitor the progress of a run under
conditions of constant power, observe the voltage increase over time. The run
is complete when the voltage stabilizes. At that point, allow the run to continue
for 30 minutes before harvesting. The total run length should not exceed
6 hours. Longer run times do not tighten the focusing and may begin to break
down the gradient.
Fig. 4.1. The maximum power that should be applied to the Rotofor cell is 12-15 W. The graph
shows the voltage and current readouts for setting a constant voltage power supply. If the current
reading is too high at the set voltage (in the danger zone), reduce the voltage until a safe power level is
obtained. Watts = voltage x current.
0
500
1000
1500
2000
V
o
lts
0 10 20 30 40 50 60 70 80 90 100 110 120
m Amps
12 W
12