Hoefer SG500 - Manual (Page 9)

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To generate an exponential gradient:
1
Make sure all parts are clean and liquid flows freely
through all channels, stopcocks and tubing.
2
Assemble the stopper. Select a one-hole rubber stop-
per that fits securely in the top of the mixing cham-
ber. Attach a short piece of flexible vinyl tubing that
can be clamped off to make an airtight seal to a rigid
piece of glass or plastic tubing that fits tightly in the
hole of the stopper. The stopper assembly should seal
the mixing chamber airtight when the slide valve is
closed and the outlet tubing is clamped off.
3
Add a magnetic stir bar of the appropriate dimen-
sions (20–30 mm long) to the mixing chamber and
place the unit on a magnetic stirrer. Connect tubing
to the outlet connector and pump, then adjust pump
speed, if needed. Position or connect the tubing to
the receiving vessel (gel casting unit, centrifuge tube,
etc.) at top or bottom, as appropriate.
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0% 20% 40% 60% 80% 100%
A
C
E
B
D
relative concentration
% of gradient delivered
Fig 3. Examples of
exponential gradients.