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3.7
Gradient Operation (Dionex RFC-30 Only)
A change in the eluent concentration during an analysis is referred to as a
gradient. The Dionex RFC can run a linear ramp gradient, which is a
uniform change in eluent concentration over a specified time.
To set up a gradient, specify a starting concentration, a gradient time, and
a final concentration. The gradient time is the number of minutes it takes
to reach the final concentration. The final concentration can be either
higher or lower than the starting concentration.
A TTL input connection to a controlling device (such as the pump,
combination pump/detector, or DX-120) is used to start and stop the
gradient. See Section B.2 for DX-320, DX-500, and DX-600 connection
instructions. See Section B.3 for DX-120 instructions.
Figure 31 shows an example linear ramp gradient with a starting
concentration of 30 mM, a gradient time of 10 minutes, and a final
concentration of 60 mM. In the example, the gradient TTL input is kept
active beyond the gradient time and the final concentration is maintained
until the TTL is turned off. The eluent concentration then returns to the
starting value.
Conc.
(mM)
Doc. 031880-04 1/12
60
Gradient
TTL On
40
20
Gradient Time
(10 Minutes)
0
2
4
6
0
Retention Time (Minutes)
Figure 31. Gradient Example
Gradient
TTL Off
8
10
12
14
Operation
29
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