Bio-Rad BioLogic Signal Import Module (SIM) - Manual (Page 188)

10.0 BUFFER BLENDING
The Maximizer is a component of the DuoFlow system that dynamically "Blends" water, salt and the
conjugate acid and base of a buffer to produce a solution with a specific salt concentration and pH. Buffer
Blending is a powerful chromatographic tool that in conjunction with the scouting feature of the DuoFlow
software can be used to optimize salt concentration, gradient slope and pH in a set of unattended
experiment. The results of these experiments can then be easily compared and analyzed using the Trace
Compare feature of the DuoFlow software.
Chromatography with a Maximizer offers three major benefits. First is its "Buffer Blending" feature that
allows the composition of the pump effluent to be defined in terms of pH and salt concentration from a single
set of reagents. Buffers at any pH within the pH range of the buffer (typically pKa ± 1) can be obtained.
Second, solution preparation is simplified since buffer salts need to only be weighed out and diluted to the
appropriate concentration. There is no need to adjust the pH of the solutions. The third benefit of using a
Maximizer is that it doubles the accessible flow rates. This occurs since gradients are no longer made by the
pumps but by the Maximizer proportioning valves. This allows both pumps to run at their full speed.
10.1 DOUBLED FLOW RATE CAPACITY USING A MAXIMIZER
The Maximizer valve system doubles the DuoFlow system flow rate capacity from 10 ml/min (F10 pump
head) and 40 ml/min (F40 pump head) to 20 ml/min and 80 ml/min respectively. This is accomplished since
the Maximizer proportioning valves, rather than the pumps, are used to change buffer composition (percent
Buffer A and Buffer B). This doubled flow rate capacity is available only when Buffer Blending is defined in
the Device Setup. The Buffer Blender feature can be used in two different ways. 1) "Buffer Blending",
where water, salt and the conjugate acid and base of a buffer are combined to produce a solution with a
specific salt concentration and pH, or 2) "Non-Blending", where two solutions of fixed composition
(i.e. Buffer A = 25 mM Tris pH 8.1 and Buffer B = 25 mM Tris pH 8.1 + 1 M NaCl) are mixed to produce a
solution with a specific salt concentration.
Buffer Blending. In "Buffer Blending", proportioning valve A is used to control the amount of acid and base
added and valve B is used to control the amount of water and salt added. The effluent from pump A and B
are then combined in the mixer. In "Buffer Blending", the effluent from pumps A and B dilute each other and
so each solution must be prepared at a 2X concentration. Buffer Blending allows buffers of any pH within the
buffer pH range to be produced. Buffer Blending is discussed further in Section 10.2.
Non-Blending. In "Non-Blending", both proportioning valves have the same function and are each used to
control the percent Buffer A and Buffer B in the pump effluent. In this case, the effluent from pump A and
pump B are identical so no dilution occurs when they are mixed. Therefore, the buffers can be prepared at
their 1X concentration. The Buffer Blender setup dialog includes a "High Flow Non-Blending (1x)" buffer
system for use in situations where a high flow rate is required but where "Buffer Blending" is not needed.
When using this method, inlet tubes A1 and B1 are placed in Buffer A and inlet tubes A2 and B2 are placed
in Buffer B.
A second high flow non-blending buffers system titled "High Flow Non-Blending", has also been included in
Buffer Blender buffer system list. This high flow non-blending method uses inlet valve A to load Buffer A and
inlet valve B to control the percent Buffer A and B in the effluent. In this case, Buffer A is plumbed to inlets
A1 and B1. Buffer B is plumbed to inlet B2 and must be prepare at 1X in buffer and 2X in salt. Inlet A2 is not
used and should be plugged.
MULTIPLE COLUMNS ADVANCED SYSTEM APPLICATIONS
10-1