Dionex UltiMate FLM-3100, Operating Instructions Manual

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UltiMate 3000 Series: Flow Managers and Column Thermostats
Operating Instructions Page 11
2.2 Theory of Operation (UltiFlow)
The fundamental requirement on a flow manager for liquid chromatography is the ability
to create constant low flow rates for nano, capillary, and micro HPLC applications, as well
as to equalize the temperature. The flow managers of the UltiMate 3000 system are fitted
with a flow splitter with integrated flow control that ensures constant flow rates, ranging
from micro liter to nano liter flows. The flow rate is influenced neither by varying column
backpressures nor by the temperature or solvent viscosity.
The flow splitter is equipped with two fluidic resistors that split the flow from the pump in
the reciprocal ratio of the resistance. To ensure identical pressure drop at both resistors, the
outputs of the flow splitter are connected via a cross arm with integrated flow meter. A
controller adjusts the unbalance flow to a very low offset value near zero to flush the cross
arm with fresh solvent permanently. To ensure this, the waste path includes an adjustable
valve that adjusts in dependence of the column pressure (
→
Fig. 1).
This innovative method creates constant low flow rates based on the split ratio and the pump
flow. Different lowest flow rates are created by different pump flow rates, but they are always
split according to the split ratio. This is independent of the solvent composition and the
column pressure.
Pump
Waste
Detector
Column
Valve
Flow splitter
Control
Flow meter
1:100
Fig. 1: Operation principle of flow splitting with control
For temperature equalization, temperature stability is more important than the absolute
precision of the setting. The flow manager contains advanced electronic circuits that can
maintain the selected temperature with a precision of ±0.1 °C.
The thermo-optimized design reduces the time required to equilibrate the temperature between
the column and the solvent. The Peltier elements of the flow manager heat up and cool down
the columns. The heat exchanger inside the column chamber also helps to bring the air and all
components in the chamber to the desired temperature, including the flow splitter and column
switching valve(s).