Agilent Technologies 1260 Infinity II User Manual page 17

What is Pump Elasticity Compensation?
The flow path of the pump consists of pump chambers, sapphire pistons,
polymer seals, stainless steel tubing of different dimension, pressure sensor,
and so forth. All of these parts deform when pressurized. The sum of this
deformation is called pump elasticity.
Let us look at a practical example: Piston 1 draws solvent at ambient pressure.
The movement direction is reversed and the piston 1 now compresses the
solvent until the operating pressure of the HPLC system is reached. The outlet
valve opens, and solvent is pumped by piston 1 into pump chamber 2. Due to
two factors, the solvent volume that is delivered into the system at high
pressure is smaller than it is supposed to be:
1 The solvent is compressible
2 The pump has a certain elasticity which causes its internal volume to
In order to compensate for these two influences, their contributions must be
known. An elasticity calibration allows separating pump properties from
solvent properties and therefore allows transferring solvent properties, which
have been obtained from one pump to another pump with different elasticity.
Elasticity calibration is done with a solvent, which properties (compressibility,
thermal expansion) are well-known and documented: pure water. When
pumping water and using its property data for controlling the pump, any
deviations from the theoretical pressure profile during solvent recompression
are caused by the elasticity of the pump.
The Pump Elasticity Calibration calculates correction factors to compensate
for the individual elasticity of the pump that is being calibrated. The elasticity
is different for every pump and may change with the replacement of parts in
the flow path, e.g. pump seals.
All binary pumps are elasticity calibrated at the factory and require recalibration
only after preventive maintenance or major repairs to the flow path. Replacement
of capillaries or PTFE frits are not considered as a major repair.
Incorrect pump elasticity calibration.
C AU T I O N
Solvent compressibility calibrations acquired with a miscalibrated pump will work, but
they are not transferable to other pumps. A correct pump elasticity calibration is an
essential prerequisite for successful solvent compressibility calibrations.
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InfinityLab LC Series 1260 Infinity II Binary Pump User Manual
increase with pressure.
Calibrate the pump elasticity correctly.
Introduction
Overview of the Hydraulic Path
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