Principles Of Operation - Agilent Technologies 1220 Infinity II LC User Manual

5
Solvent Delivery System Description

Principles of Operation

Principles of Operation

The liquid runs from the solvent reservoir through the degasser to the DCGV,
and from there to the inlet valve. The pump assembly comprises two
substantially identical plunger/chamber units. Both plunger/chamber units
comprise a ball-screw drive and a pump head containing one reciprocating
sapphire plunger.
A servo-controlled variable-reluctance motor drives the two ball-screw drives
in opposite directions. The gears for the ball-screw drives have different
circumferences (ratio 2:1), allowing the first plunger to move at twice the
speed of the second plunger. The solvent enters the pump head close to the
bottom limit and leaves it at its top. The outer diameter of the plunger is
smaller than the inner diameter of the pump head chamber, allowing the
solvent to fill the gap in between. The first plunger has a stroke volume in the
range of 20 – 100 μL depending on the flow rate. The microprocessor controls
all flow rates in a range of 1 μL/min–10 mL/min. The inlet of the first
plunger/chamber unit is connected to the inlet valve, which is opened or
closed allowing solvent to be drawn into the first plunger pump unit.
The outlet of the first plunger/chamber unit is connected through the outlet
ball valve and the damping unit to the inlet of the second plunger/chamber
unit. The outlet of the purge valve assembly is then connected to the
chromatographic system.
88 1220 Infinity II LC System User Manual