Analytical Head; Injection Valve - Agilent Technologies 1220 Infinity II LC User Manual

6
Injection System Description
Autosampler
board, while the needle-in-vial position is determined by counting the motor
steps from the upper needle-sensor position.

Analytical head

The analytical head is driven by the stepper motor connected to the drive shaft
by a toothed belt. The drive nut on the spindle converts the circular movement
of the spindle to linear motion. The drive nut pushes the sapphire plunger
against the tension of the spring into the analytical head. The base of the
plunger sits on the large bearing of the drive nut, which ensures the plunger is
always centered. A ceramic ring guides the movement of the plunger in the
analytical head. The home position of the plunger is sensed by an infra-red
sensor on the sampling unit flex board, while the sample volume is
determined by counting the number of steps from the home position. The
backward movement of the plunger (driven by the spring) draws sample from
the vial.
Table 20
Number of steps
Volume resolution
Maximum stroke
Pressure limit
Plunger material

Injection Valve

The two-position 6-port injection valve is driven by a stepper motor. Only five
of the six ports are used (port 3 is not used). A lever/slider mechanism
transfers the movement of the stepper motor to the injection valve. Two
microswitches monitor switching of the valve (bypass and mainpass end
positions).
No valve adjustments are required after replacing internal components.
108
Analytical head technical data
Standard (100 µL)
15000
7 nL/motor step
100 µL
600 bar
Sapphire
1220 Infinity II LC System User Manual