46 1100 Series WS MWS Reference Manual
2 Optimizing Performance
Injector Program with Needle Wash
The injector program includes the command NEEDLE WASH. When this
command is included in the injector program, the needle is lowered once into
the specified wash vial before injection.
For example:
1 DRAW 5 µl
2 NEEDLE WASH vial 7
3 INJECT
Line 1 draws 5 µl from the current sample vial. Line 2 moves the needle to vial
7. Line 3 injects the sample (valve switches to main pass).
Using the Flush Port
During the injection process when the sample is in the loop and when the
valve still is in Bypass, the outside of the needle can be washed in a flush port
located behind the injection port on the sampling unit. As soon the needle is in
the flush port a peristaltic pump fills the flush port with fresh solvent during a
defined time. The volume of the flush port is about 680 µl and the pump
delivers 6 ml/min. Setting the wash time to 10 seconds is sufficient to refill 2
times the flush port. In most cases this is enough to clean the needle outside.
At the end of this flush process the needle return to the injection port, the
valve is switched to the Mainpass position and directs the pump flow back
through the sample loop.
Further reduction of carry-over can be obtained using an injector program
with additional injection valve switching, see “Using an Injector Program" on
page 47
Recommended wash solvents
• water
• ethanol
• methanol
• water/acid
• water/acetonitrile
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