Smartline Autosampler 3900 Manual / Handbuch V 1508 03/2007

18 Injection Principle
Fig. 15 Partial loop fill injection: injecting sample.
The injection valve switches into the
INJECT position. The sample loop is
now part of the HPLC mobile phase
flow path: sample is transported to the
column. The analysis starts.
The next injection sequence will start with a flush of 50% of the
programmed flush volume, in case an injection from the same vial and no
wash routine is programmed. Otherwise it will start with a flush of the
programmed flush volume. If the withdrawal of sample for the next
injection will exceed the total volume of the sample buffer tubing, the
buffer tubing is rinsed before the next injection. The next injection will
start with the programmed flush.
Air segment
An air segment can be used to reduce the amount of flush volume. This
air segment is at the front of the flush volume and will not be injected.
The air segment can be selected in system settings (ON/OFF, See page
34).
With a standard needle the flush volumes must be minimal 30 µl for
injections with air segment and 35 µl for injections without air segment. If
the samples are highly viscous it may be necessary to program larger
flush volumes and reduce the syringe speed for better performance.
Fig. 16 Situation after filling the loop in case of Partial loop fill injections with (A)
or without air segment (B)
µl Pick-up injections
The switching sequence for a µl pick-up injection is schematically shown
in the following figures:
The Initial situation: the injection valve
is in the INJECT position. The sample
needle has entered the vial of
transport liquid (mobile phase, this to
avoid disturbance of the
chromatogram with an additional peak
of the transport solvent).
Fig. 17 µl pick-up injection: initial situation.