Exploring injection principles
1-17
5.
The injection valve switches to the Inject position, and the sample loop
becomes part of the flow path for the HPLC mobile phase. Sample enters
the column, and analysis starts.
Air segment with partial loop needle overfill injections
An air segment that is at the front of the flush volume, but not injected, can
minimize sample dilution caused by dispersion during aspiration.
With a standard needle, recommended flush volumes are 30 µL for injections
that incorporate air segments and 35 µL for injections that do not. To enhance
performance with highly viscous samples, larger flush volumes and reduced
syringe speeds may be needed.
Sample
Buffer tubing
Syringe
Needle
Sample loop
INJECT
Column
Pump
Needle injection loop
Buffer tubing
Sample
Eluent
Flush
Sample
Eluent
Flush
Air
With
air
Without
air
