Agilent Technologies Agilent 1260 Infinity System User's Manual page 52

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Optimization of the Agilent 1260 Infinity Binary LC
How to Achieve Lowest Carry-over
Flushing and cleaning of the autosampler to achieve near zero carry-over
During the injection routine, the sample loop, the inside of the needle, the
seat capillary, and the main channel of the injection valve are in the flow
path, and remain there throughout the duration of the run. This means
that these parts are flushed continuously with mobile phase during the
complete analysis. It is only during aspiration of the sample that the
injection valve is switched out of the flow path. In this position, the pump
effluent is led directly to the column. Prior to injection, the outside
surfaces of the needle are washed with fresh solvent. This is achieved
using the flush port of the autosampler, and prevents contamination of the
needle seat. The flush port of the autosampler is refilled with fresh
solvent by a peristaltic pump that is installed in the autosampler housing.
The flush port has a volume of about 680 µL, and the pump delivers
6 mL/min. Setting the wash time to 10 s means that the flush port
volume is refilled more than once with fresh solvent, which is sufficient in
most cases to clean the outside of the needle.
52 1260 Infinity Binary LC - System User Guide