Operating Principle - Thermo Scientific VF-F20-A Operating Manual

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3 Device Overview
3.2

Operating Principle

Page 34
The operation principle of a purification LC system is based on a setup of
an HPLC system combined with a fraction collector between the
detector and the waste container. The capillary connecting the HPLC
detector with the fraction collector is called delay capillary.
Figure 1: Operating principle of a purification LC system
Fractionation is the process of collecting the eluting liquid of interest
into target sample containers with a fraction collection valve and a
needle.
When a run is started, and the sample is injected by the autosampler the
fraction collection valve is in waste position and the needle moves to the
position of the defined sample container. When the Chromatography
Data System (CDS) triggers the start of a fraction collection the fraction
collection valve is switched to collect position, under consideration of
the delay volume between the detector outlet and needle tip, to direct
the flow into the collection sample container. The needle can be
programmed to stay above the sample container or descend into the
sample container during fraction collection. When the CDS triggers a
tube change the needle moves the next position on the sample rack. For
that step the fraction collection valve can be programmed to switch to
waste or stay in collect position. When the CDS triggers the end of the
fraction collection the fraction collection valve is switched to waste and
needle moves to the next position on the sample rack.
If the flush function is enabled and the CDS triggered the end of the
fraction collection the fraction collection valve will be switched to flush
position and the needle will stay at the current position on the sample
rack. In flush position the flush buffer loop filled with flush solvent is
Integral Fraction Collector FT (VF-F20-A) Operating Manual