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G1600A CE Fraction Collection
System Overview
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Fraction Collection
In the bioscience and pharmaceutical areas the capability of fraction
collection is frequently required in order to characterize separated
components by off-line analysis techniques such as MALDI/TOF-MS or
protein sequencing. Figure 50 shows general principle of how fraction
collection in CE works.
Figure 50
Fraction Collection
Apply pressure
or voltage
Peak detection
Buffer
Buffer
Collection vial
Fraction collection uses information from the built-in diode array detector to
find the exact time when a peak appears at the outlet electrode. A peak is
detected if the peak signal exceeds the threshold set in the diode array set up
screen. Therefore some diode array settings have to be adjusted such as
selecting spectra storing. When a new peak is detected, the time is calculated
in which the peak will leave the capillary. The length of the capillary between
the detection window and the outlet is fixed to 8.5 cm.
In addition some settings have to be entered, such as the inner diameter of
the capillary, the correct total and effective capillary length in the Capillary
Information screen, e.g. inner diameter is 100 µm, total length is 96.5 cm and
effective length 88 cm as shown in Figure 51:
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Capillary Electrophoresis
Fraction Collection
Figure 51
Capillary Information Screen
Peaks may be collected either by using pressure or electrokinetic elution.
Since peak volumes are generally in the size of nl volumes, peaks are
collected into microvials containing about 10–15 µl of an appropriate solution
(for correct selection, see Table 7). The lift offset should be set to 3 mm in the
CE Home Values menu. Applications include fraction collection from CZE,
MECC, from CGE analyses using fixed gels and even from CIEF separations.
The instrument logbook shows the steps done during fraction collection e.q.
when a peak has been detected, the vial in which the peak has been collected
etc.
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