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Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
210 Split/Splitless Inlet
The theory and procedures described in this section apply to both the
standard (10 to 30 psig) split/splitless inlet and the high-pressure (0 to
100 psig) split/splitless inlet.
Theory of operation
The split mode of operation is used when small quantities of sample need to
be introduced into a capillary column. The injected sample is vaporized and
then split between the column and an inlet vent. Typical split ratios used are
20:1 up to 500:1, where the majority of sample is vented out the inlet split vent.
The splitless mode of operation is generally used for trace analysis. In trace
analysis, sample splitting would further dilute the amount of analyte entering
the column and is not desired. In splitless mode, nearly all the analyte and
solvent enter the column.
To avoid solvent interferences, an initial column temperature of 25 to 30° C
below the solvent boiling point is recommended and an inlet purge time of
0.5 to 1.0 minute time be used. This splitless mode of operation is best for
compounds with a retention index greater than 600.
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