Columns and Oven 4
Advanced Operation Manual 155
About Columns
In all GCs, a sample—which is a mixture of several
components—is vaporized in an inlet, separated in a column,
and examined in a detector.
The column separates components in time because:
• When a vaporized component is presented with a gas
phase and a coating phase, it divides between the two
phases according to its relative attraction to the two
phases.
• The “attraction” can be solubility, volatility, polarity,
specific chemical interaction, or any other property that
differs from one component to another.
• If one phase is stationary (the coating) and the other is
moving (the carrier gas), the component will travel at a
speed less than that of the moving phase. How much less
depends on the strength of the attraction.
• If different components have different “attractions”, they
will separate in time.
Selecting the correct packed glass column type
This topic is covered in the Maintenance manual. See To
attach a packed column to the purged packed inlet for
details.
About the column modes
The flow modes available are determined by the GC inlet’s
control mode. When the inlet’s control mode is set to
Pressure control, all of the flow modes and pressure modes
below are available for the column. When the inlets control
mode is set to Flow control, the column’s mode is not
selectable. For an inlet’s mode of Flow control, only column
flow can be entered.
The flow modes
Flow rates are corrected to NTP (normal temperature and
pressure, 25 °C and 1 atmosphere.
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