Inlets 3
Advanced Operation Manual 115
These additional injections take time. The inlet and oven
temperature programs, mainly the Initial time values, must be
adjusted to allow for this. So must the various time values
that control the inlet operation. This is discussed in more
detail under “To develop a PTV method that uses large
volume injection” on page 117.
Setting parameters for solvent vent operation
Mode: The current operating mode—solvent vent.
Tempera ture Actual and setpoint initial inlet temperatures.
Initial time The time, measured from Start Run, when the
initial inlet temperature hold ends. Must be greater than Vent
end time.
Rate # Temperature program rate for inlet thermal ramps.
Final temperature # Final inlet temperature for ramps 1, 2,
and 3.
Final time # Hold time at Final temp #. This time is a
duration; it is not measured from Start Run.
Pressure Actual and setpoint inlet pressure before and after
the vent period. It sets the starting point of column head
pressure.
Vent pressure The inlet pressure during the vent period. By
decreasing the inlet pressure while venting, solvent
elimination proceeds faster. Also, the pressure reduction
decreases the amount of carrier gas—and solvent vapor—that
enters the column during this time.
Users select from 0 to 100 psig. If 0 is chosen, the inlet uses
the lowest pressure possible at the given vent flow. Table 23
shows approximate values for this minimum at various vent
flows of helium. Pressures less than those in the table are
not possible unless the flow is reduced.
Tabl e 23 Minimum attainable pressures
Vent flow (mL/min) Actual vent pressure at
“0“ psig setpoint
Actual vent pressure at
“0” kPa setpoint
50 0.7 5
100 1.3 10
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