180 Advanced Operation Manual
5 Detectors
Setting parameters for the TCD
1 Press [Front Det] or [Back Det].
2 Set the detector temperature. Do not set higher than the
maximum temperature allowed for the column because part of
the column passes through the heated block and into the cell.
3 Verify that makeup gas type is the same as that plumbed
to your instrument (next to Makeup line in the parameter
list). Change the gas type, if necessary.
4 Set the reference gas flow rate.
5 If you are using packed columns, turn off the makeup gas
(or proceed to step 6 and enter 2 to 3 mL/min, see “TCD
carrier, reference, and makeup gas” on page 176) and
proceed to step 7
6 If you are using capillary columns:, choose a flow mode
and set the makeup gas flow or combined flow.
7 Turn on the filament. Allow about 30 minutes for thermal
stabilization. A longer period may be needed for the
highest sensitivity.
8 If necessary, turn Negative polarity [On/Yes] to invert
negative- going peaks. When a sample contains
components giving both positive- and negative- going
peaks, Negative polarity can be switched on and off during
a run as a timetable event.
Example: Packed mode (packed and large capillary columns)
Column flow is 15 to 60 mL/min. Set the reference flow to
1.5 times the sum of column flow + makeup flow.
Makeup gas is recommended with all capillary columns. It
allows the column to be inserted all the way into the
detector and withdrawn 1 mm. If makeup is not used, the
column must be no more than 3 mm above the ferrule.
Minimum makeup flow is 1 mL/min.
1/8-inch stainless steel column If column flow is 30 mL/min,
set the reference flow to 30 × 1.5 = 45 mL/min. Total
detector flow is 30 + 45 = 75 mL/min.
10 m × 0.53 mm column If column flow is 15 mL/min and
makeup flow = 2 mL/min, set the reference flow to 1.5 × (15
+ 2) = 25.5 mL/min. Total detector flow is 17 + 25.5 =
42.5 mL/min.
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