Thermo Scientific ISQ, Руководство пользователя

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4
Creating a Method
Creating a Method for the GC
Thermo Scientific ISQ User Guide 57
3. Click the Carrier tab, which is used to set the carrier gas flows. The gas flow and the oven
temperature work together to determine how well the analytes are separated and how long
the analysis will take. You can select either constant pressure or constant flow. If you use
constant pressure, as the column is heated in the oven, the flow rate will fall because a
hotter column is more resistant to carrier gas flow. If you use constant flow, the carrier gas
pressure will increase as the column temperature increases to keep the flow constant.
Constant flow is more common. Typical flow rates are 1-3 mL/min. The pressure
depends on the column length and internal dimensions, so there is not a typical value.
Because the outlet of the column is in the ISQ instrument, which is under vacuum, the
vacuum compensation must be on.
Figure 44. Setting the Carrier Gas Parameters for the FOCUS GC
In an effort to reduce the amount of carrier gas used, you can activate the Gas Saver
mode. When used, the split flow will be reduced to the gas saver flow after the gas
saver time. It is not recommended to use a flow of less than 20 mL/min because
contaminants can build up in the injector, column, and ISQ instrument, which can
affect system performance.
4. Click the MS Transfer Line tab to set the temperature of the transfer line for a different
instrument. This tab is not used on the ISQ mass spectrometer.