ISQ User Guide - Write Frame of Mind

4 Creating a Method
d. Click the Left Carrier or Right Carrier tab. 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 constant pressure or constant flow. If you use
constant pressure, as the column is heated in the oven, the flow rate will fall because
the 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, which is under vacuum,
the vacuum compensation should be on.
The flow can also be operated in programmed flow or programmed pressure modes.
In these modes, you may have up to three flow rates or pressures to use during an
analytical run. This is not commonly used, but may be necessary if you have a
particularly challenging separation.
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, which can affect the
system performance.
e. Click the Run Table tab to configure how to control external valves and devices.
Consult the appropriate documentation for more detailed information.
44 ISQ User Guide Thermo Scientific