Thermo Scientific ISQ, Руководство пользователя

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4
Creating a Method
Creating a Method for the GC
Thermo Scientific ISQ User Guide 53
b. Finally, if your analysis requires a higher flow to quickly sweep the analytes into the
column, which may be needed with high temperature injectors and thermally labile
compounds, you can use the surge pressure to increase the column flow for the surge
duration time.
Figure 40. Setting the Carrier Gas Parameters on the TRACE GC Ultra
4. If you have a Programmable Temperature Vaporizer (PTV), click the Left PTV or Right
PTV tab to configure it. The PTV is a low thermal mass injector that allows the
instrument to rapidly heat or cool the inlet. You can use the PTV tab to program the
temperature of the injector. See the GC documentation for details about the PTV or
other types of injectors.
5. 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
Tip We recommend turning on the septum purge, which means an additional 5 mL/min
of carrier gas will go through the injector. This reduces the buildup of contaminants in the
injector, on the column, and in the ISQ instrument. If you perform a splitless injection,
even if the split flow is set, the split flow will be turned off for the splitless time. The
septum purge will be turned off for the stop purge time. After these times, the split flow
and septum purge will be reactivated.