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Splitless
Injection
The classical splitless injection technique involves vaporizing the sample in a
hot injector and slow transfer to the column. The split state is OFF during
the sampling period; therefore, all of the injected sample should enter the
column. The initial column temperature is maintained for at least the
sampling time to trap all sample components at the head of the column. At
the end of the sampling period (typically 0.5 to 1.5 minutes) the split state is
turned ON to vent any residual sample or solvent from the injector.
The following table describes typical method parameters for an isothermal
splitless injection.
Table 5 Splitless Injection Method Parameters
Injector Insert
4 mm ID open insert packed with glass wool
Column Position
3.7 cm from the bottom of the column nut at the base of the injector.
Injector Temperature
Initial temperature isothermal 250
°
C.
Column Temperature
50
°
C initial for 1 min, ramp to 250 °C at 20
°
C/min, hold 5 minutes.
Carrier gas control
Set the initial split mode to OFF and time program it to ON after 0.75
minutes. In this case the splitless sampling time is 0.75 minutes. The split
ratio during the split ON period should be set to 50. Set the appropriate
pressure or pressure ramp to achieve the desired column flow rate.
Note that in all the above cases the parameters given are generic and will
have to be optimized (including column position) for specific applications.
Particular care should be taken with the large volume mode of injection
where the initial injector temperature and timing of the split states have to be
carefully selected.
Testing the 1177 Injector Performance
The following procedure describes how to test the performance of the 1177
Capillary Injector. This is best done with a test sample containing an
appropriate set of components for the installed detector. The following table
lists the series of test samples available for Varian GC.
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