CP-3800 GC Operator’s Manual
65
1177 Modes of Operation
The 1177 can be operated in several modes, depending on the nature of the
sample and requirements of the analysis. When designing an injection
method the most important parameters are:
•
the injector insert used;
•
the injector and column temperature when the injection is made;
•
the carrier gas flow profile through the injector.
The following is a brief description of the method parameters used for each
injection mode. In all cases Electronic Flow Control is used for carrier gas
control.
Note
: In many cases switching from one 1177 mode to another involves
changing the glass insert. A detailed stepwise procedure to carry out this task is
given in the Maintenance section of the 3800 Getting Started manual. In most
injection modes the insert is installed with an o-ring.
Split
Injection
The split mode is used when samples are relatively concentrated and for
neat samples. This mode of injection involves rapid vaporization of the
sample followed by sample splitting. Splitting involves directing a portion of
the sample into the column while the remainder is vented. The split ratio is
defined as the proportion of sample vented to the sample entering the
column. With EFC carrier gas control this parameter can be set
automatically in the 1177 method.
Table 4 Split Injection Typical Conditions
Injector Insert
4 mm ID open insert packed with glass wool
Column Installation
3.7 cm from the bottom of the column nut at the base of the injector
Injector Temperature
Isothermal 250
°
C.
Column Temperature
50
°
C initial for 0.1 min, ramp to 250
°
C at 20
°
C/min, hold 5 min.
Carrier Gas Control
Set the split mode to ON for the duration of the run in the 1177 method
section, and set the split ratio to 100. The sample will be split upon
injection and a representative portion representing 1/100
th
of the amount
injected will enter the column. Note that the split ratio is a method specific
parameter and should be set appropriately for individual analyses. In
addition the injector pressure or pressure ramp should be set to achieve
the desired column flow rate.
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