Varian 450-GC, User Manual

Page: 128 / 205

Injectors – 1079 PTV Injector
Page: 190 User Manual 450-GC Varian, Inc.
1079 PTV Modes of Operation
The 1079 PTV 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 and the position of the column within the insert.
•
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.
In many cases switching from one 1079 PTV mode to another involves
changing the glass insert. A detailed stepwise procedure to carry out
this task is given in the Maintenance section of this manual, on page
195. In most injection modes the insert is installed with a graphite
ferrule. Use the special fixture supplied with the 1079 PTV accessory kit
to install the ferrule correctly on the insert.
Isothermal 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 1079 PTV
method.
Injector Insert Install the fritted split insert (03-926119-46) or unpacked split insert (03-
926119-45). See instructions in the Maintenance section on page 195 for
changing the 1079 PTV insert.
Column Installation 7.5 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 1079 PTV 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.
Table 34: Split Injection Typical Conditions