Varian 450-GC, User Manual

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Injectors – 1079 PTV Injector
Page: 178 User Manual 450-GC Varian, Inc.
1079 PTV Modes of Injection
The 1079 PTV injection mode is defined by the Split Vent program and by
choice of insert. The Split Vent is controller differently based on the pneumatics
installed, with EFC the split valve is controlled from the Injector section, with
manual pneumatics the external events control the split valve. The following are
brief descriptions of the various modes of injection; more detailed information
on each mode is given later in this section. The 1079 PTV is optimized for PTV
and LVI, but it is possible that he Injector can work in other modes.
Temperature Ramp Splitless Mode
The splitless temperature ramp mode is preferred for compounds that are
altered by higher temperatures (thermolabile). Also, the splitless temperature
ramp mode is used with wide boiling range mixtures (e.g., hydrocarbon
mixtures). 2 glass inserts are recommended when operating in the splitless
temperature ramp mode: 1) The 2 mm ID glass wool packed insert is used for
non-polar compounds at levels
>
1 ng; and 2) the 0.5 mm ID open insert is used
for thermolabile and/or polar compounds at trace levels (pg level).
In the splitless temperature ramp mode, the Injector is held at a temperature
that is equal to or slightly below the boiling point of the injection solvent. The
sample is deposited on the surface of the insert. After injection, the temperature
of the Injector is increased rapidly (ramped). As the temperature of the Injector
increases, the sample then vaporizes and is swept onto the column.
Large Volume
In the large volume mode of injection typically > 5 µL of sample is deposited
into the Injector slowly, the solvent is vented and then the components of
interest are transferred to the column. This is done using a special split vent
program and an Injector temperature ramp. The CP-8400/8410 AutoSampler
allows automated injection of up to 250 µL of sample.