PerkinElmer CLARUS 590 GC, Руководство пользователя

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Set up the Splitless Mode for a CAP or PSS Injector . 93
Set up the Splitless Mode for a CAP or PSS Injector
The Splitless Mode is used for trace analyses. Most of the sample is transferred onto the column, then the
split vent is opened, thereby venting any sample remaining in the injector liner. This step describes how to
set the split mode for PPC modules .
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Setting the Splitless Mode Using PPC Modules.
NOTE: In the Splitless Mode, the split vent must be opened after the sample has transferred to the head of the
column (i.e., 0.5 - 2.0 minutes after the run has started).
The procedure which follows assumes that the carrier gas pressure has been set (see Step C in this
chapter).
NOTE: The injector is shipped with a wide-bore injector liner. You may want to install a narrow-bore liner. Both
liners must be packed with quartz wool before running your analysis.
Setting the Splitless Mode Using PPC Modules
Splitless Injection w ith Pressure Pulse (Flow Pulse, Velocity Pulse) Technique
Pressure (flow or velocity) pulse injection is recommended for splitless operation, especially when analyzing
wide boiling-point mixtures and/or large volume injections. This technique increases the pressure (flow,
velocity) in the system at the time of injection to minimize the gas expansion in the injector liner and
maximize the gas sample transfer onto the column. Therefore, you should use the highest pressure that
your application will allow. This provides better peak shapes, better recovery, and no discrimination for
both low boiling and high boiling compounds.
This technique can be incorporated in your Clarus GC method. The initial pressure (flow, velocity) is high
(for example, 70 psig) and held at this high pressure for enough time (for example, 0.25 to 2.0 min) to
transfer your sample onto the column. This time needs to be experimentally determined for your sample,
injector temperature, and injector liner used. You want a time that will allow most of your sample to
transfer onto the column as well as maintain good solvent and analyte peak shape. If the time is too short,
you will lose sample; if the time is too long, the solvent will tail and possibly obscure or affect peak shape
of early analytes. The split vent is off at injection (Split Flow = zero).
The pressure (flow, velocity) is then programmed at a controlled rate, down to the normal column
operating pressure (flow, velocity). At the same time, the split vent is set back to normal flow to clean out
any remaining sample in the liner and to release the pressure in the injector. It is important not to program
the pressure (flow, velocity) down too quickly or ballistically, since this can cause backflush of the column.
This means that the sample can flow back into the injector and either be lost out the split vent or cause
peak broadening.
Creating a Pressure, Flow , or Velocity Pulse Method
1. From the System Status screen touch the Injector icon for which you wish to create a pressure,
flow, or velocity pulse method.
The status screen, similar to the one below, for the selected injector appears.