User`s guide

Method Development
230
your trap loading and column capacity and flow, figure out how
much sample you need on the trap and therefore what the outlet split
must be. Then figure out how much you need to split the tube sample
in order to put the required amount on the trap. The overall split is
the product of the two.
Zero Split (Splitless) Operation
One type of trap is offered for the TurboMatrix desorber, the “low-
flow” type which has a built in capillary to reduce dead volume.
Low Flow Trap— Desorb flows of >3mL/minute are used, not
exceeding 10mL/minute. Zero split injections are possible with
0.32mm ID capillary columns. If separation of ultra-light
compounds is required, a minimum flow of 5mL/minute is required.
Zero splitting is achieved by disabling (un-checking) both the inlet
and outlet split on the Option tab entries.
In practice, a zero split ratio is rarely required. Superior performance
will always be obtained, even with a small outlet split ratio, by
increasing the velocity of the carrier gas through the trap during
secondary desorption.
Under zero split conditions, the flow through the sample tube during
primary desorption is equal to the flow through the cold trap during
primary desorption, which is also equal to the desorb flow. Under
zero split conditions, the flow through the heated trap during
secondary desorption is equal to the column flow.
Single Split Operation
A single split may be used when between 60% and 0.33% of
adsorbed components from the sampling tube are to reach the GC
analytical column and detector. This configuration is primarily used
with high resolution capillary columns.
The single split point is usually set up on the outlet of the cold trap to
maximize the carrier gas flow through the cold trap during
secondary desorption. Single split operation is enabled by selecting
outlet split and disabling inlet split on the Option tab. Adjust the
flow rates as described in Setting the Outlet Split Flow on page 80.