User`s guide

Method Development
211
nature of chromatography it is often possible to extend the tube
desorb time, since the GC run tends to be lengthy, without affecting
productivity.
During the analysis of labile or unknown materials, it is preferable to
lower the temperatures used and extend the desorption times.
Purge Time—When the leak test has been completed, air is purged
from the tube prior to heating it for desorption. This is done to
reduce the risk of adsorbent or analyte oxidation during desorption.
The sample tube is purged with carrier gas for the duration of the
Purge Time. The minimum purge time is 0.1 minute.
Desorb Time—During the Desorb Time the tube oven is placed
around the sample tube and tube is heated with a continuous flow of
carrier gas, removing the sample from the tube to the cold trap.
If complete desorption is not obtained, you may need to increase the
desorb time. The minimum desorb is 1 minute.
NOTE: For the TurboMatrix 300 TD, 350 ATD and 650 ATD PPC
units the desorb flow time is the time your desorb pressure
will be maintained if it is different from the column
pressure.
Trap Hold Time (for TurboMatrix 100 TD and 150 ATD manual
only)—Specifies the length of time, during which the trap is held at
its high temperature for trap desorption. You can enter any value
from 0.0 to 999.0 minutes. Typically, a value of 5 minutes is
adequate.
The time for which the trap is kept hot after the start of secondary
desorption should be sufficient to allow complete desorption from
the trap. The trap high period can also be extended for up to 999
minutes to recondition the trap before the next analysis.
Standard Inject Time—If your instrument is equipped with the
Internal Standard Addition accessory (P/N M041-3335), a gaseous
internal standard can automatically be introduced onto every sample
tube prior to desorption. The standard will be added after the tube
purge. Enter an injection time between 0.1 and 9.9 minutes.
GC Cycle Time—The cycle time is defined as the interval between
one trap heat and the trap heat for the next sample, and enables