User`s guide

Method Development
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All forms of Tenax are susceptible to decomposition since they are
polymer based, so there is always some background (artifacts)
associated with its use. This can be exacerbated if the material is not
properly conditioned. If you are working at higher levels, where
hydrophobicity is perhaps a concern, and desorb temperatures to 350
°C max are acceptable, Tenax is suitable for compounds with
volatility higher than that of C6.
If you are working at very low analyste concentrations (trace levels)
you may wish to select a carbon-based sorbent, which is essentially
background free. These are materials such as Carbotrap and
Carbosieve or Carboxen.
Setting Sample Split Ratios
The ability to have sample split points on both the inlet and outlet of
the cold trap simplifies the analysis of samples containing relatively
large amounts (tens of milligrams) of water. Additionally, it
facilitates split ratio selection between zero and 100,000:1. It also
enables the ATD/TD to perform both trace level environmental
monitoring and the determination of percent levels of volatiles in
solids.
When you are configuring the instrument for single or double split
operation you must take the following information into
consideration:
• As the volume of a sampling tube is approximately 3 mL, a
minimum carrier gas flow rate of 10 mL/min is generally
required for efficient tube desorption.
• During secondary desorption, components need to be eluted
from the cold trap and transferred to the GC column as quickly
as possible in order to prevent band broadening. The carrier gas
flow rate through the cold trap during the secondary (trap)
desorption should therefore be at least 2.5 mL/min when using a
narrow bore trap or at least 10 mL/min when using a standard
cold trap tube.
• Optimum flow rates for high resolution capillary columns are
between 0.5 and 2 mL/min. For 0.32-mm i.d. columns 1.0 to 4
mL/min can be used. The tables in Appendix D provide flow
rates that correspond to a supplied gas pressure.
NOTE: In order to obtain accurate results you must measure the
column outlet flow at the end of the column during