User`s guide

Theory of Thermal Desorption

305

Inlet Split function in the ATD/TD method. See Setting Sample Split

Ratios on page 228 for details of inlet split operation.

At the end of the desorb time, SV2 is switched to B, SV3 and SV5

are closed and the heated valve is rotated to Position B.

Cooling and Unloading the Tube After Desorption—After

desorption, the sample tube is allowed to cool for 2 minutes. SV3

and SV5 are opened for 15 seconds to depressurize the sample tube,

which is then returned to the carousel.

In order to allow purging of the charcoal filter and the tubing

connected to the inlet splitter gas line, an inlet split flow, of

approximately 25 mL/min, should be set even if the inlet split

function is not being used during the sample analysis.

To set an inlet split flow even if you are not using an inlet split for

your analysis:

1. Adjust the inlet split and desorb flows as described in

Setting the Desorb and Inlet Split Flow Rates for the

Manual Pneumatics TurboMatrix Series 100 TD and

150 ATD on page 78.

2. Disable the inlet split feature on the options tab. See The

Options Tab on page 103.

Secondary (Trap) Desorption and Analyte Transfer to GC—

After completing the primary desorption, the ATD/TD verifies that

the GC is ready and SV1 and SV2 switch to divert the carrier gas

flow through the cold trap. SV3 and SV5 remain closed. The heated

valve is rotated to Position B. The cold trap is heated to its high

temperature, at the specified rate and an inject signal is sent to the

GC. The trapped volatiles are released and swept through the heated

transfer line to the GC column.

The sample can again be split by activating the outlet split function

in the method. If you have enabled the outlet split option SV4 opens.

The outlet split flow must be adjusted manually prior to beginning

your analysis. See Setting Sample Split Ratios on page 228 for

details of outlet split operation.

SV1 switches after the tube desorption, before the trap heat starts.

Three minutes after the end of trap hold, SV2 will switch back to A.