User`s guide

Troubleshooting
368
Cause: There is ice forming on the cold trap.
Action: De-ice the trap as outlined in De-Icing the Cold
Trap on page 278. Ensure that the dry air and
the carrier gas have a dew point of -50°C or
lower.
Cause: There is insufficient air flow through the instrument.
Action: Make certain that the fan at the rear of the
instrument is not blocked and that there is
sufficient space at the rear of the ATD/TD to
allow for proper air circulation. If there is no
apparent cause of reduced air flow, switch off
the ATD/TD and contact PerkinElmer Service.
Sample Carryover
Cause: There is incomplete primary (tube) desorption.
Action: Use more efficient desorption conditions.
Change the temperature or timing parameters of
the primary desorption stage until the desired
results are obtained. Save or update the method.
• Higher carrier gas flow rates during primary
(tube) desorption. The carrier gas flow rate
should exceed 10 mL/min.
• Higher tube desorption temperatures
• Longer primary desorption times.
• When thermally desorbing volatiles directly
from solid samples, desorption may be
enhanced by increasing the surface area of the
sample, e.g., by grinding the solid material.
Solid carbon dioxide or liquid nitrogen can be
added during the grinding process to minimize
the loss of volatiles.
Action: Select a weaker adsorbent for collecting the
samples
.
Cause: The sample tube is not being heated uniformly.
Action: The pen clip is preventing the tube oven from
making good contact with the sample tube. If