User`s guide

Method Development
216
degrade rapidly and leak. You may also want to install high
temperature o-rings into the fixed seal assembly. The high
temperature o-rings (P/N 0920-0092 and 0920-0093) are intended
for operation up to 300°C.
The ferrule in the mobile seal assembly may also be adversely
affected if you are regularly operating at temperatures above 225°C.
It may be necessary to replace the ferrule every 2-3 months if you
are operating at high temperatures. See Changing the O-Ring and
Filter Disk in the ATD Mobile Seal on page 253.
Lastly, you must consider the cold trap. The graphite ferrules (P/N
L427-1187) at each end of the trap can be operated at temperatures
up to 300°C. If you are using an ECD or mass spectrometer, you may
want to replace the graphite ferrules with PTFE (P/N L427-5110).
The PTFE ferrules should be used only for mass spectroscopy
applications, in order to eliminate air ingress as graphite is very
permeable to air. The PTFE ferrules are not suitable for high
temperature operation as they tend to degrade and leak. They are
also less tolerant of the temperature extremes under which the trap
normally operates. After exposure to high temperatures they tend to
stick to the trap making them difficult to remove.
At high temperatures, you must install the valve array bushing (P/N
M041-0316). This bushing eliminates a possible cold spot on the
trap between the trap enclosure and the heated valve. This part is
included with the shipping kit. It can also be installed on the trap
when you are operating at temperatures below 225°C in order to
improve chromatography. See the procedure Replacing the Cold
Trap in the Routine Maintenance chapter.
Carrier Gas Flow Rates
NOTE: For PPC, the pressure is not set manually but the pressure
that you set through the software for PPC must be able to
sustain the split flows.
Various flow rates through the ATD/TD are controlled manually
with pressure regulators. You must determine the best column,
primary and secondary desorb flow rates for your application. If
your are using the sample splitter you must also determine the