4-5
Ver.1.36
4.2.1.3 Using air as atmosphere gas
In this section, analysis in an air atmosphere is described. In this analysis, the sample is first heated
in air; the carrier gas is then switched to helium in order to purge air from the column and detector. If
the analysis is automated using the AS-1020E Auto-shot sampler, the MicroJet Cryo-Trap
(MJT-1030Ex, MJT-1035E) and Selective Sampler (SS-1010E) are required. In addition, the Carrier
Gas Selector (CGS-1050Ex) is highly recommended. The procedure for performing an automated
sequence of analysis in air is described below. Manual operation requires in-depth professional
knowledge and extensive experiences. Contact us if assistance is needed (cs@frontier-lab.com).
(1) “Check” the checkboxes for MicroJet cryo-Trap and Selective Sampler - see Fig. 4.5.
(2) If using an automated Carrier Gas Selector, select “Air” as shown in Fig. 4.5(a). If a Carrier Gas
Selector is not used or if manual control is used, select “Air” as shown in Fig. 4.5(b).
(3) “He Purge Time” (C) in Fig. 4.5(a) is the time it takes for the Carrier Gas Selector to completely
purge the helium in the Pyrolyzer with air. Normally the default value (1.0 min) is used.
(4) “He Purge Time in Column” (D) is the time it takes to completely replace the helium in the
column with air. Normally 2.0 min is used.
(5) “Air Purge Time in GC/MS” (E) is the time it takes to completely purge the air in the column and
detector with helium after the sample has completed the heating process. In particular, if a mass
spectrometer is used as a detector, air in the mass spectrometer must be completely purged
before turning on the filament. If this is the case, use a default value of 7.0 min, although this
time is somewhat dependents on the MS model.
Fig. 4.5 Accessory device set-ups when analysis is being done in an air atmosphere.
(a) Automatic control of Carrier gas selector.
(b) Automatic control of Carrier gas selector not in use.
When performing a pyrolysis in air, air is used as a carrier gas. Be sure
to allow a long purging time to completely replace air with inert gas
such as helium, before raising the oven temperature.
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