Ver.1.36
5-3
5.2 EVOLVED GAS ANALYSIS (EGA)
When a polymeric sample is heated, volatile components contained in the polymer are released and
ultimately, the polymer is degraded. The result is a plot of sample temperature vs. detector response.
Such a plot has been termed a ‘thermogram’. The thermogram provides an indication of the sample
complexity. Using a combination of extracted ion chromatograms and average mass spectra, the
thermal region containing compounds of interest can be determined
A typical instrument configuration for EGA is shown in Fig. 5.4. The pyrolyzer and a detector are
connected via a deactivated EGA tube (L=2.5 m, id.= 0.15 mm). The GC oven is normally held at
300°C. When the sample is heated, the thermally desorbed components and gases arising from the
decomposition of the polymer sample are released and detected as shown in Fig. 5.6.
The standard polystyrene solution is used to demonstrate EGA. This sample is a dichloromethane
solution of polystyrene (5 µg/µl) with methyl stearate added. An analysis example is described below.
From the EGA thermogram obtained, the thermal desorption and pyrolysis conditions can be
determined.
STEP1 Installing EGA capillary tube for evolved gas analysis
Attach the supplied EGA capillary tube (id.=0.15 mm, L=2.5 m) for evolved gas analysis.
STEP2 Setting analytical conditions for pyrolyzer and GC (see Fig. 5.6)
(1)
Set the interface temperature (ITF TEMP) to “Auto” mode.
(2)
Set the furnace temperature in the
“Direct EGA Analysis” screen.
EGA capillary tube for
Evolved Gas Analysis
(P/N: UADTM-2.5N)
Detector such as MS
Multi-Shot Pyrolyzer
GC oven: 300°C
Vent-free GC/MS Adapter
Carrier gas: He
Fig.5.4 Typical instrument configuration for Evolved Gas Analysis
