estudio y caracterización de un plasma de microondas a presión ...

Destrucción de VOCs con plasma de Helio
to be obtained provided an appropriate temperature and C2HCl3 vapor pressure were
used.
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2.2.3. Analytical techniques
The changes in gaseous by-products were monitored together with some species
present in the plasma by using an Agilent GC4890D gas chromatograph equipped with
an electron capture detector (ECD) or a flame ionization detector (FID). Compounds
were separated on an HP-5 capillary column (15 m, 0.53 mm i.d., 1.5 µm film thickness)
packed with a stationary phase containing 5% phenyl-methylpolysiloxane.
Mass spectrometric (MS) analyses were performed on a Thermo Finnigan
TraceGC gas chromatograph furnished with a split-splitless injector and a DB-1 fused
silica capillary column (60 m, 0.32 mm i.d., 5 µm film thickness). The chromatograph
was coupled to a Thermo Finnigan TraceDSQ mass spectrometer equipped with a 70 eV
electron impact (EI) ionization source and a quadrupole mass filter. This analysis system
can be used in the whole spectrum (SCAN) or selected ion monitoring (SIM) mode.
Gas samples were injected into the previous gas chromatographs via two VALCO
6-way valves furnished with a 250 µL loop wich was filled with gas from the reactor and
inserted into a chromatographic column via the split-splitless injector. Gas samples were
collected at various points inside the reactor and transferred to the input loops of the
chromatographs at a constant flow-rate of 25 mL/min by means of an SKC suction
pump. This injection method resulted in substantially reduced systematic errors arising
from liquid injections, and hence in increased reproducibility.
Spectroscopic analyses of the species present in the plasma during the destruction
of C2HCl3 allowed the resulting by-products to be detected and new pathways for the
loss of chlorine and carbon by reaction with copper in the coupler tip to be identified.
The monochromator used was Jobin-Yvon THR1000 which possessed a diffraction
grating of 1200 grooves per millimeter; its output was fitted to a LAVISION iCCD
Flamestar2 intensified camera.