2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
Fig. 2. Composition of usable experimental system for measurement
of permeation of toxic agent through protection barrier
materials
thermal desorption from solid phase sorbent (Tenax TA),
direct solvent liquid extraction (n-hexane) and solid phase
extraction (SPE) method. The IMS detector GID-3 operates
on the basis of the different mobility of ions in gaseous phase
in the homogeneous electric field.
The investigated barrier material sample was fixed
inside the alternative permeation cell (see scheme on Fig. 1.)
and contaminated from the upper side with defined amount of
liquid HD agent. The permeating agent vapors were sampled
from the permeation cell space under the material sample
by the IMS detector. The air-drying column was connected
at the front end of the permeation cell inlet to protect IMS
detector against moisture. IMS detector was connected to the
PC where the measured data was continually acquired, saved
and graphically evaluated (see chart on Fig. 3. and Fig. 4.)
with using the software BarieraSW2006 especially designed
for this purpose.
The scheme of LI/GC and TD/GC testing system is
shown on Fig. 2. The same configuration of permeation cell
including the investigated material sample placing and contamination
procedure was used. The special sampling device
equipped with a controlled air pump and flow meter was used
for permeating agent sampling by the solid phase extraction
ASSET-32 tubes, direct solvent liquid extraction (DSLE)
by n-hexane (for GC, ≥ 99.0 %) and DAAMS Tenax thermal
desorption tubes. Air flow of 100 mL/min was set up.
Agilent GC equipped with FID detector was used for analysis
of liquid sample.
Results
The results of sulphur mustard permeation through tested
materials obtained by IMS detector and GC (thermal desorption,
direct liquid extraction and solid phase extraction) are
compared in the chart on Fig. 3. and Fig. 4. Observed concentration
shift shown in the chart is probably caused by different
sensitivity of used methods. SPE method is more sensitive
than direct solvent liquid extraction and direct solvent
liquid extraction method is more sensitive than IMS method.
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Fig. 3. he IMS and LI/GC techniques (direct solvent liquid
extraction and solid phase extraction) results comparison
Fig. 4. The IMS and TD/GC techniques (thermal desorption)
results comparison
Breakthrough time of HD was determined on the basis
of graphical analysis of permeation curves called time-lag.
The permeation curve was interlayed by line13–19. The point
where the line is crossing the x-axis represents the HD breakthrough
time of investigated material (see Table I).
Table I
The values of HD breakthrough time obtain time-lag method
The used Breakthorough time of HD
techniques minutes hours
IMS 350 5 : 50
TD-GC 310 5 : 10
LI-GC (SPE) 270 4 : 30
LI-GC (DSLE) 300 5 : 00
Basically the breakthrough time is dependent also on the
other factors then the used analytical method. Temperature
is one of the most important factors, which strongly influences
the permeation process. The following experiments, held
under the same conditions, have been performed to quantify
the temperature dependence. The course of permeation was
monitoring by the IMS detector GID-3, which is preferable
for long continual measurement. The measurement was proceeded
in temperature range from 15 °C to 40 °C by 5 °C. The
lower range limit was defined by freezing point of sulphur
mustard, which is 14.5 °C. The upper limit was restricted by