2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
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Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology<br />
Fig. <strong>2.</strong> Composition of usable experimental system for measurement<br />
of permeation of toxic agent through protection barrier<br />
materials<br />
thermal desorption from solid phase sorbent (Tenax TA),<br />
direct solvent liquid extraction (n-hexane) and solid phase<br />
extraction (SPE) method. The IMS detector GID-3 operates<br />
on the basis of the different mobility of ions in gaseous phase<br />
in the homogeneous electric field.<br />
The investigated barrier material sample was fixed<br />
inside the alternative permeation cell (see scheme on Fig. 1.)<br />
and contaminated from the upper side with defined amount of<br />
liquid HD agent. The permeating agent vapors were sampled<br />
from the permeation cell space under the material sample<br />
by the IMS detector. The air-drying column was connected<br />
at the front end of the permeation cell inlet to protect IMS<br />
detector against moisture. IMS detector was connected to the<br />
PC where the measured data was continually acquired, saved<br />
and graphically evaluated (see chart on Fig. 3. and Fig. 4.)<br />
with using the software BarieraSW2006 especially designed<br />
for this purpose.<br />
The scheme of LI/GC and TD/GC testing system is<br />
shown on Fig. <strong>2.</strong> The same configuration of permeation cell<br />
including the investigated material sample placing and contamination<br />
procedure was used. The special sampling device<br />
equipped with a controlled air pump and flow meter was used<br />
for permeating agent sampling by the solid phase extraction<br />
ASSET-32 tubes, direct solvent liquid extraction (DSLE)<br />
by n-hexane (for GC, ≥ 99.0 %) and DAAMS Tenax thermal<br />
desorption tubes. Air flow of 100 mL/min was set up.<br />
Agilent GC equipped with FID detector was used for analysis<br />
of liquid sample.<br />
Results<br />
The results of sulphur mustard permeation through tested<br />
materials obtained by IMS detector and GC (thermal desorption,<br />
direct liquid extraction and solid phase extraction) are<br />
compared in the chart on Fig. 3. and Fig. 4. Observed concentration<br />
shift shown in the chart is probably caused by different<br />
sensitivity of used methods. SPE method is more sensitive<br />
than direct solvent liquid extraction and direct solvent<br />
liquid extraction method is more sensitive than IMS method.<br />
s294<br />
Fig. 3. he IMS and LI/GC techniques (direct solvent liquid<br />
extraction and solid phase extraction) results comparison<br />
Fig. 4. The IMS and TD/GC techniques (thermal desorption)<br />
results comparison<br />
Breakthrough time of HD was determined on the basis<br />
of graphical analysis of permeation curves called time-lag.<br />
The permeation curve was interlayed by line13–19. The point<br />
where the line is crossing the x-axis represents the HD breakthrough<br />
time of investigated material (see Table I).<br />
Table I<br />
The values of HD breakthrough time obtain time-lag method<br />
The used Breakthorough time of HD<br />
techniques minutes hours<br />
IMS 350 5 : 50<br />
TD-GC 310 5 : 10<br />
LI-GC (SPE) 270 4 : 30<br />
LI-GC (DSLE) 300 5 : 00<br />
Basically the breakthrough time is dependent also on the<br />
other factors then the used analytical method. Temperature<br />
is one of the most important factors, which strongly influences<br />
the permeation process. The following experiments, held<br />
under the same conditions, have been performed to quantify<br />
the temperature dependence. The course of permeation was<br />
monitoring by the IMS detector GID-3, which is preferable<br />
for long continual measurement. The measurement was proceeded<br />
in temperature range from 15 °C to 40 °C by 5 °C. The<br />
lower range limit was defined by freezing point of sulphur<br />
mustard, which is 14.5 °C. The upper limit was restricted by