B - 6
IPN 074-397-P1G
HAPSITE Smart Operating Manual
cleaning process above) while the bag is still filled with the VOC-free N, or
VOC-free air, using the HAPSITE. The detection of any target compounds in the
bag should necessitate recleaning or replacement with a bag known to be "clean".
A supply of clean Tedlar bags can be useful for quick standards preparation by
direct liquid injection of VOC's not regularly analyzed into an N
2
or air matrix in the
bags. This allows a more convenient and rapid alternative to gaseous cylinder
mixes in such uses as new applications development or verification of unknown
VOCs by component spiking. This should be qualified by saying that accurate gas
standard preparation by direct liquid injection is only recommended at levels
greater than 5 ppmv, because the minimum liquid volume deliverable by syringe at
an acceptable accuracy and precision is about 0.5
L. This corresponds to
approximately 10 ppmv in a 12 liter Tedlar bag, or approximately 3 ppmv in a 40
liter Tedlar bag. Larger Tedlar bags are available but convenience in regular
handling and the possibility of target compound adsorption on the larger interior
surface area may be matters of concern.
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