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HAPSITE ER Operating Manual
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. 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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