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Recoveries from organic free distilled water ranged from 70.5% for dichlorodifluoromethane to 107.8%
for 1,4 dichlorobenzene.

Hiatt et al. [23] developed a vacuum distillation procedure for the isolation of volatile materials from
natural sources, such as water, soil, oil, fish samples etc. The samples obtained were separated and
identified by a GC/MS tandem system. The layout of their sample collection apparatus is shown in
Figure 5.21. The samples were placed in a flask of appropriate size, which was connected in sequence
to two valves. The first valve could connect the pump to the sample vessel either directly, or via a
second valve and through a cryo-trap. The sampling procedure was as follows. The sample chamber
valve was closed and the condenser, cryo-trap, and gas lines were evacuated. The sample flask was then
cooled to the required temperature (usually -5°C). The pump valve was then rotated so that the vapors
were drawn through the first valves to the cryo-trap, which was cooled to -196°C with liquid nitrogen.
The volatile materials from the sample were condensed and collected in the trap. When collection was
complete, the sample valve was again rotated, the cryo-trap warmed, and the contents eluted onto the
GC column by a stream of helium.

Figure 5.21
The Vapor Sampling Apparatus

Not surprisingly, the recovery of the individual volatile materials was found to be related to their
boiling points. If the solubility of the substance