INFICON HAPSITE Smart Plus Chemical Identification System - Manual (Page 460)

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HAPSITE Smart Plus Operating Manual
Each compound will partition according to its solubility in the water phase and its
vapor pressure. Because only the headspace (gas phase) is sampled for the
HAPSITE analysis, the quantity of VOCs and therefore the detection limits are
dependent on the partition coefficient. Furthermore, each compound will have a
unique interaction with the specific water sample matrix and temperature, making
the partition coefficient dependent on the sampling conditions. Analyte response is
determined largely by the partitioning coefficient.
Solubility is determined by the polarity of the VOC molecule. Water is a polar
compound and therefore the more polar VOCs are more soluble in water. The polar
VOCs will partition more in the water while the less polar VOCs will readily volatilize
out of the water and partition more into the gas phase. Therefore, it is expected that
on a scale of more polar to less polar VOCs, as VOCs become less polar, detection
limits will decrease. See
Figure 14-1 .
Figure 14-1 Detection Limits
In combination with the purging characteristics described above, the duration of the
purge and trap event will determine the quantity of each analyte collected on the
trap. Analyte response is directly related to the analyte mass collected for analysis.
14.3 Physical Specifications
Dimensions (L x W x H) . . . . . . . . . . 14.25 in x 15.5 in x 7.5 in
(362 mm x 394 mm x 191 mm)
Transfer line . . . . . . . . . . . . . . . . . . . 4 ft (1.2 m) with LEMO® connectors
Probe line . . . . . . . . . . . . . . . . . . . . . 6 ft (1.8 m) with LEMO connector and
quick-connect for nitrogen purge gas
Weight (including battery). . . . . . . . . 30 lb (13.6 kg)
External Carrier Gas Input . . . . . . . . 1/8 in Swagelok® miniature quick-connect at
the back of unit. Accepts 60-100 psi input
pressure (approx. 420-700 kPa).
Low
Polar
Non-polar
High
Detection Limit
Partition Coefficient