Chemistry Reference
In-Depth Information
Gas microsyringe
Needle
Vial
Vg
Thermostat
Vc
T = const
Figure 7.6
Headspace analysis in a static mode.
7.2.6.1
Static headspace sampling
Static headspace sampling is employed with GC in numerous fields and with a variety of applications. It has
been a primary tool for analysis of volatile organic compounds in:
environmental analysis,
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flavour and fragrance analysis,
●
pharmaceuticals,
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clinical and biological analysis.
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Because of its limited sensitivity, static headspace sampling is mostly employed for applications in the high-
ppb to percent concentration ranges [57].
In static headspace sampling the liquid phase (sample) and the gaseous phase (receiving matrix) both
remain static (see Figure 7.6). The analytical process can be divided into two stages:
1.
a state of equilibrium is reached between the analysed water sample (placed in an appropriate container)
and the gaseous phase,
2.
a sample of the gas from above the surface of the liquid is collected either manually (with a syringe) or
automatically, which is subsequently sent for chromatographic analysis [59].
The detection limit of headspace analysis in a static system is influenced by:
detector sensitivity,
●
analyte boiling point,
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the partition coefficient of the analyte between the liquid (aqueous) and gaseous phase.
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