Purge and trap samplers

They describe the development of a system employing a Tenax GC filled purge and trap sampler, which collects and concentrates volatile organotins from water samples (and species volatilised by hydrodisation with sodium borohydride), coupled automatically to a gas chromatograph equipped with... 

Purge and trap samplers have been developed for analysis of nonpolar and medium-polarity pollutants in water samples. The commercially available systems are all based on the same principle. Helium is purged through the sample that is contained in a sealed system, and the volatiles are swept continuously through an adsorbent trap where they are concentrated. After a selected time, purging is stopped, the carrier gas is directed through the trap via a six-way valve, and the trap is heated rapidly to desorb the solutes. 

Purge and trap samplers have been developed for analysis of apolar and medium-polarity pollu-... 

In the purge-and-trap procedure, vials filled to the brim with the water samples are loaded into an auto-sampler, and then when the unit is operating, samples are drawn, one by one, into a tube where helium sparging occurs. Because the THMs are volatile, the helium sparging draws them out of the samples. The helium-THM gaseous mixture then flows through a trap in which the THMs are adsorbed and concentrated. This is followed by a desorption step in which the desorbed THMs are guided to the GC column. A Hall detector is used. 

Gas chromatography (GC) instruments may be equipped with various detectors to accomplish different analytical tasks. Flame ionization and thermal conductivity detectors are the most widely used detectors for routine analyses, nitrogen-phosphorus detectors are used for the trace analysis of nitrogen-containing compounds, and electron-capture detectors are used for halogen-containing compounds. GCs may also be equipped with peripheral accessories such as autosamplers, purge and trap systems, headspace samplers, or pyrolyzer probes for special needs in sample introduction. 

Westendorf, R.G. (1989a) Automatic Sampler Concepts for Purge and Trap Gas Chromatography, American Laboratory 2. 

Regardless of the sample vessel type—fritted, impinger, thermal desorption tube, or bulk sampler—its function is to remove volatile organics from the sample matrix and carry them away in the purge gas flow. The carrier gas then proceeds to the trap, where the volatiles are retained and the carrier is vented. Selection of the trapping technique and medium depends on several factors, including ... 

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