The analytical pervaporator and auxiliary units

So far, laboratory-scale pervaporators have been user-designed and built. Although pervaporation can be applied to liquid, solid and slurry samples, the basic separation unit is identical whichever the sample type, the sole difference as regards equipment requirements being the use of appropriate accessory units. An analytical pervaporator consists of two essential parts, namely the body of the separation module (including the devices for hindering gas losses) and the membrane. 

Basically, an analytical pervaporator consists of the elements shown in Fig. 4.17A, namely an upper acceptor chamber (a) with inlets and outlets through which the acceptor stream is circulated and in which the gaseous analyte (or its reaction product if the analyte is not volatile) is collected a lower, donor chamber (d) that contains the solid sample or through which the feed stream of liquid or slurry sample is circulated a thin (ca. 1 mm) membrane support (b) made of polytetrafluoroethylene (PTFE) or metal and spacers (c) of variable thickness (2-10 mm) that can be placed below or above the membrane support in order to increase the volumes of the corresponding chambers. 

The hexagonally shaped unit of Fig. 4.17B was designed with the aim of decreasing void volumes and increasing throughput through faster removal of both the sample and acceptor solutions containing the pervaporated species from the donor and acceptor chamber, respectively. 

Solid sample treatments involving the removal of volatile species 

The analytical pervaporator can be used in combination with a flow-injection manifold, either in the upper chamber when the pervaporated species must be derivatized for adaptation to the detector and/or in the lower chamber for the pervaporation of analytes from liquid samples or slurries. Alterations of either the auxiliary dynamic manifold or the pervaporator itself are required when the pervaporation step is assisted by focused microwaves, the separation step assists in the continuous monitoring of an evolving system, untreated solid samples are used or pervaporation is integrated with detection. 

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