Pervaporation, analytical detector types

The manifold into which the upper chamber is inserted does not depend on the initial state of the sample, but only on the characteristics of the pervaporated analytes, the type of detector used and its position along the manifold. Depending on the particular type of detector used, auxiliary channels will have to be included to bring the pervaporated species into contact with appropriate reagents in order to obtain products to which the detector will respond. Integrated detection and pervaporation requires altering the pervaporator but simplifies the overall manifold. As shown below, preconcentration units, solid-phase reactors (mainly enzyme reactors) and various other devices can also be connected in-line in the manifold when required. 

Pervaporators are amenable to coupling to any type of detector via an appropriate interface such as a transport tube, a microcolumn packed with adsorptive or ion-exchange material, or a gas liquid separator. The acceptor stream can be either liquid or gaseous depending on the characteristics of the detector. The detectors most frequently used are the spectroscopic - atomic or molecular, electroanalyti-cal (potentiometric, voltammetric), electron capture, and flame ionization types. The low selectivity of some of these detection techniques is overcome by that of the pervaporation step, endowing the overall analytical process with the selectivity required for the analysis of complex matrices. The potential use of the pervaporation technique for sample insertion into water-unfriendly detectors such as mass spectrometers or devices such as those based on microwave-induced plasma remains unexplored. 

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