Selective membrane conductometric

A composite polymer membrane has also been used as an effective amperometric detector for ion exchange chromatography [42] and showed detection limits similar to those obtained with a conductivity detector. An advantage of the amperometric detector based on micro-ITIES over the conductometric detector is that selectively can be tailored by proper choice of the ionophore. For instance, the selectivity of the membrane toward ammonium in the presence of an excess of sodium could be substantially increased by introducing an ammonium-selective ionophore (such as valinomycin) in the gel membrane [42]. 

Sergeyeva TA, Piletsky SA, Brovko AA, Slinchenko EA, Sergeeva LM, El skaya AV. Selective recognition of atrazine by molecularly imprinted polymer membranes. Development of conductometric sensor for herbicides detection. Anal Chim Acta 1999 392 105-111. 

R. Dunn, New Developments in Membrane-Selective Conductometric Instruments for Total Organic Carbon Determination in Water, Am. Lab., September 2004, p. 22. 

Figure 73. General composition of gas selective conductometric polymer membranes (A) and selectivity pattern against several organic solvents (B)...

A large number of flow schemes for inorganic carbon analysis are based on conductometric detection. The inherent selectivity provided by the membrane separation process makes it possible. When NaOH is used as acceptor solution, an electrical conductivity decrease is recorded with increase in TIC concentration owing to the neutralization of the sodium hydroxide. On the contrary, a raise of the conductance signal is measured when either deionized water or weak bases such as tris(hydroxymethylamino)methane or sodium acetate are present in the receptor phase. 

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