Low detection limit ion selective membrane electrodes

Details Low detection limit ion selective membrane electrodes Low detection limit ion selective membrane electrodes

1998-07-23

2000-10-03

Warden, Jill

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204416, G01N 2726

Patent

active

061268011

ABSTRACT:
A new type of ion-selective solvent polymeric or liquid membrane electrode is constructed which allows to extend the measuring range at the lower end by at least six (6) orders of magnitudes. The new method can be used with membranes based on a neutral ionophore, a charged ionophore, or an ion-exchanger. Low detection limits are achieved by maintaining a very low and constant concentration of the primary ion and a sufficiently high concentration of an interfering ion in the internal reference solution. The low and constant concentration of the primary ion is either adjusted with the help of a solution of a hydrophilic ion buffer such as ethylenediamine tetraacetic acid or by adding an excess of a salt of an ion which forms a sparingly soluble salt with the primary ion, such as NaI for the primary ion Ag.sup.+. With the new technique, ion-selective electrodes can be used, for the first time, for environmental monitoring of heavy metal ions such as Pb.sup.2+ and Cd.sup.2+ at the submicromolar level.

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