US 4,455,233 AGranted

Method and apparatus for ion analysis and detection using reverse mode suppression

AssigneeDionex Corporation

InventorsChristopher A. Pohl, Rosanne W. Slingsby, Edward L. Johnson, Leilani Angers

Life of this patent

Estimating the term…

Loading patent…

Abstract

a method of ion analysis and detection of weakly dissociated anions or cations in an eluent by first separating such ions on a chromatographic separation medium by ion exclusion chromatography or mobile phase ion exclusion chromatography. The eluent include an acid or base with a co-ion of the same charge as the ions to be separated, such co-ions being in the hydronium or hydroxide form. In one embodiment the effluent from the separation medium is contacted with one side of an ion-exchange membrane having exchangeable ions of opposite charge to the ionic species. The opposite side of the membrane includes a regenerant with salt-forming suppression ions capable of forming a weakly conducting salt with the co-ions. Then the separated ionic species are detected preferably by a conductivity detector. In another embodiment, the membrane is replaced by a resin bed with ion-exchanging sites of opposite charge to the co-ions. There, co-ions form a suppressed salt with the exchangeable ions.

Claims18

Dependent claims

A method of ion analysis and detection comprising:

(a) eluting at least two weak ionic species to be determined past a chromatographic separation medium in an eluent to separate said ionic species, said ionic species being all of positive or negative charge and being in the form of weakly dissociated acids or bases or salts of weakly dissociated acids or bases, and, after separation, being in the form of acids or bases, said eluent comprising the hydronium or hydroxide form of co-ions of the same charge as said ionic species;
and
(b) containing the effluent from said separation medium with one side of an ion-exchange membrane having exchangeable ions of an opposite charge to said ionic species and being permeable to ions of the same charge as said exchangeable ions, and which resists permeation through the membrane of ions of opposite charge;
and
(c) simultaneously with step (b) contacting the opposite side of said membrane with a regenerant, said membrane forming a permselective partition between the regenerant and the effluent, said regenerant including salt-forming suppression ions of opposite charge to said ionic species and co-ions, said membrane being permeable to said suppression ions and to corresponding hydronium or hydroxide ions, said suppression ions being capable of forming suppressed salts with said co-ions of substantially lower equivalent conductance than the corresponding hydronium or hydroxide form of said co-ions, whereby hydronium or hydroxide ions extracted from the effluent at the ion-exchange sites of the membrane are diffused through the membrane into the regenerant and said suppression ions are diffused from the regenerant into the effluent to form the suppressed salt;
and
(d) then detecting said separated ionic species.

4 more elements

Dependencies are inferred from the claim text.