Chemical suppressors and method of use

Abstract

A non-electrolytic method and apparatus for treating an aqueous sample stream including analyte ions and matrix ions of opposite charge, for pretreatment or suppression. The apparatus includes an ion exchange membrane capable of passing only ions of opposite charge to the analyte ions, a sample stream flow channel, a first aqueous stream ion receiving flow channel adjacent one side of the sample stream flow channel and separated therefrom by the first ion exchange membrane, and stationary flow-through ion exchange packing disposed in the sample stream flow channel. The ion receiving channel has an ion exchange capacity for the matrix ions less than about 25% of the ion exchange capacity for the matrix ions.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a divisional application of U.S. application Ser. No. 10 / 356,345, filed on Jan. 30, 2003.BACKGROUND OF THE INVENTION[0002]The present application relates to a chemical suppression device and method for reducing the concentration of matrix ions of opposite charge to ions to be analyzed, and specifically for use of an ion chromatography suppressor or to a pretreatment device.[0003]Ion chromatography is a known technique for the analysis of ions which typically includes a chromatographic separation stage using an eluent containing an electrolyte, and an eluent suppression stage, followed by detection, typically by an electrical conductivity detector. In the chromatographic separation stage, ions of an injected sample are eluted through a separation column using an electrolyte as the eluent. In the suppression stage, electrical conductivity of the electrolyte is suppressed but not that of the separated ions so that the latt...

AI Technical Summary

Benefits of technology

[0018]In another embodiment, a non-electrolytic method is provided for treating an aqueous sample stream including analyte ions of one charge and matrix ions of opposite charge to the analyte ions. The method comprises flowing the sample stream through a sample stream flow channel, simultaneously flowing an aqueous stream through an ion receiving flow channel separated therefrom by a first ion exchange membrane capable of passing only ions of opposite charge to the analyte ions and of blocking bulk liquid flow to reduce the concentration of the matrix ions in an effluent from the sample stream flow channel, the sample stream flow channel having stationary flow-through first packing of ion exchange material disposed in the sample stream flow channel of the same charge as the first membrane and having a first ion exchange capacity for the matrix ions. The ion receiving channel has an ion exchange capacity for the matrix ions less than about 25% of the first ion exchange capacity for the matrix ion. No electric field is applied between the sample stream flow channel and the first ion receiving flow channel.

[0019]In another embodiment, a chromatography method is provided comprising flowing an aqueous sample stream including analyte ions of one charge and matrix ions of opposite charge to the analyte ions through a chromatography separator to separate the analyte ions. The sample stream including the separated analyte ions flows through a sample stream flow channel, and simultaneously flowing an aqueous stream through an ion receiving flow channel separated therefrom by a first ion exchange membrane capable of passing only ions of opposite charge to the analyte ions and of blocking bulk liquid flow to reduce the concentration of the matrix ions in an effluent from the sample stream flow channel, the sample stream flow channel having stationary flow-through first packing of ion exchange material disposed in the sample stream flow channel of the same charge as the first membrane and having a first ion exchange capacity for the matrix ions, the ion receiving channel having an ion exchange capacity for the matrix ions less than about 25% of the first ion exchange capacity for the matrix ion.

Problems solved by technology

One problem with this electrodialytic membrane suppressor system is that very high voltages (50-500 volts DC) are required.

Such heat is detrimental to effective detection because it greatly increases noise and decreases sensitivity.

One problem with this form of suppressor is limited exchange capacity.

High concentrations of eluents, however, are not easily suppressed.

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