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Abstract

Apparatus and method for chromatographic separation and quantitation of different ions of like charges in a sample, e.g., cations or anions. Referring to anion separation, the sample is directed to a first chromatographic column of the ion exclusion type in which the weak acids (e.g., carboxylic acids) and their salts are partially or totally resolved and separated from a fraction of strong acids (e.g., mineral acids) due to Donnan exclusion. The resolved weak acids may be passed directly to a conductivity cell for quantitative detection. The strong acids may be directed to anion exchange bed with a highly ionized developing reagent and eluted in resolved form with the effluent being passed to a suppressor ion exchange bed wherein the developing reagent is converted to a weakly ionized form without destroying the anion separation. Then, a fraction of the strong acids is detected with the same or a different conductivity cell. Prior to separation, the strong acids are preferably directed through a concentrator column formed of ion exchange resin in which they are retained but not resolved while the remaining solution is removed. Thereafter, the developing agent used for separation of the strong anion is passed through the concentrator column to remove the anions for resolution. The same technique can be employed for cations. In an alternative mode, the system is employed to separate and quantitate weak acids but not the strong ones.

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