Determination of total carbonate by ligand exchange

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Abstract
An indirect spectrophotometric method is described for the determination of carbonate, based on the decoloration of dilute chloroform solutions of uranium(VI)-N-phenylbenzohydroxamic acid by shaking them with an aqueous solution of anions. Several variables affecting the decoloration (pH, shaking time, etc.) were investigated. The carbonate concentration range over which the decoloration of the chloroform solutions showed a linear dependence (30–100 µg ml–1 of carbonate in the aqueous phase) and the interferences caused by other ions were also studied. The proposed method was applied to the determination of carbonate in mineral and sea waters and pharmaceutical samples and the results obtained showed good agreement with those obtained using the back-titration method of Gripenberg.