Potentiometric precipitation titrations of selenite, selenate, tellurite and tellurate

Some precipitation titrations have been evaluated for the determination of the oxo anions of selenium and tellurium. Selenite and tellurite can be titrated with sodium diethyldithiocarbamate, using a silver ion-selective electrode as sensor. Tellurite can be titrated with cetylpyridinium chloride, using a poly(vinylchloride)/dioctylphthalate-coated graphite rod as sensor. Silver nitrate can be used to titrate selenite, tellurite, and tellurate. While the sum of tellurite and tellurate can be estimated, no sequential titration is possible. Lead nitrate can be used for the titration of selenite in the presence of selenate, in aqueous solution. In 80% methanolic solution the sum of selenite and selenate is titrated with lead nitrate. (Author)