Substoichiometric separation and determination of trace metals

Substoichiometric methods are eminently suitable for the determination of many elements. As a new application of substoichiometry, a substoichiometric speciation of the element in different chemical states is proposed. Substoichiometric speciation of As(III) and As(V) is demonstrated as an example. This is based on a highly selective substoichiometric extraction of As(III) with thionalide and As(V) with tetraphenylarsonium chloride in the presence of an excess amount of pyrogallol. Coexistence of other diverse arsenic species including methylarsenic compounds does not give any interference to the selective determination of As(III) and As(V). For substoichiometric radioactivation, a novel application of the synergistic extraction system in a combination of a substoichiometric amount of thenoyltrifluoroacetone with an excess amount of phenanthroline is demonstrated for Yb as an example. Substoichiometric speciation based on the selective speration and an application of synergistic extraction to substoichiometric separation have additional possibilities in substoichiometry.