SPECIATION AND PRECONCENTRATION OF SB(III) AND SB(V) ON ALUMINA USINGPHOSPHORIC-ACID UNDER PH-CONTROLLED CONDITIONS

A method of speciation of inorganic antimony, based on the selective r etention of Sb(III) and Sb(V) on alumina using a complexing agent unde r pH-controlled conditions, is described. The effect of pH on the rete ntion of both species was studied in five media: water, citric acid, t artaric acid, phosphoric acid and hydrochloric acid. The analytical re sults demonstrated that Sb(III) and Sb(V) can be quantitatively separa ted in phosphoric acid, since at pH 9.5 the retention of Sb(V) is negl igible (less than 1%) on the column while Sb(III) is selectively elute d. At pH 7.5 both species are retained. Retention and preconcentration do not depend on the basicity or acidity of the alumina, which sugges ts that adsorption-desorption is the prevailing mechanism on the alumi na microcolumn. The method has been successfully applied to the specia tion of Sb in spiked sea-water samples.