Novel sorbent extraction technique using a chelating agent impregnated porous PTFE filter tube : Preconcentration of In(III) with a bis(2-ethylhexyl) hydrogen phosphate (HDEHP) loaded porous PTFE filter tube

The sorption and elution of In(III) on a porous PTFE filter tube impregnated with bis(2-ethylhexyl) hydrogen phosphate (HDEHP) was studied. A 1 µg portion of In(III) in 1000 ml of sample solution was quantitatively complexed with HDEHP adsorbed onto a porous PTFE filter tube by passing the solution through the micropores of the filter tube. Preconcentrated In(III) was then quantitatively recovered provided that the elution, which consisted of cyclical filtering of 0.1 ml of 4 mol l–1 hydrochloric acid through the filter tube for 1 min, was repeated 3 times. The total volume of the eluent was only 0.3 ml in this case; therefore, over 3300-fold of enrichment was attained within 90 min of total preconcentration time. This method was applicable to the preconcentration of In(III) in highly saline samples. A 2.5 µg portion of In(III) could be quantitatively extracted from 500 ml of synthetic seawater and be recovered into 0.5 ml of 4 mol l–1 hydrochloric acid, with subsequent determination by flame AAS. The average recovery and the RSD of the results were 100% and of 1.4%, respectively (n = 5).