On-line surfactant-based extraction using ion-pair microparticles combined with ICP-OES for simultaneous preconcentration and determination of rare earth elements in aqueous samples

Abstract

We have developed an on-line and in situ method for the extraction and preconcentration of rare earth elements prior to their determination by inductively coupled plasma optical emission spectrometry. The cationic surfactant dodecyltrimethylammonium bromide and the chelator PAN are first added to the aqueous sample, followed by hexafluorophosphate (acting as an ion-pairing agent), upon which solutions turn cloudy due to formation of an ion pair between the surfactant and hexafluorophosphate. The solid microparticles were passed through a microcolumn filter of μm pore size, and the adsorbed microparticles (containing the REE–PAN complex) were then eluted with acid which was directly introduced into the ICP-OES nebulizer. Several factors affecting the preconcentration and determination steps were optimized. Under the optimized conditions and preconcentration of 20 mL of sample, the enhancement factors of 90–102 and the detection limits of 0.02–1 μg L⁻¹ were obtained.