Magnetic solid phase extraction for the determination of trace antimony species in water by inductively coupled plasma mass spectrometry.

A new magnetic solid phase extraction (MSPE) method using octyl-immobilized silica-coated magnetic Fe3O4 (C8-Fe3O4@SiO2) nanoparticles as the MSPE adsorbent combined with inductively coupled plasma mass spectrometry (ICP-MS) has been developed for speciation analysis of Sb(III) and Sb(V). At pH 5.0, Sb(III) forms a hydrophobic complex with ammonium pyrrolidine dithiocarbamate (APDC) and is retained on C8-Fe3O4@SiO2 nanoparticles, whereas Sb(V) remains as free species in aqueous solution. At pH 2.0, both Sb species (total Sb) form hydrophobic APDC complexes, being retained on the adsorbent. Thus, sensitive speciation analysis of Sb(III) and Sb(V) could be achieved by selective SPE of either Sb(III) or total Sb under different pH on C8-Fe3O4@SiO2 nanoparticles. The experimental parameters, such as pH of solution, concentration of APDC, eluent type and sample volume were optimized in detail. The limits of detection (LOD, 3δ, n=10) of this MSPE method was 0.001 μg L(-1) and 0.004 μg L(-1), respectively, for Sb(III) and Sb(V). The precision of the method (Relative standard deviation, RSD, n=6) for Sb(III) and Sb(V) at 1.0 μg L(-1) was 3.4% and 4.6%, respectively. In order to verify the accuracy of the method, certified reference material (GSB 07-1376-2001) of environmental water was analyzed and the result obtained was in good agreement with the certified values. This proposed method is simple, accurate and sensitive, and can be applied to the speciation of Sb(III) and Sb(V) in environmental waters without any pre-reduction or pre-oxidation operation.