Chitosan modified magnetic nanoparticles based solid phase extraction combined with ICP-OES for the speciation of Cr(iii) and Cr(vi)

Abstract

Chitosan-modified magnetic nanoparticles were synthesized by an emulsion method and were characterized. The prepared chitosan-modified magnetic nanoparticles exhibit excellent adsorption performance for Cr(III) at pH 9 and total Cr (Cr(III) and Cr(VI)) at pH 6. Therefore, a new method by combining magnetic solid phase extraction with inductively coupled plasma optical emission spectrometry was developed for the speciation of Cr(III) and Cr(VI) in environmental water samples. The parameters affecting extraction and desorption of the target chromium species, such as pH, extraction time, sedimentation time and sample volume, were investigated and the optimized conditions were established. With a preconcentration factor of 100-fold, the limits of detection (LODs) were 0.02 and 0.03 ng mL⁻¹ with the relative standard deviations of 4.8% and 5.6% (n = 7, c = 1 ng mL⁻¹) for Cr(III) and Cr(total), respectively. The method was successfully applied to analyze East Lake water (Wuhan) and tap water at the campus of Wuhan University. In order to validate the accuracy of the proposed method, the certified reference material GSBZ50009-88 was analyzed, and the determined values were in good agreement with the certified values. The proposed method, with the merits of simple operation, rapid adsorption/desorption dynamics, high enrichment factor and low LODs, is suitable for the speciation of inorganic chromium in environmental water samples.