New magnetic chelating sorbent for chromium speciation by magnetic solid phase extraction on-line with inductively coupled plasma optical emission spectrometry

A novel sorbent material employing magnetic nanoparticles (MNPs) coupled to graphene oxide (GO) function-alized with 4-aminobenzenesulfonic acid (M@GO-ABS) has been synthesized and applied to develop an inex-pensive and automatic method for Cr(III) and Cr(VI) speciation in environmental samples; the developed method combines inductively coupled plasma optical emission spectrometry (ICP-OES) with on-line magnetic solid phase extraction (MSPE). Two magnetic-knotted reactors containing M@GO-ABS were installed in the eight-port in-jection valve of a flow injection (FI) manifold. Two different eluents were used, one for Cr(VI) (the most toxic chromium species) and one for total Cr concentration. Cr(III) concentration was calculated by the difference between Cr(VI) concentration and total Cr concentration. The optimized method presented detection limits (LOD, peak height) of 0.1 mu g L-1 for chromium (VI) and 0.08 mu g L-1 for total chromium, and enrichment factors of 15 and 23, respectively. Certified reference materials (TMDA 54.5 fortified lake water and SPS-SW2 surface water) and spiked aqueous samples were used to validate the developed method. The developed method was fruitfully applied to chromium speciation in environmental water samples such as seawater, well water and tap water collected in M ' alaga (Spain). The obtained values were in good agreement with the certified values, and the recoveries were found in the range of 91-108% for the spiked samples.

Automated summary

A novel method for Cr(III) and Cr(VI) speciation in environmental samples was developed using magnetic nanoparticles coupled to graphene oxide. The method combined inductively coupled plasma optical emission spectrometry with on-line magnetic solid phase extraction. The synthesized sorbent material showed good performance with low detection limits and high enrichment factors. The developed method was successfully applied to analyze chromium speciation in environmental water samples, showing good agreement with certified values and high recoveries for spiked samples.