Dextran modified magnetic nanoparticles based solid phase extraction coupled with linear sweep voltammetry for the speciation of Cr(VI) and Cr (III) in tea, coffee, and mineral water samples

A simple and fast solid phase microextraction method using magnetic dextran (Sephadex G-150) as a sorbent was developed for the extraction, separation and speciation analysis of chromium ions. The retained Cr(VI) ions on the magnetic dextran sorbents were eluted and detected by linear sweep voltammetry at the gold nanoparticles modified screen- printed carbon electrode. The linear range, detection limit, quantification limit, and preconcentration factor of the established method for Cr(VI) and Cr(III) were calculated to be 0.5-10 mu M, 0.01 mu M, 0.1 mu M, and 40, respectively. Chromium(III) concentration was determined after conversion of Cr(III) to Cr(VI) by H2O2 in alkaline media (NH4OH). The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in artificial water and food samples using the standard addition method. The applicability of the method was confirmed by analysis of real food samples yielding good recovery values (92% and 102%).