Analytical Sciences

Speciation of Chromium in Water Samples by Solid-Phase Extraction on a New Synthesized Adsorbent

Orhan HAZER and Dilara DEMIR

Bozok University, Faculty of Arts and Sciences, Department of Chemistry, TR-66100 Yozgat, Turkey

Poly(1,3-thiazol-2-yl methacrylamide-co-4-vinyl pyridine-co-divinylbenzene) was prepared and used as a sorbent for the solid-phase extraction of Cr(VI) ions from aqueous solution. Two forms of chromium showed different exchange capacities at different pH values; Cr(VI) was selectively retained especially at pH 2. The total chromium was determined after the oxidization of Cr(III) to Cr(VI) by potassium permanganate as an oxidizing agent. Then, Cr(III) was calculated by subtracting the Cr(VI) concentration from the total chromium concentration. The optimum conditions were found for species of Cr(VI) (pH 2; eluent, 4 mol L⁻¹ NH₃; sample flow rates, 2 mL min⁻¹ and eluent flow rates, 1 mL min⁻¹ etc.). The adsorption capacity and binding equilibrium constant were calculated to be 80.0 mg g⁻¹ and 0.018 L mg⁻¹, respectively. A preconcentration factor of 30 and a three-sigma detection limit of 2.4 μg L⁻¹ (n = 20) were achieved for Cr(VI) ions. The developed method was applied to stream water and waste water samples. At the same time, the polymer was applied to a certified reference material (CRM) (TMDA-52.3) sample.

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