Chromium Speciation Using Flow-injection Preconcentration on Xylenol Orange Functionalized Amberlite XAD-16 and...

A speciation method for Cr(III) and Cr(VI) by on-line solid-phase extraction using a flow-injection system with FAAS has been proposed. The Cr(III) was selectively retained at pH 5 on the AXAD16-XO chelating resin and was eluted using 0.5 mol L(-1) HNO3. The preconcentration factor and the detection limit (3σ) of 73 and 0.11 μg L(-1), respectively, were obtained for a 120-s preconcentration time. The precision (%RSD) at the 100 μg L(-1) level was 1.08%. The linearity for Cr(III) measurements was up to 600 μg L(-1). The total chromium was determined by reducing Cr(VI) to Cr(III) using hydroxylamine hydrochloride, and the Cr(VI) concentration was obtained by subtraction from the total chromium concentration. The effect of interfering ions was examined towards the selectivity of the proposed system for Cr(III). Spike recovery studies in industrial water samples were carried out using standard Cr(III) and Cr(VI) solutions traceable to NIST. The proposed method was validated using SRM 1643e (Trace Elements in Water) supplied by NIST, USA.