On-line speciation of chromium using a modified chelating resin and determination in industrial water samples by flame atomic absorption spectrometry

Abstract

A flow injection-flame atomic absorption spectrometry (FI-FAAS) system for the speciation of Cr(III)/Cr(VI) based on solid phase extraction (SPE) has been proposed. A newly synthesized resin, Amberlite XAD-16 modified with α-benzoin oxime was used as a solid phase extractor for the speciation of chromium. The sorbed Cr(III) on the resin was desorbed with 0.2 mol L⁻¹ HNO₃. The influence of various chemical and flow parameters on Cr(III) sorption was investigated. The selectivity of the proposed method towards Cr(III) sorption in the presence of interfering ions was also studied. The preconcentration factor and the limit of detection for the preconcentration time of 300 s were 76 and 0.14 ng mL⁻¹, respectively. The relative standard deviation was 1.0% (n = 6). The determination of total chromium was done after reducing Cr(VI) to Cr(III) using hydroxylamine hydrochloride. The concentration of Cr(VI) was then calculated by subtracting the Cr(III) concentration from the total chromium concentration. The proposed system was applied to industrial water samples and recoveries of spiked samples were >95%. The accuracy of the proposed method was studied by analyzing the standard reference material (SRM 1643e, Trace Elements in Water) supplied by NIST, USA.