Abstract

Increasingly stringent environmental standards makes it necessary to determine chromium(VI) ion in chromium(III )-bearing samples. However, high concentrations of Cr3+ ion significantly interferes with the determination of trace amounts of Cr(VI). A simple flow-injection manifold, which has dual functions of adsorption and determination, was therefore developed to remove Cr(III ) interference and to determine trace Cr(VI) automatically. Reverse adsorption tests were conducted by applying an adsorption column in the flow injection manifold for on-line removal of Cr3+ ion prior to determination. A new spherical cellulose adsorbent, SCAM-1, was used as the adsorption column filling. Tests of precision, recovery and linear range were also conducted to evaluate the above method. The results show that the variation coefficients are less than 4.0% with recoveries ranging from 95.2% to 104.8%. Three calibration curves were obtained over the concentration range of 0.052 to 52.0 mg/L. The detection limit of the method developed for Cr(VI) ion is 0.009±0.0003 mg/L. Moreover, tolerable concentrations of co-existing Cr(III ) can reach 312.0 g/L. Consequently, the manifold and the proposed method are ready for automatic on-line determination of trace Cr(VI) when present in large amounts of Cr(III ).