Chemiluminescence flow system for the monitoring of chromium(VI) in water

A novel chemiluminescence(CL) system has been developed for determining chromium(VI) in water. The analytical reagents involved in the CL reaction, including luminol and hexacyanoferrate(II) were both immobilized on an anion exchange resin column. While a volume of sodium phosphate was passed through the column, these two reagents were eluted from the resins and then mixed with a chromium(VI) stream containing hydrochloric acid. By the fast oxidation reaction between chromium(VI) and hexacyanoferrate(II), hexacyanoferrate(III) was generated, which then reacted with luminol in alkaline aqueous solution to produce CL. The CL emission intensity was correlated with the chromium(VI) concentration in the range 4 × 10−8 to 1 × 10−6 g ml−1, and the detection limit was 1.4 × 10−8 g ml−1 chromium(VI). Interfering metal ions present in water were effectively separated by a pre-column cation exchanger. A complete analysis, including sampling and washing, could be performed in 1 min with a relative standard deviation of less than 5%. The system was stable for over 200 analyses and has been applied successfully to the determination of chromium(VT) in water samples.