Determination of trace amounts of chromium (VI) by flow injection analysis with chemiluminescence detection

A new sensitive chemiluminescence (CL) method combined with continuous flow injection analysis is described for the determination of Cr(VI). Strong CL signals were generated by Cr(VI)-catalysed oxidation of gallic acid in the presence of potassium permanganate and hydrogen peroxide. Effects of reagent concentrations, temperature, pH, flow rates, mixing coil length and mixing flow sequences on the chemiluminescence intensity were studied. Under the optimised experimental conditions, the relationship between the logarithm of concentration (log C) of Cr(VI) and the logarithm of intensity (log I) is linear over the range of 2 x 10(-11)-5 x 10(-4) mol L-1, with the detection limit (3 sigma) of 4 x 10(-12) mol L-1. Relative standard deviation of ten measurements of 1 x 10(-9) mol L-1 Cr(VI) is 1.7%. This flow injection analysis (FIA) system proved to be able to analyse up to 40 samples h(-1). Effects of various interferences possibly present in the water samples were investigated. Most cations and anions, as well as organic compounds, did not interfere with the determination of Cr(VI) in water samples. The experimental results obtained for chromium in reference materials were also in good agreement with the certified values.