Enhancement of peroxyoxalate chemiluminescence by copper (II) in flow-injection analysis: optimization by factorial design analysis.

A flow injection analysis (FIA) system with peroxyoxalate chemiluminescence (CL) detection was optimized by factorial design analysis in the absence and presence of Cu(II) ions. The carrier stream was a mixture of acetonitrile and an aqueous imidazole solution of pH 7.0. The effect of the metal ions was determined by adding Cu(II) nitrate to the imidazole solution. A mixture of 5 mM bis(2-nitrophenyl)oxalate solution in acetonitrile and hydrogen peroxide was used as reagent solution. The fluorophore used was 3-aminofluoranthene dissolved in acetonitrile to a concentration of 12.5 nM. The parameters of the factorial design experiment in the absence of Cu(II), were the concentration of hydrogen peroxide and imidazole, the percentage of acetonitrile and the length of the mixing coil; those of experiments in the presence of the metal ions, the concentration of imidazole and Cu(II) and the length of the mixing coil. The enhancement of the chemiluminescence intensity by Cu(II) in the FIA system was found to be 70%.