Study on the mechanism and applications of the fluorescence reactions among cobalt (II), H2O2 and two new derivatives of 8-sulfonamidoquinoline

The fluorescence intensities of the reaction systems of Co(II) with two new 8-sulfonamidoquinoline derivatives, 5-(4-Chlorophenylazo)-8-(benzenesulfonamido)-quinoline (CPBSQ), which was firstly synthesized and characterized, and 5-(3-fluo-4-chlorophenylazo)-8-(benzenesulfonamido)quinoline (FCPBSQ), could be enhanced by H2O2. The mechanism and analytical characters of these reactions in the presence of H2O2 were investigated in this paper. CPBSQ and FCPBSQ reacted with Co(II) in the presence of H2O2 and in the basic medium forming a chelate, which exhibited an intensive fluorescence in ultraviolet region. The fluorescence intensities were proportional to the concentration of Co(II) over the range of 0.1–100 and 0.5–200 μg/l with the detection limits of 0.05 and 0.10 μg/l for the CPBSQ and FCPBSQ systems, respectively. A lot of metal ions included Cu(II) and Ni(II) did not interfere the determinations for both the systems. The methods, which are high sensitive and more selective, have been successfully applied to the determination of trace amount of cobalt in environmental and biological samples.