Two sensitive fluorescence methods for the determination of cobaltous in food and hair samples

Fluorescence reactions among Co(II), with two new 8-sulfonamidoquinoline derivatives, 5-(4-chlorophenylazo)-8-(benzenesulfonamido)quinoline (CPBSQ), and 5-(3-fluo-4-chlorophenylazo)-8-(benzenesulfonamido)quinoline (FCPBSQ), and H2O2 were investigated. CPBSQ or FCPBSQ reacted with cobalt(II) in the presence of H2O2, and basic medium forming a chelate, which exhibited intensive fluorescence in ultraviolet region. The fluorescence intensities were proportional to the concentration of cobalt(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 CPBSQ and FCPBSQ systems, respectively. A range of metal ions, including Cu(II) and Ni(II) did not interfere with the determinations for both systems. The methods, which are high sensitive and more selective, have been successfully applied to the determination of trace amount of cobalt in food and hair samples.