Spectrofluorimetric determination of zinc using 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid

A sensitive and a selective spectrofluorimetric method have been developed for the rapid determination of zinc. The method is based on the complex formation between zinc and 8-hydroxy-7-(4-sulfo-1-naphthylazo)-5-quinoline sulfonic acid (HSNQ). The optimum conditions for the complex formation were metal to ligand stoichiometric ratio of 1:1 at pH 8.0 with 0.2 M acetate buffer. The fluorescence of the complex is monitored at an emission wavelength of 545 nm with excitation at 360 nm. Under these conditions linear calibration curves were obtained from 50 ppb to 400 ppb. The detection limit was 7 ppb. The maximum relative standard deviation of the method was 2% for water samples, 4% for milk samples and 7% for hair samples (n = 5). The method was successfully applied for the determination of zinc in drinking water, hair and milk samples. The results were found to be in good agreement with those obtained by flame atomic absorption spectrophotometric methods. The t-test and F-test indicated no significant difference at 95% confidence level.