Catalytic-Kinetic Fluorophotometric Determination of Trace Amounts of Manganese(Ⅱ) with the Reagent 3-(4′-Chlorophenyl)-5-(2′-Carboxylphenylazo)-Rhodanine

A catalytic kinetic fluorophotometric method for determination of trace amounts of manganese(Ⅱ) was proposed based on the catalytic effect of Mn(Ⅱ) on oxidation of the reagent mentioned in the title by H2O2 in a phthalate buffer medium of pH 5.2. The resulting increase in intensity of fluorescence (ΔF) was measured at the wavelengths (λex/λem) 308 nm/404 nm. Linear relationship between values of ΔF and concentration of Mn(Ⅱ) was obtained in the range within 0.014 mg·L-1 as shown by the linear regression equation ΔF=-4.47+1 038.75 C,where C is the concn. of Mn(Ⅱ) in 10 mL of solution (r=0.988 6). Detection limit of the method was found to be 1.78×10-6g·L-1. The proposed method was applied to analysis of samples of tap water and sewage,giving results in consistency with the results obtained by AAS. Values of RSD′s (n=6) calculated from the analytical results were less than 2.5%. Test for recovery was made by standard addition method,and the results obtained were in the range of 95.6%-103.4%.