Spectrophotometric Determination of Trace Amount of Zinc in Water

A new chromogenic reagent, 5-［4-(p-methoxy) benzyl ammonium pyridinium］-10,15,20-tris(4-N-pyridinium) porphyrin bromide was used to react with Zn(Ⅱ) in potassium acid phthalate-HCl buffer medium of pH 1.2 to form a coordination complex with molar ratio of 1 to 1. Absorption maximum of the complex lies at the wavelength of 424 nm with its molar absorptivity of 4.96×105L·mol-1·cm-1. Linear relationship between values of absorbance and mass concentration of zinc was kept in the range within 800 μg·L-1. In the reaction, this new reagent not only acted as a chromogenic reagent but also as a surfactant. Three water samples were analyzed by the present method, giving values of recovery and RSD′s (n=5) in the ranges of 96.0%-97.1% and 0.43%-0.63% respectively.