In basic NH3-NH4Cl buffer solutions,the molecules of complex of some metal（Ⅱ） ions with dithizone can associate one another to produce stable micro-particles,which exhibit resonance photo scattering effect and different color.There is a strongest resonance scattering peak at 605 nm for Zn（Ⅱ）,at 540 nm for Pb（Ⅱ）,at 600 nm for Co（Ⅱ）,at 560 nm for Ni（Ⅱ）,at 560 nm for Cd（Ⅱ）, at 570 nm for Cu（Ⅱ） and at 560 nm for Hg（Ⅱ） in their corresponding particle systems.There is a linear relationship between the scattering intensity and metal ion concentration.Among them,the system of Zn（Ⅱ）-dithizone is most sensitive and is therefore chosen for the determination of Zn concentration in the range of 2.0×10-81.54×(10-6 g/mL),with a detection limit of 8.0×10-9 g/mL.This method has been applied to the determination of microelement Zn in samples with satisfactory sensitivity,simplicity and reproducibility.
