Abstract: In NH₃-NH₄Cl buffer solutions,the reactions of ammonium pyrrolidinedithiocarbamate with some metal ions such as Cu(Ⅱ),Ag(Ⅰ),Pd(Ⅱ),Ni(Ⅱ) and Co(Ⅱ) form chelate complex particles and yield a liquid-solid surface,which show different colors and resonance light scattering (RLS) effects.The five chelate particle systems,Cu(Ⅱ)-APDC,Ag(Ⅰ)-APDC,Pd(Ⅱ)-APDC,Ni(Ⅱ)-APDC and Co(Ⅱ)-APDC,exhibit resonance scattering peaks at 310 nm,360 nm,360 nm,360 nm and 400 nm,respectively.Under the chosen conditions,there is a good linear relationship between the metal ion concentrations and the RLS intensity.When APDC in (Cu-APDC) was oxidized by ClO₂,the RLS intensity of this system was reduced linearly with its concentration.Based on this fact,a new resonance scattering spectral method is proposed for the determination of 7.56×10^-9~756×10^-9 g/mL ClO₂,with a detection limit of 3.0×10^-9 g/mL ClO₂.Its regress equation is ΔI=87.9 c_Cl+0.55,with a relative coefficient of 0.997 8.It was applied to the analysis of ClO₂ in water samples with a satisfactory result.