Determination of trace mercury by solid substrate-room temperature phosphorimetry based on catalytic effect of Hg2+ on formation of the ion association complex [Fe(bipy)3]2+[(FinBr4)2]2−

A new solid substrate-room temperature phosphorimetry method for the determination of trace mercury has been established. It bases on the fact that in acetic acid medium, Hg2+ ion can catalyze the substitute reaction of CN− ligand in [Fe(CN)6]4− by 2,2′-bipyridyl (bipy), and the resultant [Fe(bipy)3]2+ cation can react with FinBr4− anion of tetrabromofluorescein (HFinBr4) to form ion association complex [Fe(bipy)3]2+[(FinBr4)2]2− which can emit phosphorescent signal on filter paper substrate. Under the optimum condition, the linear dynamic range of this method is 1.6–16 fg per spot with a detection limit (LD) of 0.18 fg per spot (0.4 μl sample solution per spot), and the regression equation of working curve is ΔIp=1.058+7.671 CHg2+ (fg per spot ), n=7, correlation coefficient is 0.9990. This method has been applied to the determination of trace mercury in hair and cigarette samples with satisfactory result. The reaction mechanism for formation of the ion association complex is also discussed.