Dual-wavelength Spectrophotometry Determination of Micro Amounts of Indium(Ⅲ) in Radioactive ~(111)InCl_3 Solution

A dual wavelength spectrophotometric method is applied to analyze micro amounts of indium(Ⅲ) in radioactive ~(111)InCl_3 solution produced by an accelerator.Indium with phenyfluorone (PF) forms stable complex in the presence of cetylpyridium bromide(CPB) at pH6.5.The maximum absorption of the complex is the absolute amplitude between peaks measured at wavelength of 568 nm and 520 nm.The molar absorptivity is 2.6×10~4 m~2/mol. Beer's law is obeyed for indium in the range of 0～0.4 mg/L. The mole ratio of indium, n(In):n(PF)∶n(CPB)=1∶2∶2. The relative standard deviation is less than 5% and In(Ⅲ) recovery is 96%～108%.