PHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF IODIDE WITH VICTORIA BLUE BO

In a hydrochloric acid medium,and in the presence of bromine water,iodide in the sample solution was transformed into IO-3.After removal of excess bromine by adding sodium formate solution,more iodide (in form of KI) was added to react with IO-3 to liberate iodine which was complexed with excess iodide to form I-3.In a NaH2PO4-H3PO4 buffer medium of pH around 2,and in the presence of non-ionic surfactant OP,an association complex between I-3 and victoria blue BO (VB-BO) was formed which showed a gorgeous blue color.The absorption of the colored complex was measured at its absorption maxima of 580 nm,where the apparent molar absorptivity was found to be 1.84×105L·mol-1·cm-1.Beer′s law was obeyed in the range of 0 to 0.5 mg·L-1 of iodide.The proposed method has been applied to the analysis of table salt samples,giving RSD′s less than 2%,and recoveries in the range from 98.7% to 100.6%.