FIELD DETERMINATION OF IODIDE IN WATER

A simple, fast and sensitive spectrophotometric method for the quantif ication of iodine and iodide in waters is described. Firstly iodide ha s been oxidised by sodium nitrite to iodine in HCl medium and the resu lting I2Cl- has been preconcentrated into toluene. This can be subsequ ently determined in the extract with brilliant green. A ten-fold preco ncentration is obtained, the molar absorptivity is (4.2 x 10(4)) l mol (-1) cm(-1) at 635 nm. A detection limit of 4 ng/ml iodide in water ca n be reached. The effect of common anions and cations have been invest igated. The method has been applied to the determination fo free iodin e, total iodine and iodide in river, pond and well water.