Flow analysis determination of iodide at nanogram levels in water.

This paper describes a new method for flow injection analysis (FIA) determination of iodide at nanogram levels in water based on the catalytic destruction of the colour of Fe(III)-SCN--CP (cetylpyridinium chloride) complex. The apparent molar absorptivity of the complex in terms of iodide is (6"90) x 105l mole-’ cm-’ at a maximum absorption of 470 nm. The detection limit of the method is 0"1 ng I-,/ml. The FIA variables for the determination of iodide in the water were optimized. Sample throughput was 50 samples/h. The method is particularly useful for characterization of iodide at lower nanogram levels in rain, surface and ground water samples.