Derivative spectrophotometric determination of iridium after preconcentration of its 1-(2-pyridylazo)-2-naphthol complex on microcrystalline naphthalene.

Iridium is preconcentrated from the large volume of its aqueous solution using 1-(2-pyridylazo-2-naphthol) (PAN) on microcrystalline naphthalene in the pH range of 4.5-6.0. The solid mass after filtration is dissolved with 5 ml of dimethylformamide (DMF) and the metal determined by first derivative spectrophotometry. The detection limit is 20 ppb (signal to noise ratio = 2) and the calibration curve is linear over the concentration range 0.25-75.0 mug in 5 ml of the final DMF solution with a correlation coefficient of 0.9996 and relative standard deviation of +/- 1.1%. Various parameters such as the effect of pH, volume of aqueous phase, choice of solvent, reagent and naphthalene concentration, shaking time and interference of a number of metal ions on the determination of trace amount of iridium have been studied in detail to optimize the conditions for its determination in synthetic samples corresponding to various standard alloys and environmental samples.