Development of surfactant assisted spectrophotometric method for determination of selenium in waste water samples

A new, simple and highly selective method for spectrophotometric determination of selenium in waste water samples is described. Selenium(IV) oxidizes I− ions into I2 which subsequently reacts with excess of I− ion in the acidic media to give tri-iodide ions (I3−), and it further reacts with cetylpyridinium cation (CP+) to give a violet colored species. The value of molar absorptivity of the ion-associate species in terms of selenium is 1.80 × 104 L mol−1 cm−1 at λmax 510 nm. The detection limit of the method is 10 ng mL−1 Se. The calibration curve is linear over 50-1000 ng mL−1 Se with slope, intercept and co-relation coefficient of 0.23, −4.0 × 10−4 and +0.99, respectively. None of the tested diverse ions interfered in the present method. The method has been tested for the determination of selenium in waste water samples.