USE OF LISSAMINE GREEN-B AS A SPECTROPHOTOMETRIC REAGENT FOR THE DETERMINATION OF LOW RESIDUALS OF CHLORINE DIOXIDE

A method for the spectrophotometric determination of chlorine dioxide in the presence of other chlorine species, viz., free chlorine, chlorite, chloramine and chlorate, has been developed. The method overcomes the major problem found with the commonly used NN'-diethyl-p-phenylenediamine method for determining chlorine dioxide, namely interference from free and combined chlorine. The detection limit of the proposed method is 0.03 +/- 0.01 ppm of chlorine dioxide; the calibration graph is linear over the range 0-0.5 ppm of chlorine dioxide. Cyclic voltammetric studies of the chlorine species were used to verify the findings of the spectrophotometric work.