A simple, rapid and sensitive spectrophotometric method has been developed for the determination of hypochlorite using Rhodamine B. The proposed method reports the reaction of hypochlorite with potassium iodide in an acid medium with iodine liberation. The liberated iodine bleaches the pinkish red color of the Rhodamine B and can be measured at 553 nm. This decrease in absorbance is directly proportional to the hypochlorite concentration and obeys Beer's law in the range of 0.1 - 4.0 µg mL-1of hypochlorite. The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 2.57×10(5) L mol-1 cm-¹, 2.01×10-3 µg cm-2, 0.070 µg mL-1 and 0.212 µg mL-1 respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of the hypochlorite in various samples of tap water, natural water and milk.
hypochlorite determination; spectrophotometry; Rhodamine B
