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A simple, rapid, and sensitive spectrophotometric method has been developed for the determination of hypochlorite using thionin. The method is based on the reaction of hypochlorite with potassium iodide in acidic medium to liberate iodine. The liberated iodine bleaches the violet color of thionin, which is measured at 600 nm. The decrease in absorbance is directly proportional to the concentration of hypochlorite. Beer's law is obeyed in the range 0.2-1.2 µ g/mL of hypochlorite. The molar absorptivity, Sandell's sensitivity, detection limit, and quantitation limit are found to be 1.489 × 10 4 L/(mol cm), 3.25 × 10 -3 µ g cm -2 , 0.1026 µ g/mL, and 0.3112 µ g/mL, respectively. The method has been successfully applied to the determination of hypochlorite in various samples of natural water, tap water, milk, etc.

ABSTRACT.A simple, rapid and sensitive spectrophotometric method has been developed for the determination of iodate (IO3 -) in table salt and sea water. The proposed method is based on the reaction of iodate with potassium iodide in an acid medium to liberate iodine. The liberated iodine bleaches the blue color of methylene blue and is measured at 665.6 nm. This decrease in absorbance is directly proportional to the iodate concentration and obeys Beer's law in the range of 0.5-14 µgmL -1 of IO3 -. The molar absorptivity, Sandell's sensitivity, detection limit and quantitation limit of the method were found to be 1.24 x 10 4 Lmol -1 cm -1 , 1.41 x 10 -2 µgcm -2 , 0.048 µgmL -1 and 0.145 µgmL -1 , respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination has been described. The proposed method has been successfully applied to the determination of the iodate in the table salt and sea water.

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