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Abstract.A simple and highly selective spectrophotometric method is described for the determination of nitrite. The method is based on the measurement of decrease in absorbance at 525 nm of rhodamine 6 G in sulphuric acid medium. The decrease in absorbance is instantaneous on addition of nitrite and remains stable for 2 h. Linear calibration graph passing through the origin was obtained in the range 0.01-0.6/~g/ml nitrite. The method is free from interference of Cu 2 +, Fe 3+ and SO 2-which normally interfe, re in other procedures. The method was applied successfully to the determination of nitrite in well and sea water samples and in KNO3, NaNO3, table salt, sugar and milk powder samples.

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A method for the simultaneous determination of Mn, Co, Zn and Ni which combines Ion-chromatography and a post column reaction with xylenol orange is described. Using 0.07 M oxalic acid (pH adjusted to 5.5 with lithium hydroxide) as eluent, Mn, Co, Zn and Ni were first separated on a 4x250mmIonpacCS-5 column having both sulphonic acid and Alkyl quaternary ammonia functional groups and then transferred to a post-column reaction coil, where the elements react with xylenol orange. The coloured complexes formed were