Kinetic Spectrophotometric Method for Determination of S032- Using Methylen blue

The present work reports a kinetic spectrophotometric method for the determination of traceamounts of sulphite that is based on inhibitory effect of sulphite on the oxidation of Methyleneblue (MB) in acidic media. The reaction is followed spectrophotometrically by monitoring thedecrease in absorbance of MB at 664 nm with a fixed time of 0.5-4.5 minutes. It was found thatsulphite exert a strong inhibitory effect on this reaction. The method is applicable in the range of0.05-120 mg L-1 sulphite and the lower limit of detection is 0.04 mg L-1 (3o). The relativestandard deviation for 6 replicated determinations was 0.9 and 0.5 % for 4.0 and 20.0 mg L-1,receptively. This method was successfully applied for the determination of sulphite in realsamples.