Kinetic Spectrophotometric Method for Determination of S032- Using Methylen blue

Abstract

The present work reports a kinetic spectrophotometric method for the determination of trace<br />amounts of sulphite that is based on inhibitory effect of sulphite on the oxidation of Methylene<br />blue (MB) in acidic media. The reaction is followed spectrophotometrically by monitoring the<br />decrease in absorbance of MB at 664 nm with a fixed time of 0.5-4.5 minutes. It was found that<br />sulphite exert a strong inhibitory effect on this reaction. The method is applicable in the range of<br />0.05-120 mg L-1 sulphite and the lower limit of detection is 0.04 mg L-1 (3o). The relative<br />standard deviation for 6 replicated determinations was 0.9 and 0.5 % for 4.0 and 20.0 mg L-1,<br />receptively. This method was successfully applied for the determination of sulphite in real<br />samples.