Kinetic Spectrophotometric Method for Determination of S032- Using Methylen blue

Document Type : Research Paper




The present work reports a kinetic spectrophotometric method for the determination of trace
amounts of sulphite that is based on inhibitory effect of sulphite on the oxidation of Methylene
blue (MB) in acidic media. The reaction is followed spectrophotometrically by monitoring the
decrease in absorbance of MB at 664 nm with a fixed time of 0.5-4.5 minutes. It was found that
sulphite exert a strong inhibitory effect on this reaction. The method is applicable in the range of
0.05-120 mg L-1 sulphite and the lower limit of detection is 0.04 mg L-1 (3o). The relative
standard 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 real