NEW SPECTROPHOTOMETRIC METHOD FOR SULFITE DETERMINATION

A highly selective spectrophotometric method for the determination of aqueous sulfite was developed. Sulfite was found to react with o-phtha ldialdehyde in presence of ammonia yielding a deep blue colored comple x the absorbance of which is sensitive to trace sulfite concentrations . The method is simple, very sensitive, and convenient for the determi nation of as little as 5X10(-6) M sulfite. The molar absorptivity of t he colored complex is about 1.2X10(4) L cm(-1) mol(-1). The proposed m ethod is more sensitive and selective for sulfite than the widely used Ellman reagent method. Absorbance is measured at 628 nm which is the best of the two absorption maxima that are exhibited by the compound.