Extraction Spectrophotometric Determination of Sulfur(IV) in Atmosphere with Leuco Crystal Violet and N-Chlorosuccinimide

A new and sensitive method is described for the determination of sulfur(IV). Sulfur(IV) is passed through potassium iodate solution and liberated iodine is then reacted with N-chlorosuccinimide and leuco crystal violet. The crystal violet dye formed shows maximum absorbance at 605 nm and has apparent molar absorptivity of 5.2 × 104 mol liter−1 cm−1 Beer′s law is obeyed in the range of 0.006-0.09 μg ml−1 sulfur(IV). The dye is extractable in toluene and is stable for 2 days. The method is fairly reproducible with coefficient of variation ± 1.69% for five replicate analyses. The method is superior to the other reported methods in terms of manipulation, use of nontoxic and easily available reagents, and selectivity. The method has been applied for spectrophotometric determination of sulfur dioxide in polluted and ambient air samples.